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Artykuły w czasopismach na temat "Primary Visual Cortex (area V1)"
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Beltramo, Riccardo, i Massimo Scanziani. "A collicular visual cortex: Neocortical space for an ancient midbrain visual structure". Science 363, nr 6422 (3.01.2019): 64–69. http://dx.doi.org/10.1126/science.aau7052.
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Visual responses in the cerebral cortex are believed to rely on the geniculate input to the primary visual cortex (V1). Indeed, V1 lesions substantially reduce visual responses throughout the cortex. Visual information enters the cortex also through the superior colliculus (SC), but the function of this input on visual responses in the cortex is less clear. SC lesions affect cortical visual responses less than V1 lesions, and no visual cortical area appears to entirely rely on SC inputs. We show that visual responses in a mouse lateral visual cortical area called the postrhinal cortex are independent of V1 and are abolished upon silencing of the SC. This area outperforms V1 in discriminating moving objects. We thus identify a collicular primary visual cortex that is independent of the geniculo-cortical pathway and is capable of motion discrimination.
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Watanabe, Takeo, Yuka Sasaki, Satoru Miyauchi, Benno Putz, Norio Fujimaki, Matthew Nielsen, Ryosuke Takino i Satoshi Miyakawa. "Attention-Regulated Activity in Human Primary Visual Cortex". Journal of Neurophysiology 79, nr 4 (1.04.1998): 2218–21. http://dx.doi.org/10.1152/jn.1998.79.4.2218.
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Watanabe, Takeo, Yuka Sasaki, Satoru Miyauchi, Benno Putz, Norio Fujimaki, Matthew Nielsen, Ryosuke Takino, and Satoshi Miyakawa. Attention-regulated activity in human primary visual cortex. J. Neurophysiol. 79: 2218–2221, 1998. Effects of attention to a local contour of a moving object on the activation of human primary visual cortex (area V1) were examined. Local cerebral oxygenation changes (an index of neuronal activity) in human area V1 were measured with functional magnetic resonance imaging (fMRI) in conditions including the following two: 1) when attention was selectively directed toward one side of a moving wedge (the attention condition) and 2) when the wedges were viewed passively (the passive condition). Activation in area V1 was found to be higher in the attention condition than in the passive condition. To our knowledge, this is the first finding that attention to motion activates as early as area V1. We suggest that attentional activation of area V1 is task dependent.
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Froudarakis, Emmanouil, Paul G. Fahey, Jacob Reimer, Stelios M. Smirnakis, Edward J. Tehovnik i Andreas S. Tolias. "The Visual Cortex in Context". Annual Review of Vision Science 5, nr 1 (15.09.2019): 317–39. http://dx.doi.org/10.1146/annurev-vision-091517-034407.
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In this article, we review the anatomical inputs and outputs to the mouse primary visual cortex, area V1. Our survey of data from the Allen Institute Mouse Connectivity project indicates that mouse V1 is highly interconnected with both cortical and subcortical brain areas. This pattern of innervation allows for computations that depend on the state of the animal and on behavioral goals, which contrasts with simple feedforward, hierarchical models of visual processing. Thus, to have an accurate description of the function of V1 during mouse behavior, its involvement with the rest of the brain circuitry has to be considered. Finally, it remains an open question whether the primary visual cortex of higher mammals displays the same degree of sensorimotor integration in the early visual system.
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White, Brian J., Janis Y. Kan, Ron Levy, Laurent Itti i Douglas P. Munoz. "Superior colliculus encodes visual saliency before the primary visual cortex". Proceedings of the National Academy of Sciences 114, nr 35 (14.08.2017): 9451–56. http://dx.doi.org/10.1073/pnas.1701003114.
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Models of visual attention postulate the existence of a bottom-up saliency map that is formed early in the visual processing stream. Although studies have reported evidence of a saliency map in various cortical brain areas, determining the contribution of phylogenetically older pathways is crucial to understanding its origin. Here, we compared saliency coding from neurons in two early gateways into the visual system: the primary visual cortex (V1) and the evolutionarily older superior colliculus (SC). We found that, while the response latency to visual stimulus onset was earlier for V1 neurons than superior colliculus superficial visual-layer neurons (SCs), the saliency representation emerged earlier in SCs than in V1. Because the dominant input to the SCs arises from V1, these relative timings are consistent with the hypothesis that SCs neurons pool the inputs from multiple V1 neurons to form a feature-agnostic saliency map, which may then be relayed to other brain areas.
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Seydell-Greenwald, Anna, Xiaoying Wang, Elissa L. Newport, Yanchao Bi i Ella Striem-Amit. "Spoken language processing activates the primary visual cortex". PLOS ONE 18, nr 8 (11.08.2023): e0289671. http://dx.doi.org/10.1371/journal.pone.0289671.
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Primary visual cortex (V1) is generally thought of as a low-level sensory area that primarily processes basic visual features. Although there is evidence for multisensory effects on its activity, these are typically found for the processing of simple sounds and their properties, for example spatially or temporally-congruent simple sounds. However, in congenitally blind individuals, V1 is involved in language processing, with no evidence of major changes in anatomical connectivity that could explain this seemingly drastic functional change. This is at odds with current accounts of neural plasticity, which emphasize the role of connectivity and conserved function in determining a neural tissue’s role even after atypical early experiences. To reconcile what appears to be unprecedented functional reorganization with known accounts of plasticity limitations, we tested whether V1’s multisensory roles include responses to spoken language in sighted individuals. Using fMRI, we found that V1 in normally sighted individuals was indeed activated by comprehensible spoken sentences as compared to an incomprehensible reversed speech control condition, and more strongly so in the left compared to the right hemisphere. Activation in V1 for language was also significant and comparable for abstract and concrete words, suggesting it was not driven by visual imagery. Last, this activation did not stem from increased attention to the auditory onset of words, nor was it correlated with attentional arousal ratings, making general attention accounts an unlikely explanation. Together these findings suggest that V1 responds to spoken language even in sighted individuals, reflecting the binding of multisensory high-level signals, potentially to predict visual input. This capability might be the basis for the strong V1 language activation observed in people born blind, re-affirming the notion that plasticity is guided by pre-existing connectivity and abilities in the typically developed brain.
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Pereira, Catia M., Marco Aurelio M. Freire, José R. Santos, Joanilson S. Guimarães, Gabriella Dias-Florencio, Sharlene Santos, Antonio Pereira i Sidarta Ribeiro. "Non-visual exploration of novel objects increases the levels of plasticity factors in the rat primary visual cortex". PeerJ 6 (23.10.2018): e5678. http://dx.doi.org/10.7717/peerj.5678.
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Background Historically, the primary sensory areas of the cerebral cortex have been exclusively associated with the processing of a single sensory modality. Yet the presence of tactile responses in the primary visual (V1) cortex has challenged this view, leading to the notion that primary sensory areas engage in cross-modal processing, and that the associated circuitry is modifiable by such activity. To explore this notion, here we assessed whether the exploration of novel objects in the dark induces the activation of plasticity markers in the V1 cortex of rats. Methods Adult rats were allowed to freely explore for 20 min a completely dark box with four novel objects of different shapes and textures. Animals were euthanized either 1 (n = 5) or 3 h (n = 5) after exploration. A control group (n = 5) was placed for 20 min in the same environment, but without the objects. Frontal sections of the brains were submitted to immunohistochemistry to measure protein levels of egr-1 and c-fos, and phosphorylated calcium-dependent kinase (pCaKMII) in V1 cortex. Results The amount of neurons labeled with monoclonal antibodies against c-fos, egr-1 or pCaKMII increased significantly in V1 cortex after one hour of exploration in the dark. Three hours after exploration, the number of labeled neurons decreased to basal levels. Conclusions Our results suggest that non-visual exploration induces the activation of immediate-early genes in V1 cortex, which is suggestive of cross-modal processing in this area. Besides, the increase in the number of neurons labeled with pCaKMII may signal a condition promoting synaptic plasticity.
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Shi, Li, Qi Ming Ye i Xiao Ke Niu. "Orientation Coding by Population of Neurons in Rats' Primary Visual Cortex". Applied Mechanics and Materials 427-429 (wrzesień 2013): 2089–93. http://dx.doi.org/10.4028/www.scientific.net/amm.427-429.2089.
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Research on Primate visual cortex (V1 area) neurons orientation coding mechanism is the base of revealing the whole visual cortex information processing mechanism. Firstly, this paper adopted different orientation grating to stimulate visually on rats. Meanwhile, gather response signals of population neurons from V1 area using multi-electrode arrays. Then, screen effective response channels according to the orientation selection of different neurons in different channels. Besides, extract Spike average fire rate and LFPγ band power feature in every effective channel signals within specific stimulus response time to construct population response joint features. Finally, taking Lasso regression model as coding model, use joint features to differentiate grating orientation, in order to research on V1 areas population neurons orientation coding. The consequences indicate that the results of population response joint features coding for six different orientation are superior to the results of any single feature of population response coding, and remarkably better than the results of single channel response feature coding.
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Andelin, Adrian K., Jaime F. Olavarria, Ione Fine, Erin N. Taber, Daniel Schwartz, Christopher D. Kroenke i Alexander A. Stevens. "The Effect of Onset Age of Visual Deprivation on Visual Cortex Surface Area Across-Species". Cerebral Cortex 29, nr 10 (18.12.2018): 4321–33. http://dx.doi.org/10.1093/cercor/bhy315.
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Abstract Blindness early in life induces permanent alterations in brain anatomy, including reduced surface area of primary visual cortex (V1). Bilateral enucleation early in development causes greater reductions in primary visual cortex surface area than at later times. However, the time at which cortical surface area expansion is no longer sensitive to enucleation is not clearly established, despite being an important milestone for cortical development. Using histological and MRI techniques, we investigated how reductions in the surface area of V1 depends on the timing of blindness onset in rats, ferrets and humans. To compare data across species, we translated ages of all species to a common neuro-developmental event-time (ET) scale. Consistently, blindness during early cortical expansion induced large (~40%) reductions in V1 surface area, in rats and ferrets, while blindness occurring later had diminishing effects. Longitudinal measurements on ferrets confirmed that early enucleation disrupted cortical expansion, rather than inducing enhanced pruning. We modeled the ET associated with the conclusion of the effect of blindness on surface area at maturity (ETc), relative to the normal conclusion of visual cortex surface area expansion, (ETdev). A final analysis combining our data with extant published data confirmed that ETc occurred well before ETdev.
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Dagnino, Bruno, Marie-Alice Gariel-Mathis i Pieter R. Roelfsema. "Microstimulation of area V4 has little effect on spatial attention and on perception of phosphenes evoked in area V1". Journal of Neurophysiology 113, nr 3 (1.02.2015): 730–39. http://dx.doi.org/10.1152/jn.00645.2014.
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Previous transcranial magnetic stimulation (TMS) studies suggested that feedback from higher to lower areas of the visual cortex is important for the access of visual information to awareness. However, the influence of cortico-cortical feedback on awareness and the nature of the feedback effects are not yet completely understood. In the present study, we used electrical microstimulation in the visual cortex of monkeys to test the hypothesis that cortico-cortical feedback plays a role in visual awareness. We investigated the interactions between the primary visual cortex (V1) and area V4 by applying microstimulation in both cortical areas at various delays. We report that the monkeys detected the phosphenes produced by V1 microstimulation but subthreshold V4 microstimulation did not influence V1 phosphene detection thresholds. A second experiment examined the influence of V4 microstimulation on the monkeys' ability to detect the dimming of one of three peripheral visual stimuli. Again, microstimulation of a group of V4 neurons failed to modulate the monkeys' perception of a stimulus in their receptive field. We conclude that conditions exist where microstimulation of area V4 has only a limited influence on visual perception.
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Jiang, Fei, Jian-Wen Fang, Yin-Quan Ye, Yan-Jin Tian, Xian-Jun Zeng i Yu-Lin Zhong. "Altered effective connectivity of primary visual cortex in primary angle closure glaucoma using Granger causality analysis". Acta Radiologica 61, nr 4 (7.08.2019): 508–19. http://dx.doi.org/10.1177/0284185119867644.
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Background Previous neuroimaging studies demonstrated that primary angle closure glaucoma patients were associated with abnormal intrinsic brain activity in primary visual cortex (V1). Purpose The purpose of this study was to investigate the effective connectivity patterns of V1 in patients with primary angle closure glaucoma. Material and Methods Thirty-seven patients with primary angle closure glaucoma (20 men, 17 women) and 36 healthy controls (20 men, 16 women) closely matched for age, sex, and education, underwent resting-state MRI scans. A voxel-wise Granger causality analysis method was performed to explore different effective connectivity pattern of V1 between the two groups. Results Compared with healthy controls, patients with primary angle closure glaucoma showed decreased effective connectivity from the left V1 to left cuneus and increased effective connectivity from the left V1 to left precentral gyrus and right supplementary motor area. Meanwhile, patients with primary angle closure glaucoma showed decreased effective connectivity from left precentral gyrus to left V1 and right frontal middle gyrus to left V1. In addition, patients with primary angle closure glaucoma showed a decreased effective connectivity from the right V1 to left cuneus/calcarine and increased effective connectivity from the right V1 to left inferior frontal gyrus and right caudate. Meanwhile, patients with primary angle closure glaucoma showed decreased effective connectivity from right middle frontal gyrus/precentral gyrus to right V1 and left precentral gyrus to right V1. Conclusion Our results highlighted that patients with primary angle closure glaucoma had abnormal effective connectivity between V1 and higher visual area, motor cortices, somatosensory cortices, and frontal lobe, which indicated that they might present with abnormal top-down modulations, visual imagery, vision-motor function, and vision-related higher cognition function.
Rozprawy doktorskie na temat "Primary Visual Cortex (area V1)"
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Thulin, Nilsson Linnea. "The Role of Primary Visual Cortex in Visual Awareness". Thesis, Högskolan i Skövde, Institutionen för biovetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-11623.
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Despite its great complexity, a great deal is known about the organization and information-processing properties of the visual system. However, the neural correlates of visual awareness are not yet understood. By studying patients with blindsight, the primary visual cortex (V1) has attracted a lot of attention recently. Although this brain area appears to be important for visual awareness, its exact role is still a matter of debate. Interactive models propose a direct role for V1 in generating visual awareness through recurrent processing. Hierarchal models instead propose that awareness is generated in later visual areas and that the role of V1 is limited to transmitting the necessary information to these areas. Interactive and hierarchical models make different predictions and the aim of this thesis is to review the evidence from lesions, perceptual suppression, and transcranial magnetic stimulation (TMS), along with data from internally generated visual awareness in dreams, hallucinations and imagery, this in order to see whether current evidence favor one type of model over the other. A review of the evidence suggests that feedback projections to V1 appear to be important in most cases for visual awareness to arise but it can arise even when V1 is absent.
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Stevens, Jean-Luc Richard. "Spatiotemporal properties of evoked neural response in the primary visual cortex". Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/31330.
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Understanding how neurons in the primary visual cortex (V1) of primates respond to visual patterns has been a major focus of research in neuroscience for many decades. Numerous different experimental techniques have been used to provide data about how the spatiotemporal patterns of light projected from the visual environment onto the retina relate to the spatiotemporal patterns of neural activity evoked in the visual cortex, across disparate spatial and temporal scales. However, despite the variety of data sources available (or perhaps because of it), there is still no unified explanation for how the circuitry in the eye, the subcortical visual pathways, and the visual cortex responds to these patterns. This thesis outlines a research project to build computational models of V1 that incorporate observations and constraints from an unprecedented range of experimental data sources, reconciling each data source with the others into a consistent proposal for the underlying circuitry and computational mechanisms. The final mechanistic model is the first one shown to be compatible with measurements of: (1) temporal firing-rate patterns in single neurons over tens of milliseconds obtained using single-unit electrophysiology, (2) spatiotemporal patterns in membrane voltages in cortical tissues spanning several square millimeters over similar time scales, obtained using voltage-sensitive-dye imaging, and (3) spatial patterns in neural activity over several square millimeters of cortex, measured over the course of weeks of early development using optical imaging of intrinsic signals. Reconciling this data was not trivial, in part because single-unit studies suggested short, transient neural responses, while population measurements suggested gradual, sustained responses. The fundamental principles of the resulting models are (a) that the spatial and temporal patterns of neural responses are determined not only by the particular properties of a visual stimulus and the internal response properties of individual neurons, but by the collective dynamics of an entire network of interconnected neurons, (b) that these dynamics account both for the fast time course of neural responses to individual stimuli, and the gradual emergence of structure in this network via activity-dependent Hebbian modifications of synaptic connections over days, and (c) the differences between single-unit and population measurements are primarily due to extensive and wide-ranging forms of diversity in neural responses, which become crucial when trying to estimate population responses out of a series of individual measurements. The final model is the first to include all the types of diversity necessary to show how realistic single-unit responses can add up to the very different population-level evoked responses measured using voltage-sensitive-dye imaging over large cortical areas. Additional contributions from this thesis include (1) a comprehensive solution for doing exploratory yet reproducible computational research, implemented as a set of open-source tools, (2) a general-purpose metric for evaluating the biological realism of model orientation maps, and (3) a demonstration that the previous developmental model that formed the basis of the models in this thesis is the only developmental model so far that produces realistic orientation maps. These analytical results, computational models, and research tools together provide a systematic approach for understanding neural responses to visual stimuli across time scales from milliseconds to weeks and spatial scales from microns to centimeters.
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Kogan, Cary. "The expression of neurofilament protein and mRNA levels in the lateral geniculate nucleus and area V1 of the developing and adult vervet monkey (Ceorcopithicus aethiops) /". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0028/MQ50807.pdf.
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FONTENELE, NETO Antonio Jorge. "Implementação de um protocolo experimental para estudo de propriedades de resposta visual de neurônios do córtex visual primário (V1) em ratos utilizando matrizes de eletrodos". Universidade Federal de Pernambuco, 2015. https://repositorio.ufpe.br/handle/123456789/17698.
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O córtex visual primário (V1) é a região do córtex cerebral responsável pela primeira etapa de processamento da informação visual capturada pela retina. Por ser uma das áreas corticais melhor compreendidas, V1 constitui um dos principais paradigmas de compreensão do processamento sensorial. Desde os anos 70 há uma extensa literatura que estuda propriedades de resposta de neurônios de V1, principalmente com eletrodos individuais e utilizando-se como modelo animal gatos e macacos. Tem-se conhecimento de onde partem seus principais inputs e quais estímulos fazem os neurônios dispararem (grades senoidais com determinadas frequências espaciais e temporais). Mais recentemente, com o uso de matrizes de eletrodos, se tornou possível a investigação de propriedades coletivas da atividade e codificação neurais, que não eram possíveis de serem desvendadas com eletrodos individuais. Além disso, no estado da arte tecnológico atual, o uso do rato como modelo animal permite o registro da atividade neural com os animais em comportamento livre (sem anestesia ou contenção). No entanto, pouco se sabe sobre especificidades das propriedades de resposta dos neurônios do córtex visual do rato. Este trabalho teve por objetivo desenvolver um aparato e um protocolo experimental no Laboratório de Neurociência de Sistemas e Computacional adequado para estudo das propriedades de resposta de neurônios de V1 de ratos usando matrizes de eletrodos. Finalmente, apresentamos resultados experimentais onde caracterizamos respostas de neurônios de V1 a diferentes estímulos visuais (Funções de Gabor ou Grades) seja em ruído denso ou rarefeito, variando as propriedades de frequências temporal e espacial de estimulação, densidades de estímulos, velocidade, etc. Concluímos que implementamos com sucesso a técnica experimental, que abre inúmeras perspectivas futuras de pesquisas nesta linha no Departamento de Física da Universidade Federal de Pernambuco.
The primary visual cortex (V1) is the cerebral cortex region responsible for the first processing step of the visual information captured by the retina. Being one of the most studied and well described cortical sensory areas, V1 is one of the main paradigms for the study of sensory processing. Since the 70s, there is a vast literature that studies properties of V1’s neurons, specially using single electrodes and using cats and monkeys as animal models. The anatomical conectivity of the visual pathway is known, from the retina to the lateral geniculate nucleus to V1, as well as the main visual stimulations that make V1 neurons fire (sinusoidal gratings with certain spatial and temporal frequencies). More recently, using multielectrode arrays, it became possible to study coletive properties of the activity and neural codification, that could not be unveiled with single electrodes. Furthermore with, the current state of the art in multielectrode recordings it is possible to record the neural activity in frelly behaving rats (without anesthesia or restraint). This represents an advantage in using the rat as animal model. However, little is known about specificities of the V1 neurons response properties in the rat. The aim of this work is to develop, in the Laboratório de Neurociência de Sistemas e Computacional, an apparatus and an experimental protocol suitable for the study of visual response properties of V1’s neurons in rats, using multielectrode array recordings. Finally, we present experimental results that characterize the response of V1’s neurons with different visual stimuli (Gabor or Grating Functions), either in dense os sparse noise modes, varying the spatial and temporal stimulation frequencies, stimulus density, speed, etc. We conclude that the experimental technique was implemented successfully. These results open important perspectives of future research on this field for the Departamento de Física at the Universidade Federal de Pernambuco.
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Bohi, Amine. "Descripteurs de Fourier inspirés de la structure du cortex visuel primaire humain : Application à la reconnaissance de navires dans le cadre de la surveillance maritime". Thesis, Toulon, 2017. http://www.theses.fr/2017TOUL0002/document.
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Dans cette thèse, nous développons une approche supervisée de reconnaissance d’objets basée sur l’utilisation de nouveaux descripteurs d’images globaux inspirés du modèle du cortex visuel humain primaire V1 en tant que groupe de roto-translations semi-discrètes SE (2,N)=R² x ZN produit semi-direct entre R² et ZN. La méthode proposée est basée sur des descripteurs de Fourier généralisés et rotationnels définis sur le groupe SE (2,N), qui sont invariants aux transformations géométriques (translations, et rotations). De plus, nous montrons que ces descripteur de Fourier sont faiblement complets, dans le sens qu’ils permettent de discriminer sur un ensemble ouvert et dense L² (SE(2,N)) de fonctions à support compact, donc distinguer entre des images réelles. Ces descripteurs sont ensuite utilisés pour alimenter un classifieur de type SVM dans le cadre de la reconnaissance d’objets. Nous avons mené une séries d’expérimentations dans le but d’évaluer notre méthode sur les bases de visages RL, CVL et ORL et sur la base d’images d’objets variés COIL-100, et de comparer ses performances à celles des méthodes basées sur des descripteurs globaux et locaux. Les résultats obtenus ont montré que notre approche est en mesure de concurrencer de nombreuses techniques de reconnaissance d’objets existantes et de surpasser de nombreuse autres. Ces résultats ont également montré que notre méthode est robuste aux bruits. Enfin, nous avons employé la technique proposée pour reconnaître des navires dans un contexte de surveillance maritimeIn this thesis, we develop a supervised object recognition method using new global image descriptors inspired by the model of the human primary visual cortex V1. Mathematically speaking, the latter is modeled as the semi-discrete roto-translation group SE (2,N)=R² x ZN semi-direct product between R² and ZN. Therefore, our technique is based on generalized and rotational Fourier descriptors defined in SE (2,N) , and which are invariant to natural geometric transformations (translations, and rotations). Furthermore, we show that such Fourier descriptors are weakly complete, in the sense that they allow to distinguish over an open and dense set of compactly supported functions in L² (SE(2,N)) , hence between real-world images. These descriptors are later used in order to feed a Support Vector Machine (SVM) classifier for object recognition purposes. We have conducted a series of experiments aiming both at evaluating and comparing the performances of our method against existing both local - and global - descriptor based state of the art techniques, using the RL, the CVL, and the ORL face databases, and the COIL-100 image database (containing various types of objects). The obtained results have demonstrated that our approach was able to compete with many existing state of the art object recognition techniques, and to outperform many others. These results have also shown that our method is robust to noise. Finally, we have applied the proposed method on vessels recognition in the framework of maritime surveillance
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Cavalcante, André Borges. "Campos receptivos similares às wavelets de Haar são gerados a partir da codificação eficiente de imagens urbanas;V1". Universidade Federal do Maranhão, 2008. http://tedebc.ufma.br:8080/jspui/handle/tede/314.
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Previous issue date: 2008-02-25Efficient coding of natural images yields filters similar to the Gabor-like receptive fields of simple cells of primary visual cortex. However, natural and man-made images have different statistical proprieties. Here we show that a simple theoretical analysis of power spectra in a sparse model suggests that natural and man-made images would need specific filters for each group. Indeed, when applying sparse coding to man-made scenes, we found both Gabor and Haar wavelet-like filters. Furthermore, we found that man-made images when projected on those filters yielded smaller mean squared error than when projected on Gabor-like filters only. Thus, as natural and man-made images require different filters to be efficiently represented, these results suggest that besides Gabor, the primary visual cortex should also have cells with Haar-like receptive fields.
A codificação eficiente de imagens naturais gera filtros similares às wavelets de Gabor que relembram os campos receptivos de células simples do córtex visual primário. No entanto, imagens naturais e urbanas tem características estatísticas diferentes. Será mostrado que uma simples análise do espectro de potência em um modelo eficiente sugere que imagens naturais e urbanas requerem filtros específicos para cada grupo. De fato, aplicando codificação eficiente à imagens urbanas, encontramos filtros similares às wavelets de Gabor e de Haar. Além disso, observou-se que imagens urbanas quando projetadas nesses filtros geraram um menor erro médio quadrático do que quando projetadas somente em filtros de similares a Gabor. Desta forma, como imagens naturais e urbanas requerem filtros diferentes para serem representadas de forma eficiente, estes resultados sugerem que além de Gabor, o córtex visual primário também deve possuir células com campos receptivos similares às wavelets de Haar.
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Hurdal, Monica Kimberly. "Mathematical and computer modelling of the human brain with reference to cortical magnification and dipole source localisation in the visual cortx". Thesis, Queensland University of Technology, 1998.
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Das, Aritra. "Effect of Stimulus Normalization and Visual Attention at multiple scales of Neural Integration". Thesis, 2022. https://etd.iisc.ac.in/handle/2005/5986.
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The effect of visual attention on neural signals has been extensively studied using various techniques such as macaque neurophysiology and human electro/magneto encephalogram (EEG/MEG). Depending on the technique, different neural measures are typically used for studying attention. For example, in neurophysiology experiments involving macaques, many studies have focused on the modulation in spiking activity or the change in oscillatory power at different frequency bands such as alpha (8-12 Hz) or gamma (30-80 Hz) with attention, or the change in the relationship of spikes with these oscillations. In contrast, human EEG studies, in addition to studying alpha and gamma modulation, often use flickering stimuli that produce a specific neural response called steady-state visually evoked potential (SSVEP), which is also modulated by attention. However, due to the differences in stimuli and task paradigms in such studies, it is difficult to determine the effectiveness of these various neural measures for capturing attentional modulation. To address this, we designed a task paradigm which included both static and counterphase flickering stimuli to generate all the relevant neural measures (alpha/gamma power as well as SSVEPs) under identical recording conditions, which allowed us to compare their effectiveness in studying attention.
Since several reports suggest that attention modulates these neural measures through a canonical neural mechanism called normalization, in the first study of this thesis, we varied the normalization strength parametrically as a proxy for attentional modulation and tested its effect on various neural measures. We manipulated normalization strength by presenting static as well as flickering orthogonal superimposed gratings (plaids) at varying contrasts to two female monkeys while recording multiunit activity (MUA) and LFP from the primary visual cortex (area V1). We quantified the modulation in MUA, gamma (32-80 Hz), high-gamma (104-248 Hz) power, and SSVEP. Even under similar conditions, normalization strength was different for the four measures; and increased as: spikes, high-gamma, SSVEP, and gamma. However, these results could be explained using a normalization model, modified for population responses by varying the tuned normalization parameter and semi-saturation constant.
In the second part of the thesis, we tested the predictions of the gamma phase coding hypothesis in the context of stimulus contrast and visual attention. The gamma phase coding hypothesis posits that the intensity of the incoming stimulus is encoded in the position of the spike relative to the gamma rhythm. Using chronically implanted microelectrode arrays in the primary visual cortex of macaques engaged in an attention task while presenting stimuli of varying contrasts, we tested whether the phase of the gamma rhythm relative to spikes varied as a function of stimulus contrast and attentional state. We analyzed spikes and LFP from different electrodes and found a weak but significant effect of attention, but not stimulus contrast, on the gamma phase relative to spikes. Although we found a significant effect of attention, we argue that a small magnitude of phase shift as well as the dependence of phase angles on gamma power and center frequency, limits the potential role of gamma in phase coding in area V1.
In the third part of the thesis, we recorded EEG signals from 26 human participants while they were engaged in an attention task and analyzed alpha and gamma band powers for both static and flickering stimuli and SSVEP power for flickering stimuli. We report two main results. First, attentional modulation was comparable for SSVEP and alpha. Second, we found that non-foveal stimuli produced weak gamma despite various stimulus optimizations and therefore showed a negligible effect of attention although the same participants showed robust gamma activity for full-screen gratings. Thus, alpha and SSVEP won over gamma in capturing attentional modulation in human EEG. This result was in contrast to the findings of a comparable study in monkeys, where gamma and alpha won over SSVEPs. This study highlights the effectiveness of various neural measures in studying visual spatial attention and further implicates their usefulness in decoding behavior and attentional state in humans.DBT-Wellcome Trust India Alliance (Grant IA/S/18/2/504003), Tata Trusts, DBT-IISc Partnership Programme
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Khaytin, Ilya. "Analysis of cortical and thalamic contributors to functional organization of primate primary visual cortex (V1)". Diss., 2008. http://etd.library.vanderbilt.edu/ETD-db/available/etd-03272008-134041/.
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Lai, Jimmy. "Pulvinar modulates contrast response function of neurons in the primary visual cortex". Thèse, 2017. http://hdl.handle.net/1866/19712.
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The pulvinar, which is located in the posterior thalamus, establishes reciprocal connections with nearly all of the visual cortical areas and is consequently in a strategic position to influence their stimulus decoding processes. Projections from the pulvinar to the primary visual cortex (V1) are thought to be modulatory, altering the response of neurons without changing their basic receptive field properties. Here, we investigate this issue by studying V1 single unit responses to sine wave gratings during the reversible inactivation of the lateral posterior nucleus (LP) - pulvinar complex in the cat. We also studied the contrast response function of V1 neurons, before and during the inactivation of the LP-pulvinar complex. No change in the preferred orientation or direction selectivity of V1 neurons was observed during pulvinar inactivation. However, for the majority of the cells tested the response amplitude to the optimal stimulus was reduced. The contrast response function of neurons was fitted with the Naka-Rushton function and analysis of the effects of pulvinar deactivation revealed a diverse set of modulations: 35% of cells had a decrease in their peak response, 11% had an increase in their C50, 6% showed modulations of the slope factor and 22% exhibited changes in more than one parameter. Our results suggest that the pulvinar modulates activity of V1 neurons in a contrast dependent manner and provides gain control at lower levels of the visual cortical hierarchy.Le pulvinar, localisé dans le thalamus postérieur, établit des connections réciproques avec la vaste majorité des aires visuelles corticales et il est ainsi dans une position stratégique afin d’influencer les processus de décodage de celles-ci. Les projections du pulvinar au cortex visuel primaire (V1) sont considérées comme étant des projections modulatrices, qui modifieraient les réponses neuronales sans toutefois changer les propriétés de base des champs récepteurs. Dans la présente étude, nous avons étudié les réponses des neurones de V1 suite à l’inactivation réversible du complexe noyau latéral postérieur (LP)-pulvinar chez le chat. Des courbes de réponse au contraste ont été générées par la présentation de réseaux ayant plusieurs niveaux de contraste pendant l’inactivation du LP-pulvinar. Aucun changement n’a été observé concernant l’orientation préférée ou la sélectivité à la direction des neurones de V1 lors de l’inactivation du pulvinar. Néanmoins, pour la majorité des cellules testées, l’amplitude de la réponse aux stimuli optimaux a été réduite. La fonction de Naka-Rushton a été appliquée aux courbes de réponse au contraste et l’analyse des effets de l’inactivation du pulvinar a montré une panoplie d’effets modulateurs : 35% des cellules ont présenté une réduction de leur réponse maximale, 11% ont eu une augmentation de leur C50, 6% ont montré une modulation de la pente et 22% des neurones ont présenté des changements dans plus d’un paramètre. Nos résultats suggèrent que le pulvinar module l’activité des neurones de V1 d’une façon dépendante du contraste et qu’il contrôle le gain des réponses des neurones des aires primaires du cortex visuel.
Książki na temat "Primary Visual Cortex (area V1)"
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Chirimuuta, Mazviita, i Ian Gold. The Embedded Neuron, the Enactive Field? Redaktor John Bickle. Oxford University Press, 2009. http://dx.doi.org/10.1093/oxfordhb/9780195304787.003.0010.
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This article examines the concept of the receptive field (RF) of visual neurons. It introduces the concept of visual RFs by discussing the classical picture of primary visual cortex (V1) physiology and discusses the psychophysics and computational vision of contrast discrimination to place the visual neurophysiology in context. It evaluates some recent data which questioned the classical conception of the RF and considers some options available for absorbing these data into visual theory.
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Gori, Simone. The Rotating Tilted Lines Illusion. Oxford University Press, 2017. http://dx.doi.org/10.1093/acprof:oso/9780199794607.003.0066.
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This chapter describes the Rotating-Tilted-Lines illusion , which is a new motion illusion that arises in a circular pattern composed by black, radial lines tilted to the right and presented on a white background. When one approaches the stimulus pattern, the radial lines appear to rotate in the counterclockwise direction, whereas when one recedes from it, they appear to rotate clockwise. It is the simplest pattern able to elicit illusory rotatory motion in presence of physical radial expansion. This surprising misperception of motion seems to be a result of the competition between two motion processing units in the primary visual cortex (V1, V5)
Części książek na temat "Primary Visual Cortex (area V1)"
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Mandal, Atanendu Sekhar. "Contextual Effects in the Visual Cortex Area 1 (V1) and Camouflage Perception". W Perception and Machine Intelligence, 35–41. Berlin, Heidelberg: Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-27387-2_5.
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Leigh, R. John, i David S. Zee. "The Neural Basis for Conjugate Eye Movements". W The Neurology of Eye Movements, 386–473. Oxford University Press, 2015. http://dx.doi.org/10.1093/med/9780199969289.003.0007.
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This chapter draws on a range of studies of macaque and humans to forge an anatomical scheme for the control of gaze. At each stage, this scheme is used to predict effects of focal lesions on the control of gaze, with video examples. Contributions include the abducens nucleus, medial longitudinal fasciculus (MLF), and paramedian pontine reticular formation (PPRF) to horizontal gaze; the rostral interstitial nucleus of the medial longitudinal fasciculus (RIMLF), interstitial nucleus of Cajal, and posterior commissure to vertical gaze; cerebellar flocculus, paraflocculus, dorsal vermis, fastigial nucleus, and inferior olive to adaptive optimization of gaze. Cortical control of gaze by structures including primary visual cortex (V1), middle temporal visual area (MT, V5), medial superior temporal visual area (MST), posterior parietal cortex, frontal eye fields, supplementary eye fields, dorsolateral prefrontal cortex, cingulate cortex, descending pathways, thalamus, pulvinar, caudate, substantia nigra pars reticulata, subthalamic nucleus, and superior colliculus are each discussed.
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Caselli, Richard J., i David T. Jones. "Cortex: Topography and Organization". W Mayo Clinic Neurology Board Review, redaktor Kelly D. Flemming, 175–78. Oxford University Press, 2021. http://dx.doi.org/10.1093/med/9780197512166.003.0021.
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The cerebral cortex is involved in various simple and complex activities. It consists of layers of neuronal cell bodies (ie, gray matter) that are organized into gyri (convolutions).The cortex can be divided into functional components in several ways. Various schemes are based on function, cytoarchitecture, topography, or Brodmann areas. The terminology can be confusing because the same area of cortex could be designated by several names. For instance, Brodmann area 17 is also called the primary visual cortex, the striate cortex, and the calcarine cortex. Brodmann designated 52 regions of the cerebral cortex according to cytoarchitecture.
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Afef, Ouelhazi, Rudy Lussiez i Molotchnikoff Stephane. "Cortical Plasticity under Ketamine: From Synapse to Map". W Sensory Nervous System - Computational Neuroimaging Investigations of Topographical Organization in Human Sensory Cortex [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.104787.
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Sensory systems need to process signals in a highly dynamic way to efficiently respond to variations in the animal’s environment. For instance, several studies showed that the visual system is subject to neuroplasticity since the neurons’ firing changes according to stimulus properties. This dynamic information processing might be supported by a network reorganization. Since antidepressants influence neurotransmission, they can be used to explore synaptic plasticity sustaining cortical map reorganization. To this goal, we investigated in the primary visual cortex (V1 of mouse and cat), the impact of ketamine on neuroplasticity through changes in neuronal orientation selectivity and the functional connectivity between V1 cells, using cross correlation analyses. We found that ketamine affects cortical orientation selectivity and alters the functional connectivity within an assembly. These data clearly highlight the role of the antidepressant drugs in inducing or modeling short-term plasticity in V1 which suggests that cortical processing is optimized and adapted to the properties of the stimulus.
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Shibasaki, Hiroshi, i Mark Hallett. "Posture and gait". W The Neurologic Examination, 211–15. Oxford University Press, 2022. http://dx.doi.org/10.1093/med/9780197556306.003.0022.
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This chapter discusses the anatomic basis related to control of head and trunk posture, and symptom and syndromes caused by its impairment. The spinal cord contains machinery for stepping, the locomotor generator. However, the spinal cord is under the control of supraspinal centers. In human walking, intention or attention takes part to various degrees, from fully attended walking to nearly automatic walking. Multiple structures of the central nervous system are known to be involved in the central control of walking. In addition to the sensorimotor areas directly related to leg movement such as the pre-SMA, SMA proper, anterior cingulate gyrus, lateral premotor areas, and the foot areas of the primary sensorimotor cortices, the cortical areas related to visual information processing, such as the occipital cortex and the posterior parietal area, are also important. Furthermore, the brainstem gait center, cerebellum, and basal ganglia also play an important part.
Streszczenia konferencji na temat "Primary Visual Cortex (area V1)"
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Yan, Tian-yi, Feng-zhe Jin i Jing-long Wu. "Visual field representation and location of visual area V1 in human visual cortex by functional MRI". W 2009 ICME International Conference on Complex Medical Engineering - CME 2009. IEEE, 2009. http://dx.doi.org/10.1109/iccme.2009.4906645.
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Dehsorkh, Sajjad Abdi, i Reshad Hosseini. "Predicting the neural response of primary visual cortex (v1) using deep learning approach". W 2023 28th International Computer Conference, Computer Society of Iran (CSICC). IEEE, 2023. http://dx.doi.org/10.1109/csicc58665.2023.10105321.
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Maunsell, John H. R. "Motion processing in visual cortex". W OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1989. http://dx.doi.org/10.1364/oam.1989.tuj2.
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Many lines of anatomical and physiological evidence have shown that the visual system contains a distinct pathway that is responsible for most motion analysis. In primates this pathway originates in the retinal ganglion cells that send their axons to the magnocellular layers of the lateral geniculate nucleus (LGN). The outputs from the magnocellular LGN layers directly provide the primary excitatory drive to structures like layer 4B in striate cortex and the middle temporal area (MT) in extrastriate cortex. Both of these structures contain a high proportion of neurons that are selective for the direction of stimulus motion. Later stages of motion processing in parietal cortex appear to contribute to analyzing more complex types of movement such as rotation or looming.
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Songnian, Zhao, Zou Qi, Jin Zhen, Xiong Xiaoyun, Yao Guozheng, Yao Li i Liu Yijun. "A Computational Model that Realizes a Sparse Representation of the Primary Visual Cortex V1". W 2009 WRI World Congress on Software Engineering. IEEE, 2009. http://dx.doi.org/10.1109/wcse.2009.40.
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Moore, Michael J., Richard Linderman, Morgan Bishop i Robinson Pino. "A columnar primary visual cortex (V1) model emulation using a PS3 Cell-BE array". W 2010 International Joint Conference on Neural Networks (IJCNN). IEEE, 2010. http://dx.doi.org/10.1109/ijcnn.2010.5596903.
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Baseler, H. A., B. A. Wandell, A. B. Morland, S. R. Jones i K. H. Ruddock. "Activity in the visual cortex of a hemianope measured using fMRI". W Vision Science and its Applications. Washington, D.C.: Optica Publishing Group, 1997. http://dx.doi.org/10.1364/vsia.1997.suc.3.
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Functional magnetic resonance imaging (fMRI) can be used to identify and map visual areas in the cerebral cortex of visually normal humans (Engel et al., in press). Here, we use the methods that have been developed on normal observers to assess the neural responses in subject, G.Y., who has cortical damage that includes left area V1. This subject has reported limited sensation of select stimuli beyond 2.5 deg in his right peripheral visual field (Barbur et al. 1980). Here we report preliminary analyses of the organization of this subject’s visual areas, and we describe some of the cortical signals that occur when stimuli are presented to the subject’s “blind” visual field.
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Schwartz, Eric L. "Recent experimental measurements of topographic-map structure in primate V-1 and presentation of a miniature space-variant active vision system". W OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1993. http://dx.doi.org/10.1364/oam.1993.thv.1.
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This paper will present the history and current status of understanding of the spatial architecture of primary visual cortex (V-l, striate cortex, area 17) in primates. Special emphasis will be placed on experimental techniques, mathematical and computational analyses, and the relevance of V-l architecture to current work in machine vision. The intention is to provide an overview of the difficulties, both conceptual and experimental, which have characterized this field for the past fifty years, and to provide some insight into the importance of spatial architecture in visual cortex to both biological and machine vision.
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Moreira da Silva, Fernando. "Color processing and human perception". W Intelligent Human Systems Integration (IHSI 2023) Integrating People and Intelligent Systems. AHFE International, 2023. http://dx.doi.org/10.54941/ahfe1002840.
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Color processing is a complex phenomenon, which involves distinct variables, not being a relatively simple human capacity, as was long thought. Neurosciences have been helping to achieve new discoveries, recontextualizing existing knowledge and raising new questions.The brain is the organ responsible for decoding electrical signals into experiences that make sense for humans to perceive the world. Color vision is closely associated with visual processing and human perception. Cones, visual receptors in the human eye specialized for color vision, transform electromagnetic waves into electrical stimuli, which in turn are conducted to the human cortex through the geniculostriate pathway. The visual cortex is divided into at least five areas, present in the occipital lobe and designated according to their structure and function (V1, V2, V3, V4, and V5), each of these areas playing a specific role when it comes to visual processing. In previous studies, we have shown that areas V1 and V2 are mainly responsible for initial visual processing. However, more recent investigations have led to the conclusion that color processing is largely associated with the V4 area, since this area becomes significantly more active when performing tasks in which color processing is necessary, in addition to lesions in this region causing achromatopsia, dysfunction linked to chromatic identification and perception. We have been developing a quasi-experience with humans, in order to help the understanding of brain reactions to different color dimensions, especially color processing and human perception and cognition, comparing the results obtained with those of other projects previously developed. The study has also focused on color constancy, that is, the human tendency to perceive a given object as having the same color regardless of changes in lighting, angle or distance. This paper presents the work developed so far with the participation of various groups of individuals, with different ages and genders, as well as the results obtained by the application of the chosen methodology. Although at first glance it seems like a relatively simple human ability, color processing is a very complex phenomenon, involving distinct variables, many of which are still a mystery to researchers. It is hoped that this investigation may add knowledge, especially at the level of color processing and human perception, with a view to its future use and application in projects focused on the use of color.