The ventral temporal cortex vtc rapidly and flexibly categorizes visual stimuli. Visual cortex in the macaque comprises about 60 per cent of neocortex. The ventral temporal cortex vtc in humans includes functionally defined regions that preferentially respond to objects, faces, and places. The world is full of rich and dynamic visual information. Aging reduces neural specialization in ventral visual cortex. Citeseerx document details isaac councill, lee giles, pradeep teregowda.
Evidence is strong that the visual pathway is segregated into two distinct streamsventral and dorsal. Gaba levels in ventral visual cortex decline with age and. What is striking in humans, however, is that this mosaic of specialized regions is partially changed by the culture we live in. However, the mechanisms that cause increases in neural synchrony with attention in. Download figure open in new tab download powerpoint. The fusiform face area ffa responds preferentially to faces kanwisher et al. Maps in lateral occipital are numbered as lox, maps in ventral. In monkeys and apes the visual cortex takes up much of their brain. To avoid information overload, the human brain groups inputs into categories such as faces, houses, or tools.
The ventral network comprises the temporoparietal junction tpj and the ventral frontal cortex vfc fig. Sleep deprivation impairs objectselective attention. Pdf the role of primary visual cortex v1 in visual awareness. Abstractvisual motion perception is fundamental to many aspects of visual perception. The ventral stream, thought to be involved in visual recognition, begins in v1 and extends ventrally into the occipitotemporal cortex. The impact of density and ratio on objectensemble representation in human anteriormedial ventral visual cortex.
Gateways of ventral and dorsal streams in mouse visual cortex. Ventral hippocampal projections to the medial prefrontal. We studied ventral visual cortex, an area of the brain that responds selectively to visual categories faces, places, and words in young adults, and that shows little atrophy with age. The visual cortex of the brain is that part of the cerebral cortex which processes visual. The ventral stream begins with v1, goes through visual area v2, then through visual area v4, and to the inferior temporal cortex it cortex. The visual system is the part of the central nervous system which gives organisms the ability to process visual detail as sight, as well as enabling the formation of several nonimage photo response functions. A standard organization separates visual maps into 2 distinct clusters within ventral and dorsal cortex. We combined fmri, diffusion mri, and fiber tractography to identify a major white matter pathway, the vertical occipital fasciculus vof, connecting maps within the. In monkeys and apes the visual cortex take up much of their brain.
It detects and interprets information from visible light to build a representation of the surrounding environment. For the eccentricity measurements, the fovea is denoted in red and the periphery in blue. It surrounds and extends into a deep sulcus called the calcarine sulcus. The brains ability to recognize visual categories is guided by categoryselective ventraltemporal cortex vtc. Temporal tuning properties along the human ventral visual. Whether visual experience is required for the functional organization of vtc into distinct functional subregions remains unknown, hampering our understanding of the mechanisms that drive category recognition. These neurons could represent a gravityrelated reference frame for object vision. Development of visual category selectivity in ventral.
Major human white matter pathway between dorsal and ventral. Here, we evaluated the effects of sd on the topdown biasing of activation of ventral visual cortex and on functional connectivity. It is well known that a bias towards faster and stronger responses to darks is present in the retina, lateral geniculate nucleus and primary visual cortex. Musical literacy shifts asymmetries in the ventral visual. In humans, psychophysical and neurophysiological data indicate that darks are better detected than brights, suggesting that the dark bias found in early visual areas is transmitted across. Here, we demonstrate that vtc in individuals who were blind since birth.
The number of these representations the number of visual areas in monkeys is more than 20 10. Conceptual size representation in ventral visual cortex. Physically, the visual cortex is at the back of the brain in the occipital lobe david hubel and torsten wiesel did research on the visual cortex for many years. Previous functional neuroimaging studies of reading in skilled readers, acquired dyslexia and developmental dyslexia have all shown that the left ventral occipitotemporal cortex vot is involved in visual word recognition. The primary visual cortex makes up a small portion of the visible surface of the cortex in the occipital lobe, but because it stretches into the calcarine sulcus, it makes up a significant portion of cortical surface overall. Prosopagnosia is characterized by a profound impairment in recognizing faces, despite normal sensory vision and intelligence. The timing of emotional discrimination in human amygdala. Which brain circuit motifs are most responsible for computing and transmitting these putative recurrent signals to it. This method combined functional magnetic resonance imaging fmri data with magnetoencephalography meg data using representational similarity analysis and revealed a hierarchical progression from primary visual cortex through the dorsal and ventral streams. Conversely, in lowlevel visual cortex, there was a nearlinear benefit from longer sensory exposure. It is also associated with storage of longterm memory. In both human and nonhuman primates, the ventral visual cortex comprises multiple specialized subregions that are involved in the visual recognition of image categories such as objects, faces, or places 15. A part of the brain called the ventral occipitotemporal cortex votc helps categorize visual information.
Two proposals theorize that the pathways are segregated in function. We used an elliptical prf population receptive field model to test the prediction that ventral and dorsal divisions of evc early visual cortex differentially sample visual space fig. It has been hypothesized that mib reflects an antagonistic interplay between cortical representations of the static target and moving. The ventral stream begins with v1, goes through visual area v2, then through visual area v4, and. In contrast with acquired prosopagnosia, which typically results from a neurological insult to the ventral visual cortex in premorbidly normal individuals. V1 transmits information to two primary pathways, called the ventral stream and the dorsal stream. Along with the visual ventral pathway being important for visual processing, there is also a ventral auditory pathway emerging from the primary auditory cortex. Ventral and dorsal processing streams the visual cortex contains more than a dozen areas that are thought to be organized in two main processing streams. A distinct pattern of response was found for each stimulus category.
Vof cortical projections in the ventral visual field maps. Development of visual category selectivity in ventral visual cortex. In contrast with acquired prosopagnosia, which typically results from a neurological insult to the ventral visual cortex in premorbidly normal individuals, individuals with congenital prosopagnosia have impaired face recognition, apparently from birth, and in the. Cortical visual processing is commonly thought to proceed along two distinct pathways. The ventral visual stream hosts a set of regions preferentially responding to one category of objects more than to others. Stronger responses to darks along the ventral pathway of. The functional architecture of the ventral temporal cortex. Earlier functional imaging studies on visually induced selfmotion perception vection disclosed a bilateral network of activations within primary and secondary visual cortex areas which was combined with signal decreases, i. Ventral and dorsal streams processing visual motion. Distributed neural population spiking patterns in macaque inferior temporal it cortex that support core visual object recognition require additional time to develop for specific latesolved images suggesting the necessity of recurrent processing in these computations. Differential sampling of visual space in ventral and dorsal early.
Reliability and generalizability of similaritybased. Background most prior studies on selective attention in the setting of total sleep deprivation sd have focused on behavior or activation within frontoparietal cognitive control areas. Visual field representations and locations of visual areas v123 in. Retinotopic organization of human ventral visual cortex journal. Spatial frequency tolerant visual object representations. Major human white matter pathway between dorsal and. Specific parts of the votc prefer different types of visual input. The ventral, objectprocessing pathway in primate visual cortex is now known to contain neurons sensitive to largescale environmental shape. In particular, we argue that the ventral visual pathway is a recurrent and highly interactive occipitotemporal network linking early visual areas and the anterior inferior temporal cortex along multiple routes through which visual information is processed. Alternatively, if ventral visual cortex is only engaged when motion contributes to form perception, then a ventral visual lesion should only impair motion perception when form representations are evoked e. These pathways were identified in monkeys as anatomically and functionally distinct systems of multisynaptic connections emerging from the striate cortex. The experimental findings show that the retinal images are mapped into multiple cortical areas.
Areas in the prefrontal cortex pfc and parietal cortex may be sources of the topdown attentional feedback to ventral stream areas, which could enhance firing rates with attention 1, 4, 8. In contrast to the dorsal nodes fef and ips for which homologue areas are well. Motioninduced blindness mib is a visual phenomenon in which a salient static target spontaneously fluctuates in and out of visual awareness when surrounded by a moving mask pattern. The ventral stream processes information about object identity, whereas the dorsal stream, according to one model, processes information about either object location, and according to another, is responsible in executing. It has been proposed that circuits in the rodent visual system are organized in similar fashion kolb, 1990. In early visual cortex evc, the upper visual field is processed ventrally, with the lower visual field processed dorsally. The present study investigated whether neural structures become less functionally differentiated and specialized with age. Representation of gravityaligned scene structure in.
Citeseerx opposite neural signatures of motioninduced. Visual perception of emotionally arousing, relative to nonemotional stimuli is associated with greater blood oxygen level dependent bold signal across widespread regions of the ventral visual system, including inferotemporal it and extrastriate occipital cortex bradley et al. Here, we evaluated the effects of sd on the topdown biasing of activation of ventral visual cortex and on functional connectivity between cognitive control and other brain regions. The ventral stream, sometimes called the what pathway, is associated with form recognition and object representation. Second, for simplicity, we include only one area in the ventral stream either left mtg or left mfg, one area in the dorsal stream either left ant ips or left spl in each model. A lateraltomesial organization of human ventral visual. Fast recurrent processing via ventral prefrontal cortex is. Third, we hypothesized that the input to the tool network comes from the primary visual cortex v1. Recent developmental studies suggest that the face selective region in the fusiform gyrus fusiform face area, ffa undergoes a prolonged development involving substantial increases in its volume after 7 years of age. Cortical visual field maps of the central 12 deg were measured using rotating wedge and expanding ring stimuli.
Highfrequency, longrange coupling between prefrontal and. Longterm excitation of mpfcprojecting vhip neurons in wildtype mice. Functional mri was used to estimate neural activity in this cortical area, while young. The visual cortex is a part of the brain that allows vision. Ventral occipitotemporal cortex function and anatomical. Reduced structural connectivity in ventral visual cortex.
In contrast with acquired prosopagnosia, which typically results from a neurological insult to the ventral visual cortex in premorbidly normal individuals, individuals with congenital. Vaziri and connor show how such neurons respond to a variety of parallel and orthogonal planes and edges. The visual system carries out a number of complex tasks, including the. Significance statement neural representations in the ventral visual cortex are less distinguishable in older compared to younger humans, and this neural dedifferentiation is associated with agerelated cognitive deficits. The information then joins the visual ventral stream at the middle temporal gyrus and temporal pole. Before systematically comparing ventral and dorsal divisions of evc, we established the reliability of the elliptical prf estimates. The role of human ventral visual cortex in motion perception. Most prior studies on selective attention in the setting of total sleep deprivation sd have focused on behavior or activation within frontoparietal cognitive control areas. In this pathway, phonemes are processed posteriorly to syllables and environmental sounds. Inputs from the ventral hippocampus vhip to the medial prefrontal cortex mpfc are implicated in several neuropsychiatric disorders.
Differential development of the ventral visual cortex. The primary visual cortex is found in the occipital lobe in both cerebral hemispheres. The functional architecture of the object vision pathway in the human brain was investigated using functional magnetic resonance imaging to measure patterns of response in ventral temporal cortex while subjects viewed faces, cats, five categories of manmade objects, and nonsense pictures. Development of visual category selectivity in ventral visual cortex does not. Much of the visual cortex is organized into visual field maps. Both in mid and highlevel ventral visual cortex, response strength for a given rate was near maximal even with the shortest durations of stimulus exposure that we tested and did not increase significantly with longer stimulus exposure times. In human adults, ventral extrastriate visual cortex contains a mosaic of functionally specialized areas, some responding preferentially to natural visual categories such as faces fusiform face area or places parahippocampal place area and others to cultural inventions such as written words and numbers visual word form and number form areas. This finding led to the concept of a reciprocal inhibitory interaction between the visual and vestibular systems.
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