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Gene-Cos, N. "Mismatch negativity in anxiety disorders." Thesis, Queen Mary, University of London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.515466.
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Ferreira, Dulce Azevedo. "Caracterização do Mismatch Negativity em crianças." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/163755.
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Objetivo: Caracterizar as respostas do Mismatch Negativity (MMN) em crianças com limiares auditivos dentro dos padrões de normalidades e sem queixas auditivas. Métodos: Estudo do tipo transversal. Participaram desta pesquisa crianças de cinco a onze anos, sem queixas auditivas. Todos os participantes realizaram avaliação audiológica periférica com medidas de imitância acústica, audiometria tonal e audiometria vocal previamente à realização do MMN. Para a execução do procedimento eletrofisiológico, MMN, foi utilizado o equipamento Masbe ATC Plus da marca Contronic. Os eletrodos foram fixados nas posições Fpz (eletrodo ativo), M1 e M2 (eletrodos referência) e na fronte (eletrodo terra). A intensidade utilizada para evocar o potencial foi de 80 dBNA, o estímulo frequente utilizado foi de 1.000 Hz e o estímulo raro de 2.000 Hz. Os estímulos foram apresentados em ambas as orelhas de modo monoaural. As crianças realizaram a avaliação sentadas e foram condicionadas a assistirem a um vídeo sem som, no tablet, enquanto o procedimento era realizado. Resultados: Para o grupo feminino, a média das latências e amplitudes foi de 177,3 ms e 5,01 μV na orelha direita e de 182,4 ms e 5,39 μV na orelha esquerda. Quanto ao grupo masculino, a média das latências foi de 194,4 ms na orelha direita e 183,6 ms na orelha esquerda, com amplitude de 5,11 μV na orelha direita e 5,83 μV na orelha esquerda. Não houve diferença estatisticamente significante nos valores de latência e amplitude entre orelhas (p=0,867 e p=0,178), idade (p>0,20) e sexo dos participantes (p>0,05). Conclusão: Os valores encontrados nas latências e amplitudes do potencial MMN são semelhantes aos observados na literatura científica compulsada, em crianças com desenvolvimento típico e sem queixas auditivas.<br>Aim: To characterize the answers of Mismatch Negativity (MMN) in children with hearing thresholds within the normality patterns and without auditory complaints. Methods: Transversal type study. Children between 5 and 11 years old without auditory complaints have participated in this research. All the participants have done peripheral audiological evaluation with acoustic immittance measures, tonal audiometry and vocal audiometry previously to MMN execution. To perform the electrophysiological procedure, MMN, it was used Masbe ATC Plus equipment from Contronic brand. The electrodes were fixed in Fpz (active electrode), M1 and M2 (reference electrodes) and front (earth electrode) positions. The intensity used to evoke the potential was 80 dBNA, the frequent stimulus used was 1.000 Hz and the rare stimulus was 2.000 Hz. The stimuli were presented in both ears monoaurally. Children performed the assessment sat and they were conditioned to watch a video without sound, on a tablet computer, while the procedure was performed. Results: For the female group, the average of the latencies and amplitudes was 177,3 ms and 5,01 μV for the right ear and 182,4 ms and 5,39 μV for the left ear. Regarding the male group, the average of latencies was 194,4 ms for the right ear and 183,6 ms for the left ear, with an amplitude of 5,11 μV for the right ear and 5,83 μV for the left ear. There was no significant statistically difference for the values of latency and amplitude among ears (p=0,867 and p=0,178), age (p>0,20) and gender of the participants (p>0,05). Conclusion: The values found in the latencies and amplitudes of MMN potential are similar to those observed in the scientific literature examined, in children with typical development and without auditory complaints.
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Engeland, Christopher. "Nicotine and the mismatch negativity in Alzheimer's disease." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ27048.pdf.
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Engeland, Christopher (Christopher Gerald) Carleton University Dissertation Psychology. "Nicotine and the mismatch negativity in Alzheimer's disease." Ottawa, 1997.
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Doerfling, Paul. "The negative difference and mismatch negativity as measures of attention." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ56173.pdf.
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MacLean, Shannon Elizabeth. "Temporo-frontal phase synchronization supports hierarchical network for mismatch negativity." Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/33788.
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Several cortical regions appear active when the mismatch negativity (MMN) scalp potential is evoked automatically in response to detectable auditory changes. It remains debatable whether the activation of regions beyond the auditory cortex is coincidental or functionally significant to the MMN response. We used independent component analysis (ICA) to separate high density EEG data (64-channel) prior to dipole fitting for two reasons: 1) to enhance the spatial resolution of EEG and 2) to provide temporal and frequency information about the cortical sources needed to evaluate their functional relationships during the MMN response. For a group of young adults (n = 12) passively listening to infrequent changes in complex tones while watching a silent movie, event-related activity within sources localized to the orbitofrontal cortex (OFC) and the bilateral superior temporal gyrus (STG) regions accounted for most of the scalp response variance implicating these regions as driving forces in the MMN. For a second group (n = 14) performing both passive and active listening across the same paradigm, cross-coherence (phase synchronization) during the MMN response was consistently found between the OFC and the STG bilaterally. During both paradigms the source in the right inferior frontal gryus (R IFG) was also synchronous with the STG-OFC network. When responding to deviant targets in the active paradigm, synchrony was more bilaterally distributed across the network. For a third group (n = 14) passively listening to infrequent changes in speech syllables, synchrony during the MMN response was found between the STG-OFC again as well as with regions in the R IFG and Broca’s area. This same subject group later attended to the speech syllables responding to deviants and standards with a different button press. Synchrony between the STG-OFC, and Broca’s area was found, as well synchrony with a source in the right anterior cingulate. All paradigms showed synchronous interactions both within and between the temporo-frontal regions that were modulated differentially by deviant and standard stimulus conditions as well as by task demands providing the first evidence of functional coupling within a hierarchical network coinciding with the MMN response evoked at the scalp.
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Abu, Qouta Nedal. "Auditiv mismatch negativity (MMN) : under hög och låg visuell belastning." Thesis, Stockholms universitet, Psykologiska institutionen, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-157556.
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Auditiv mismatch negativity (MMN) är en neurologisk hjärnrespons som visar hur känslig hjärnan är för auditiva förändringar. Perceptuell load teorin argumenterar att krävande visuella sökuppgifter eliminerar auditiva distraktorer från att bearbetas i arbetsminnet. Syftet är att observera event-related potential (ERP) händelser för att se om avvikande ljud exkluderas under hög visuell belastning. Ett korsmodalt uppmärksamhetstest utfördes där deltagarna (N = 26) fick utföra en visuell sökuppgift med två svårighetsgrader samtidigt som de skulle ignorera tonfrekvenser som spelades upp i bakgrunden. Resultatet visade auditiv MMN-respons under både låg och hög visuell belastning. Det fanns ingen tydlig skillnad på MMN mellan låg och hög belastning. Hörselcortex registrerade en avvikande ton i oddball och att samma ton fanns i kontroll-upplägget. Argument för att distraktorer bearbetas under kontrollerad uppmärksamhet. Ytterligare studier med större stickprov och olika ljudfrekvenser, naturliga och icke naturliga, krävs för att se hur ljuden påverkar bearbetningsprocessen.
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O'Reilly, Jamie Alexander. "Characterising mismatch negativity biomarker signatures in preclinical models relevant to schizophrenia." Thesis, University of Strathclyde, 2017. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=28635.
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Mismatch negativity (MMN) has been hailed as a 'break-through biomarker in predicting psychosis onset' (Naatanen 2015). This is because deficits have been found in clinical populations diagnosed with psychotic syndromes such as schizophrenia. MMN is an auditory evoked potential (AEP) difference waveform produced by subtracting standard from deviant stimuli AEPs elicited by an oddball paradigm; purportedly arising from any discriminable change in auditory stimulation. Despite nearly four decades of basic research into MMN the underlying mechanisms are not fully understood. Although popular theories suggest that it reflects a sensory-memory trace disruption and/or differential adaptation of responses to standard and deviant/oddball stimuli, there remains considerable debate over the neural mechanism and its interpretation. Nevertheless, associations made between N-methyl-d-aspartate (NMDA) receptors in schizophrenia and findings showing that NMDA receptor antagonists (e.g. ketamine) induce MMN deficits in healthy volunteers suggests abnormal MMNs share common traits and support its use as a biomarker from an electrophysiological perspective. However, this is still speculative and there is great impetus on developing reliable preclinical models of MMN in order to examine the underpinning neurophysiology and therefore its reliance on NMDA receptors as a test of pathology in schizophrenia. A question this thesis aims to address is whether a mismatch response (MMR) exists in rodents which is analogous to the human MMN, and whether its modification by NMDA receptor antagonists or as a result of schizophrenia-related genetic modification sheds light on its utility as a biomarker in disease models of schizophrenia. This thesis describes three experiments performed using mitogen activated protein kinase kinase 7 heterozygous (Map2k7+/-) mice and their wild-type littermates, incorporating NMDA receptor antagonism with ketamine (10 mg/kg i.p.). The MAP2K7 gene is associated with schizophrenia and codes for a post-synaptic intracellular signalling enzyme which is activated following glutamatergic excitation, for instance via NMDA receptors. The MMR to stimuli duration, frequency and intensity changes in oddball paradigms are characterised in urethane-anaesthetised and conscious animals, followed by an examination of laminar auditory cortex activity in response to these physical changes. Data recorded throughout this series of experiments includes cortical electroencephalography (EEG), video footage, and intra-cortical spiking information. These data were then analysed using various time, frequency and time-frequency domain techniques; although mainly focussing on the event-related potential (ERP) approach. Recordings demonstrated substantial differences in the AEP waveform evoked from urethane-anaesthetised and conscious animals, with the latter displaying considerably more dynamic responses, although onset and offset of auditory stimuli induced comparable waveform features in both states. Effects of varying physical properties of stimuli in oddball and control paradigms have been identified as key determinants of the AEP and correspondingly the MMR difference waveform amplitudes. The finding that NMDA receptor disruption in conscious animals by ketamine acutely diminishes a specific AEP feature (≈20-50 ms post stimulus onset) which may impact the resulting MMR tentatively links this study in mice with findings from humans noted above. Ketamine was also found to enhance animal movement and increase EEG spectral power in the 50-70 Hz (gamma-band) frequency range, observed for approximately 10 minutes following drug administration. Both anaesthetised and conscious cohorts of Map2k7+/- mice displayed a significantly enhanced onset response (≈0-20 ms) in the AEP. Interestingly, ketamine did not appear to have a differential effect on Map2k7+/- mice compared with the wild-type group, suggesting that NMDA receptor-mediated neurotransmission is unimpaired in this genetic model relevant to schizophrenia. Overall, the findings suggest that the MMR in mice is fundamentally influenced by the physical properties of stimuli employed; ketamine causes an acute, specific alteration to the AEP in conscious mice in addition to other electrophysiological and behavioural changes; and Map2k7 gene disruption causes a specific and replicable change in AEP amplitude. Overall this study indicates that mouse models are useful for exploring the effects of different pharmacological and genetic manipulations on the auditory evoked response; however, MMN data in clinical cohorts still needs to be interpreted with care. In order to address whether the rodent MMR is analogous to human MMN, it would be necessary to probe how influencing factors revealed in the rodent studies impact on the human response. Whilst the rodent MMR and human MMN show some degree of translation, their potential as schizophrenia biomarkers requires further characterisation and validation.
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Wei, Dawei. "Early and automatic processing of written Chinese : visual mismatch negativity studies." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/47161/.
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Fluent reading entails multiple levels of analysis including orthography, syntax and semantics but is also characterised by fast speed and apparent ease in understanding the various linguistic input. This thesis therefore focuses on the earliness and automaticity of single word recognition, which is a fundamental component of reading process. Exactly when a visual stimulus is recognised as a word and comprehended, and to what extent this is an automatic and not a controlled process, are two of the most debated issues in psycholinguistic research. A series of six Event-Related Potential (ERP) studies were carried out in this study, with the first five of these investigating Chinese single character words and pseudowords and the sixth investigating Spanish words and word-like strings. The critical ERP component of interest is visual Mismatch Negativity (vMMN), a visual counterpart of the well-documented auditory MMN (Näätänen, Gaillard, & Mäntysalo, 1978). VMMN has recently been demonstrated to be a neural index of automatic processing of not only generic visual features but also written words. To overcome the compounding of physical differences between stimulus conditions, a “same-stimulus” identity oddball paradigm was adopted throughout the studies. The vMMN was computed by comparing the ERP responses to deviant and standard stimuli of the same lexical/semantic category. It was found that lexical and semantic vMMN effects could be obtained within the first 250 ms after the stimulus onset, even when the critical words were presented briefly and outside of the focus of attention (perifoveally) and participants were instructed to carry out a non-linguistic distraction task, indicating automaticity of processing. The similarity in the timing of these early vMMN responses lends support to parallel processing models of linguistic information processing. In addition, vMMN to changes in lexicality was subject to configurations in the cognitive system, with attention and the magnitude of deviance revealed as two important variables. Language vMMN effects in normal adults as revealed in this thesis may serve as a benchmark for assessing the reading abilities of first or second language readers, as well as of people with linguistic impairments, such as dyslexia.
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Perry, Elizabeth Anne. "Brain Mapping of the Mismatch Negativity Response in Vowel Formant Processing." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3226.
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The mismatch negativity (MMN) response, a passively-elicited component of the auditory event-related potential (ERP), reflects preattentive identification of infrequent changes in acoustic stimuli. In the current study, the MMN response was examined closely to determine what extent natural speech sounds evoke the MMN. It was hypothesized that a significant MMN response results during the presentation of deviant stimuli from which spectral energy within formant bands critical to vowel identification has been removed. Localizations of dipoles within the cortex were hypothesized to yield information pertaining to the processing of formant-specific linguistic information. A same/different discrimination task was administered to 20 adult participants (10 female and 10 male) between the ages of 18 and 26 years. Data from behavioral responses and ERPs were recorded. Results demonstrated that the MMN may be evoked by natural speech sounds. Grand-averaged brain maps of ERPs created for all stimulus pairs showed a large preattentive negativity. Additionally, amplitudes of the MMN were greatest for pairs of auditory stimuli in which spectral energy not corresponding to formant frequencies was digitally eliminated. Dipoles reconstructed from temporal ERP data were located in cortical areas known to support language and auditory processing. Significant differences between stimulus type and reaction time were also noted. The current investigation confirms that the MMN response is evoked by natural speech sounds and provides evidence for a theory of preattentive formant-based processing of speech sounds.
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Elangovan, Saravanan, Jerry L. Cranford, Letitia Walker, and Andrew Stuart. "A Comparison of the Mismatch Negativity and a Differential Waveform Response." Digital Commons @ East Tennessee State University, 2005. https://dc.etsu.edu/etsu-works/1556.
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A mismatch negativity response (MMN) and a new differential waveform were derived in an effort to evaluate a neural refractory or recovery effect in adult listeners. The MMN was elicited using oddball test runs in which the standard and deviant stimuli differed in frequency. To derive the differential waveform, the same standard and deviant stimuli were presented alone. MMN responses were obtained by subtracting the averaged responses to standards from the deviants. The differential waveforms were obtained by subtracting the averaged responses to standards presented alone from deviants presented alone. Scalp topography for the MMN and differential waveforms were similar. A significant (p
Se obtuvo una respuesta de negatividad desigual (MMN) y una nueva onda ?diferencial? en un esfuerzo por evaluar un efecto neural refractario o de recuperación en sujetos adultos. La MMN fue generada utilizando cursos peculiares de prueba en los que el estimulo estándar y el alterado tenían frecuencias diferentes. Para derivar la onda diferencial, se presentaron el mismo estímulo estándar y el alterado en forma aislada. Las respuestas MMN se obtuvieron restando las respuestas promediadas estándar de las alteradas. Las formas de onda diferenciales se obtuvieron restando las respuestas promediadas a estímulos estándar presentados aisladamente, de los estímulos alterados presentados también en forma aislada. La topografía craneana de los MMN y las onda diferenciales fueron similares. Se encontraron correlaciones positivas y negativas significativas (p
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Milovan, Denise L. "Generation of mismatch negativity in a sample of treatment-resistant schizophrenia patients." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0022/MQ39943.pdf.
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Singhal, Anthony. "Attentional workload and the ERPs, negative difference (Nd) and mismatch negativity (MMN)." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ39233.pdf.
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Krljes, Sanya. "Mismatch negativity (MMN) deficit in schizophrenia : specificity and relationship to cognitive deficits." Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.422339.
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Lilge, Anja [Verfasser]. "Ist eine objektive Darstellung der Ordnungsschwelle mittels Mismatch Negativity möglich ? / Anja Lilge." Berlin : Medizinische Fakultät Charité - Universitätsmedizin Berlin, 2009. http://d-nb.info/1023582236/34.
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Pierce, Dana Lynn. "Mismatch Negativity Event Related Potential Elicited by Speech Stimuli in Geriatric Patients." BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/7487.
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Hearing loss, as a result of old age, has been linked to a decline in speech perception despite the use of additional listening devices. Even though the relationship between hearing loss and decreased speech perception has been well established, research in this area has often focused on the behavioral aspects of language and not on the functionality of the brain itself. In the present study, the mismatch negativity, an event related potential, was examined in order to determine the differences in speech perception between young adult participants, geriatric normal hearing participants, and geriatric hearing-impaired participants. It was hypothesized that a significantly weaker mismatch negativity would occur in the geriatric hearing-impaired participants when compared to the young adult participants and the geriatric normal hearing participants. A passive same/different discrimination task was administered to 10 young adult controls (5 male, 5 female) and eight older adult participants with and without hearing loss (4 male, 4 female). Data from behavioral responses and event related potentials were recorded from 64 electrodes placed across the scalp. Results demonstrated that the mismatch negativity occurred at various amplitudes across all participants tested; however, an increased latency in the presence of the mismatch negativity was noted for the geriatric normal hearing and the geriatric hearing-impaired participants. Dipoles reconstructed from temporal event related potential data were located in the cortical areas known to be instrumental in auditory and language processing for the young adult participants; however, within the geriatric normal hearing and the geriatric hearing-impaired participants, dipoles were seen in multiple locations not directly associated with language and auditory processing. Although not conclusive, it appears that within the geriatric normal hearing and the geriatric hearing-impaired participants there is slower processing of the speech information, as well as some cognitive confusion which leads to fewer available resources for interpretation.
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Jansson-Verkasalo, E. (Eira). "Auditory event-related potentials as indices of language impairment in children born preterm and with Asperger syndrome." Doctoral thesis, University of Oulu, 2004. http://urn.fi/urn:isbn:9514272447.
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Abstract
The main objective of the present follow-up study was to investigate auditory processing by using auditory event related potentials (ERPs), and language development to determine whether a correlation exists between auditory ERPs and language development.
Auditory processing was investigated in very low birth weight (VLBW) preterm children and matched controls at mean ages of 4 and 6 years to determine whether there are differences in ERPs between VLBW preterm children and controls. Language development was measured at the mean ages of 2, 4 and 6 years to investigate the developmental course of language learning and to determine whether a relationship exists between ERPs, especially mismatch negativity (MMN), and language development. Auditory ERPs were also measured in children with AS (mean age 9;1 years) and matched controls to assess whether differences can be found between these two groups of children. Language development in children with AS was not investigated for this study.
VLBW preterm children exhibited difficulties in the auditory processing at the level of obligatory ERPs, MMN, late MMN (lMMN) and behavioural tests. Both language comprehension and production were deficient in the preterm group compared to their controls. Lexical development was the most prominent phenomenon differentiating preterm children from their controls. MMN and lMMN amplitudes were attenuated most in children with naming difficulty at the ages of 4 and 6 years. Weak or totally missing MMN at the age of 4 years was mainly found in children with naming difficulties.
Children with AS also displayed abnormalities in auditory processing, as indexed by delayed MMN latency. MMN was most delayed in the right hemisphere and specifically for tones.
In conclusion: VLBW preterm children and children with AS exhibited difficulties in auditory processing. MMN correlated well with language development in preterm children. Therefore, auditory ERPs, especially MMN, should be used in combination with language measures to identify the children at a risk for deficient auditory processing and language delays.
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Pettigrew, Catharine Melainie. "Automatic processing of spoken words in normals and aphasics : a mismatch negativity study /." St. Lucia, Qld, 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17891.pdf.
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Vajsar, Jiri. "The mismatch negativity evoked by changes in the frequency of an auditory stimulus." Thesis, University of Ottawa (Canada), 1990. http://hdl.handle.net/10393/5679.
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This thesis deals with some of the unknown issues in slow auditory evoked potentials (AEPs). Slow AEPs were recorded in 10 healthy reading subjects. A change in the frequency of the tonebursts elicited an additional negativity--the mismatch negativity (MMN). The amplitude and latency of MMN changed with the magnitude of frequency deviance between stimuli which was varied between 50 and 2000 Hz. The voltage distributions of the MMN and N1 were significantly different from that of the SP. The MMN and N1 had their maximal amplitudes in the fronto-central areas, whereas the maximal amplitude of the SP was recorded frontally. The topographic mapping and statistical analysis of voltage distribution of individual waves enabled us to recognize and differentiate between the possible generators of the MMN, N1 and SP. Both the MMN and N1 are generated in the auditory cortices. The SP is more complexed and may consist of more than one component. (Abstract shortened by UMI.)
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Quandt, Daniel. "Ereigniskorrelierte Potenziale und mismatch negativity zur Objektivierung vorbewusster Phonem- und Tonhöhendiskrimination bei unauffälligen Säuglingen." [S.l.] : [s.n.], 2004. http://www.diss.fu-berlin.de/2004/252/index.html.
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Chen, J. "Mismatch negativity in health and dystonia and its modulation by non-invasive brain stimulation." Thesis, University College London (University of London), 2014. http://discovery.ucl.ac.uk/1437736/.
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MMN has been characterized as an automatic, pre-attentive, error detection mechanism that may aid switch in attention towards a salient stimulus as well as assisting with contrast enhancement of sensory data. There is interest clinically in the MMN given its abnormality in a number of neurological/neuropsychiatric disorders. This thesis explores tDCS as a practical tool to modulate MMN in health, to assess impaired somatosensory error detection as an explanation of the underlying mechanism of dystonia by utilising somatosensory mismatch negativity (MMN) and to explore the role of the cerebellum in both error detection and dystonia using tDCS. We found that tDCS is a reliable way to alter the generation of MMN perhaps through homeostatic interaction in frontal auditory MMN generator. Subsequently, we found a reliable way to generate somatosensory MMN and then by using tDCS stimulation were able to give more evidence of the relationship between the cerebellum and somatosensory MMN. Finally, we have demonstrated an abnormality in somatosensory MMN in patients with dystonia which is strongly correlated with somatosensory temporal discrimination threshold. Additionally, we showed that there was no modulation of sMMN after cerebellar tDCS in patients with dystonia. This thesis suggests that, in health, tDCS is able to modulate both auditory and somatosensory MMN. These experiments provide evidence for a new way in which MMN might be modulated for experimental purposes and potentially for clinical/therapeutic purposes. The finding of reduced somatosensory MMN (but not auditory MMN) in dystonia suggests a specific deficit in error detection in the somatosensory domain in dystonia. The correlation of somatosensory MMN with somatosensory temporal discrimination threshold, which is robustly abnormal in dystonia, implies a shared mechanism between the two phenomena. We suggest that somatosensory temporal discrimination could be subsumed within somatosensory MMN as an error detection task. The dependence we have demonstrated for somatosensory MMN on the cerebellum in healthy people fits with a role for the cerebellum in the pathophysiology of dystonia. We could not modulate somatosensory MMN in patients with dystonia with tDCS as we could in healthy people, and this provides some additional evidence that cerebellar dysfunction might be relevant both for the abnormal somatosensory MMN in dystonia but also for the clinical manifestation of dystonia itself.
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Duda, Victoria. "Measuring Mismatch Negativity Responses to Gaps in Noise for a Better Understanding of Tinnitus." Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/38226.
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Hearing in noise is facilitated by the auditory system’s ability to separate sound into small auditory segments. Separation of sound is achieved using an auditory mechanism called temporal resolution that codes for small silent gaps in an acoustic stimulus. This thesis proposes a new method for measuring temporal resolution and applied it to a small pilot group of individuals with tinnitus.
Previous studies have postulated that tinnitus can “fill” in silent gaps thereby making gap detection more difficult. This was shown in studies using the gap prepulse inhibition acoustic startle where the amplitude of a startle response indicates the subject’s ability to detect a small silent gap. However studies using behavioural gap detection do not show significant differences in people with reported tinnitus. Thus the behavioural evidence does not appear to support the hypothesis that tinnitus can “fill” in silent gaps.
In this thesis a new method was proposed for measuring neural gap detection: the mismatch negativity response (MMN). The mismatch negativity responses were compared to behavioural measures of gap detection in thirty-five normal hearing adults: five with reported tinnitus and thirty without tinnitus. They underwent recordings to gapped stimuli ranging from 2- to 40-ms gap durations. The stimuli were either a broadband or narrowband noise presented in the absence or presence of a filler noise.
Results of these experiments found the broadband and narrowband noises elicited MMNs to silent gaps. The amplitude of the MMN increased with larger gap durations. When filled, the amplitude of the entire waveform was proportionally reduced for all gap durations. However, for the tinnitus group the filler reduced the largest gap durations elicited MMNs amplitudes disproportionately more than for the smaller gap durations. The high and low filler noise reduced the amplitude of the 40-ms gap MMNs. This was not reflective in the behavioural performance of gap detection as there were no significant group differences.
These studies show that neural gap detection can be measured using mismatch negativities. Reduced behavioural gap detection performance is reflected by a smaller amplitude of the MMN for suprathrehold gaps. This was shown in both normal hearing participants with elevated behavioural gap detection thresholds and participants with tinnitus. Therefore, electrophysiological recordings to gaps may provide further information on the underlying mechanisms involved in impaired gap detection that may not be captured by behavioural measures alone.
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Schuller, Marietta [Verfasser], and Ulrich [Akademischer Betreuer] Bogdahn. "Die Mismatch Negativity (MMN) als Indikator müdigkeits- bzw. schläfrigkeitsassoziierter Aufmerksamkeitsdefizite / Marietta Schuller ; Betreuer: Ulrich Bogdahn." Regensburg : Universitätsbibliothek Regensburg, 2018. http://d-nb.info/1156780276/34.
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Alzaher, Mariam. "Mismatch negativity, un marqueur neuronal de la plasticité spatiale auditive chez les sujets sourds unilatéraux." Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30253.
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Cette thèse évalue les différentes fonctions d'audition spatiale chez 3 types de populations : Normaux entendants (NE), sourds unilatéraux (SU) et sourds bilatéraux (SB). Afin de découvrir les mécanismes qui soulignent les stratégies spatio-auditives adaptative qui sont observés chez les SU avec surdité acquise. Le but principal de la thèse est de vérifier si la MMN pourrait être un marqueur neuronal de la plasticité spatiale auditive observée chez les patients SU, et de vérifier se les corrélats neuronaux sont cohérentes avec les performances spatiales auditives. Deux types d'investigations ont été appliqués sur 20 sujets NE, 21 SU et 14 SB. La première investigation s'agit d'un test d'identification de source sonore mesuré par l'erreur quadratique moyenne (RMS). La deuxième évaluation est une étude électroencéphalographie qui sert à analyser la MMN. La MMN étant défini comme un potentiel évoqué qui reflète la capacité du cerveau à détecter un changement dans les propriétés physiques d'un son. Nous avons utilisé un son standard dans une position de référence (50°) avec 3 déviation par rapport au standard (10°, 20° et 100°) dans des conditions binaurales et monaurales. Les sujets sourds unilatéraux ont été divisé en 3 groupes selon leur performance spatiale. Le groupe des bons performeurs (SU low rms) a montré des meilleurs scores RMS en comparaison avec les NE munie d'un bouchon d'oreille (NE-mon), avec des performances similaires à ceux des sujets NE en binaurale. Une augmentation progressive de la MMN avec l'angle de la déviation par rapport au standard a été noté chez tous les groupes. Avec une réduction importante de la MMN chez les NH en monaurale quand le bouchon a été appliqué du côté du standard. La MMN a montré des résultats cohérents avec nos observations comportementales, ou les sujets SU avec un bon score RMS avait également des amplitudes de la MMN plus importantes que celles des sujets NE en condition monaurale et similaires à celles des NE en condition binaurale. Les sujets SU possèdent des stratégies adaptatives saptio-auditives. Notre étude a pu démontré que la plasticité corticale spatio-auditive qui a lieu suite à la surdité est reflété par la MMN. Les observations neuronales (MMN) sont corrélées avec les observations comportementaux de localisation spatiale. Ce qui signifie que la plasticité corticale qui a lieu chez ces sujets, n'est pas limités aux fonctions d'identification de la source sonores, mais dépasse ces capacités vers des mécanismes plus complexes tel que la détection de déviation et la mémoire à court terme, qui interviennent dans la fonction de discrimination spatiale des sons<br>This thesis investigates different spatial hearing functions in 3 types of populations: Normal Hearing Subjects (NHS), Unilateral Hearing Loss patients (UHL) and Bilateral Hearing Loss patients ( BHL). To discover the mechanisms underlying the adaptive strategies that are observed in UHL with acquired deafness. The main aim of the thesis is to verify whether spatial Mismatch Negativity (MMN) could be a neuronal marker of spatial auditory plasticity observed in UHL patients, and to verify whether these neural correlates are consistent with the spatial auditory performance. Two types of investigations were applied to 20 NHS, 21 UHL and 14 BHL. The first investigation is a sound source identification task measured by the root mean square error (RMS). The second assessment is an electroencephalography (EEG) study where we analyzed the amplitude and latency of the MMN. MMN is defined as an auditory evoked potential that reflects the brain's ability to detect a change in one physical property of a sound. We used a standard sound in a reference position (50°) with three deviations from the standard (10° , 20°, and 100°), in binaural and monaural conditions. UHL patients were divided into 3 groups according to their spatial performances. The group of good performers (UHL {low rms}) showed better RMS scores in comparison with NHS with earplugs (NHS-mon), with performances similar to those of NHS subjects in binaural condition. A progressive increase of the MMN with the angle of deviation from the standard was noted in all groups. With a significant reduction of MMN amplitude in monaural NHS when the ear plug was applied on the ipsilateral side of the standard. MMN showed consistent variation with the behavioral observations, where UHL {low rms} patients had larger MMN amplitudes than those of monaural NHS and similar to those of binaural NHS. UHL patients have adaptive spatial auditory strategies. Our study was able to demonstrate that spatial auditory plasticity that occurs after deafness can be reflected by the MMN. Neural observations (i.e. the MMN) are correlated with behavioral observations of spatial source identification. This means that the spatial cortical plasticity, that took place in these subjects, is not limited to the functions of identification of the sound source, but exceeds these capacities towards more complex mechanisms such as deviance detection and short-term memory, that are involved in the spatial discrimination function
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Smith, Lyndsy Marie. "Brain Mapping of the Mismatch Negativity Response to Vowel Variances of Natural and Synthetic Phonemes." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/3890.
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The mismatch negativity (MMN) is a specific event-related potential (ERP) component used frequently in the observation of auditory processing. The MMN is elicited by a deviant stimulus randomly presented in the presence of repeating stimuli. The current study utilized the MMN response in order to determine the temporal (timing) and linguistic processing of natural and synthetic vowel stimuli. It was hypothesized that a significant MMN response would be elicited by natural and synthetic vowel stimuli. Brain mapping of the MMN response was hypothesized to yield temporal resolution information, which would provide detail regarding the sequential processing differences between natural and synthetic vowel stimuli. It was also hypothesized that the location of dipoles within the cortex would provide information pertaining to differences in cortical localization of processing for natural and synthetic stimuli. Vowel stimuli were presented to twenty participants (10 females and 10 males between the ages of 18 and 26 years) in a three-forced-choice response paradigm. Data from behavioral responses, reaction times, and ERPs were recorded for each participant. Results demonstrated that there were differences in the behavioral and electrophysiological responses between natural and synthesized vowels presented to young, normal hearing adults. In addition, significant MMN responses were evoked by both natural and synthetic vowel stimuli. Greater reaction times existed for the synthetic vowel phonemes compared to the natural vowel phonemes. Electrophysiological differences were primarily seen in the processing of the synthetic /u/ stimuli. Scalp distribution of cognitive processing was essentially the same for naturally produced phonemes. Processing of synthetic phonemes also had similar scalp distributions; however, the synthetic /u/ phoneme required more complex processing compared to the synthetic /æ/ phoneme. The most significant processing localizations were located in the superior temporal gyrus, which is known for its role in linguistic processing. Continued processing in the frontal lobe was observed, suggesting continual evaluation of natural and synthetic phonemes throughout processing.
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Hutton, Brittany A. "Exploring Echoic Memory and Auditory Cognition in the Atlantic Bottlenose dolphin, Tursiops truncatus, with Mismatch Negativity." University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1613741639578729.
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Roser, Patrik [Verfasser]. "Auswirkungen von Δ9-Tetrahydrocannabinol und standardisiertem Cannabis-Extrakt auf die akustisch evozierte Mismatch Negativity / Patrik Roser". Berlin : Medizinische Fakultät Charité - Universitätsmedizin Berlin, 2007. http://d-nb.info/1021937169/34.
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Neff, Skylee Simmons. "Brain Mapping of the Mismatch Negativity and the P300 Response in Speech and Nonspeech Stimulus Processing." BYU ScholarsArchive, 2010. https://scholarsarchive.byu.edu/etd/2254.
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Previous studies have found that behavioral and P300 responses to speech are influenced by linguistic cues in the stimuli. Research has found conflicting data regarding the influence of phonemic characteristics of stimuli in the mismatch negativity (MMN) response. The current investigation is a replication of the study designed by Tampas et al. (2005), which studied the effects of linguistic cues on the MMN response. This current study was designed to determine whether the MMN response is influenced by phonetic or purely acoustic stimuli, and to expand our knowledge of the scalp distribution of processing responses to within- and across-category speech and nonspeech stimuli. The stimuli used in this study consisted of within-category synthetic speech stimuli and corresponding nonspeech frequency glides. Participants consisted of 21 (11 male and 10 female) adults between the ages of 18 and 30 years. A same/different discrimination task was administered to all participants. Data from behavioral responses and event-related potentials (MMN and P300) were recorded. Results provided additional evidence that the MMN response is influenced by linguistic information. MMN responses elicited by the nonspeech contrasts had more negative peak amplitudes and longer latencies than MMN responses elicited by speech contrasts. Brain maps of t scores for speech vs. nonspeech contrasts showed significant differences in areas of cognitive processing for all contrast pairs over the left hemisphere near the temporal and parietal areas. The present investigation confirms that there are significant differences in the cortical processing of speech sounds vs. nonspeech sounds.
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Weise, Annekathrin, Sabine Grimm, Nelson J. Trujillo-Barreto, and Erich Schröger. "Timing matters." Universitätsbibliothek Leipzig, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-146962.
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The human central auditory system can automatically extract abstract regularities from a variant auditory input. To this end, temporarily separated events need to be related. This study tested whether the timing between events, falling either within or outside the temporal window of integration (~350 ms), impacts the extraction of abstract feature relations. We utilized tone pairs for which tones within but not across pairs revealed a constant pitch relation (e.g., pitch of second tone of a pair higher than pitch of first tone, while absolute pitch values varied across pairs). We measured the mismatch negativity (MMN; the brain’s error signal to auditory regularity violations) to second tones that rarely violated the pitch relation (e.g., pitch of second tone lower). A Short condition in which tone duration (90 ms) and stimulus onset asynchrony between the tones of a pair were short (110 ms) was compared to two conditions, where this onset asynchrony was long (510 ms). In the Long Gap condition, the tone durations were identical to Short (90 ms), but the silent interval was prolonged by 400 ms. In Long Tone, the duration of the first tone was prolonged by 400 ms, while the silent interval was comparable to Short (20 ms). Results show a frontocentral MMN of comparable amplitude in all conditions. Thus, abstract pitch relations can be extracted even when the within-pair timing exceeds the integration period. Source analyses indicate MMN generators in the supratemporal cortex. Interestingly, they were located more anterior in Long Gap than in Short and Long Tone. Moreover, frontal generator activity was found for Long Gap and Long Tone. Thus, the way in which the system automatically registers irregular abstract pitch relations depends on the timing of the events to be linked. Pending that the current MMN data mirror established abstract rule representations coding the regular pitch relation, neural processes building these templates vary with timing.
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Mengler, Elise Dione. "Neurophysiologically mediated auditory processing insensitivity in children with specific language impairment : behavioural discrimination and the mismatch and late discriminative negativities." University of Western Australia. School of Psychology, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0154.
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[Truncated abstract] Some children with Specific Language Impairment (SLI) show poor performance on behavioural tasks designed to measure rapid auditory processing, such as the Repetition Test developed by Tallal and colleagues. Stemming from concerns about whether this task reflects higher-order, cognitive variables, this thesis sought to determine whether the performance deficits SLI children show were evident at the neurophysiological level, with minimal cognitive influences, such as attention, using paradigms designed to elicit the mismatch negativity (MMN) and late discriminative negativity (LDN). In the first two studies, a MMN paradigm, equivalent to the Repetition Test, was trialled with a group of 8 adults. In this paired paradigm, the second tone of a pair of pure tones ascending in frequency ('low'-'high') was occasionally replaced with a 'low' tone. The aim was to determine a 'long' and 'short' intra-pair interval (IPI) with which MMN was generated utilizing this paradigm and that were congruent with the Repetition Test findings (i.e., a long IPI at which SLI were able to perform the task, and a short IPI at which SLI children's performance was selectively impaired). In Study One, MMN to a within-pair frequency change was generated with the 30 ms IPI, but not the 700 ms IPI. The grouping parameters of the temporal window of integration (TWI) and temporal distinctiveness were considered less than optimal for the grouping of the pairs presented at 700 ms IPI for the pre-attentive system to register the within-pair frequency change. ... The frequency difference limens (DLs) of the SLI group were significantly higher than a group of 18 normally developing age- and intelligence-matched peers, but there was no significant difference between the groups in their performance on a control intensity discrimination task. The iii SLI group also showed poorer reading skills, yet frequency discrimination was related to oral language ability only. In the final study, MMN was measured to examine the pre-attentive neurophysiological basis of the SLI group's frequency discrimination deficit. Two frequency deviants that were just above each group's 75% DL on the frequency discrimination task were employed in a simple frequency change paradigm: 40 Hz difference for the control group, and 80 Hz difference for the SLI group. MMN and LDN were elicited in the group of 15 normally developing children to their 40 Hz suprathreshold frequency difference and to the 80 Hz difference. A significant MMN was not observed in the group of 13 SLI children to the 40 Hz difference, which was below their threshold level. However, despite discrimination at the behavioural level, MMN did not reach significance in the SLI group to their 80 Hz suprathreshold frequency difference, yet LDN was observed. MMN was larger in both groups for the 80 Hz difference. Furthermore, MMN and LDN amplitude to the suprathreshold deviants were predictive of both frequency and intensity DLs. These results suggested that SLI children have a pre-attentive neurophysiologically mediated insensitivity to small frequency differences, and that MMN (and LDN) to suprathreshold frequency deviants is a sensitive indicator of group discrimination differences and brain-behaviour relationships in children with and without SLI.
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Gottberg, Friedrich Wilhelm Verfasser], and Jesko L. [Akademischer Betreuer] [Verhey. "Untersuchung trainingsbedingter Veränderungen der Richtungsunterscheidung von Gleittönen mit der Mismatch Negativity / Friedrich Wilhelm Gottberg. Betreuer: Jesko L. Verhey." Magdeburg : Universitätsbibliothek, 2015. http://d-nb.info/1076590292/34.
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Freire, Izabela Lyon. "Is the Mismatch Negativity a symmetrical measure of change?: mathematico-philosophical and experimental investigations aimed at mapping psychotopologies." Universidade Federal de Minas Gerais, 2010. http://hdl.handle.net/1843/BUOS-9NMLCY.
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The event-related potential known as the Mismatch Negtivity (MMN) is a psychophysical measure of discriminable change. It is most simply evoked through experiments in the oddball paradigm, in which two stimuli are presented in random alternation, one more happening more frequently, thereby called the standard, and another more rarely, thereby called the deviant. The MMN is the waveform computed as the subtraction of the response to the standard from the response to the deviant. The literature characterizes the MMN as a waveform whose peak amplitude increases and peak latency decreases with decrements in the probability of presentation of deviant and with the difference between standard and deviant stimuli. This characterization of the MMN is in its essence incomplete, as it does not determine how to measure the difference between standard and deviant stimuli, and many metric spaces can be used for the domain of physical stimuli. The literature commonly assumes that the MMN is a symmetrical measure of change and that reversing roles of standard and deviant for the physical stimuli employed in the experiments will not affect the MMN. Differences observed between the MMNs obtained in the pair of experiments determined by the swapping of roles have been explained by differences in other event-related potentials being recorded in the experiments. This work shows that the MMN symmetry assumption is ill-defined, lacking in mathematical rigour, and proposes an experimental framework for cleanly investigating whether the MMN behaves as a symmetrical measure of change under a given metric for the space of physical stimuli. Furthermore, experimental results for the frequency MMN, under the metric absolute value of difference, in Hertz, between the fundamental frequency of three-harmonics complex tones, are presented, and it is shown that, in this metric space for physical stimuli, the MMN is an asymmetrical measure of change. If it is assumed, a priori, that the MMN is a symmetrical measure of change, then searching for metric spaces for physical stimuli, under which the MMN behaves as such, can be used as a tool for mapping the psychotopology of processing that sort of stimuli.<br>O potencial evocado conhecido como Negatividade do Desviante (Mismatch Negativity, MMN) é uma medida psicofísica de mudança discriminável. A forma mais simples de evocá-lo é através de experimentos no paradigma da bolota estranha no qual dois estímulos são apresentados em alternância aleatória: um deles acontecendo mais frequentemente, chamado de padrão, e outro acontecendo mais raramente, chamado de desviante. O MMN é a forma de onda calculada como a subtração da resposta ao padrão da resposta ao desviante. A literatura caracteriza o MMN como uma forma de onda cuja amplitude do pico aumenta e latência do pico diminui tanto com decrementos em probabilidade de apresentação do desviante quanto com a diferença entre estímulos utilizados nos papéis de padrão e desviante. Tal caractarização do MMN é em essência incompleta, já que não determina como fazer essa medida da diferença entre estímulos padrão e desviante, e as possibilidades de escolha de espaços métricos para o domínio dos estímulos físicos são várias. A literatura comumente assume que o MMN é uma medida simétrica de mudança e que uma reversão de papéis de padrão e desviante para os estímulos físicos utilizados no experimento da bolota estranha não afetaria a forma de onda do MMN. Diferenças observadas entre MMNs obtidos no par de experimentos determinados pela troca de papéis são, na literatura, explicadas por diferenças em outros potenciais evocados sendo gravados durante o experimento. Este texto mostra que a hipótese de simetria do MMN é mal-definida, faltando-lhe rigor matemático, e propõe um paradigma experimental para a investigação da questão da simetria do MMN sob determinado espaço métrico para os estímulos físicos. Em termos experimentais, é demonstrado que o MMN para frequências se comporta de forma assimétrica sob a métrica diferença absoluta, em Hertz, entre a frequência fundamental de tons complexos de três hamônicos. Se for admitida a hipótese de que o MMN seja, em essência, uma medida simétrica de mudança, então a busca por espaços métricos para estímulos, sob os quais o MMN se comporte como tal, pode ser utilizada como ferramenta para o mapeamento da psicotopologia do processamento daquele tipo de estímulo.
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Makepeace, Shawn. "Using Bioacoustical Methodologies to Evaluate Equine Hearing Capabilities and Cognition." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1368026497.
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Kaur, Manreena. "Reconceptualising neurophysiological biomarkers of schizophrenia: an investigation of the MMN/P3a complex in early stage psychiatric disorders." Thesis, The University of Sydney, 2013. http://hdl.handle.net/2123/10104.
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This thesis investigated two established neurophysiological biomarkers of schizophrenia: mismatch negativity (MMN) and P3a; purported indices of the deviance detection and orienting response, respectively. In light of recent interest into a shared diathesis model between schizophrenia- and affective-spectrum disorders, this thesis evaluated the utility of MMN/P3a in informing the underlying neurobiology of early stages of schizophrenia- and affective-spectrum disorders. Despite differences in the composition of schizophrenia- and affective-spectrum subgroups, the first two studies showed that MMN/P3a was similarly impaired in the two diagnostic spectrums, with the schizophrenia-spectrum displaying more severe/widespread impairments. The third study utilised a data-driven method and determined three clusters with distinct patterns of MMN/P3a amplitudes among patients with emerging schizophrenia- and affective-spectrum disorders. Critically, about half of the cluster with the greatest neurophysiological impairments consisted of schizophrenia-spectrum patients. The last study explored the stability of MMN/P3a over time and its value in predicting functional outcomes in schizophrenia- and affective-spectrum patients. This study showed that MMN impairments worsen over time, suggestive of ongoing pathophysiological processes. Additionally, greater deficits in MMN amplitudes at baseline were associated with the most severe levels of later disability. In conclusion, this work has been a substantial contribution to the somewhat limited literature on MMN and P3a in early psychotic (and related) disorders. Critically, this thesis supports a re-conceptualisation of the proposed neurophysiological biomarkers of schizophrenia by demonstrating a broader application of MMN and P3a (in early schizophrenia- and affective-spectrum disorders). Accordingly, these studies also provide neurophysiological evidence of a shared diathesis between schizophrenia- and bipolar-spectrum disorders.
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Moreira, Renata Rodrigues. "Mismatch negativity: análise dos efeitos da hipotermia e do treinamento auditivo a partir de um modelo de estudo experimental." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/5/5159/tde-08072008-150937/.
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INTRODUÇÃO: Lesões cerebrais isquêmicas ocorrem em índices bastante significativos, podendo levar a alterações cognitivas de graus variados, cujas repercussões clínicas podem ser de extrema gravidade para os pacientes acometidos. Para avaliar as conseqüências destas lesões nos aspectos funcionais, pode-se utilizar um dos componentes dos potenciais evocados auditivos relacionados a eventos, o Mismatch Negativity (MMN). OBJETIVOS: verificar se o MMN é capaz de detectar mudanças eletrofisiológicas em gerbils submetidos à isquemia cerebral e a hipotermia; verificar se o treinamento auditivo pode gerar mudanças eletrofisiológicas detectáveis pelo MMN, e comparar as latências do potencial com as células sobreviventes do hipocampo de gerbils submetidos à isquemia e a hipotermia. MÉTODOS: Estudo 1: 44 gerbils (Meriones Unguiculatus) adultos foram anestesiados com halotano e submetidos à isquemia cerebral através da oclusão bilateral das carótidas por sete minutos, e à captação do MMN. Os animais foram divididos nos grupos SHAM, HIPO, NORMO e HIPER, de acordo com a temperatura a que foram submetidos. Estudo 2: 28 gerbils foram submetidos a uma sessão de treinamento auditivo com duração de 300 segundos em caixa de esquiva com gerador de eletrochoque, e ao registro do MMN. Estudo 3: foi captado o MMN de 27 gerbils e, após terem sido sacrificados, foi realizada a quantificação de células sobreviventes da região CA1 do hipocampo através de cortes histológicos. RESULTADOS: Estudo 1: houve 100% de presença do MMN no grupo HIPO, não houve diferença estatisticamente significante entre os grupos SHAM e HIPO. Estudo 2: não houve diferença estatisticamente significante entre as latências do MMN antes e depois do treinamento auditivo. Estudo 3: observou-se maior número de células sobreviventes no hipocampo nos animais do grupo HIPO, e foi detectada baixa correlação entre o número de células sobreviventes e a latência do MMN. CONCLUSÕES: o MMN detectou as mudanças eletrofisiológicas geradas pelo efeito neuroprotetor da hipotermia, porém, o protocolo do treinamento auditivo utilizado neste estudo não gerou mudanças neurais nos animais que pudessem ser detectadas pelo MMN, e foi observada baixa correlação entre a latência do MMN e o número de células sobreviventes na região CA1 do hipocampo de gerbils submetidos à isquemia e a hipotermia.<br>INTRODUCTION: Significant ischemic cerebral lesions may result in cognitive disorders of varying degrees, with clinical repercussions that could be extremely severe for the affected patients. In order to evaluate the consequences of such lesions upon functional aspects, one of the components of event-related auditory evoked potentials, the Mismatch Negativity (MMN), may be used. AIM: to verify whether the MMN is able to identify electrophysiological changes in gerbils submitted to cerebral ischemia and hypothermia; to verify if auditory training may generate electrophysiological changes detectable by MMN, and to compare the potential\'s latencies with the surviving cells of the hippocampus of gerbils submitted to cerebral ischemia and hypothermia. METHODS: Study 1: 44 adult gerbils (Meriones Unguiculatus) were sedated with halothane and underwent cerebral ischemia through bilateral occlusion of the carotids for seven minutes, and the MMN was registered. Animals were divided in four groups, SHAM, HIPO, NORMO and HIPER, according to the temperature they were exposed. Study 2: 28 gerbils underwent a session of auditory training of 300 seconds in a passive shuttle box with an electroshock generator, and the MMN was registered. Study 3: the MMN of 27 gerbils were registered and after their scarifice, the amount of surviving cells in the CA1 region of the hippocampus was quantified through histological cuts. RESULTS: Study 1: the MMN was 100% present in the HIPO group, there was no significant statistical difference between groups SHAM and HIPO. Study 2: there was no significant statistical difference between the MMN latencies before and after the auditory training. Study 3: a greater number of surviving cells was observed in the hippocampus of animals from group HIPO, and a low correlation between the number of surviving cells and the MMN latency was detected. CONCLUSIONS: MMN detected electrophysiological changes generated by the neuroprotector effect of hypothermia, nevertheless the auditory training protocol used in this study did not generate neural changes in the animals that could be detected by MMN, and a low correlation between the MMN latency and the number of surviving cells in the CA1 region of the hippocampus of gerbils submitted to ischemia and hypothermia was observed.
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Merl, Volker. "Die Beeinflussung der Encodierung im echoischen Gedächtnis durch Ketamin, gemessen mit Hilfe der mismatch negativity eine Untersuchung an gesunden Probanden /." [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=974508462.
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Muller-Gass, Alexandra. "The effect of task demands on the processing of attended and unattended auditory inputs as indexed by the mismatch negativity." Thesis, University of Ottawa (Canada), 2004. http://hdl.handle.net/10393/29145.
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The main interest of this dissertation was to examine the role of attention in early auditory processing using event-related potential (ERP) recording techniques. The Mismatch Negativity (MMN), a component of the ERP, is an index of early auditory deviance detection. In the present research, the MMN was used to probe the extent to which auditory stimuli were processed when these stimuli were or were not within the focus of attention. Four experiments were carried out. The aim of Experiments 1 and 2 was to investigate whether the demands of common diversion tasks modulated the MMN. In these experiments, subjects were instructed to ignore the auditory sequence and engage in tasks that varied in the amount of attention required to complete them. The results of Experiment 1 indicated that the MMN elicited by small frequency deviants was sensitive to the nature of the task (although this effect could not be clearly related to attention). In contrast, the MMNs elicited by small intensity deviants in Experiment 2 did not vary based on the diversion task demands. A limitation of Experiments 1 and 2 was the absence of an independent measure of task demands. This limitation was addressed in Experiments 3 and 4. A visual discrimination task was employed that permitted quantification of task demands. The visual task was either easy or difficult to perform. Hence, in Experiments 3 and 4, the extent to which the attentional demands of the visual task affected the passively-elicited MMN could be more rigorously examined. Importantly, the MMNs elicited by small frequency and intensity deviants were not significantly modulated by task difficulty, in spite of a wide variation in performance measures between the easy and difficult visual tasks. Experiments 3 and 4 also investigated whether the direction of attention had an effect on the MMN. Subjects were subsequently asked to divide their attention between the visual and auditory channels and to detect all visual and auditory deviant stimuli. This allowed a comparison of the MMN when it was elicited by stimuli within or outside the focus of attention. The results of Experiment 3 indicated that the frequency MMN was unaffected by the direction of attention; the intensity MMN, however, was larger during active attention of the auditory sequence. The attentional modulation of the intensity but not frequency MMN may be due to specific deviant features being more sensitive to the effects of attention. Alternatively, these results could be explained by the difference in perceptual discriminability of the intensity and frequency deviants from the standard (the frequency deviants were detected more accurately and more rapidly than the intensity deviants). Experiment 4 tackled this issue by increasing the discriminability of the intensity deviant while decreasing the discriminability of the frequency deviant. The results showed that the frequency MMN was significantly affected by the direction of attention, whereas the intensity MMN was not. Together, the results suggest that the attentional modulation of the MMN may be limited to the processing of small stimulus changes. Attention may be viewed as a means to sharpen the memory trace of the attended stimuli and consequently enhance the processing of small auditory changes. This explanation would also be consistent with the present findings that the passively-elicited MMN is insensitive to variations in visual task difficulty.
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Smith, Marjorie A. "Phonemic Categorization of Eight-to-Ten Year Old Children with an Articulation Disorder." Diss., CLICK HERE for online access, 2009. http://contentdm.lib.byu.edu/ETD/image/etd2941.pdf.
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Afyonoglu, Kirbas Yeliz. "Neuronal activity to environmental sounds when presented together with semantically related words : An MMN study on monolingual and bilingual processing of homophones." Thesis, Stockholms universitet, Avdelningen för allmän språkvetenskap, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-170303.
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Neuronal activity of monolingual and bilinguals to environmental sounds and words that are semantically related to them were studied using the mismatch negativity (MMN) component of event-related potentials. MMN was expected to reflect the language selection process in bilinguals on the bases of semantics and phonology. In this regard, as lexical stimuli, interlingual homophones ‘car’ and ‘kar’ (snow) were presented together with semantically related environmental sounds in a passive auditory oddball paradigm. The lexical stimuli were recorded by a native English speaker. Three Turkish-English late bilinguals and one native English speaker participated in the study. An early MMN was elicited in both groups with a distribution over the fronto-central and central areas across the scalp with highest peak amplitude at -2.5 with a 113 ms latency. This response indicates that participants of the study were sensitive to the acoustic changes in two different types of stimuli. The further investigation of the interplay between environmental sounds and semantics displayed no conclusive result due to lack of data. Finally, the brain responses gathered from the bilinguals were not enough to draw a conclusion. Whether the bilinguals were sensitive to the sub-phonemic cues in the presented auditory lexical stimuli or not were inconclusive.<br>Neuronal aktivitet av en- och tvåspråkiga till miljöljud och ord som är semantiskt relaterade till dem studerades med hjälp av Mismatch Negativity (MMN) komponent av event-relaterade potentialer. MMN förväntades spegla språkvalsprocessen i tvåspråkiga baserad på semantik och fonologi. I detta avseende presenterades interlingual-homofoner ’car’ (bil) och ’kar’ (snö) som lexikala stimuli tillsammans med semantiskt besläktade miljöljud i ett passivt auditivt oddball paradigm. De lexikala stimuli spelades in av en modersmålstalare av engelska. Tre turkiska-engelska sena tvåspråkiga och en modersmålstalare av engelska deltog i studien. En tidig MMN framkallades i båda grupperna med en fördelning över de främre central- och centrala områdena över skalp med amplitud vid -2,5 med 113 ms latens. Detta indikerar att deltagarna var sensitiva till de akustiska förändringarna mellan de två olika typerna av stimuli. Den vidare undersökningen av samspelet mellan miljöljud och semantik visade inget avgörande resultat. Dessutom, var det också ett inkonklusivt resultat som handlade om att huruvida tvåspråkiga deltagarna använde subfonemiska signalerna i de presenterade auditiva lexikala stimuli eller inte.
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Macdonald, Margaret. "Are Stimuli Representing Increases in Acoustic Intensity Processed Differently? An Event-Related Potential Study." Thèse, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/30394.
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The present thesis employed event-related potentials, the minute responses of the brain, to examine the differences in processing of increases and decreases in auditory intensity. The manner in which intensity was manipulated (i.e., whether it represented physical or psychological change) varied across the studies of the thesis.
Study 1 investigated the processing of physical intensity change during wakefulness and natural sleep. An oddball paradigm (80 dB standard, 90 dB increment, 60 dB decrement) was presented to subjects during the waking state and during sleep. The increment elicited a larger deviant-related negativity and P3a than the decrement in the waking state. During sleep, only the increment deviant continued to elicit ERPs related to the detection of change. The waking and sleeping findings support the notion that increases in intensity are more salient to an observer. Studies 2 and 3 of this thesis determined the degree to which this differential salience could be attributed to the fact that intensity increments result in increased activation of the change and transient detection systems while intensity decrements result in greater activation of only the change detection system. In order to address this question, an alternating intensity pattern was employed (HLHLHLHL) with deviants created by the repetition of a tone in the sequence (HLHLHHHL) that violated the expectancy for a higher (psychological decrements) or lower intensity tone (psychological increments). Because deviant stimuli were physically identical to preceding standards, this manipulation should not have led to increased output of the transient detection system (N1 enhancement), permitting isolation of the output of the change detection system (Mismatch Negativity, MMN). The findings of these studies indicated that psychological increments resulted in shorter latency and larger amplitude MMNs than psychological decrements and that these differences could not be explained by the physical differences between deviant stimuli or temporal integration.
This thesis provides convincing evidence that stimuli representing increments in intensity result in faster and more robust change detection. Further, the increased salience of increment stimuli cannot be solely explained by the contribution of transient detector activation, as it persists even when deviance-related processing is isolated to the change detection system.
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Sorensen, David Olonzo. "Cross-Lingual Diphthong Perception: A Simultaneous EEG/fMRI Investigation." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/7602.
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Previous research indicates that humans develop a phonological library in infancy. As humans grow into adulthood, their phonological library becomes well established. Upon encountering phonemes from a new language, humans process these phonemes by comparison to their native phonological library. Event-related potentials (ERP), specifically the mismatch negativity, have been shown to indicate that this process of comparing non-native phonemes to our native phonological library is not improved through learning the new language as an adult. An alternative explanation may be that there is an underlying change in the neural generators as the non-native phonemes are learned, but that this change is not reflected in the ERP. The current study seeks to examine this hypothesis through the simultaneous collection of ERP and blood-oxygen-level-dependent functional MRI (fMRI) data. The findings of the ERP and fMRI data are inconclusive. The study also explores the processing of diphthongs, a category of phonemes rarely tested before, through both behavioral and neuroimaging methods. The study presents behavioral data demonstrating that non-native diphthongs are processed based upon the separate elements of the phonemes, rather than as complete units.
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Stothart, George. "Deficits and compensation in healthy ageing, mild cognitive impairment and Alzheimer’s disease : a mismatch negativity study of visual, auditory and audiovisual processing." Thesis, University of Bristol, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.616567.
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An increasing ageing population presents the challenge of understanding how healthy ageing and dementia affect brain function. Improved understanding of healthy ageing can provide a baseline against which to examine Mild. - Cognitive Impairment (MCI) and Alzheimer's disease (AD) in which there is a great need for better characterisation and early diagnostic tools. Examining sensory processing can reveal how the ageing brain copes and reacts to changes in peripheral sensory deficits and can inform theories of cognitive ageing. Additionally sensory processing has largely been neglected in the examination of MCI and AD, and may provide further understanding of the early stages of the disease processes, unaffected by the educational and cultural confounds that can often hamper measures of higher level processing. This thesis explored sensory processing in healthy ageing, MCI and AD with two distinct aims: 1) to test and further inform cognitive theories of healthy ageing and 2) to identify changes in sensory processing due to MCI and AD that may be further developed as diagnostic markers. Electroencephalography was used to measure sensory processing across four paradigms designed to examine visual, auditory and audiovisual processing. Early sensory evoked potentials and the mismatch negativity response were measured in healthy younger and older adults, MC! patients and AD patients. -The results indicated that older adults experience modality specific changes in sensory processing, with patterns of a frontal lobe inhibitory deficit emerging in auditory processing, and cortical compensation to reduced peripheral input in visual processing. AD patients showed deficits in sensory association area processing that manifested as reduced audiovisual binding and reduced visual evoked potentials. MC! patients showed high intra and inter individual variability in visual processing and a broad attentional deficit in evoked potentials across both auditory and visual modalities. This thesis demonstrates that the healthily ageing brain adapts to changes in peripheral sensory processing in an adaptive, compensatory manner that is specific to the sensory modality examined. Both MCI and AD show specific changes in sensory processing that with future improvements in individual subject analyses provide considerable potential for improved early classification and diagnosis.
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Johansson, Daniel. "Neural bearbetning av regelbunden och oregelbunden aspektböjning i modern grekiska : En MMN-studie." Thesis, Stockholms universitet, Institutionen för lingvistik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-169650.
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Skillnader i morfologisk komplexitet mellan språk har inte fått mycket fokus i forskningen kring neural bearbetning av morfologisk information. Trots detta har slutsatser dragits gällande böjningsmorfologi argumenterande för en skild bearbetning baserat på regelbundenhet, dvs. dekompositionell och holistisk bearbetning av regelbundna och oregelbundna böjningar respektive. För att tillföra forskningen en större morfologisk komplexitet och för att undersöka relationen mellan det kontinuerliga regelbundenhetspektrat och dikotomin av dekompositionell-holistisk bearbetning, undersökte denna uppsats den neurala bearbetningen av aspektböjning i modern grekiska, ett språk med hög grad av komplex böjningsmorfologi. Den tidiga auditiva ERP-komponenten MMN användes för att undersöka detta genom exploatering av dess påvisade relation till långtidsminnet genom att återspegla högre språkliga processer så som syntaktisk (sMMN) och lexikal (lMMN) bearbetning. Resultaten visade två MMN pikar, en tidigare vid 120-175 ms och en senare vid 240-300 ms, vilka modulerades enligt en sMMN-elicitering för både regelbunden och oregelbunden aspektböjning. Dessa resultat talar för en dekompositionell bearbetning av oregelbunden aspektböjning genom svag suppletion (/vɣázo/ → /vɣálo/) och argumenterades indikera avsaknaden av nödvändig morfologisk regelbundenhet för en möjlig dekompositionell böjningsbearbetning.<br>Differences in morphological complexity between languages have not recieved much attention within the field of neural processing of morphological information. Conclusions have though been drawn regarding inflectional morphology, arguing for different processing of regular and irregular inflections, i.e. decompositional and holistic processing respectively. To provide the research with higher morphological complexity and to investigate the relationship between the continuous regularity spectra and the dichotomy of decompositional-holistic processing, this thesis investigated the neural processing of aspectual inflection in modern Greek, a highly inflected language with complex verbal morphology. The early auditory ERP-component MMN was used to investigate this by exploiting it's shown longterm memory connections, reflecting higher linguisic processes such as syntactic (sMMN) and lexical (lMMN) processing. Results showed two MMN peaks, one earlier at around 120-175 ms and one later at around 240-300 ms. The peaks were modulated according to an sMMN elicitation for both regular and irregular inflections. These results, speaking for a decompositional processing of a irregular verb by weak suppletion (/vɣázo/ → /vɣálo/), were argued to indicate a lack of necessity of morphological regularity for a decompositional processing of inflection.
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Giunchi, Lorenzo. "Analisi dei potenziali evocati cerebrali ottenuti mediante paradigma oddball di tipo uditivo e di tipo visivo." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/19546/.
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Questo lavoro analizza i potenziali evocati cerebrali in risposta a una sequenza di stimoli uditivi e visivi. In particolare, si sono analizzate le componenti N100, MMN (Mismatch Negativity), P300. A tale scopo si sono implementati, tramite Arduino e un circuito su breadboard, tre paradigmi attivi di oddball differenti, due uditivi e uno visivo. Il paradigma oddball consiste nel presentare stimoli deviant (infrequenti) all’interno di una sequenza di stimoli standard (frequenti). I due paradigmi uditivi si differenziano per un diverso divario di tonalità tra gli stimoli sonori deviant e standard, molto marcato in un caso e piccolo nell’altro. Nel paradigma visivo, gli stimoli standard e deviant si differenziano per il colore del led. Utilizzando paradigmi oddball diversi si è voluto investigare come le componenti N100, MMN e P300 dei potenziali evocati si modificano in base al paradigma eseguito, sia per la diversa natura sensoriale degli stimoli (visivo e uditivo) sia per la maggiore o minore difficoltà di riconoscimento dello stimolo deviant (paradigmi uditivi). Le risposte cerebrali di 8 soggetti in ciascuno dei tre paradigmi sono state acquisite tramite un sistema EEG (OpenBCI) disponibile nel laboratorio LIB (DEI, Campus di Cesena). Dai segnali EEG, mediante la tecnica dell’averaging implementata in Matlab, si sono estratti i potenziali evocati. e le caratteristiche di ampiezza e latenza delle componenti N100, MMN e P300 sono state esaminate. Si osserva che la componente N100 non varia fra la risposta agli stimoli standard e deviant di ogni paradigma; l’ampiezza della componente MMN è maggiormente accentuata in condizioni di maggiore differenziazione fra stimolo standard e deviant; la componente P300 mostra ampiezza minore in risposta agli stimoli acustici rispetto agli stimoli visivi; inoltre tra i due paradigmi uditivi la P300 tende ad avere ampiezza maggiore e latenza minore nel caso di una maggior discrepanza fra gli stimoli standard e deviant.
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Garrapa, Luigia. "Vowel processing in Italian pediatric cochlear-implant users: A behavioral and neurophysiological study." Doctoral thesis, Università degli studi di Padova, 2014. http://hdl.handle.net/11577/3424083.
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Multichannel cochlear implant (CI) devices partially restore the auditory sensation in children affected by congenital, bilateral, and severe-to-profound sensorineural hearing loss, especially in the absence of background noise, provided that CI surgery takes place during the sensitive period for maturation of the auditory pathways, which is presumed to end at 3.5 years [Sharma et al. 2002abc, 2005, 2007; 2009; Gilley et al. 2008].
A few previous studies on Italian pediatric CI users investigated the general auditory abilities as well as the speech intelligibility of deaf children [cf. Santarelli et al. 2009; Colletti et al. 2012; Caselli et al. 2012; Martines et al. 2013], by using the usual tests administered by speech therapists. Plenty of previous studies investigated detection, categorization, and discrimination of speech sounds, both consonants and vowels, at the cortical level (automatically), in CI children exposed to languages other than Italian, such English [Kileny et al. 1997; Sharma et al. 2002abc, 2005, 2007; 2009; Gilley et al. 2008; Henkin et al. 2008], Dutch [Beynon et al. 2002], German [Ortmann et al. 2013], Hebrew [Singh et al. 2004], and Croatian [Munivrana & Mildner 2013].
As compared to the above-mentioned studies, the present research introduces three methodological innovations: i) it investigates the processing of vowels; ii) it relies on natural speech stimuli, only minimally normalized; and iii) it combines the use of behavioral measures (e.g., tests of categorization and discrimination of speech sounds, administered attentively) with the use of neurophysiological measures (e.g., the EEG recording for subsequent extraction of the auditory ERPs indexing speech sound detection, categorization, and discrimination).
The present study investigates the processing of single vowels (e.g., /u/, /i/, /e/, /o/, /a/) as well as of same-vowel pairs (e.g., /u/-/u/, /i/-/i/, /e/-/e/, /o/-/o/, /a/-/a/) and of different-vowel pairs (e.g., /u/-/i/, /i/-/u/, /e/-/i/, /i/-/e/, /o/-/a/, /a/-/o/) at the behavioral (e.g., conscious) and at the neurophysiological (e.g., automatic) levels in a group of deaf Italian children implanted during the sensitive period for central auditory maturation (range of age at surgery: 2.1 – 4.4 years) and who had been using their CI for at least 2 years (range of duration of CI stimulation: 2.4 – 8.1 years). At the behavioral level, tests of vowel detection and of vowel categorization were administered. At the neurophysiological level, the EEG activity was passively recorded when children were watching a silent movie while hearing vowel stimuli on the background. Subsequently, the P1, N1, and MMN responses of the auditory ERPs are the neural correlates of (speech) sound detection, categorization, and discrimination, in turn, were extracted. The vowel processing performance of the CI children will be compared against the performance exhibited by a group of normal-hearing (NH) children matched for biological age with the CI children. This study also investigated whether, and to what extent, some external factors were able to constrain vowel processing at the behavioral and neurophysiological level in CI children. These factors are the following ones: i) vowel quality; ii) the articulatory characteristics of the five vowels; iii) the larger vs. smaller Euclidean distance characterizing the vowel pairs; iv) the different distinctive feature specification and, more particularly, the direction of change in the distinctive feature specification between the first and the second vowel of each pair; v) the earlier vs. later age at surgery; and vi) the longer vs. shorter duration of CI use.
The main findings of the present study are the following ones. First, the main difference between the behavioral and the neurophysiological levels of processing in CI children consists in the fact that the processing of vowel pairs is partially impaired for accuracy only at the behavioral level, whereas the processing of single vowels is partially impaired for accuracy, and rarely delayed, only at the neurophysiological level. Second, at the neurophysiological level, CI children are impaired at the auditory, not at the cognitive, level. In fact, in spite of typically being less accurate in detection and categorization of single vowels, CI children are not impaired in the processing of vowel pairs. Third, age at surgery and duration of implant stimulation are irrelevant for behavioral vowel processing, whereas they constrain cortical vowel processing, although not systematically: deaf children implanted before 3.4 years and/or who had been using their CI for at least 5.8 years may process single vowels as well as vowel pairs faster and more accurately. Vowel quality, the articulatory characteristics of the five vowels, the Euclidean, and the direction of change in the distinctive feature specification, on the other hand, turn out to be irrelevant in constraining vowel processing either at the behavioral and at the neurophysiological level.<br>Gli impianti cocleari (IC) multicanale ripristinano parzialmente la sensazione uditiva nei bambini affetti da ipoacusia neurosensoriale congenita a livello bilaterale, soprattutto se l’IC viene chirurgicamente inserito prima del compimento di 3.5 anni [Sharma et al. 2002abc, 2005, 2007, 2009; Gilley et al. 2008].
Precedenti studi su bambini italiani portatori di IC unilaterale si sono concentrati sulle abilità uditive generali e sull’intelligibilità del parlato dei bambini sordi italiani [cf. Santarelli et al. 2009; Colletti et al. 2012; Caselli et al. 2012; Martines et al. 2013], ricorrendo esclusivamente a test logopedici somministrati a livello attentivo e concentrandosi prevalentemente su bambini sottoposti alla chirurgia per l’inserimento dell’IC dopo i 3.5 anni. Moltissimi studi hanno, invece, indagato l’elaborazione di singoli suoni linguistici e di coppie di suoni linguistici a livello corticale in bambini con IC non italiani che apprendono l’inglese [Kileny et al. 1997; Sharma et al. 2002abc, 2005, 2007; 2009; Gilley et al. 2008; Henkin et al. 2008], l’ebraico [Singh et al. 2004], l’olandese [Beynon et al. 2002] il tedesco [Ortmann et al. 2013] e il croato [Munivrana & Mildner 2013], ecc.
Il presente lavoro si differenzia dagli studi precedenti per i seguenti motivi: i) questo studio si concentra sull’elaborazione corticale delle vocali; ii) ai soggetti pediatrici selezionati vengono presentati stimoli vocalici elicitati naturalmente e poi adeguatamente normalizzati per renderli acusticamente stabili ed omogenei, senza inficiarne la ‘genuinità’; iii) questo studio affianca all’uso di misure neurofisiologiche (gli ERPs uditivi) che monitorano l’elaborazione automatica delle vocali a livello corticale, l’uso di test comportamentali che monitorano l’elaborazione delle vocali a livello cosciente, ossia tramite l’emissione di una ‘risposta’.
Il presente studio monitora l’elaborazione di cinque vocali singole (/u/, /i/, /e/, /o/, /a/) e di coppie di vocali, sia uguali (/u/-/u/, /i/-/i/, /e/-/e/, /o/-/o/, /a/-/a/) che diverse (/u/-/i/, /i/-/u/, /e/-/i/, /i/-/e/, /o/-/a/, /a/-/o/), sia a livello comportamentale (attentivo) che a livello neurofisiologico (automatico), in un gruppo di bambini sordi italiani portatori di IC unilaterale. Questi bambini hanno ricevuto l’IC ad un’età compresa fra 2.1 e 4.4 anni ed usano l’IC da almeno 2 anni (range: 2.4 – 8.1 anni). A livello comportamentale, ai bambini sono stati somministrati dei test di categorizzazione e di discriminazione vocalica. A livello neurofisiologico, invece, è stata registrata passivamente l’attività EEG mentre i bambini guardavano un cartone animato senza audio e, al posto dell’audio del cartone, venivano presentate loro acusticamente le vocali in sottofondo. Dall’attività EEG acquisita sono state estratte le componenti P1, N1 e MMN che indicizzano la detezione, la categorizzazione e la discriminazione degli stimoli uditivi, sia di tipo linguistico, a livello neurale nella corteccia uditiva. Le performances dei bambini con IC sono state confrontate con quelle di un gruppo di bambini normoacusici (NH) matchato in base all’età dei bambini con IC. Questo studio ha anche esplorato se, e in che misura, alcuni fattori esterni fossero eventualmente suscettibili di influire sull’elaborazione delle vocali nei bambini con IC. Questi fattori sono: i) il timbro vocalico; ii) le caratteristiche articolatorie delle vocali; iii) la maggior vs. minor distanza Euclidea che caratterizza le coppie di vocali; iv) la differente specificazione delle vocali in termini di tratti fonologici e, più in particolare, la direzionalità del cambiamento nella stessa fra la prima e la seconda vocale di ciascuna coppia; v) la maggior vs. minor precocità con cui avviene la chirurgia; e vi) il maggior vs. minor periodo di uso dell’IC.
I principali risultati del presente studio sono i seguenti. La principale differenza emersa fra il livello comportamentale e quello neurofisiologico consiste nel fatto che i bambini con IC incontrano delle difficoltà nell’elaborazione delle coppie di vocali a livello comportamentale, ma non a livello neurofisiologico; al contrario, per quanto riguarda l’elaborazione delle singole vocali, i bambini con IC incontrano delle difficoltà a livello neurofisiologico, ma non a livello comportamentale. Inoltre, a livello neurofisiologico, i bambini con IC risultano avere delle difficoltà a livello uditivo, ma non a livello cognitivo. In effetti, sebbene i bambini con IC siano meno precisi di quanto dovrebbero nella detezione e nella categorizzazione delle singole vocali, che sono processi uditivi, essi non incontrano alcuna difficoltà nella discriminazione delle coppie di vocali, che è un processo cognitivo. Né l’età alla chirurgia né il periodo di uso dell’IC influiscono in alcun modo sull’elaborazione delle vocali a livello comportamentale. Tuttavia, a livello neurofisiologico, può succedere che i bambini che hanno ricevuto l’IC prima di 3.4 anni e/o che lo usano da almeno 5.8 anni riescano ad elaborare le singole vocali e le coppie di vocali in maniera più efficace e/o più accurata. Gli altri fattori esterni studiati, ossia il timbro vocalico, le caratteristiche articolatorie delle vocali, la distanza Euclidea che caratterizza le coppie di vocali e la differente specificazione delle vocali in termini di tratti fonologici, invece, non influiscono in maniera significativa sull’elaborazione delle vocali né a livello comportamentale né a livello neurofisiologico.
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Garagnani, Max. "Understanding language and attention : brain-based model and neurophysiological experiments." Thesis, University of Cambridge, 2009. https://www.repository.cam.ac.uk/handle/1810/243852.
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This work concerns the investigation of the neuronal mechanisms at the basis of language acquisition and processing, and the complex interactions of language and attention processes in the human brain. In particular, this research was motivated by two sets of existing neurophysiological data which cannot be reconciled on the basis of current psycholinguistic accounts: on the one hand, the N400, a robust index of lexico-semantic processing which emerges at around 400ms after stimulus onset in attention demanding tasks and is larger for senseless materials (meaningless pseudowords) than for matched meaningful stimuli (words); on the other, the more recent results on the Mismatch Negativity (MMN, latency 100-250ms), an early automatic brain response elicited under distraction which is larger to words than to pseudowords. We asked what the mechanisms underlying these differential neurophysiological responses may be, and whether attention and language processes could interact so as to produce the observed brain responses, having opposite magnitude and different latencies. We also asked questions about the functional nature and anatomical characteristics of the cortical representation of linguistic elements. These questions were addressed by combining neurocomputational techniques and neuroimaging (magneto-encephalography, MEG) experimental methods. Firstly, a neurobiologically realistic neural-network model composed of neuron-like elements (graded response units) was implemented, which closely replicates the neuroanatomical and connectivity features of the main areas of the left perisylvian cortex involved in spoken language processing (i.e., the areas controlling speech output – left inferior-prefrontal cortex, including Broca’s area – and the main sensory input – auditory – areas, located in the left superior-temporal lobe, including Wernicke’s area). Secondly, the model was used to simulate early word acquisition processes by means of a Hebbian correlation learning rule (which reflects known synaptic plasticity mechanisms of the neocortex). The network was “taught” to associate pairs of auditory and articulatory activation patterns, simulating activity due to perception and production of the same speech sound: as a result, neuronal word representations distributed over the different cortical areas of the model emerged. Thirdly, the network was stimulated, in its “auditory cortex”, with either one of the words it had learned, or new, unfamiliar pseudoword patterns, while the availability of attentional resources was modulated by changing the level of non-specific, global cortical inhibition. In this way, the model was able to replicate both the MMN and N400 brain responses by means of a single set of neuroscientifically grounded principles, providing the first mechanistic account, at the cortical-circuit level, for these data. Finally, in order to verify the neurophysiological validity of the model, its crucial predictions were tested in a novel MEG experiment investigating how attention processes modulate event-related brain responses to speech stimuli. Neurophysiological responses to the same words and pseudowords were recorded while the same subjects were asked to attend to the spoken input or ignore it. The experimental results confirmed the model’s predictions; in particular, profound variability of magnetic brain responses to pseudowords but relative stability of activation to words as a function of attention emerged. While the results of the simulations demonstrated that distributed cortical representations for words can spontaneously emerge in the cortex as a result of neuroanatomical structure and synaptic plasticity, the experimental results confirm the validity of the model and provide evidence in support of the existence of such memory circuits in the brain. This work is a first step towards a mechanistic account of cognition in which the basic atoms of cognitive processing (e.g., words, objects, faces) are represented in the brain as discrete and distributed action-perception networks that behave as closed, independent systems.
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Impey, Danielle. "Assessment of Transcranial Direct Current Stimulation (tDCS) on MMN-Indexed Auditory Sensory Processing." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/35576.
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Transcranial direct current stimulation (tDCS) is a non-invasive form of brain stimulation which uses a very weak constant current to temporarily excite or inhibit activity in the brain area of interest via electrodes placed on the scalp, depending on the polarity and strength of the current. Presently, tDCS is being used as a tool to investigate frontal cognition in healthy controls and to improve symptoms in neurological and psychiatric patients. Relatively little research has been conducted with respect to tDCS and the auditory cortex (AC). The primary aim of this thesis was to elucidate the effects of tDCS on auditory sensory discrimination, assessed with the mismatch negativity (MMN) event-related potential (ERP). In the first pilot study, healthy participants were assessed in a randomized, double-blind, sham-controlled design, in which participants received anodal tDCS over the primary AC (2 mA for 20 minutes) in one session and ‘sham’ stimulation (i.e. no stimulation) in the other. Pitch MMN was found to be enhanced after receiving anodal tDCS, with the effects being evidenced in individuals with relatively low (vs. high) baseline amplitudes. No significant effects were seen with sham stimulation. A second study examined the separate and interacting effects of anodal and cathodal tDCS on MMN measures. MMN was assessed pre- and post-tDCS (2 mA, 20 minutes) in 2 separate sessions, one involving sham stimulation, followed by anodal stimulation, and one involving cathodal stimulation, followed by anodal stimulation. Only anodal tDCS over the AC increased pitch MMN in baseline-stratified groups, and while cathodal tDCS decreased MMN, subsequent anodal stimulation did not significantly alter MMNs. As evidence has shown that tDCS lasting effects may be dependent on N-methyl-D-aspartate (NMDA) receptor activity, a pharmacological study investigated the use of dextromethorphan (DMO), an NMDA antagonist, to assess possible modulation of tDCS’ effects on both MMN and working memory (WM) performance. The study involved four test sessions that compared pre- and post-anodal tDCS over the AC and sham stimulation with both DMO (50 mL) and placebo administration. MMN amplitude increases were only seen with anodal tDCS with placebo administration, not with sham stimulation, nor with DMO administration. In the sham condition, DMO decreased MMN amplitudes. Anodal tDCS improved WM performance in the active drug condition. Findings from this study contribute to the understanding of underlying neurobiological mechanisms mediating tDCS-sensory and memory improvements. As cognitive impairment has been proposed to be the core feature of schizophrenia disorder (Sz) and MMN is a putative biomarker of Sz, a pilot study was conducted to assess the effects of pre- and post-tDCS on MMN measures in 12 Sz patients, as well as WM performance. Temporal, frontal and sham tDCS were applied in separate sessions. Results demonstrated a trend for pitch MMNs to increase with anodal temporal tDCS, which was significant in a subgroup of Sz individuals with auditory hallucinations, who had low MMNs at baseline. Anodal frontal tDCS significantly increased WM performance, which was found to positively correlate with MMN-tDCS effects. The findings contribute to our understanding of tDCS effects for MMN-indexed sensory discrimination and WM performance in healthy participants and individuals with Sz disorder and may have implications for treatment of sensory processing deficits in neuropsychiatric illness.
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Naeije, Gilles. "Insights into the neural bases of tactile change detection from magnetoencephalography." Doctoral thesis, Universite Libre de Bruxelles, 2018. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/268050.
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The objectives of my PhD were to identify the spatial and the temporal dynamics of the brain areas involved in tactile change detection as well as the neural mechanisms responsible for the processing of tactile change detection. To that aim, three specific MEG studies were performed; each of them is addressing specific research aims.The first study investigated the spatiotemporal dynamics of the multilevel cortical processing of tactile change detection in human healthy subjects. This study disclosed a hierarchical organization from unimodal early tactile change detection at secondary somatosensory cortex to multi modal complex processing at bilateral temporo-parietal junctions, posterior parietal cortex and supplementary motor areas. The second study aimed at discriminating between debated neural mechanisms responsible for the genesis of the somatosensory mismatch negativity (sMMN). To do so, we manipulated the predictability of the deviant stimuli and the response to omissions in different kind of oddballs, the response to deviant stimuli paired with standards and occurring alone. We found out that mechanisms for early tactile change detection reflected by the sMMN were better explained by the predictive coding theory compared to the adaptation and adjustment theories. Finally we sought to characterize the alterations in early cortical tactile change detection in Friedreich Ataxia (FRDA); a neurological disorder characterized by somatosensory and cerebellar pathways degeneration. The aim of this work was to study the role of the cerebellum in the genesis of sMMN and its potential selectivity for somatosensory change detection compared to auditory. This study demonstrated that, in FRDA, both tactile and auditory pathways are affected at the level of primary sensory neurons and dorsal root/spiral ganglia in a genetically determined. By contrasts, early cortical sensory change detection in FRDA was impaired only in the tactile modality in line with the sMMN impairment described in patients with acquired cerebellar lesions or during cerebellar inhibition by trans cranial magnetic stimulation. These data brought novel empirical evidence supporting the contribution of spinocerebellar tracts in sMMN genesis at cSII cortex.In conclusion, this PhD contributed to identify the network responsible for tactile change detection that involves cuneocerebellar spinocerebellar tract and cSII cortex as somatosensory specific areas and TPJ, SMA & PPC as multimodal brain areas. We further provided evidence that early change detection mechanisms at SII cortex fall under the predictive coding framework and that change detection is hierarchically organized with inputs from low level areas for genesis of an adequate generative model of our environment and conscious representation of our body.<br>Doctorat en Sciences médicales (Médecine)<br>info:eu-repo/semantics/nonPublished
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Shockley, Natalie. "Schizophrenia & information processing : a comparison of the prepulse inhibition, latent inhibition, P-50 gating, and mismatch negativity paradigms, with schizophrenia, bipolar and well control samples /." [St. Lucia, Qld.], 2003. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17131.pdf.
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Mahmoudian, Saeid [Verfasser]. "Effects of Residual Inhibition Phenomenon on Early Auditory Evoked Potentials and Topographical Maps of the Mismatch Negativity Obtained With the Multi-Feature Paradigm in Tinnitus / Saeid Mahmoudian." Hannover : Bibliothek der Tierärztlichen Hochschule Hannover, 2015. http://d-nb.info/107389004X/34.
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