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Dissertations / Theses on the topic 'Optic lobe'
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Gold, Katrina Sarah. "Neural stem cell regulation in the Drosophila optic lobe." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610391.
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Ray, Nandita. "Characterisation of an α-bungarotoxin binding component of chick optic lobe." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/46521.
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Guffey, David. "The Localization of GABA-Like Immunoreactivity in the Optic Lobe Neuropils and Optic Tracts of the Cockroach Leucophaea Maderae." TopSCHOLAR®, 1999. http://digitalcommons.wku.edu/theses/780.
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Gamma aminobutyric acid (GABA) is a prominent neurotransmitter found in both vertebrates and invertebrates. The action of GABA has been accepted to be inhibitory in nature, but recent evidence suggests it is both inhibitory and excitatory, depending upon time of day. The amount of GABA measured in the brain of the cockroach Leucophaea maderae was discovered to fluctuate in a circadian pattern similar to the pattern of electrical output measured from the optic nerve in L. maderae. Considering the circadian oscillator for L. maderae has been localized to the optic lobes of the brain, the discovery of GABA-like immunoreactivity in the optic lobes and optic tract could be an important first step in localizing cells that comprise the circadian oscillator(s) that control the temporal pattern of many physiological, biochemical and behavioral activities, such as locomotor activity and metabolism. Through the use of monoclonal antibodies and the enzyme alkaline phosphatase, GABA-like immunoreactivity has been discovered associated with neuropils of the optic lobes (lamina, medulla, lobula) and in the optic tract of the cockroach L. maderae. The localization of GABA-like immunoreactivity in the optic lobes and tract of L. maderae is consistent with findings in other invertebrates, including other species of cockroaches.
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Hussey, Dominic Anthony. "Morphology and electrophysiology of retinal photoreceptor terminations in the octopus (Eledone cirrosa) optic lobe." Thesis, University of Plymouth, 1999. http://hdl.handle.net/10026.1/2323.
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Cephalopods possess a well-developed visual system encompassing a pair of camera-type eyes attached to specific visual processing regions of the central nervous system known as the optic lobes. The retina contains a single type of photoreceptive cell, which send axons via a dorso-ventral chiasma to the optic lobes. Although electrophysiological recordings have been routinely obtained from the retina there are few recordings from the optic lobe. This study investigated the morphology and electrophysiology of the first synapse in the Octopus (Eledone cirrosa) visual system. The morphology and innervation patterns of individual optic nerves onto the optic lobe were revealed using the carbocyanine dye, Oil. Optic nerves had characteristic mapping patterns depending upon where they entered the optic lobe. Nerves innervating central regions of the optic lobe spread laterally in both directions for equal distances. Optic nerves that entered the lobe on the dorsal and ventral surfaces of the lobes spread for greater distances in only one direction. The morphology of the photoreceptor terminations in the cortex were comparable to the morphologies revealed in previous studies. A brain slice preparation of the octopus optic lobe was developed in order to make the first in vitro electrophysiological recordings from the first synapse in the visual pathway. Extracellular pre- and postsynaptic responses were recorded from the optic lobe and these were characterised. Using a variety of techniques (paired-pulse tests, frequency inhibition, ionic substitution) the different evoked field potentials recorded from different layers of the optic lobe slice were separated into pre- and postsynaptic components. Postsynaptic responses obtained in the outer regions of the plexiform zone were polysynaptic and negative in inflection whilst those obtained from the inner granular cell layer and medulla were positive. The effects of altering the extracellular concentrations of Ca2+, Mg2+ and K+ were all investigated. The resultant electrical activity after orthodromic stimulation of a single optic nerve was mapped in the optic lobe slice and plots of lines of isopotential produced. Pharmacological studies using the in vitro slice preparation in conjunction with specific antagonists to vertebrate receptors were employed to reveal the identity of the neurotransmitter released from the retinal photoreceptor terminations. The abolishment of postsynaptic responses with alpha-bungarotoxin and the increase with the acetylcholinesterase inhibitor (eserine) indicated that the transmitter released is acetylcholine. Histochemical and immunohistochemical localisations of putative neurotransmitters (or their synthetic enzymes) in the cephalopod optic lobe were attempted. No neurotransmitter-like immunoreactivity was seen in the optic lobe, this was probably due to the primary antibodies used not recognising antigens in the tissue. In the decapod squid, Alloteuthis subulata and Loligo forbesii, AChE histochemistry revealed precise anatomical localisation of this enzyme which concurred with previous studies on other decapod species. This study has enhanced the understanding of the cephalopod visual system by providing a preparation of the optic lobe from which electrophysiological recordings can repeatabley be obtained. This preparation has been used to provide information about how visual information is passed from the retina to the central nervous system.
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Boergens, Kevin Verfasser], and Alexander [Akademischer Betreuer] [Borst. "Connectomic analysis of mouse barrel cortex and fly optic lobe / Kevin Boergens ; Betreuer: Alexander Borst." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2018. http://d-nb.info/1156533538/34.
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Lin, Chan, and Nicholas Strausfeld. "A precocious adult visual center in the larva defines the unique optic lobe of the split-eyed whirligig beetle Dineutus sublineatus." BioMed Central, 2013. http://hdl.handle.net/10150/610139.
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INTRODUCTION:Whirligig beetles (Coleoptera: Gyrinidae) are aquatic insects living on the water surface. They are equipped with four compound eyes, an upper pair viewing above the water surface and a lower submerged pair viewing beneath the water surface, but little is known about how their visual brain centers (optic lobes) are organized to serve such unusual eyes. We show here, for the first time, the peculiar optic lobe organization of the larval and adult whirligig beetle Dineutus sublineatus.RESULTS:The divided compound eyes of adult whirligig beetles supply optic lobes that are split into two halves, an upper half and lower half, comprising an upper and lower lamina, an upper and lower medulla and a bilobed partially split lobula. However, the lobula plate, a neuropil that in flies is known to be involved in mediating stabilized flight, exists only in conjunction with the lower lobe of the lobula. We show that, as in another group of predatory beetle larvae, in the whirligig beetle the aquatic larva precociously develops a lobula plate equipped with wide-field neurons. It is supplied by three larval laminas serving the three dorsal larval stemmata, which are adjacent to the developing upper compound eye.CONCLUSIONS:In adult whirligig beetles, dual optic neuropils serve the upper aerial eyes and the lower subaquatic eyes. The exception is the lobula plate. A lobula plate develops precociously in the larva where it is supplied by inputs from three larval stemmata that have a frontal-upper field of view, in which contrasting objects such as prey items trigger a body lunge and mandibular grasp. This precocious lobula plate is lost during pupal metamorphosis, whereas another lobula plate develops normally during metamorphosis and in the adult is associated with the lower eye. The different roles of the upper and lower lobula plates in supporting, respectively, larval predation and adult optokinetic balance are discussed. Precocious development of the upper lobula plate represents convergent evolution of an ambush hunting lifestyle, as exemplified by the terrestrial larvae of tiger beetles (Cicindelinae), in which activation of neurons in their precocious lobula plates, each serving two large larval stemmata, releases reflex body extension and mandibular grasp.
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Kolodziejczyk, Agata. "Chemical circuitry in the visual system of the fruitfly, Drosophila melanogaster." Doctoral thesis, Stockholms universitet, Zoologiska institutionen, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-60160.
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Signal processing in the visual system is mediated by classic neurotransmission and neuropeptidergic modulatory pathways. In Dipteran insects, especially in the fruitfly Drosophila melanogaster, the morphology of the visual system is very well described. However neurotransmitter and neuropeptidergic circuits within the optic lobe neuropil are only partially known. Using several transgenic fly lines and antibodies we determined the localization of the classical neurotransmitters GABA, acetylcholine and glutamate in the visual system, and their putative targets via detecting several neurotransmitter receptors. We paid particular attention to the peripheral neuropil layer called the lamina, where the light signals are filtered, channeled and amplified (Paper I). We discovered four new types of efferent tangential neurons branching distally to the lamina. Among them was the first neuropeptidergic neuron (LMIo) in this region of Drosophila. The LMIo expresses myoinhibitory peptide (MIP) and has its cell body located close to the main lateral clock neurons that express the neuropeptide pigment-dispersing factor (PDF)(Paper II). Since in other Dipteran species PDF is expressed in processes distally to the lamina, we performed comparative anatomical studies of the MIP, PDF, Ion Transport Peptide (ITP) and serotonin (5-HT) distribution in the visual system of the flies Drosophila and Calliphora. Our data suggest that PDF signaling distal to the lamina of the blowfly might be replaced by MIP signaling in the fruitfly, while ITP and 5-HT expression is conserved in the two species (Paper III). Serotonin is crucial in light adaptation during the daily light-dark cycles. We analyzed putative serotonergic circuits in the lamina. We found that LMIo neurons express the inhibitory receptor 5-HT1A, while 5-HT1B and 5-HT2 are both expressed in the epithelial glia of the lamina. Another novel wide-field neuron with lamina branches expresses the excitatory serotonin receptor 5-HT7. Our studies have identified a fairly complex neuronal circuitry in the tangential plexus above the lamina. (Paper IV). Finally we tested circadian locomotor activity rhythms in flies with the GABAB receptor knocked down on the lateral PDF-expressing clock neurons. We observed significant changes in the activity periods and diminished strength of rhythmicity during DD suggesting a modulatory role of GABA in clock function (Paper V).At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Manuscript. Paper 5: Manuscript.
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Gibbs, Sarah Margaretha. "Regulation of Drosophila visual system development by nitric oxide and cyclic GMP /." Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/10651.
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Antonio, David Santos Marco. "Processos celulares no desenvolvimento do olho composto de Apis mellifera." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/17/17135/tde-10102008-144722/.
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Os processos que regem o desenvolvimento dos olhos compostos em insetos têm sido amplamente estudados em Drosophila melanogaster onde estes se originam a partir de discos imaginais. Pouco se sabe, porém, sobre o desenvolvimento do lóbulo óptico e da retina em outros insetos que, na sua grande maioria, não possuem discos imaginais de olhos separados do sistema nervoso central. Neste sentido, a análise comparada do desenvolvimento dos olhos de Apis mellifera pode contribuir não somente para aspectos evo-devo entre as grandes famílias dos insetos holometábolos, quanto pode elucidar questões de plasticidade de desenvolvimento pois os olhos compostos apresentam fortes características sexo e casta-específicas. Com o objetivo primário de elucidar os padrões de divisão e diferenciação celular durante o desenvolvimento do olho em A. mellifera realizamos análises histológicas e de imunomarcação durante o desenvolvimento pós-embrionário, juntamente com análise de expressão do gene roughest em tempo real. Para imunomarcação utilizamos o anticorpo anti-fosfo-histona H3 fosforilada que marca células em fase M do ciclo celular. Foram analisadas larvas operárias entre o terceiro instar larval (L3) até pupas de olho branco, rosa e marrom, com foco sobre o quinto instar larval que fica subdividida em fase de alimentação e crescimento (L5F), fases de tecelagem de casulo (L5S) e prepupa (PP). O desenvolvimento do lóbulo óptico em Apis mellifera ocorre por dobramento neuroepitelial, a partir de um centro de diferenciação, seqüencialmente gerando as camadas neurais do lóbulo óptico (lóbula, medula e lâmina). A lâmina (última a surgir) 6 apresentou-se com desenvolvimento mais lento e em duas fases antes da metamorfose: a primeira fase é o seu surgimento no começo do quinto instar larval acompanhando o primeiro pico de expressão de roughest e a segunda fase ocorre durante a tecelagem de casulo com o desenvolvimento do córtex acompanhando o segundo pico de expressão de roughest. Ainda durante o segundo pico de expressão de roughest os rabdômeros da retina começam a ficar visíveis, assim como os feixes axonais. Estes porém estarão completamente formados somente após a metamorfose.. O desenvolvimento completo da lâmina, lóbula e medula e da retina ocorre somente após a metamorfose. Durante a fase pupal as estruturas do lóbulo óptico estão prontas, porém na retina observa-se ainda gradual pigmentação, encurtamento dos feixes axonais e alongamento dos rabdômeros até atingirem o seu comprimento final logo antes da emergência.The processes that drive compound eye development in insects have been broadly studied in Drosophila melanogaster in which they arise from imaginal discs. Little is known about optic lobe and retina development in other insects, most of which do not have imaginal eye discs attached to the nervous system. For this reason, a comparative analysis of eye development in the honey bee, Apis mellifera, not only contributes to evo-devo aspects comparing the major families of holometabolous insects, but also may elucidate questions about developmental plasticity because the compound eyes of the honeybee show strong sex and caste-specific differences. Since our primary objective was to elucidate the pattern of cellular differentiation and division during eye development we performed histological and immunolabelling analyses during the postembrionic stages of development, concomitant with a realtime analysis of roughest gene expression. For the immunolabelling experiments we used an anti-phospho-histone H3 antibody that labels cells in M phase. We analyzed eye development in worker larvae starting with the third instar until white, pink and browneyed pupae, paying special attention to the fifth instar which was subdivided into feeding phase (L5F), cocoon spinning phase (L5S) and prepupae (PP). Optic Lobe development in Apis mellifera occurs by neuroepithelial folding initiating from a differentiation center, in the larval brain. This center sequentially produces the neural layers of the optic lobe (medulla, lobula and lamina). Development of the lamina, which is the last layer to be formed, takes more time and happens in two steps before metamorphosis. The first step is emergence at the beginning of the fifth larval instar coinciding with the first peak of roughest gene expression. The second step 8 occurs during the cocoon spinning phase and is marked by its inner differentiation, again accompanied by a second peak of roughest expression. During this second peak of roughest expression the rabdomers in the retina become visible. These, however, cplete thir development only during the pupal stage. The development of the lamina, lobula and medulla is not complete until after metamorphosis, even though these optic lobe structures are structurally defined already at the beginning of the pupal phase. Retinal development in this phase is marked by gradual pigmentation, axonal bundle shortening and rabdomer elongation, which reach their final size just prior to emergence of the bees from their brood cells.
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Antonio, David Santos Marco. "Processos Celulares e Moleculares no Desenvolvimento do Sistema Visual em Operárias e Zangões de Apis mellifera." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/17/17135/tde-22042013-103859/.
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Mecanismos que regem o desenvolvimento do olho composto e lóbulo óptico tem sido amplamente estudados em Drosophila melanogaster onde a retina é formada a partir de um disco imaginal anexado com o cérebro e os lóbulos opticos a partir do primórdio óptico externo. Através de histologia comparativa e análise de expressão gênica no desenvolvimento do sistema visual em Apis mellifera nós procuramos elucidar questões sobre plasticidade do desenvolvimento subjacente a fortes diferenças sexo- e casta-específico no olho assim como contribuir com aspectos evo-devo. O desenvolvimento dos lóbulos ópticos ocorre por dobramento neuroepitelial a partir de um centro de diferenciação no cérebro larval. Deste centro, a medula, lamina e lóbula surgem ao mesmo tempo em operárias e zangões. Dois passos marcam a diferenciação da lâmina (i) sua origem a partir da diferenciação de neuroblastos da camada mais externa da medula, isso coincidindo com o primeiro pico de expressão de roughest, e (ii) 24 horas mais tarde o aparecimento dos omatideos hexagonais coincidindo com o segundo pico de expressão de roughest. Com a inclusão de genes candidatos relacionados com o desenvolvimento do olho e lóbulos ópticos em insetos [small optic lobe (sol), eyes absent (eya), minibrain (mnb), sine oculis (so), embryonic lethal, abnormal vision (elav) e epidermal growth factor receptor (egfr)] nós encontramos distintos picos de expressão para sol, eya, mnb e so em níveis de transcritos e tempo de aparição do pico diferindo entre operárias e zangões. Enquanto estes quatro genes mostraram relativa sincronia durante o desenvolvimento em zangões, o mesmo não ocorreu em operárias. Além disso, em operárias sol é muito mais expresso na pré-pupa do que em zangões. Ambos os sexo mostraram padrões muito similares de expressão de elav, exceto por um atraso em zangões. Em contraste, a expressão de egfr ocorre antes em zangões. Durante a phase chave no desenvolvimento do sistema visual, uma análise global do transcriptoma, por meio de micro-arranjos mostrou vários genes relacionados com ciclo celular entre os diferencialmente expressos. Em conclusão, a relação entre tempo e eventos morfológicos com os padrões de expressão gênica revelou diferenças possivelmente relacionadas com mecanismos subjacentes ao desenvolvimento do sistema visual altamente dimorfico de Apis mellifera.Developmental mechanisms governing compound eye development in insects have been broadly studied in Drosophila melanogaster, where the retina is formed from an imaginal disc attached to the larval brain. However little is known about eye development in other insects, most of which do not have such imaginal eye discs. Through a comparative histological and gene expression analysis of eye development in the honey bee, Apis mellifera, we intended to elucidate questions about developmental plasticity underlying the marked sex and castespecific differences in eye size, as well as to contribute to evo-devo aspects. Optic lobe development occurs by neuroepithelial folding initiating from a differentiation center in the larval brain. From this center, the medula, lamina and lobula arise at the same time in drones and workers. Two steps mark the differentiation of the lamina (i) its origin from neuroblasts differentiating in the outer layer of the medula, this coinciding with the first peak of roughest expression during the feeding stage of the fifth larval instar, and (ii) 24 hours later, the appearance of hexagonal ommatidia, coinciding with a second peak in roughest expression. Upon including further candidate genes related to insect eye development [small optic lobe (sol), eyes absent (eya), minibrain (mnb), sine oculis (so), embryonic lethal, abnormal vision (elav) and epidermal growth factor receptor (egfr)] we found distinct expression peaks for sol, eya, mnb and so, with timing and relative transcript levels differing between drones and workers. Whereas these four genes showed a relatively synchronous pattern of expression in drones in the fifth larval instar, this was not so in workers. Furthermore, in prepupae sol was higher expressed in workers than the other three genes, and also in comparison to drones. Both sexes showed a strikingly similar expression pattern for elav, except for some delay in drones. In contrast, egfr expression was found to occur earlier in drones. Through a global transcriptom analysis, done at a key step of larval development, several genes were reveled as diffetentially expressed, many of these regulating cell cycle steps. In conclusion, the relationship in the timing of morphological events with gene expression patterns revealed differences possibly related to mechanisms underlying development of the highly dimorphic compound eye in the honey bee.
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Tavakoli, Aydin. "Cadherin involvement in axonal branch stability in the Xenopus retinotectal system." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=112312.
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Retinal ganglion cell (RGC) axon arbors within the optic tectum are refined in development through a dynamic process of activity-dependent remodeling. The synaptic adhesion molecule N-cadherin is a candidate for mediating selective stabilization and elaboration of RGC axons due to its localization to perisynaptic sites and its modifiability by neural activity. RGCs of Xenopus tadpoles were co-transfected with plasmids encoding a dominant negative N-cadherin (N-cadDeltaE) and eGFP or eYFP. Using two-photon in vivo time-lapse imaging, we found that axons expressing N-cadDeltaE became less elaborate than controls over three days of daily live imaging. Shorter interval time-lapse imaging of axons expressing synaptophysin-GFP to visualize putative synaptic sites revealed that N-cadDeltaE expressing axons form fewer stable branches than controls and that stabilization of axonal branches at synaptic sites is altered. We conclude that N-cadherin participates in the stabilization of axonal branches in the Xenopus retinotectal system.
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Hjartarson, Örn. "Separation of lobes in Multispectral Digital Holography." Thesis, Umeå universitet, Institutionen för fysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-64314.
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Through a holographic recording a property from the third dimension, the depth, is obtained in the form of a phase map of the incident light. One wavelength holography will have a unique phase for the depth range corresponding to the wavelength of the light and outside this range the real depth can not be resolved. By introducing more wavelengths to the measurement the unique phase combination of the waves will have a wider range and larger objects can be resolved. Up to six wavelengths can be simultaneous recorded by making them occupy different spatial frequencies. A set of spatial frequencies together describing a property of the wave is referred to as a lobe. For more than 6 wavelengths and a larger depth range produced by a more seldom repeated unique phase combination the individual waves will occupy the same frequencies, i.e. the lobes overlap. The separation of overlapping lobes is essential in order to make precise and time independent measurements of large and/or moving objects. To separate the lobes the complex fields, i.e. the phases together with the amplitudes, were simulated to propagate a distance and again recorded. The propagation leads to a phase shift of the spatial frequencies which reveals the complex fields in the case of two overlapping wavelengths. For three overlapping wavelengths the resolution, i.e spatial frequencies describing the object, has to be reduced in order to determine the individual complex fields. Since the propagation is a linear transformation for the frequencies that do not overlap, only the overlapping elements whose propagation is nonlinear produce new information. The new information gained is therefore independent of the number of wavelengths used which limits the exact determination of the fields to two wavelengths. Through the holographic recording another property of the complex field is obtained which is the superimposed individual intensities. This bounds the complex fields to certain values, i.e. restricts the possible amplitude of the waves. The recording in the two planes produces two intensity distributions which both must be satisfied by the complex fields. The optimization model for this was formulated and a simple optimization algorithm was implemented. Instead of an equality constraint of the intensities the inequality constraint was implemented, mainly due to that the optimization process was out of the scope of the thesis and the inequality constraint resulted in a simple implementation. The result pointed out important properties even though the optimization could not separate the fields satisfactorily for more than three wavelengths. The inequality constraint contains enough information to solve the case of three overlapping wavelengths.
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Vogt, Katrin [Verfasser], and Mark [Akademischer Betreuer] Hübener. "A new circuit for visual memory formation : from the optic lobes to the mushroom bodies of Drosophila / Katrin Vogt. Betreuer: Mark Hübener." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2014. http://d-nb.info/1078224528/34.
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Dieulangard, Anthony. "Nouvelles configurations d'interaction pour l'optimisation conjointe des performances des composants acouto-optiques." Thesis, Valenciennes, 2014. http://www.theses.fr/2014VALE0027/document.
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Une description des différentes configurations d’interaction ayant lieu dans les matériaux usuellement employés dans le domaine acousto-optique est proposée. Un exemple d’application illustre les caractéristiques déterminantes propres à chaque fonction que permet l’interaction acousto-optique, à savoir la modulation, la déviation, le décalage en fréquence et le filtrage d’un faisceau optique. Cette thèse est plus particulièrement consacrée aux interactions acousto-optiques anisotropes dans le cristal de Paratellurite, matériau majoritairement employé pour les applications de déflexion et de filtrage de par ses qualités photo-élastiques remarquables et son large domaine de transparence optique. Ces propriétés optiques, acoustiques et acousto-optiques sont décrites en détail. Nous nous intéressons plus particulièrement aux caractéristiques de l’interaction NPM (Narrow Phase Mismatch) et TPM (Tangent Phase Mismatch), respectivement employées pour le filtrage et la déflexion. Ceci nous conduit à l’étude de la bande passante spectrale d’un déflecteur et de sa potentielle application en tant que réseau de diffraction à bande passante et périodicité spatiale modulable. Ensuite nous proposons la mise en cascade d’un déflecteur et d’un filtre dans le but de concevoir un décaleur de fréquence variable à faible décalage. Enfin, nous proposons une configuration originale pour répondre aux contraintes d’utilisation rencontrées avec l’interaction NPM pour les applications de filtrage. La conception et la réalisation d’un composant multiélectrodes à interaction double est alors présentée dans la gamme spectrale [400; 650 nm]. La configuration proposée permet à la fois de réduire de 50% l’intensité des lobes secondaires tout en homogénéisant la bande passante optique du filtre sur sa bande spectrale de travailThe different configurations of acousto-optic interactions taking place in usual employed materials are presented. For each function (modulation, deflection, shifting and filtering), an exemple of application highlights the decisive characteristics of the component. This thesis is particularly devoted to the anisotropic interactions occuring in Paratellurite crystal. Such material is widely used for filtering and deflection applications due to its high figure of merit and also for its large optical transparency domain, from Ultra-Violet to Infra-Red. Optical, acoustical and acoustooptical properties of Paratellurite cristal are detailed. More precisely, we are interested in anisotropic interactions, in particular NPM (Narrow Phase Mismatch) and TPM (Tangent Phase Mismatch), respectively employed for Acousto-Optic Tunable Filters (AOTF) and Acousto-Optic Deflectors (AOD). This leads to the study of the optical bandwidth of a deflector with a potential application as a tunable transmissive grating beam splitter for multiple laser line separation. Then, we propose to cascade an AOTF with an AOD in order to get a wide bandwidth tunable optical low frequency shifter. Finally, we present the design and fabrication of a multi-transducer component based on dual anisotropic interaction in the visble spectral range, from 400 to 650 nm. A significative reduction of sides lobes is observed (-50%) with an homogenisation of the optical bandwidth of the filter on its spectral working range
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Haddad, Hassan. "Techniques de contrôle de la réflexion d’une onde plane à l’aide de l’optique de transformation et la modulation d’impédance de surface - application à l’aplatissement du réflecteur rétro-directif." Thesis, Rennes, INSA, 2018. http://www.theses.fr/2018ISAR0025/document.
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Ces dernières années, un intérêt croissant est porté aux réflecteurs rétro-directifs aplatis dans le but de remplacer le réflecteur diédrique conventionnel, trop encombrant pour de nombreuses applications. Dans un premier temps, cette thèse étudie deux techniques différentes permettant de réduire l’épaisseur d’un réflecteur diédrique. L’Optique de transformation modifie la constitution matérielle de son volume intérieur alors que la modulation d’impédance de surface introduit une distribution d’impédance à sa surface. On examine également la possibilité de combiner ces deux techniques pour tirer le meilleur parti de chacune d’elle. La deuxième partie de cette thèse étudie l’origine des réflexions parasites pour les panneaux utilisant la modulation d’impédance de surface et propose de nouvelles règles de conception pour atténuer leurs niveaux. Finalement, une mise en oeuvre pratique est proposée pour une modulation d'impédance de surface généralisée qui utilise des impédances complexes et surpasse les performances de la modulation d’impédance classiqueIn recent years, increasing interest incompact reflectors with retrodirective response is perceived since the conventional dihedral reflector is too bulky to be integrated within most applications. First, this thesis investigates two different techniques that might lead to lower profiles of the dihedral reflector. It explores the use of Transformation Optics that modifies the filling volume of such a device and Surface Impedance Modulation that introduces an impedance distribution over its surface. It also inspects the possibility of combining those two techniques to take benefit of their complementary advantages. The second part of this thesis investigates the source of parasitic lobes for surface impedance modulated panels and proposes new design rules to mitigate their levels. Finally, it also proposes a practical implementation for a specific setting of the generalized surface impedance modulation that makes use of complex impedances and outperforms a panel implementing the classical modulation
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Chollet, Franck. "RÉALISATION D'UN FILTRE SPECTRAL ACCORDABLE ÉTROIT À 1.55 μm EN OPTIQUE INTÉGRÉE SUR NIOBATE DE LITHIUM. ÉTUDE DES LIMITATIONS IMPOSÉES PAR LA TECHNOLOGIE." Phd thesis, Université de Franche-Comté, 1995. http://tel.archives-ouvertes.fr/tel-00724359.
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L'augmentation exponentielle de la quantité d'information à transmettre afin d'assurer les télécommunications futures amène à rechercher de nouvelles voies pour faire face à ces nouveaux besoins. L'optique peut, pour suppléer aux systèmes électroniques essoufflés, répondre à ces défis naissant en autorisant le multiplexage en longueur d'onde (WDM). Celui ci permet non seulement d'accroître fortement le débit en ligne (ici une fibre optique), mais autorise l'existence de réseaux dont les fonctions sont assurées par voie optique. L'implantation de ces nouvelles architectures repose sur des composants clefs comme le filtre spectral accordable. Cette thèse a concerné l'étude théorique, la conception, la réalisation pratique et les perspectives d'application et d'amélioration d'un filtre accordable étroit intégré sur niobate de lithium et fonctionnant à une longueur d'onde proche de 1.55 μm. Nous avons tout d'abord comparé différents principes de filtre accordable intégré et avons retenu un dispositif fonctionnant entièrement par effet électrooptique qui présentait une vitesse de commutation élevée. Son fonctionnement est similaire à celui du filtre biréfringent de Šolc qui est constitué d'un convertisseur de polarisation sélectif en longueur d'onde placé entre polariseurs croisés. En approfondissant l'étude de la propagation de la lumière dans le filtre nous montrons que les irrégularités que présente la transmittance en intensité du dispositif sont dues à l'existence de variations anormales de la différence d'indice de phase dans le guide d'onde diffusé. Ces variations peuvent être reliées à des défauts dans le procédé de fabrication. Cette constatation nous amène à faire une étude théorique complète des effets de différents types de défauts dont on retrouve expérimentalement la trace sur le filtrage. Poussés par ces simulations, nous étudions en détail les différentes étapes du procédé technologique d'intégration sur niobate de lithium et en proposons des améliorations afin d'atteindre expérimentalement les caractéristiques théoriques du filtre. Finalement nous présentons des applications du filtre (laser à fibre accordable et modulable) et discutons de ses perspectives de développement (insensibilité à la polarisation).
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Clamens-Nanni, Frédéric. "Regarder son amour se défaire devant soi : Le roman de la fin du couple selon Jean-Philippe Toussaint, Christian Oster et Jacques Serena." Thesis, Université Clermont Auvergne (2017-2020), 2020. http://www.theses.fr/2020CLFAL009.
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Bien qu’ils n’aient pas à proprement parler un air de famille, Toussaint, Oster et Serena écrivent des romans de la fin du couple qui rendent compte d’un « travail du négatif », trait saillant du roman minuitard depuis les années 1980 selon Fabien Gris. Ces fictions se polarisent désormais plus sur la séparation que sur la rencontre. Elles se donnent comme autant de modulations d’une situation que l’on peut, en paraphrasant Toussaint, caractériser par cette formule : regarder son amour se défaire devant soi. C’est sous les yeux du narrateur que la fin du couple s’accomplit, donc selon sa perspective, son optique. Cette thèse analyse la disjonction des personnages au fil d’un itinéraire visuel en trois étapes. La première montre comment ces récits nient la formule rituelle Leurs yeux se rencontrèrent, infléchissant alors le roman sentimental et ses topoï. Il n’est plus de première vue décisive pour sceller la destinée du couple. Le face à face bascule vers un face à dos, objet de la deuxième étape. Le dos y est envisagé à travers le pivotement qu’il exécute et comme motif à la croisée des arts visuels et du roman. Il s’impose dans le champ de vision du spectateur à qui il oppose une fin de non-recevoir. Après le pivotement, la femme de dos s’éloigne puis disparaît. La troisième étape se construit autour du vide laissé par celle qui s’en est allée et qui occupe une zone aveugle. Toujours en position de spectateur, le narrateur se figure son absence. Telle est l’ultime étape de cet itinéraire visuel : le blanc devant lui devient écran de projection sur lequel défilent les images d’une vie qui se déroule dorénavant sans lui. Le blanc se fait appel du vide, vide vertigineux, gouffre, ou surface réfléchissant sa propre vacuité quand il se retrouve seul avec lui-mêmeDespite their obvious differences, the novels written by Toussaint, Oster and Serena narrate the end of the love story, with a particular emphasis on negativity – which, according to Fabien Gris, constitutes a defining feature of the Minuit novels since the 1980s. These works of fiction focus more on the breakup than on the first time the lovers met. They describe a series of situations that one could classify with this phrase, borrowed from Jean-Philippe Toussaint: “Watching as your love story unravels before your eyes.” The end of the relationship happens right before the eyes of the narrator, and is portrayed according to his perspective, his viewpoint. This dissertation analyzes the separation of the characters according to three visual steps. The first step shows how those novels undo the traditional formula “when their eyes met” (Jean Rousset), and differ from the pattern of the sentimental novel and its topoi. There is no decisive first encounter anymore that determines the destiny of the couple. There is no more face-to-face for the characters, but rather a “face-to-back”, which is the object of the second chapter. The back is studied as both a symbol of the loved one turning around and as a motif situated at the crossing between visual arts and writing. For the spectator, the back symbolizes a final refusal. After she turns around, the loved woman walks away and then disappears. The third step of the argument focuses on the void she leaves behind as she moves on, a blind spot. Left in the position of a spectator, the narrator has to picture her absence. This is the final stage of this visual itinerary: the emptiness before him turns into a projection screen on which pictures of a life are shown, pictures now happening without him. This white page stands in for a void, a vacuity, an abyss – and also a white canvas reflecting the emptiness in the narrator’s life
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Fabian, Joseph Mahandas. "A Neurobiological Investigation of Visual Target Detection and the Optic Lobe of Dragonflies." Thesis, 2017. http://hdl.handle.net/2440/122257.
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For many decades the insect nervous system has provided novel insights into the mechanisms of visual processing. Despite commonly being labelled as ‘simple’, recent evidence suggests that some insects have remarkably complex brains. Guided by a brain the size of a poppy seed, dragonflies detect and pursue prey amongst cluttered backgrounds with high success rates (Olberg et al. 2000; Combes et al. 2013). These pursuits are not simple reactionary processes, instead the brain uses internal models and selective attention to maximise performance in challenging conditions (Wiederman and O’Carroll 2013; Mischiati et al. 2015). However until now we have no detailed and up-to-date description of how the dragonfly optic lobe is organised, and little understanding of the strategies optic lobe neurons use to detect and track visual features. My initial work describes the morphology and organisation of the dragonfly optic lobe, the most complex optic lobe of any insect studied to date. I demonstrate that in contrast to recent reports, the dragonfly lobula complex differs substantially from its dipteran counterparts. Furthermore, both the second and third optic ganglia contain approximately twice as many synaptic layers as any other insect. Next I performed a series of electrophysiological experiments that investigated the effects of target trajectory on the responses of target-detecting neurons. A small feature drifting across the retina generates a weak and variable signal. For this reason the human brain has adopted a strategy where target movement is integrated across a trajectory in a predictive manner, improving signal strength while ignoring distractors (Watamaniuk et al. 1995). I demonstrate that a facilitation mechanism modulates gain across the receptive field of target-detecting neurons, maximising responses to targets presented at a predicted location and suppressing responses to targets elsewhere. This modulation of gain results in large improvements in local contrast sensitivity, and also induces strong direction selectivity that matches the direction of stimuli in the recent past. I then investigated how different parameters of a targets trajectory affect the intensity and spatial spread of gain modulation. Targets of differing velocity, contrast, size, duration and trajectory length were drifted through the receptive field, before quantifying the strength of gain modulation. I show that gain modulation is gated by target contrast, and that the magnitude of modulation is dependent on complex interactions between the parameters of a primers trajectory and the probe that follows. Finally, I investigated whether this gain modulation was a mechanism underlying the selective attention previously reported in target-detecting neurons (Wiederman and O’Carroll 2013). When presented with two targets simultaneously, target-detecting neurons select and respond to one, and ignore the presence of the other. With the use of a novel frequency-tagging stimulus, I demonstrated that when presented with two competing targets, both the selected and unselected target trajectories induced an increase in gain ahead of their path. This result suggests that predictive gain modulation is not a mechanism of selective attention, but a parallel processing strategy that acts to improve signal strength in challenging conditions. Finally, I characterised the physiological responses of a population of neurons sensitive to the movement of larger features or patterns. Controlling flight at highspeed would benefit from the detection of low frequency patterns in the environment. We show that bar-sensitive neurons in the dragonfly lobula complex have highly abnormal responses to stimulus velocity. Our data describes the diverse physiological properties of these neurons, including their tuning for motion direction, height, width and velocity, and their sensitivity to contrast of different polarities. Together, my thesis provides a significant contribution to our knowledge of the visual system of dragonflies. In a broader sense, these findings build our understanding of the structure and function of nervous systems, and the strategies implemented to efficiently solve challenging sensory tasks such as small target detection.Thesis (Ph.D.) -- University of Adelaide, Adelaide Medical School, 2017
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Liu, Tsung-Han, and 劉璁翰. "Neural organization of the optic lobe for controlling body patterns in oval squids Sepioteuthis lessoniana." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/k2x2re.
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博士國立清華大學
分子醫學研究所
105
Cephalopods have highly dynamic skin coloration changes that allow rapid camouflage and intraspecies communication. The optic lobe is thought to play a key role in controlling the expression of the chromatophores that give rise to their diverse body patterns. However, the functional organization of the optic lobe and neural control of the various body patterns by the optic lobe are largely unknown. We applied electrical stimulation within the optic lobe to investigate the neural basis of body patterning in the oval squid, Sepioteuthis lessoniana. Most areas in the optic lobe mediated predominately ipsilateral expression of chromatophores present on the mantle, but not on the head and arms; furthermore, the expanded areas after electrical stimulation were positively correlated with an increase in stimulating voltage and stimulation depth. These results suggest a unilaterally dominant and vertically converged organization of the optic lobe. Furthermore, analyzing 14 of the elicited body pattern components and their corresponding stimulation sites revealed that the same components can be elicited by stimulating different parts of the optic lobe and that various subsets of these components can be coactivated by stimulating the same area. These findings suggest that many body pattern components may have multiple motor units in the optic lobe and that these are organized in a mosaic manner. The multiplicity associated with the nature of the neural controls of these components in the cephalopod brain thus reflects the versatility of the individual components during the generation of diverse body patterns.
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Striemer, Christopher. "ATTENTION AND THE PARIETAL CORTEX: INVESTIGATIONS OF SPATIAL NEGLECT, OPTIC ATAXIA, AND THE INFLUENCE OF PRISM ADAPTATION ON ATTENTION." Thesis, 2008. http://hdl.handle.net/10012/3618.
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Some authors have argued that the primary function of the posterior parietal cortex is to control visual attention and awareness, whereas others have argued that the posterior parietal cortex is specialized for controlling actions. The purpose of the present thesis was to examine the influence of prism adaptation – a visuomotor adaptation technique – on visual attention deficits in patients with lesions of parietal cortex. Lesions to dorsal regions of the posterior parietal cortex lead to optic ataxia – a disorder in which visually guided reaching is disrupted. In contrast lesions to ventral (i.e. inferior) regions of the posterior parietal cortex of the right hemisphere lead to spatial neglect – a disorder in which patients are unaware of people or objects in contralesional (left) space. Chapter 1 presents an overview of the organization of the posterior parietal cortex, as well as an introduction to the disorders of spatial neglect and optic ataxia and the use of prism adaptation as a treatment for spatial neglect. Chapter 2 examined the influence of prism adaptation on attentional deficits in patients with right brain damage. Results demonstrated that prism adaptation reduced both the disengage deficit and the rightward attentional bias, two of the classic attentional deficits in neglect. Chapter 3 investigated the role of the dorsal posterior parietal cortex in controlling both reflexive and voluntary attention in two patients with optic ataxia. Lesions to the dorsal posterior parietal cortex led to both a disengage deficit and a rightward attentional bias, similar to patients with neglect, even though neither of the patients had any clinical symptoms of neglect. Contrary to previous work these results indicated that dorsal portions of the posterior parietal cortex – a region not commonly damaged in neglect – are important for controlling the orienting and reorienting of both reflexive and voluntary attention. Furthermore, these results indicated that optic ataxia is not purely a visuomotor disorder that is independent of any perceptual or attentional deficits as was previously assumed. Based on the results of Chapters 2 and 3 it was hypothesized that the beneficial effects of prism adaptation on attention may operate via the superior parietal lobe, a region which is typically undamaged in neglect, and is known to be important for controlling attention and action. Chapter 4 provided support for this hypothesis by demonstrating that a patient with lesions to the superior parietal lobe, who had the same attentional deficits as the right brain damaged patients tested in Chapter 2, failed to demonstrate any beneficial effects of prism adaptation on his attentional performance. Specifically, prism adaptation had no influence on his disengage deficit or his rightward attentional bias. Therefore, these data provide direct evidence that the beneficial effects of prisms on attention rely, at least in part, on the superior parietal lobe. Finally, Chapter 5 concludes with a summary of the research findings from the present thesis, and puts forward a new theory to conceptualize the mechanisms underlying the beneficial effects of prisms in patients with neglect.
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Ramos, Traslosheros Lopez Luis Giordano. "Receptive field organization of motion computation in the fly: a study of cell types and their variability." Doctoral thesis, 2019. http://hdl.handle.net/21.11130/00-1735-0000-0005-1507-C.
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Kamei, Makoto. "Molecular characterization of homologues of Drosophila melanogaster small optic lobes gene." Phd thesis, 2001. http://hdl.handle.net/1885/148093.
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Alves, Carolina dos Santos. "Regenerative neurogenesis in Drosophila melanogaster: The influence of age and activity in the adult brain." Master's thesis, 2017. http://hdl.handle.net/10400.12/6406.
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Dissertação de Mestrado apresentada no ISPA - Instituto Universitário para obtenção de grau de Mestre na especialidade em Neurociências Cognitivas e Comportamentais.Sendo o Encéfalo um dos órgãos mais importantes do organismo, a descoberta de que o processo de neurogénese continuava presente durante a fase adulta do animal foi uma das grandes revelações científcas da última metade do século XX. Assim, uma das vantagens na investigação deste processo: Neurogénese Adulta, é a sua aplicação em diversos organismos, que posteriormente possibilitará uma compreensão mais completa e aprofundada do mesmo. A Drosophila melanogaster foi recentemente apresentada como um óptimo modelo de estudo devido à sua acessibilidade genética e grande capacidade neuroregenerativa após lesão, contribuindo para o acesso a aspectos até então inexplorados. O objectivo principal deste trabalho foi o estudo da regulação do processo de Neurogénese regenerativa com foco na acção de dois factores: a Idade e a Actividade. Tal foi possível através da aplicação de um sistema de sensível de “lineage tracing”, o qual permite a visualização e quantificação de neurónios recentemente produzidos após uma lesão. Nos resultados obtidos, destacou-se a evidência de que o envelhecimento não promove uma diminuição na capacidade regenerativa no cérebro adulto da mosca, e persiste num nível constante até às 6 semanas de idade, o é próximo da vida inteira. Diferentes protocolos foram realizados para estudar o efeito da actividade física na neurogénese regenerativa. As experiências optimizadas ainda estão a decorrer e não poderam ser concluídas, porém dados preliminares indicam, que as moscas que têm um maior espaço envolvente anteriormente à lesão podem regenerar mais facilmente comparado com moscas que estão confinadas num espaço reduzido. No futuro, será importante será importante investigar quais os genes que regulam a ativação de células progenitoras neurais adultas induzida através de lesão, e ainda quais os fatores que controlam a diferenciação neuronal para obter uma compreensão mais detalhada de como a idade e a atividade influenciam a regeneração no cérebro adulto.
Being the brain one of the most important organs, the discovery that neurogenesis was continuous even in the adult phases was one of the great scientific revelations of the last century. The research of adult neurogenesis in several model systems will allow a better and complete understanding of this process. Drosophila melanogaster has been proposed as a novel model due to its genetic accessibility and its ability to regenerate neurons after injury, thereby opening the way to unexplored aspects. The main goal of the present project was to study the regulation of regenerative neurogenesis with respect to Age and Activity. This was achieved by applying sensitive lineage tracing, which allowed the visualization and quantification of the newly generated neurons upon injury. The observed results demonstrate that the regenerative capacity in adult fly brains does not decrease with age and persists on a constant level up to 6 weeks of age, which is close to the entire life span. Different paradigms were tested to study the effect of physical activity on regenerative neurogenesis. Experiments with the optimized set-up are still ongoing and could not be concluded, but preliminary data indicates, that flies that could move in a large compartment before injury may regenerate more favorably compared to flies that were kept in a more confined space. In the future, it will be important to gain further insight into which genes regulate injury-induced activation of adult neural progenitor cells and which factors control neuronal differentiation to gain a more detailed understanding of how age and activity impinge on regeneration.
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LIN, HSIAO-CHUN, and 林校群. "The patterns of chromatic information processing in the optic lobes of the honeybee, Apis mellifera." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/85182600688147349672.
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碩士國立中興大學
昆蟲學系
91
Honeybee, Apis mellifera L., is one of a few animals which have color vision proven by behavioral tests. Previous studies on honeybee color vision emphasized the relationship between spectral sensitivities of photoreceptors and color discrimination behavior; however, the knowledge about neural mechanisms of color vision is known limitedly so far. This study investigated the patterns of chromatic information processing of visual neurons in the lobula of honeybee, using intracellular recording and three light emitting diodes, whose emitting spectra approximately match the spectral sensitivity peaks of honeybee, as light stimuli source. The recorded visual neurons can be divided into non-color opponent cells group and color opponent cells group. In non-color opponent cells group, six response patterns of broad band neurons and four response patterns of narrow band neurons were recorded, the former might detect brightness of the environment or function as chromatic input channel, the later might supply for specific chromatic input. In color opponent cells group, color opponency is a principal mechanism of color vision, and eight response patterns of color opponent cells were recorded. Thus it can be seen that color vision of honeybee might possess multi-function color coding neurons, and color opponency is still the main neural mechanism in color coding.
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Liu, Yung-Chieh, and 劉永傑. "Comparison of morphological features of the optic lobes in the cuttlefish, oval squid, and giant squid." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/253te5.
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Sen, Aditya [Verfasser]. "Optomotor-blind and the horizontal and vertical system cells of the Drosophila optic lobes : molecular and laser ablation studies / vorgelegt von Aditya Sen." 2006. http://d-nb.info/979007488/34.
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