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Hausmann, Markus, and Onur Güntürkün. "Der Einfluss von Sexualhormonen auf funktionelle cerebrale Asymmetrien." Zeitschrift für Neuropsychologie 11, no. 4 (November 2000): 203–15. http://dx.doi.org/10.1024//1016-264x.11.4.203.
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Zusammenfassung: Die Organisation cerebraler Asymmetrien ist geschlechtsabhängig angelegt. Während bei Männern die meisten lateralisierten Funktionen ausgeprägte Links-Rechts-Unterschiede aufweisen, belegen viele Studien eine symmetrischere Hirnorganisation bei Frauen. Neuere Untersuchungen konnten zahlreiche neuroanatomische Korrespondenzen für diese Geschlechtsunterschiede der cerebralen Asymmetrie nachweisen. Darüber hinaus gibt es vermehrt Hinweise auf kurzfristige Veränderungen der Lateralisation während des Monatszyklus. Diese Daten machen es wahrscheinlich, dass cerebrale Asymmetrien auf einer sehr kurzen Zeitskala durch die Aktivierung von Steroidrezeptoren moduliert werden können. Wir schlagen ein Modell vor, nach dem Lateralisationen aus der gemeinsamen Wirkung anatomischer Hirnasymmetrien und dynamischer, interhemisphärischer Interaktionen resultieren. Wir vermuten, dass vor allem Progesteron während der Midlutealphase des Zyklus die synaptische Effizienz der kortiko-kortikalen Transmission reduzieren und damit die Asymmetrie von Hirnfunktionen Lateralisationen verringern kann.
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Sturm, Walter. "Kommentar: Sexualhormone und funktionelle cerebrale Asymmetrie: ergänzende Aspekte." Zeitschrift für Neuropsychologie 11, no. 4 (November 2000): 222–23. http://dx.doi.org/10.1024//1016-264x.11.4.222.
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Levine, Steven R., K. M. A. Welch, James R. Ewing, and Wendy M. Robertson. "Asymmetric Cerebral Blood Flow Patterns in Migraine." Cephalalgia 7, no. 4 (December 1987): 245–48. http://dx.doi.org/10.1046/j.1468-2982.1987.0704245.x.
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Although asymmetric EEG abnormalities have been reported during the headache-free period in migraineurs, asymmetries of regional cerebral blood flow (rCBF) have not been studied. Headache-free rCBF values measured by 133Xe inhalation were lower in migraineurs than in controls. Interhemispheric CBF and regional (anterior versus posterior) CBF did not differ between the groups. When a novel scoring system was used to obtain a mean asymmetry index (MAI), the MAI of the classiccomplicated group was significantly higher than that of the controls but not significantly different from that of the common migraine group. These data suggest that in the headache-free interval rCBF asymmetries, variable in location, exist in classiccomplicated migraineurs. These rCBF changes may be related to the cause or the effect of the focal neurologic dysfunction that occurs during an attack in these patients
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güntürkün, onur. "darwin's legacy and the evolution of cerebral asymmetries." Behavioral and Brain Sciences 28, no. 4 (August 2005): 599–600. http://dx.doi.org/10.1017/s0140525x0533010x.
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vallortigara & rogers (v&r) assume that the alignment of escape responses in gregarious species is the central evolutionary organizer of a wide range of cerebral asymmetries. although it is indeed likely that the benefits of a population asymmetry in social species outweigh its costs, it is hard to see (a) why the population should not oscillate between two subgroups with mirror-image asymmetries, (b) why solitary animals should keep their inherited population asymmetry despite a resulting fitness reduction, and (c) and why so many vertebrate species have comparable cerebral asymmetries.
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Corballis, Michael C. "The evolution and genetics of cerebral asymmetry." Philosophical Transactions of the Royal Society B: Biological Sciences 364, no. 1519 (December 4, 2008): 867–79. http://dx.doi.org/10.1098/rstb.2008.0232.
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Handedness and cerebral asymmetry are commonly assumed to be uniquely human, and even defining characteristics of our species. This is increasingly refuted by the evidence of behavioural asymmetries in non-human species. Although complex manual skill and language are indeed unique to our species and are represented asymmetrically in the brain, some non-human asymmetries appear to be precursors, and others are shared between humans and non-humans. In all behavioural and cerebral asymmetries so far investigated, a minority of individuals reverse or negate the dominant asymmetry, suggesting that such asymmetries are best understood in the context of the overriding bilateral symmetry of the brain and body, and a trade-off between the relative advantages and disadvantages of symmetry and asymmetry. Genetic models of handedness, for example, typically postulate a gene with two alleles, one disposing towards right-handedness and the other imposing no directional influence. There is as yet no convincing evidence as to the location of this putative gene, suggesting that several genes may be involved, or that the gene may be monomorphic with variations due to environmental or epigenetic influences. Nevertheless, it is suggested that, in behavioural, neurological and evolutionary terms, it may be more profitable to examine the degree rather than the direction of asymmetry.
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Robertson, Lynn C., and Richard Ivry. "Hemispheric Asymmetries." Current Directions in Psychological Science 9, no. 2 (April 2000): 59–63. http://dx.doi.org/10.1111/1467-8721.00061.
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A computational theory of hemispheric asymmetries in perception (double filtering by frequency) is described. Its central tenet is that the cerebral hemispheres first perform symmetric filtering of visual and auditory information. Functional hemispheric asymmetry arises from a second filtering stage (containing filters skewed in different directions in the two hemispheres). The first stage selects a range of task-relevant spatial or auditory frequencies from the absolute values. This range is passed to the asymmetric filters. In this way, the hemispheric difference becomes one of relative rather than absolute information. Behavioral deficits due to unilateral lesions in neurological patients and neuroimaging and electrophysiological measures in normal subjects implicate posterior cortex in these hemispheric differences.
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Corballis, Michael C., and Isabelle S. Häberling. "The Many Sides of Hemispheric Asymmetry: A Selective Review and Outlook." Journal of the International Neuropsychological Society 23, no. 9-10 (October 2017): 710–18. http://dx.doi.org/10.1017/s1355617717000376.
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AbstractHemispheric asymmetry is commonly viewed as a dual system, unique to humans, with the two sides of the human brain in complementary roles. To the contrary, modern research shows that cerebral and behavioral asymmetries are widespread in the animal kingdom, and that the concept of duality is an oversimplification. The brain has many networks serving different functions; these are differentially lateralized, and involve many genes. Unlike the asymmetries of the internal organs, brain asymmetry is variable, with a significant minority of the population showing reversed asymmetries or the absence of asymmetry. This variability may underlie the divisions of labor and the specializations that sustain social life. (JINS, 2017, 23, 710–718)
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Wang, Danhong, Randy L. Buckner, and Hesheng Liu. "Cerebellar asymmetry and its relation to cerebral asymmetry estimated by intrinsic functional connectivity." Journal of Neurophysiology 109, no. 1 (January 1, 2013): 46–57. http://dx.doi.org/10.1152/jn.00598.2012.
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Asymmetry of the human cerebellum was investigated using intrinsic functional connectivity. Regions of functional asymmetry within the cerebellum were identified during resting-state functional MRI ( n = 500 subjects) and replicated in an independent cohort ( n = 500 subjects). The most strongly right lateralized cerebellar regions fell within the posterior lobe, including crus I and crus II, in regions estimated to link to the cerebral association cortex. The most strongly left lateralized cerebellar regions were located in lobules VI and VIII in regions linked to distinct cerebral association networks. Comparison of cerebellar asymmetry with independently estimated cerebral asymmetry revealed that the lateralized regions of the cerebellum belong to the same networks that are strongly lateralized in the cerebrum. The degree of functional asymmetry of the cerebellum across individuals was significantly correlated with cerebral asymmetry and varied with handedness. In addition, cerebellar asymmetry estimated at rest predicted cerebral lateralization during an active language task. These results demonstrate that functional lateralization is likely a unitary feature of large-scale cerebrocerebellar networks, consistent with the hypothesis that the cerebellum possesses a roughly homotopic map of the cerebral cortex including the prominent asymmetries of the association cortex.
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Kong, Xiang-Zhen, Samuel R. Mathias, Tulio Guadalupe, David C. Glahn, Barbara Franke, Fabrice Crivello, Nathalie Tzourio-Mazoyer, Simon E. Fisher, Paul M. Thompson, and Clyde Francks. "Mapping cortical brain asymmetry in 17,141 healthy individuals worldwide via the ENIGMA Consortium." Proceedings of the National Academy of Sciences 115, no. 22 (May 15, 2018): E5154—E5163. http://dx.doi.org/10.1073/pnas.1718418115.
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Hemispheric asymmetry is a cardinal feature of human brain organization. Altered brain asymmetry has also been linked to some cognitive and neuropsychiatric disorders. Here, the ENIGMA (Enhancing NeuroImaging Genetics through Meta-Analysis) Consortium presents the largest-ever analysis of cerebral cortical asymmetry and its variability across individuals. Cortical thickness and surface area were assessed in MRI scans of 17,141 healthy individuals from 99 datasets worldwide. Results revealed widespread asymmetries at both hemispheric and regional levels, with a generally thicker cortex but smaller surface area in the left hemisphere relative to the right. Regionally, asymmetries of cortical thickness and/or surface area were found in the inferior frontal gyrus, transverse temporal gyrus, parahippocampal gyrus, and entorhinal cortex. These regions are involved in lateralized functions, including language and visuospatial processing. In addition to population-level asymmetries, variability in brain asymmetry was related to sex, age, and intracranial volume. Interestingly, we did not find significant associations between asymmetries and handedness. Finally, with two independent pedigree datasets (n = 1,443 and 1,113, respectively), we found several asymmetries showing significant, replicable heritability. The structural asymmetries identified and their variabilities and heritability provide a reference resource for future studies on the genetic basis of brain asymmetry and altered laterality in cognitive, neurological, and psychiatric disorders.
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Perlmutter, Joel S., William J. Powers, Peter Herscovitch, Peter T. Fox, and Marcus E. Raichle. "Regional Asymmetries of Cerebral Blood Flow, Blood Volume, and Oxygen Utilization and Extraction in Normal Subjects." Journal of Cerebral Blood Flow & Metabolism 7, no. 1 (February 1987): 64–67. http://dx.doi.org/10.1038/jcbfm.1987.9.
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Positron emission tomography (PET) and 15O-labeled radiotracers were used to measure regional CBF, cerebral blood volume (CBV), CMRO2, and oxygen extraction in 32 right-handed subjects at rest. Mean left hemispheric CBF (46.2 ± 6.8 ml/100 g/min) and CMRO2 (2.60 ± 0.59 ml/100 g/min) were significantly lower than right hemispheric values (47.4 ± 7.2 and 2.66 ± 0.61 ml/100 g/min, respectively; p < 0.0001 for both), whereas left and right hemispheric CBV and oxygen extraction were not significantly different. We further investigated these asymmetries by comparing left- and right-sided values for specific cortical and subcortical regions. We found that left-sided CBF and CMRO2 were significantly lower than right-sided values for sensorimotor, occipital, and superior temporal regions, whereas only left-sided CBF values were lower for anterior cingulum. CBV was asymmetric for the anterior cingulate and midfrontal regions, and oxygen extraction was asymmetric for the sensorimotor area. No asymmetries were observed in inferior parietal cortex, thalamus, putamen, or pallidum. Knowledge of these normal physiological asymmetries is essential for proper interpretation of PET studies of physiology and pathology. Furthermore, the ability to detect asymmetries with PET may lead to a better understanding of the lateralization of specific functions in the human brain.
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Dinomais, Mickael, Eva Chinier, Isabelle Richard, Emmanuel Ricalens, Christophe Aubé, Sylvie N’Guyen The Tich, and Aram Ter Minassian. "Hemispheric Asymmetry of Supplementary Motor Area Proper: A Functional Connectivity Study of the Motor Network." Motor Control 20, no. 1 (January 2016): 33–49. http://dx.doi.org/10.1123/mc.2014-0076.
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Cerebral asymmetry is a common feature of human functions. However, there are discrepancies in the literature about functional hemispheric asymmetries in the supplementary motor area (SMA), specifically in the posterior part (SMA-proper). We used resting state functional connectivity MRI to investigate the left-right asymmetries of the functional networks associated with primary motor cortex (M1) and SMA-proper using a “seed”-based correlation analysis in 30 healthy right-handed subjects. We showed that left M1 was more connected with areas involved in the motor system than right M1, and that right SMA-proper had more functional connections than its left counterpart. Our results are in agreement with a leftward asymmetry for M1 connectivity, whereas there is a rightward asymmetry of the SMA-proper connectivity.
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Spocter, Muhammad A., Chet C. Sherwood, Steven J. Schapiro, and William D. Hopkins. "Reproducibility of leftward planum temporale asymmetries in two genetically isolated populations of chimpanzees ( Pan troglodytes )." Proceedings of the Royal Society B: Biological Sciences 287, no. 1934 (September 9, 2020): 20201320. http://dx.doi.org/10.1098/rspb.2020.1320.
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Once considered a hallmark of human uniqueness, brain asymmetry has emerged as a feature shared with several other species, including chimpanzees, one of our closest living relatives. Most notable has been the discovery of asymmetries in homologues of cortical language areas in apes, particularly in the planum temporale (PT), considered a central node of the human language network. Several lines of evidence indicate a role for genetic mechanisms in the emergence of PT asymmetry; however, the genetic determinants of cerebral asymmetries have remained elusive. Studies in humans suggest that there is heritability of brain asymmetries of the PT, but this has not been explored to any extent in chimpanzees. Furthermore, the potential influence of non-genetic factors has raised questions about the reproducibility of earlier observations of PT asymmetry reported in chimpanzees. As such, the present study was aimed at examining both the heritability of phenotypic asymmetries in PT morphology, as well as their reproducibility. Using magnetic resonance imaging, we evaluated morphological asymmetries of PT surface area (mm 2 ) and mean depth (mm) in captive chimpanzees ( n = 291) derived from two genetically isolated populations. Our results confirm that chimpanzees exhibit a significant population-level leftward asymmetry for PT surface area, as well as significant heritability in the surface area and mean depth of the PT. These results conclusively demonstrate the existence of a leftward bias in PT asymmetry in chimpanzees and suggest that genetic mechanisms play a key role in the emergence of anatomical asymmetry in this region.
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PURDON, SCOT E., NEIL D. WOODWARD, and PIERRE FLOR-HENRY. "Asymmetrical hand force persistence and neuroleptic treatment in schizophrenia." Journal of the International Neuropsychological Society 7, no. 5 (July 2001): 606–14. http://dx.doi.org/10.1017/s1355617701755087.
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The recent development of an isometric instrument for the precise quantification of hand force persistence has created a novel opportunity for the evaluation of potential motor asymmetries in schizophrenia and their response to treatment. A study of asymmetries in the unmedicated state may provide insight into the pathogenesis of schizophrenia, whereas alterations of asymmetries in response to antipsychotic medication could assist the delineation of a cerebral mechanism for the effects of pharmacotherapy. The hand force persistence of 21 unmedicated patients with schizophrenia was compared to 21 age, gender, and handedness matched normal controls. The effect of neuroleptic treatment on hand force persistence was then evaluated on a subset of 10 patients after at least 30 days of treatment. The anticipated asymmetry was evident in the unmedicated sample that showed impaired right hand force persistence compared to the normal control sample. The prospective comparison showed an alleviation of the asymmetry resulting from an improvement of right hand force persistence with treatment. In addition to providing further support to a primary left hemisphere cerebral involvement in schizophrenia, the present results suggest that prior investigations of motor asymmetry may have been compromised by the study of medicated patients. The apparently paradoxical improvement of motor skill may relate to the substantial number of patients treated with 2nd generation neuroleptic medications which may implicate an improvement in left hemisphere physiology in the cognitive advantages of the novel treatments. (JINS, 2001, 7, 606–614.)
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Cappellini, Germana, Francesca Sylos-Labini, Michael J. MacLellan, Annalisa Sacco, Daniela Morelli, Francesco Lacquaniti, and Yury Ivanenko. "Backward walking highlights gait asymmetries in children with cerebral palsy." Journal of Neurophysiology 119, no. 3 (March 1, 2018): 1153–65. http://dx.doi.org/10.1152/jn.00679.2017.
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To investigate how early injuries to developing motor regions of the brain affect different forms of gait, we compared the spatiotemporal locomotor patterns during forward (FW) and backward (BW) walking in children with cerebral palsy (CP). Bilateral gait kinematics and EMG activity of 11 pairs of leg muscles were recorded in 14 children with CP (9 diplegic, 5 hemiplegic; 3.0–11.1 yr) and 14 typically developing (TD) children (3.3–11.8 yr). During BW, children with CP showed a significant increase of gait asymmetry in foot trajectory characteristics and limb intersegmental coordination. Furthermore, gait asymmetries, which were not evident during FW in diplegic children, became evident during BW. Factorization of the EMG signals revealed a comparable structure of the motor output during FW and BW in all groups of children, but we found differences in the basic temporal activation patterns. Overall, the results are consistent with the idea that both forms of gait share pattern generation control circuits providing similar (though reversed) kinematic patterns. However, BW requires different muscle activation timings associated with muscle modules, highlighting subtle gait asymmetries in diplegic children, and thus provides a more comprehensive assessment of gait pathology in children with CP. The findings suggest that spatiotemporal asymmetry assessments during BW might reflect an impaired state and/or descending control of the spinal locomotor circuitry and can be used for diagnostic purposes and as complementary markers of gait recovery.NEW & NOTEWORTHY Early injuries to developing motor regions of the brain affect both forward progression and other forms of gait. In particular, backward walking highlights prominent gait asymmetries in children with hemiplegia and diplegia from cerebral palsy and can give a more comprehensive assessment of gait pathology. The observed spatiotemporal asymmetry assessments may reflect both impaired supraspinal control and impaired state of the spinal circuitry.
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Alqadah, Amel, Yi-Wen Hsieh, Rui Xiong, and Chiou-Fen Chuang. "Stochastic left–right neuronal asymmetry in Caenorhabditis elegans." Philosophical Transactions of the Royal Society B: Biological Sciences 371, no. 1710 (December 19, 2016): 20150407. http://dx.doi.org/10.1098/rstb.2015.0407.
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Left–right asymmetry in the nervous system is observed across species. Defects in left–right cerebral asymmetry are linked to several neurological diseases, but the molecular mechanisms underlying brain asymmetry in vertebrates are still not very well understood. The Caenorhabditis elegans left and right amphid wing ‘C’ (AWC) olfactory neurons communicate through intercellular calcium signalling in a transient embryonic gap junction neural network to specify two asymmetric subtypes, AWC OFF (default) and AWC ON (induced), in a stochastic manner. Here, we highlight the molecular mechanisms that establish and maintain stochastic AWC asymmetry. As the components of the AWC asymmetry pathway are highly conserved, insights from the model organism C. elegans may provide a window onto how brain asymmetry develops in humans. This article is part of the themed issue ‘Provocative questions in left–right asymmetry’.
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Wittling, Werner. "Brain Asymmetry and Autonomic Control of the Heart." European Psychologist 2, no. 4 (January 1997): 313–27. http://dx.doi.org/10.1027/1016-9040.2.4.313.
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Neurocardiology has shown that the dynamic performance of the heart is strongly influenced by the brain, including the cerebral cortex. Neural control is mediated by sympathetic and parasympathetic fibers innervating the pacemaker, conductile, and contractile tissues of the heart. In this review, evidence is presented that autonomic control of the heart is lateralized, each brain side influencing cardiac activity in a different manner. Moreover, it is shown that asymmetries observed at the level of the cerebral hemispheres are characterized by different principles than asymmetries at the levels of the lower brain stem and the peripheral pathways. Findings on lateralized control of the heart are integrated into a general model of brain asymmetry, in which it is postulated that each hemisphere has a unique and comprehensive response system characterizing its cognitive, emotional, and physiological functioning.
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Brittain, Ann W. "Creativity and Hemispheric Functioning: A Second Look at Katz's Data." Empirical Studies of the Arts 3, no. 1 (January 1985): 105–7. http://dx.doi.org/10.2190/7ne5-b43t-hc8m-xkat.
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A review of Katz's 1983 article “Creativity and Individual Differences in Asymmetric Cerebral Hemispheric Functioning” in the first issue of this journal shows that the data presented do not support the conclusion that creative people have a tendency toward right-hemisphere lateralization in problem solving and verbal processing, but instead suggest that creativity is associated with a pattern of reduced hemispheric asymmetry.
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Burlakoti, Arjun, Jaliya Kumaratilake, David J. Taylor, and Maciej Henneberg. "Quantifying asymmetry of anterior cerebral arteries as a predictor of anterior communicating artery complex aneurysm." BMJ Surgery, Interventions, & Health Technologies 2, no. 1 (December 2020): e000059. http://dx.doi.org/10.1136/bmjsit-2020-000059.
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ObjectivesThe aim of this study was to establish an anatomical index for early prediction of the risk of development of aneurysms in anterior communicating arterial complex (AcomAC). The asymmetric diameter of one anterior cerebral artery (ACA) to other could alter haemodynamics and may contribute to formation of aneurysms in AcomAC and be a reliable predictor of the risk of development of aneurysms.Design and settingThis is a retrospective, observational and quantitative study, which used cerebral computed tomography angiography (CCTA) scans in South Australia.ParticipantsCCTA scans of 166 adult patients of both sexes were studied.Main outcome measuresThe internal diameters of the proximal segments of ACAs (A1s) were measured. Position and presence or absence of aneurysms in AcomAC were determined. The ratio of A1 diameters was taken as a measure of A1 asymmetry.ResultsThe ratio of diameters of A1s correlated with the occurrence of AcomAC aneurysms. The risk of development of aneurysms in AcomAC was much greater (80%, OR=47.3) when one A1 segment’s radius was at least 50% larger (ie, 2.25 times cross-sectional area) than the other.ConclusionThe general information on asymmetric A1 has been published previously. The present findings have significant contribution since the A1s asymmetry ratios have been categorised in ascending order and matched with the presence of AcomAC aneurysms. The asymmetry ratio of the A1 is a good predictor for the development of AcomAC aneurysms. Reconstruction of the asymmetric A1 could be done if the technology gets advanced.
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Corballis, Michael C. "Double Vision." Journal of the International Neuropsychological Society 5, no. 3 (March 1999): 266–67. http://dx.doi.org/10.1017/s1355617799223107.
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“The asymmetry of the mammalian brain,” goes the first sentence in this book, “took hundreds of years to discover.” This is not a promising beginning. Hundreds of years from when? And do the authors really mean the mammalian brain? We are indeed beginning to discover all kinds of asymmetries in the brains of mammals, from mice to chimpanzees, but the only mammal that features in the book is Homo sapiens. Cerebral asymmetry in humans is scarcely news, having been discovered by Dax as early as 1836, and a great many volumes have been produced on the subject.
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Vasung, Lana, Caitlin K. Rollins, Hyuk Jin Yun, Clemente Velasco-Annis, Jennings Zhang, Konrad Wagstyl, Alan Evans, et al. "Quantitative In vivo MRI Assessment of Structural Asymmetries and Sexual Dimorphism of Transient Fetal Compartments in the Human Brain." Cerebral Cortex 30, no. 3 (October 11, 2019): 1752–67. http://dx.doi.org/10.1093/cercor/bhz200.
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Abstract Structural asymmetries and sexual dimorphism of the human cerebral cortex have been identified in newborns, infants, children, adolescents, and adults. Some of these findings were linked with cognitive and neuropsychiatric disorders, which have roots in altered prenatal brain development. However, little is known about structural asymmetries or sexual dimorphism of transient fetal compartments that arise in utero. Thus, we aimed to identify structural asymmetries and sexual dimorphism in the volume of transient fetal compartments (cortical plate [CP] and subplate [SP]) across 22 regions. For this purpose, we used in vivo structural T2-weighted MRIs of 42 healthy fetuses (16.43–36.86 gestational weeks old, 15 females). We found significant leftward asymmetry in the volume of the CP and SP in the inferior frontal gyrus. The orbitofrontal cortex showed significant rightward asymmetry in the volume of CP merged with SP. Males had significantly larger volumes in regions belonging to limbic, occipital, and frontal lobes, which were driven by a significantly larger SP. Lastly, we did not observe sexual dimorphism in the growth trajectories of the CP or SP. In conclusion, these results support the hypothesis that structural asymmetries and sexual dimorphism in relative volumes of cortical regions are present during prenatal brain development.
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Levitan, Svetlana, and James A. Reggia. "A Computational Model of Lateralization and Asymmetries in Cortical Maps." Neural Computation 12, no. 9 (September 1, 2000): 2037–62. http://dx.doi.org/10.1162/089976600300015051.
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While recent experimental work has defined asymmetries and lateralization in left and right cortical maps, the mechanisms underlying these phenomena are currently not established. In order to explore some possible mechanisms in theory, we studied a neural model consisting of paired cerebral hemispheric regions interacting via a simulated corpus callosum. Starting with random synaptic strengths, unsupervised (Hebbian) synaptic modifications led to the emergence of a topographic map in one or both hemispheric regions. Because of uncertainties concerning the nature of hemispheric interactions, both excitatory and inhibitory callosal influences were examined independently. A sharp transition in model behavior was observed depending on callosal strength. For excitatory or weakly inhibitory callosal interactions, complete and symmetric mirror-image maps generally appeared in both hemispheric regions. In contrast, with stronger inhibitory callosal interactions, partial to complete map lateralization tended to occur, and the maps in each hemispheric region often became complementary. Lateralization occurred readily toward the side having a larger cortical region or higher excitability. Asymmetric synaptic plasticity, however, had only a transitory effect on lateralization. These results support the hypotheses that interhemispheric competition occurs, that multiple underlying asymmetries may lead to function lateralization, and that the effects of asymmetric synaptic plasticity may vary depending on whether supervised or unsupervised learning is involved. To our knowledge, this is the first computational model to demonstrate the emergence of topographic map lateralization and asymmetries.
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Hamdy, Shaheen, John C. Rothwell, David J. Brooks, Dale Bailey, Qasim Aziz, and David G. Thompson. "Identification of the Cerebral Loci Processing Human Swallowing With H2 15O PET Activation." Journal of Neurophysiology 81, no. 4 (April 1, 1999): 1917–26. http://dx.doi.org/10.1152/jn.1999.81.4.1917.
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Identification of the cerebral loci processing human swallowing with H2 15O PET activation. Lesional and electrophysiological data implicate a role for the cerebral cortex in the initiation and modulation of human swallowing, and yet its functional neuroanatomy remains undefined. We therefore conducted a functional study of the cerebral loci processing human volitional swallowing with 15O-labeled water positron emission tomography (PET) activation imaging. Regional cerebral activation was investigated in 8 healthy right handed male volunteers with a randomized 12-scan paradigm of rest and water swallows (5 ml/bolus, continuous infusion) at increasing frequencies of 0.1, 0.2, and 0.3 Hz, which were visually cued and monitored with submental electromyogram (EMG). Group and individual linear covariate analyses were performed with SPM96. In five of eight subjects, the cortical motor representation of pharynx was subsequently mapped with transcranial magnetic stimulation (TMS) in a posthoc manner to substantiate findings of hemispheric differences in sensorimotor cortex activation seen with PET. During swallowing, group PET analysis identified increased regional cerebral blood flow (rCBF) ( P < 0.001) within bilateral caudolateral sensorimotor cortex [Brodmann’s area (BA) 3, 4, and 6], right anterior insula (BA 16), right orbitofrontal and temporopolar cortex (BA 11 and 38), left mesial premotor cortex (BA 6 and 24), left temporopolar cortex and amygdala (BA 38 and 34), left superiomedial cerebellum, and dorsal brain stem. Decreased rCBF ( P < 0.001) was also observed within bilateral posterior parietal cortex (BA 7), right anterior occipital cortex (BA 19), left superior frontal cortex (BA 8), right prefrontal cortex (BA 9), and bilateral superiomedial temporal cortex (BA 41 and 42). Individual PET analysis revealed asymmetric representation within sensorimotor cortex in six of eight subjects, four lateralizing to right hemisphere and two to left hemisphere. TMS mapping in the five subjects identified condordant interhemisphere asymmetries in the motor representation for pharynx, consistent with the PET findings. We conclude that volitional swallowing recruits multiple cerebral regions, in particular sensorimotor cortex, insula, temporopolar cortex, cerebellum, and brain stem, the sensorimotor cortex displaying strong degrees of interhemispheric asymmetry, further substantiated with TMS. Such findings may help explain the variable nature of swallowing disorders after stroke and other focal lesions to the cerebral cortex.
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Gómez-Robles, Aida, William D. Hopkins, Steven J. Schapiro, and Chet C. Sherwood. "The heritability of chimpanzee and human brain asymmetry." Proceedings of the Royal Society B: Biological Sciences 283, no. 1845 (December 28, 2016): 20161319. http://dx.doi.org/10.1098/rspb.2016.1319.
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Human brains are markedly asymmetric in structure and lateralized in function, which suggests a relationship between these two properties. The brains of other closely related primates, such as chimpanzees, show similar patterns of asymmetry, but to a lesser degree, indicating an increase in anatomical and functional asymmetry during hominin evolution. We analysed the heritability of cerebral asymmetry in chimpanzees and humans using classic morphometrics, geometric morphometrics, and quantitative genetic techniques. In our analyses, we separated directional asymmetry and fluctuating asymmetry (FA), which is indicative of environmental influences during development. We show that directional patterns of asymmetry, those that are consistently present in most individuals in a population, do not have significant heritability when measured through simple linear metrics, but they have marginally significant heritability in humans when assessed through three-dimensional configurations of landmarks that reflect variation in the size, position, and orientation of different cortical regions with respect to each other. Furthermore, genetic correlations between left and right hemispheres are substantially lower in humans than in chimpanzees, which points to a relatively stronger environmental influence on left–right differences in humans. We also show that the level of FA has significant heritability in both species in some regions of the cerebral cortex. This suggests that brain responsiveness to environmental influences, which may reflect neural plasticity, has genetic bases in both species. These results have implications for the evolvability of brain asymmetry and plasticity among humans and our close relatives.
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Petit, Laurent, Laure Zago, Mathieu Vigneau, Frédéric Andersson, Fabrice Crivello, Bernard Mazoyer, Emmanuel Mellet, and Nathalie Tzourio-Mazoyer. "Functional Asymmetries Revealed in Visually Guided Saccades: An fMRI Study." Journal of Neurophysiology 102, no. 5 (November 2009): 2994–3003. http://dx.doi.org/10.1152/jn.00280.2009.
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Because eye movements are a fundamental tool for spatial exploration, we hypothesized that the neural bases of these movements in humans should be under right cerebral dominance, as already described for spatial attention. We used functional magnetic resonance imaging in 27 right-handed participants who alternated central fixation with either large or small visually guided saccades (VGS), equally performed in both directions. Hemispheric functional asymmetry was analyzed to identify whether brain regions showing VGS activation elicited hemispheric asymmetries. Hemispheric anatomical asymmetry was also estimated to assess its influence on the VGS functional lateralization. Right asymmetrical activations of a saccadic/attentional system were observed in the lateral frontal eye fields (FEF), the anterior part of the intraparietal sulcus (aIPS), the posterior third of the superior temporal sulcus (STS), the occipitotemporal junction (MT/V5 area), the middle occipital gyrus, and medially along the calcarine fissure (V1). The present rightward functional asymmetries were not related to differences in gray matter (GM) density/sulci positions between right and left hemispheres in the precentral, intraparietal, superior temporal, and extrastriate regions. Only V1 asymmetries were explained for almost 20% of the variance by a difference in the position of the right and left calcarine fissures. Left asymmetrical activations of a saccadic motor system were observed in the medial FEF and in the motor strip eye field along the Rolando sulcus. They were not explained by GM asymmetries. We suggest that the leftward saccadic motor asymmetry is part of a general dominance of the left motor cortex in right-handers, which must include an effect of sighting dominance. Our results demonstrate that, although bilateral by nature, the brain network involved in the execution of VGSs, irrespective of their direction, presented specific right and left asymmetries that were not related to anatomical differences in sulci positions.
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Stojanović, Kostić, Mitić, Berilažić, and Radisavljević. "Association between Circle of Willis Configuration and Rupture of Cerebral Aneurysms." Medicina 55, no. 7 (July 3, 2019): 338. http://dx.doi.org/10.3390/medicina55070338.
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Background and Objectives: Intracranial hemorrhage caused by the rupture of brain aneurysms occurs in almost 10 per 100,000 people whereas the incidence of such aneurysms is significantly higher, accounting for 4–9%.Linking certain factors to cerebral aneurysm rupture could help in explaining the significantly lower incidence of their rupture compared to their presence. The aim of this study is to determine the association between the corresponding circle of Willis configurations and rupture of cerebral aneurysms. Materials and Methods: A group of 114 patients treated operatively for aruptured cerebral aneurysm and a group of 56 autopsied subjects were involved in the study. Four basic types of the circle of Willis configurations were formed—two symmetric types A and C, and two asymmetric types B and D. Results: A statistically significantly higher presence of asymmetry of the circle of Willis was determined in the group of surgically-treated subjects (p = 0.001),witha significant presence of asymmetric Type B in this group (p < 0.001). The changeson the A1 segment in the group of surgically-treated subjects showed a statistically significant presence compared to the group of autopsied subjects (p = 0.001). Analyzing the presence of symmetry of the circle of Willis between the two groups, that is, the total presence of symmetric types A and C, indicated their statistically significant presence in the group of autopsied patients (p < 0.001). Conclusions: Changes such as hypoplasia or aplasia of A1 and the resulting asymmetry of the circle of Willis directly affect the possibility of the rupture of cerebral aneurysms. Detection of the corresponding types of the circle of Willis after diagnostic examination can be the basis for the development of a protocol for monitoring such patients.
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Reggia, James A., Sharon Goodall, and Yuri Shkuro. "Computational Studies of Lateralization of Phoneme Sequence Generation." Neural Computation 10, no. 5 (July 1, 1998): 1277–97. http://dx.doi.org/10.1162/089976698300017458.
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The mechanisms underlying cerebral lateralization of language are poorly understood. Asymmetries in the size of hemispheric regions and other factors have been suggested as possible underlying causal factors, and the corpus callosum (interhemispheric connections) has also been postulated to play a role. To examine these issues, we created a neural model consisting of paired cerebral hemispheric regions interacting via the corpus callosum. The model was trained to generate the correct sequence of phonemes for 50 monosyllabic words (simulated reading aloud) under a variety of assumptions about hemispheric asymmetries and callosal effects. After training, the ability of the full model and each hemisphere acting alone to perform this task was measured. Lateralization occurred readily toward the side having larger size, higher excitability, or higher learning-rate parameter. Lateralization appeared most readily and intensely with strongly inhibitory callosal connections, supporting past arguments that the effective functionality of the corpus callosum is inhibitory. Many of the results are interpretable as the outcome of a “race to learn” between the model's two hemispheric regions, leading to the concept that asymmetric hemispheric plasticity is a critical common causative factor in lateralization. To our knowledge, this is the first computational model to demonstrate spontaneous lateralization of function, and it suggests that such models can be useful for understanding the mechanisms of cerebral lateralization.
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Katz, Elionora, Jessica A. Burket, Stephanie M. Rosse, Richard B. Rosse, Barbara L. Schwartz, and Stephen I. Deutsch. "Cerebral Ventricular Asymmetry and Ventriculomegaly Interact to Increase Risk for Schizophrenia: A Case Report and Recommendation for Routine Fetal Sonography." CNS Spectrums 15, no. 9 (September 2010): 574–78. http://dx.doi.org/10.1017/s1092852900000547.
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ABSTRACTA 60-year-old patient with a clinical diagnosis of schizophrenia underwent a magnetic resonance imaging (MRI) scan related to the evaluation of isolated seizures that emerged while medicated with clozapine. Unexpectedly, the MRI scan revealed evidence of asymmetric and enlarged cerebral ventricles that were interpreted as congenital in origin. The presence of both congenital lateral ventricular asymmetry and ventriculomegaly may interact to increase risk of schizophrenia. The history and clinical features, including cognitive testing, of the illustrative patient are presented.
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Roe, James M., Didac Vidal-Piñeiro, Markus H. Sneve, Kristiina Kompus, Douglas N. Greve, Kristine B. Walhovd, Anders M. Fjell, and René Westerhausen. "Age-Related Differences in Functional Asymmetry During Memory Retrieval Revisited: No Evidence for Contralateral Overactivation or Compensation." Cerebral Cortex 30, no. 3 (August 13, 2019): 1129–47. http://dx.doi.org/10.1093/cercor/bhz153.
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Abstract Brain asymmetry is inherent to cognitive processing and seems to reflect processing efficiency. Lower frontal asymmetry is often observed in older adults during memory retrieval, yet it is unclear whether lower asymmetry implies an age-related increase in contralateral recruitment, whether less asymmetry reflects compensation, is limited to frontal regions, or predicts neurocognitive stability or decline. We assessed age-related differences in asymmetry across the entire cerebral cortex, using functional magnetic resonance imaging data from 89 young and 76 older adults during successful retrieval, and surface-based methods allowing direct homotopic comparison of activity between cortical hemispheres . An extensive left-asymmetric network facilitated retrieval in both young and older adults, whereas diverse frontal and parietal regions exhibited lower asymmetry in older adults. However, lower asymmetry was not associated with age-related increases in contralateral recruitment but primarily reflected either less deactivation in contralateral regions reliably signaling retrieval failure in the young or lower recruitment of the dominant hemisphere—suggesting that functional deficits may drive lower asymmetry in older brains, not compensatory activity. Lower asymmetry predicted neither current memory performance nor the extent of memory change across the preceding ~ 8 years in older adults. Together, these findings are inconsistent with a compensation account for lower asymmetry during retrieval and aging.
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Chen, Peii, Kelly M. Goedert, Elizabeth Murray, Karen Kelly, Shpresa Ahmeti, and Anna M. Barrett. "Spatial Bias and Right Hemisphere Function: Sex-Specific Changes with Aging." Journal of the International Neuropsychological Society 17, no. 3 (February 15, 2011): 455–62. http://dx.doi.org/10.1017/s135561771100004x.
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AbstractPatterns of cerebral asymmetry related to visuospatial functions may change with age. The typical leftward bias on a line bisection task may reflect cerebral asymmetry. With age, such leftward bias decreases. This study demonstrated that the age-related decrease of leftward bias may actually be sex-specific. In addition, previous research suggests that young adults’ deviation in line bisection may reflect asymmetric hemispheric activation of perceptual–attentional “where” spatial systems, rather than motor-intentional “aiming” spatial systems; thus, we specifically fractionated “where” and “aiming” bias of men and women ranging in age from 22 to 93 years old. We observed that older men produced greater rightward line bisection errors, of primarily “where” spatial character. However, women's errors remained leftward biased, and did not significantly change with age. “Where” spatial systems may be linked to cortico-cortical processing networks involving the posterior part of the dorsal visuospatial processing stream. Thus, the current results are consistent with the conclusion that reduced right dorsal spatial activity in aging may occur in the male, but not female, adult spatial system development. (JINS, 2011, 17, 455–462)
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vallortigara, giorgio, and lesley j. rogers. "survival with an asymmetrical brain: advantages and disadvantages of cerebral lateralization." Behavioral and Brain Sciences 28, no. 4 (August 2005): 575–89. http://dx.doi.org/10.1017/s0140525x05000105.
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recent evidence in natural and semi-natural settings has revealed a variety of left-right perceptual asymmetries among vertebrates. these include preferential use of the left or right visual hemifield during activities such as searching for food, agonistic responses, or escape from predators in animals as different as fish, amphibians, reptiles, birds, and mammals. there are obvious disadvantages in showing such directional asymmetries because relevant stimuli may be located to the animal's left or right at random; there is no a priori association between the meaning of a stimulus (e.g., its being a predator or a food item) and its being located to the animal's left or right. moreover, other organisms (e.g., predators) could exploit the predictability of behavior that arises from population-level lateral biases. it might be argued that lateralization of function enhances cognitive capacity and efficiency of the brain, thus counteracting the ecological disadvantages of lateral biases in behavior. however, such an increase in brain efficiency could be obtained by each individual being lateralized without any need to align the direction of the asymmetry in the majority of the individuals of the population. here we argue that the alignment of the direction of behavioral asymmetries at the population level arises as an “evolutionarily stable strategy” under “social” pressures occurring when individually asymmetrical organisms must coordinate their behavior with the behavior of other asymmetrical organisms of the same or different species.
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Pinel, Philippe, and Stanislas Dehaene. "Beyond Hemispheric Dominance: Brain Regions Underlying the Joint Lateralization of Language and Arithmetic to the Left Hemisphere." Journal of Cognitive Neuroscience 22, no. 1 (January 2010): 48–66. http://dx.doi.org/10.1162/jocn.2009.21184.
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Language and arithmetic are both lateralized to the left hemisphere in the majority of right-handed adults. Yet, does this similar lateralization reflect a single overall constraint of brain organization, such an overall “dominance” of the left hemisphere for all linguistic and symbolic operations? Is it related to the lateralization of specific cerebral subregions? Or is it merely coincidental? To shed light on this issue, we performed a “colateralization analysis” over 209 healthy subjects: We investigated whether normal variations in the degree of left hemispheric asymmetry in areas involved in sentence listening and reading are mirrored in the asymmetry of areas involved in mental arithmetic. Within the language network, a region-of-interest analysis disclosed partially dissociated patterns of lateralization, inconsistent with an overall “dominance” model. Only two of these areas presented a lateralization during sentence listening and reading which correlated strongly with the lateralization of two regions active during calculation. Specifically, the profile of asymmetry in the posterior superior temporal sulcus during sentence processing covaried with the asymmetry of calculation-induced activation in the intraparietal sulcus, and a similar colateralization linked the middle frontal gyrus with the superior posterior parietal lobule. Given recent neuroimaging results suggesting a late emergence of hemispheric asymmetries for symbolic arithmetic during childhood, we speculate that these colateralizations might constitute developmental traces of how the acquisition of linguistic symbols affects the cerebral organization of the arithmetic network.
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GÜNTÜRKÜN, ONUR. "How asymmetry in animals starts." European Review 13, S2 (August 22, 2005): 105–18. http://dx.doi.org/10.1017/s1062798705000694.
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This review aims to present a speculation about mechanisms that shape the brains of humans and other animals into an asymmetrical organization. To this end, I will proceed in two steps: first, I want to recapitulate evidence from various experiments that show that some but not all asymmetries of the avian brain result from a prehatch light stimulation asymmetry. This should make it clear that avian embryos have a genetic predisposition to turn their head to the right. This results in a higher level of prehatch light stimulation of their right eye. The concomitant left–right difference in sensory input alters the brain circuits of the animal for the entire lifespan in a lateralized way. In the second part of the paper I will present evidence that some of the asymmetries of the human brain take a similar ontogenetic path as those observed in birds. This review provides the evidence that critical ontogenetic processes discovered in animal models could also be involved in the ontogeny of human cerebral asymmetries.
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Taher, Md Abu, Fattah Ahma, Md Anwar Pasha, Md Mofazzal Sharif, Md Mohit Ul Alam, Nayeema Rahman, and Md Towhidur Rahman. "Dyke Davidoff Masson Syndrome A Case Report." BIRDEM Medical Journal 3, no. 2 (December 1, 2013): 106–9. http://dx.doi.org/10.3329/birdem.v3i2.17215.
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A 10 year old male child reported to paediatric neurology OPD of BIRDEM General Hospital with the complaints of weakness of left side of body, seizure and facial asymmetry for 2 years. He was on regular anti convulsive therapy and failed to control seizure. General examination revealed no significant abnormality neither delayed mile stones of development happened. Neurological examination revealed left sided spastic hemiparesis, brisk tendon reflexes and extensor planter on left side. With detailed history and examination he was diagnosed as a case of infantile seizure and undergone CT scan of brain followed by MRI scan. Both the reports revealed severe atrophy of right cerebral hemisphere, thinning of cortical gyri, widening of sulci and dilatation of right lateral ventricle with ipsilateral midline shift and was concluded as hemiatrophy of right cerebral hemisphere with suspicion of Dyke Davidoff Masson Syndrome (DDMS), Hemimegalencephaly and Sturge-Weber syndrome. Dyke-Davidoff-Masson syndrome (DDMS) is a rare condition characterized by asymmetric cerebral hemispheric growth with unilateral atrophy, ipsilateral compensatory osseous hypertrophy, hyperpneumatization of the paranasal sinuses and mastoid cells, and contralateral paresis. Varying degrees of hemiparesis, hemiplegia, seizures, mental retardation, and facial asymmetry can be associated with DDMS. Considering clinical history and imaging findings, final Diagnosis was Dyke Davidoff Masson Syndrome. Birdem Med J 2013; 3(2): 196-109 DOI: http://dx.doi.org/10.3329/birdem.v3i2.17215
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Schultheiss, Oliver C., Olivia S. Schwemmer, and Ksenia Khalaidovski. "Motives and Laterality: Exploring the Links." Adaptive Human Behavior and Physiology 7, no. 2 (March 30, 2021): 133–65. http://dx.doi.org/10.1007/s40750-021-00165-5.
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Abstract Objectives We explored associations between the needs for power, achievement, and affiliation and functional cerebral asymmetries (FCAs), guided by three established hypotheses about the nature of these associations. Methods One-hundred-and-seven participants completed picture-story measures of dispositional motives and activity inhibition (AI), a frequent moderator of motive-behavior associations, tasks measuring FCAs (line bisection, chimeric emotional face judgments, turning bias, perceptual and response asymmetries on the Poffenberger task), self-reported laterality preferences (handedness, footedness, ear and eye preference), and interhemispheric interaction (crossed-uncrossed difference). They also completed an experiment manipulating hand contractions (left, right, both, neither) while they worked on a second picture-story motive measure. Results Dispositional power motivation was associated with stronger rightward asymmetry and less interhemispheric transfer in high-AI and stronger leftward asymmetry and more interhemispheric transfer in low-AI individuals. For the affiliation motive, findings were fewer and in the opposite direction of those for the power motive. These findings emerged for men, but not for women. Left- or right-hand contractions led to increases in power and achievement motivation, but not affiliation motivation. Only left-hand contractions led to decreased AI. Conclusions We discuss these findings in the context of sex-dimorphic organizing and activating effects of steroids on motives and laterality.
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Silva, Guilherme, and Alberto Citterio. "Hemispheric asymmetries in dorsal language pathway white-matter tracts: A magnetic resonance imaging tractography and functional magnetic resonance imaging study." Neuroradiology Journal 30, no. 5 (July 12, 2017): 470–76. http://dx.doi.org/10.1177/1971400917720829.
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Introduction Previous studies have shown that the arcuate fasciculus has a leftward asymmetry in right-handers that could be correlated with the language lateralisation defined by functional magnetic resonance imaging. Nonetheless, information about the asymmetry of the other fibres that constitute the dorsal language pathway is scarce. Objectives This study investigated the asymmetry of the white-matter tracts involved in the dorsal language pathway through the diffusion tensor imaging (DTI) technique, in relation to language hemispheric dominance determined by task-dependent functional magnetic resonance imaging (fMRI). Methods We selected 11 patients (10 right-handed) who had been studied with task-dependent fMRI for language areas and DTI and who had no language impairment or structural abnormalities that could compromise magnetic resonance tractography of the fibres involved in the dorsal language pathway. Laterality indices (LI) for fMRI and for the volumes of each tract were calculated. Results In fMRI, all the right-handers had left hemispheric lateralisation, and the ambidextrous subject presented right hemispheric dominance. The arcuate fasciculus LI was strongly correlated with fMRI LI ( r = 0.739, p = 0.009), presenting the same lateralisation of fMRI in seven subjects (including the right hemispheric dominant). It was not asymmetric in three cases and had opposite lateralisation in one case. The other tracts presented predominance for rightward lateralisation, especially superior longitudinal fasciculus (SLF) II/III (nine subjects), but their LI did not correlate (directly or inversely) with fMRI LI. Conclusion The fibres that constitute the dorsal language pathway have an asymmetric distribution in the cerebral hemispheres. Only the asymmetry of the arcuate fasciculus is correlated with fMRI language lateralisation.
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Oldendorf, William H. "CT and Cerebral Asymmetries." Psychiatric Annals 15, no. 7 (July 1, 1985): 453–56. http://dx.doi.org/10.3928/0048-5713-19850701-11.
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Goldblatt, D. "Morphologic Cerebral Asymmetries and Handedness." Archives of Neurology 52, no. 12 (December 1, 1995): 1137–38. http://dx.doi.org/10.1001/archneur.1995.00540360015003.
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Foundas, Anne L. "Morphologic Cerebral Asymmetries and Handedness." Archives of Neurology 52, no. 5 (May 1, 1995): 501. http://dx.doi.org/10.1001/archneur.1995.00540290091023.
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Bear, David. "Quantitative Analysis of Cerebral Asymmetries." Archives of Neurology 43, no. 6 (June 1, 1986): 598. http://dx.doi.org/10.1001/archneur.1986.00520060060019.
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Sadler, Andrew J., and Ian J. Deary. "Cerebral asymmetries in inspection time?" Neuropsychologia 34, no. 4 (April 1996): 283–95. http://dx.doi.org/10.1016/0028-3932(95)00105-0.
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Jeeves, M. A., and A. Lamb. "Cerebral asymmetries and interhemispheric processes." Behavioural Brain Research 29, no. 3 (August 1988): 211–23. http://dx.doi.org/10.1016/0166-4328(88)90026-5.
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Ramesh, Perla, Devatha Suman, and Koti Reddy. "Asymmetric Synthetic Strategies of (R)-(–)-Baclofen: An Antispastic Drug." Synthesis 50, no. 02 (October 20, 2017): 211–26. http://dx.doi.org/10.1055/s-0036-1590938.
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Baclofen is an antispastic drug used as a muscle relaxant in the treatment of the paroxysmal pain of trigeminal neuralgia, spasticity of the spinal cord and cerebral origin. Baclofen resides biological activity exclusively in its (R)-(–)-enantiomer. In this review, various asymmetric synthetic strategies for (R)-(–)-baclofen are described.1 Introduction2 Resolution Synthetic Approaches2.1 Chemical Resolution2.2 Biocatalytic Resolution3 Asymmetric Desymmetrization3.1 Catalytic Enantioselective Desymmetrization3.2 Enzymatic Desymmetrization4 Chiral Auxiliary Induced Asymmetric Synthesis4.1 Asymmetric Michael Addition4.2 Asymmetric Aldol Addition4.3 Asymmetric Nucleophilic Substitution5 Asymmetric Reduction5.1 Catalytic Asymmetric Hydrogenation5.2 Bioreduction6 Catalytic Asymmetric Conjugate Addition7 Conclusion
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Kelley, Michael P. "Schizotypy and Hemisphericity." Psychological Reports 109, no. 2 (October 2011): 533–52. http://dx.doi.org/10.2466/02.03.09.19.pr0.109.5.533-552.
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There is considerable evidence that schizophrenia spectrum disorders are associated with a variety of abnormal asymmetries of brain structure, function, and behavior. Schizotypy is a personality trait dimension extending into the normal range, which at its extreme, is associated with a vulnerability to schizophrenia spectrum disorders. Schizotypy in the normal range is also associated with a variety of neurobiological characteristics associated with schizophrenia spectrum disorders, including abnormal brain and behavioral asymmetries. Previous studies have suggested that normal schizotypy (as well as belief in the paranormal) is associated with an increased reliance on the right hemisphere in a variety of tasks. Hemisphericity is a trait-related characteristic preference for the cognitive mode of one or the other cerebral hemispheres, putatively related to hemispheric activation asymmetry. A sample of 256 undergraduates was administered five schizotypy scales, as well as three hemisphericity measures. Higher schizotypy scores were associated with an increase in right hemisphericity and a decrease in integrated hemisphericity. Although the construct of hemisphericity has been criticized, there is evidence to suggest that questionnaire and eye movement measures of hemisphericity may yet have construct validity, and further research on hemisphericity may be warranted.
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Sawada, Kazuhiko. "Cerebral Sulcal Asymmetry in Macaque Monkeys." Symmetry 12, no. 9 (September 14, 2020): 1509. http://dx.doi.org/10.3390/sym12091509.
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The asymmetry of the cerebral sulcal morphology is particularly obvious in higher primates. The sulcal asymmetry in macaque monkeys, a genus of the Old World monkeys, in our previous studies and others is summarized, and its evolutionary significance is speculated. Cynomolgus macaques displayed fetal sulcation and gyration symmetrically, and the sulcal asymmetry appeared after adolescence. Population-level rightward asymmetry was revealed in the length of arcuate sulcus (ars) and the surface area of superior temporal sulcus (sts) in adult macaques. When compared to other nonhuman primates, the superior postcentral sulcus (spcs) was left-lateralized in chimpanzees, opposite of the direction of asymmetry in the ars, anatomically-identical to the spcs, in macaques. This may be associated with handedness: either right-handedness in chimpanzees or left-handedness/ambidexterity in macaques. The rightward asymmetry in the sts surface area was seen in macaques, and it was similar to humans. However, no left/right side differences were identified in the sts morphology among great apes, which suggests the evolutionary discontinuity of the sts asymmetry. The diversity of the cortical lateralization among primate species suggests that the sulcal asymmetry reflects the species-related specialization of the cortical morphology and function, which is facilitated by evolutionary expansion in higher primates.
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Herzog, Nitsa J., and George D. Magoulas. "Brain Asymmetry Detection and Machine Learning Classification for Diagnosis of Early Dementia." Sensors 21, no. 3 (January 24, 2021): 778. http://dx.doi.org/10.3390/s21030778.
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Early identification of degenerative processes in the human brain is considered essential for providing proper care and treatment. This may involve detecting structural and functional cerebral changes such as changes in the degree of asymmetry between the left and right hemispheres. Changes can be detected by computational algorithms and used for the early diagnosis of dementia and its stages (amnestic early mild cognitive impairment (EMCI), Alzheimer’s Disease (AD)), and can help to monitor the progress of the disease. In this vein, the paper proposes a data processing pipeline that can be implemented on commodity hardware. It uses features of brain asymmetries, extracted from MRI of the Alzheimer’s Disease Neuroimaging Initiative (ADNI) database, for the analysis of structural changes, and machine learning classification of the pathology. The experiments provide promising results, distinguishing between subjects with normal cognition (NC) and patients with early or progressive dementia. Supervised machine learning algorithms and convolutional neural networks tested are reaching an accuracy of 92.5% and 75.0% for NC vs. EMCI, and 93.0% and 90.5% for NC vs. AD, respectively. The proposed pipeline offers a promising low-cost alternative for the classification of dementia and can be potentially useful to other brain degenerative disorders that are accompanied by changes in the brain asymmetries.
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Kertesz, Andrew, Sandra E. Black, Marsha Polk, and Janice Howell. "Cerebral Asymmetries on Magnetic Resonance Imaging." Cortex 22, no. 1 (March 1986): 117–27. http://dx.doi.org/10.1016/s0010-9452(86)80036-3.
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Hutsler, Jeffrey, and Ralf A. W. Galuske. "Hemispheric asymmetries in cerebral cortical networks." Trends in Neurosciences 26, no. 8 (August 2003): 429–35. http://dx.doi.org/10.1016/s0166-2236(03)00198-x.
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Ellis, Ronald J., and Marlene Oscar-Berman. "Alcoholism, aging, and functional cerebral asymmetries." Psychological Bulletin 106, no. 1 (1989): 128–47. http://dx.doi.org/10.1037/0033-2909.106.1.128.
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Foundas, A. L., C. M. Leonard, and K. M. Heilman. "Morphologic Cerebral Asymmetries and Handedness-Reply." Archives of Neurology 52, no. 12 (December 1, 1995): 1138. http://dx.doi.org/10.1001/archneur.1995.00540360015004.
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Badzakova-Trajkov, Gjurgjica, Isabelle S. Häberling, Reece P. Roberts, and Michael C. Corballis. "Cerebral Asymmetries: Complementary and Independent Processes." PLoS ONE 5, no. 3 (March 12, 2010): e9682. http://dx.doi.org/10.1371/journal.pone.0009682.
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