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Nancy Kanwisher - One of the best experts on this subject based on the ideXlab platform.
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visual word processing and experiential origins of functional selectivity in human Extrastriate Cortex
Proceedings of the National Academy of Sciences of the United States of America, 2007Co-Authors: Chris I Baker, Jia Liu, Lawrence L Wald, Kenneth K Kwong, Thomas Benner, Nancy KanwisherAbstract:How do category-selective regions arise in human Extrastriate Cortex? Visually presented words provide an ideal test of the role of experience: Although individuals have extensive experience with visual words, our species has only been reading for a few thousand years, a period not thought to be long enough for natural selection to produce a genetically specified mechanism dedicated to visual word recognition per se. Using relatively high-resolution functional magnetic resonance imaging (1.4 × 1.4 × 2-mm voxels), we identified a small region of Extrastriate Cortex in most participants that responds selectively to both visually presented words and consonant strings, compared with line drawings, digit strings, and Chinese characters. Critically, we show that this pattern of selectivity is dependent on experience with specific orthographies: The same region responds more strongly to Hebrew words in Hebrew readers than in nonreaders of Hebrew. These results indicate that extensive experience with a given visual category can produce strong selectivity for that category in discrete cortical regions.
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location and spatial profile of category specific regions in human Extrastriate Cortex
Human Brain Mapping, 2006Co-Authors: Nancy Kanwisher, Mona Spiridon, Bruce FischlAbstract:Subjects were scanned in a single functional MRI (fMRI) experiment that enabled us to localize cortical regions in each subject in the occipital and temporal lobes that responded significantly in a variety of contrasts: faces objects, body parts objects, scenes objects, objects scrambled objects, and moving stationary stimuli. The resulting activation maps were coregistered across subjects using spherical surface coordinates (Fischl et al., Hum Brain Mapp 1999;8:272-284) to produce a "percentage overlap map" indicating the percentage of subjects who showed a significant response for each contrast at each point on the surface. Prominent among the overlapping activations in these contrasts were the fusiform face area (FFA), Extrastriate body area (EBA), parahippocampal place area (PPA), lateral occipital complex (LOC), and MT/V5; only a few other areas responded consistently across subjects in these contrasts. Another analysis showed that the spatial profile of the selective response drops off quite sharply outside the standard borders of the FFA and PPA (less so for the EBA and MT/V5), indicating that these regions are not simply peaks of very broad selectivities spanning centimeters of Cortex, but fairly discrete regions of Cortex with distinctive functional profiles. The data also yielded a surprise that challenges our understanding of the function of area MT: a higher response to body parts than to objects. The anatomical consistency of each of our functionally defined regions across subjects and the spatial sharpness of their activation profiles within subjects highlight the fact that these regions constitute replicable and distinctive landmarks in the functional organization of the human brain. Hum Brain Mapp 27:77- 89, 2006. © 2006 Wiley-Liss, Inc.
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the fusiform face area subserves face perception not generic within category identification
Nature Neuroscience, 2004Co-Authors: Kalanit Grillspector, Nicholas Knouf, Nancy KanwisherAbstract:The function of the fusiform face area (FFA), a face-selective region in human Extrastriate Cortex, is a matter of active debate. Here we measured the correlation between FFA activity measured by functional magnetic resonance imaging (fMRI) and behavioral outcomes in perceptual tasks to determine the role of the FFA in the detection and within-category identification of faces and objects. Our data show that FFA activation is correlated on a trial-by-trial basis with both detecting the presence of faces and identifying specific faces. However, for most non-face objects (including cars seen by car experts), within-category identification performance was correlated with activation in other regions of the ventral occipitotemporal Cortex, not the FFA. These results indicate that the FFA is involved in both detection and identification of faces, but that it has little involvement in within-category identification of non-face objects (including objects of expertise).
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Binocular rivalry and visual awareness in human Extrastriate Cortex.
Neuron, 1998Co-Authors: F. Tong, J. T. Vaughan, K. Nakayama, Nancy KanwisherAbstract:We used functional magnetic resonance imaging (fMRI) to monitor stimulus-selective responses of the human fusiform face area (FFA) and parahippocampal place area (PPA) during binocular rivalry in which a face and a house stimulus were presented to different eyes. Though retinal stimulation remained constant, subjects perceived changes from house to face that were accompanied by increasing FFA and decreasing PPA activity; perceived changes from face to house led to the opposite pattern of responses. These responses during rivalry were equal in magnitude to those evoked by nonrivalrous stimulus alternation, suggesting that activity in the FFA and PPA reflects the perceived rather than the retinal stimulus, and that neural competition during binocular rivalry has been resolved by these stages of visual processing.
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The fusiform face area: a module in human Extrastriate Cortex specialized for face perception.
The Journal of neuroscience : the official journal of the Society for Neuroscience, 1997Co-Authors: Nancy Kanwisher, J. Mcdermott, M M ChunAbstract:Using functional magnetic resonance imaging (fMRI), we found an area in the fusiform gyrus in 12 of the 15 subjects tested that was significantly more active when the subjects viewed faces than when they viewed assorted common objects. This face activation was used to define a specific region of interest individually for each subject, within which several new tests of face specificity were run. In each of five subjects tested, the predefined candidate "face area" also responded significantly more strongly to passive viewing of (1) intact than scrambled two-tone faces, (2) full front-view face photos than front-view photos of houses, and (in a different set of five subjects) (3) three-quarter-view face photos (with hair concealed) than photos of human hands; it also responded more strongly during (4) a consecutive matching task performed on three-quarter-view faces versus hands. Our technique of running multiple tests applied to the same region defined functionally within individual subjects provides a solution to two common problems in functional imaging: (1) the requirement to correct for multiple statistical comparisons and (2) the inevitable ambiguity in the interpretation of any study in which only two or three conditions are compared. Our data allow us to reject alternative accounts of the function of the fusiform face area (area "FF") that appeal to visual attention, subordinate-level classification, or general processing of any animate or human forms, demonstrating that this region is selectively involved in the perception of faces.
Gregory Mccarthy - One of the best experts on this subject based on the ideXlab platform.
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Face-Specific Processing in the Human Fusiform Gyrus
Journal of Cognitive Neuroscience, 1997Co-Authors: Gregory Mccarthy, Aina Puce, John C. Gore, Truett AllisonAbstract:The perception of faces is sometimes regarded as a specialized task involving discrete brain regions. In an attempt to identi$ face-specific Cortex, we used functional magnetic resonance imaging (fMRI) to measure activation evoked by faces presented in a continuously changing montage of common objects or in a similar montage of nonobjects. Bilateral regions of the posterior fusiform gyrus were activated by faces viewed among nonobjects, but when viewed among objects, faces activated only a focal right fusiform region. To determine whether this focal activation would occur for another category of familiar stimuli, subjects viewed flowers presented among nonobjects and objects. While flowers among nonobjects evoked bilateral fusiform activation, flowers among objects evoked no activation. These results demonstrate that both faces and flowers activate large and partially overlapping regions of inferior Extrastriate Cortex. A smaller region, located primarily in the right lateral fusiform gyrus, is activated specifically by faces.
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differential sensitivity of human visual Cortex to faces letterstrings and textures a functional magnetic resonance imaging study
The Journal of Neuroscience, 1996Co-Authors: Aina Puce, Truett Allison, John C. Gore, Maryam M Asgari, Gregory MccarthyAbstract:Twelve normal subjects viewed alternating sequences of unfamiliar faces, unpronounceable nonword letterstrings, and textures while echoplanar functional magnetic resonance images were acquired in seven slices extending from the posterior margin of the splenium to near the occipital pole. These stimuli were chosen to elicit initial category-specific processing in Extrastriate Cortex while minimizing semantic processing. Overall, faces evoked more activation than did letterstrings. Comparing hemispheres, faces evoked greater activation in the right than the left hemisphere, whereas letterstrings evoked greater activation in the left than the right hemisphere. Faces primarily activated the fusiform gyrus bilaterally, and also activated the right occipitotemporal and inferior occipital sulci and a region of lateral Cortex centered in the middle temporal gyrus. Letterstrings primarily activated the left occipitotemporal and inferior occipital sulci. Textures primarily activated portions of the collateral sulcus. In the left hemisphere, 9 of the 12 subjects showed a characteristic pattern in which faces activated a discrete region of the lateral fusiform gyrus, whereas letterstrings activated a nearby region of Cortex within the occipitotemporal and inferior occipital sulci. These results suggest that different regions of ventral Extrastriate Cortex are specialized for processing the perceptual features of faces and letterstrings, and that these regions are intermediate between earlier processing in striate and peristriate Cortex, and later lexical, semantic, and associative processing in downstream cortical regions.
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human Extrastriate visual Cortex and the perception of faces words numbers and colors
Cerebral Cortex, 1994Co-Authors: T. Allison, Gregory Mccarthy, Aina Puce, Anna C. Nobre, Aysenil BelgerAbstract:: Electrophysiological correlates of the processing of visual information were studied in epileptic patients with electrodes chronically implanted on the surface of striate and Extrastriate Cortex. In separate experiments patients viewed faces, letter strings (words and non-words), numbers, and control stimuli. A negative potential, N200, was evoked by faces, letter strings, and numbers, but not by the control stimuli. N200 was recorded bilaterally from discrete regions of the fusiform and inferior temporal gyri. These category-specific face, letter-string, and number "modules" vary in location. In most cases there was no overlap in the location of face and letter-string modules, suggesting a mosaic of functionally discrete regions. In some cases letter-string and number N200s were recorded from the same location, suggesting that these modules may be less spatially and functionally discrete. Face N200-like potentials can be recorded from temporal scalp, allowing the possibility of studying early face processing in normal subjects. Longer-latency face-specific potentials were recorded from the inferior surface of the anterior temporal lobe. Potentials evoked by colored checkerboards were recorded from a region of the fusiform gyrus posterior to the fusiform region from which category-specific N200s were recorded. These results suggest that there are several processing streams in inferior Extrastriate Cortex. In addition to object recognition systems previously proposed for faces and words, our preliminary results suggest a separate system dealing with numbers. Postulated systems dealing with larger manipulable objects and animals have not been detected.
Jean-philippe Thiran - One of the best experts on this subject based on the ideXlab platform.
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Normalization of aberrant pretherapeutic dynamic functional connectivity of Extrastriate visual system in patients who underwent thalamotomy with stereotactic radiosurgery for essential tremor: a resting-state functional MRI study
Journal of Neurosurgery, 2019Co-Authors: Constantin Tuleasca, Thomas Bolton, Jean Regis, Elena Najdenovska, Tatiana Witjas, Nadine Girard, Francois Delaire, Marion Vincent, Mohamed Faouzi, Jean-philippe ThiranAbstract:OBJECTIVE: The tremor circuitry has commonly been hypothesized to be driven by one or multiple pacemakers within the cerebello-thalamo-cortical pathway, including the cerebellum, contralateral motor thalamus, and primary motor Cortex. However, previous studies, using multiple methodologies, have advocated that tremor could be influenced by changes within the right Extrastriate Cortex, at both the structural and functional level. The purpose of this work was to evaluate the role of the Extrastriate Cortex in tremor generation and further arrest after left unilateral stereotactic radiosurgery thalamotomy (SRS-T). METHODS: The authors considered 12 healthy controls (HCs, group 1); 15 patients with essential tremor (ET, right-sided, drug-resistant; group 2) before left unilateral SRS-T; and the same 15 patients (group 3) 1 year after the intervention, to account for delayed effects. Blood oxygenation level-dependent functional MRI during resting state was used to characterize the dynamic interactions of the right Extrastriate Cortex, comparing HC subjects against patients with ET before and 1 year after SRS-T. In particular, the authors applied coactivation pattern analysis to extract recurring whole-brain spatial patterns of brain activity over time. RESULTS: The authors found 3 different sets of coactivating regions within the right Extrastriate Cortex in HCs and patients with pretherapeutic ET, reminiscent of the "cerebello-visuo-motor," "thalamo-visuo-motor" (including the targeted thalamus), and "basal ganglia and Extrastriate" networks. The occurrence of the first pattern was decreased in pretherapeutic ET compared to HCs, whereas the other two patterns showed increased occurrences. This suggests a misbalance between the more prominent cerebellar circuitry and the thalamo-visuo-motor and basal ganglia networks. Multiple regression analysis showed that pretherapeutic standard tremor scores negatively correlated with the increased occurrence of the thalamo-visuo-motor network, suggesting a compensatory pathophysiological trait. Clinical improvement after SRS-T was related to changes in occurrences of the basal ganglia and Extrastriate Cortex circuitry, which returned to HC values after the intervention, suggesting that the dynamics of the Extrastriate Cortex had a role in tremor generation and further arrest after the intervention. CONCLUSIONS: The data in this study point to a broader implication of the visual system in tremor generation, and not only through visual feedback, given its connections to the dorsal visual stream pathway and the cerebello-thalamo-cortical circuitry, with which its dynamic balance seems to be a crucial feature for reduced tremor. Furthermore, SRS-T seems to bring abnormal pretherapeutic connectivity of the Extrastriate Cortex to levels comparable to those of HC subjects.
Raymond J Dolan - One of the best experts on this subject based on the ideXlab platform.
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effects of cholinergic enhancement on visual stimulation spatial attention and spatial working memory
Neuron, 2004Co-Authors: Paul Bentley, Masud Husain, Raymond J DolanAbstract:We compared behavioral and neural effects of cholinergic enhancement between spatial attention, spatial working memory (WM), and visual control tasks, using fMRI and the anticholinesterase physostigmine. Physostigmine speeded responses nonselectively but increased accuracy selectively for attention. Physostigmine also decreased activations to visual stimulation across all tasks within primary visual Cortex, increased Extrastriate occipital Cortex activation selectively during maintained attention and WM encoding, and decreased parietal activation selectively during maintained attention. Finally, lateralization of occipital activation as a function of the visual hemifield toward which attention or memory was directed was decreased under physostigmine. In the case of attention, this effect correlated strongly with a decrease in a behavioral measure of selective spatial processing. Our results suggest that, while cholinergic enhancement facilitates visual attention by increasing activity in Extrastriate Cortex generally, it accomplishes this in a manner that reduces expectation-driven selective biasing of Extrastriate Cortex.
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neural response to emotional faces with and without awareness event related fmri in a parietal patient with visual extinction and spatial neglect
Neuropsychologia, 2002Co-Authors: Patrik Vuilleumier, Masud Husain, Jorge Armony, Karen Clarke, Julia Driver, Raymond J DolanAbstract:This study examined whether differential neural responses are evoked by emotional stimuli with and without conscious perception, in a patient with visual neglect and extinction. Stimuli were briefly shown in either right, left, or both fields during event-related fMRI. On bilateral trials, either a fearful or neutral left face appeared with a right house, and it could either be extinguished from awareness or perceived. Seen faces in left visual field (LVF) activated primary visual Cortex in the damaged right-hemisphere and bilateral fusiform gyri. Extinguished left faces increased activity in striate and Extrastriate Cortex, compared with right houses only. Critically, fearful faces activated the left amygdala and Extrastriate Cortex both when seen and when extinguished; as well as bilateral orbitofrontal and intact right superior parietal areas. Comparison of perceived versus extinguished faces revealed no difference in amygdala for fearful faces. Conscious perception increased activity in fusiform, parietal and prefrontal areas of the left-hemisphere, irrespective of emotional expression; while a differential emotional response to fearful faces occurring specifically with awareness was found in bilateral parietal, temporal, and frontal areas. These results demonstrate that amygdala and orbitofrontal Cortex can be activated by emotional stimuli even without awareness after parietal damage; and that substantial unconscious residual processing can occur within spared brain areas well beyond visual Cortex, despite neglect and extinction.
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a neuromodulatory role for the human amygdala in processing emotional facial expressions
Brain, 1998Co-Authors: J S Morris, Karl J Friston, Christian Buchel, C D Frith, Andrew W Young, Andrew J Calder, Raymond J DolanAbstract:Localized amygdalar lesions in humans produce deficits in the recognition of fearful facial expressions. We used functional neuroimaging to test two hypotheses: (i) that the amygdala and some of its functionally connected structures mediate specific neural responses to fearful expressions; (ii) that the early visual processing of emotional faces can be influenced by amygdalar activity. Normal subjects were scanned using PET while they performed a gender discrimination task involving static grey-scale images of faces expressing varying degrees of fear or happiness. In support of the first hypothesis, enhanced activity in the left amygdala, left pulvinar, left anterior insula and bilateral anterior cingulate gyri was observed during the processing of fearful faces. Evidence consistent with the second hypothesis was obtained by a demonstration that amygdalar responses predict expression-specific neural activity in Extrastriate Cortex.
Aina Puce - One of the best experts on this subject based on the ideXlab platform.
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Face-Specific Processing in the Human Fusiform Gyrus
Journal of Cognitive Neuroscience, 1997Co-Authors: Gregory Mccarthy, Aina Puce, John C. Gore, Truett AllisonAbstract:The perception of faces is sometimes regarded as a specialized task involving discrete brain regions. In an attempt to identi$ face-specific Cortex, we used functional magnetic resonance imaging (fMRI) to measure activation evoked by faces presented in a continuously changing montage of common objects or in a similar montage of nonobjects. Bilateral regions of the posterior fusiform gyrus were activated by faces viewed among nonobjects, but when viewed among objects, faces activated only a focal right fusiform region. To determine whether this focal activation would occur for another category of familiar stimuli, subjects viewed flowers presented among nonobjects and objects. While flowers among nonobjects evoked bilateral fusiform activation, flowers among objects evoked no activation. These results demonstrate that both faces and flowers activate large and partially overlapping regions of inferior Extrastriate Cortex. A smaller region, located primarily in the right lateral fusiform gyrus, is activated specifically by faces.
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differential sensitivity of human visual Cortex to faces letterstrings and textures a functional magnetic resonance imaging study
The Journal of Neuroscience, 1996Co-Authors: Aina Puce, Truett Allison, John C. Gore, Maryam M Asgari, Gregory MccarthyAbstract:Twelve normal subjects viewed alternating sequences of unfamiliar faces, unpronounceable nonword letterstrings, and textures while echoplanar functional magnetic resonance images were acquired in seven slices extending from the posterior margin of the splenium to near the occipital pole. These stimuli were chosen to elicit initial category-specific processing in Extrastriate Cortex while minimizing semantic processing. Overall, faces evoked more activation than did letterstrings. Comparing hemispheres, faces evoked greater activation in the right than the left hemisphere, whereas letterstrings evoked greater activation in the left than the right hemisphere. Faces primarily activated the fusiform gyrus bilaterally, and also activated the right occipitotemporal and inferior occipital sulci and a region of lateral Cortex centered in the middle temporal gyrus. Letterstrings primarily activated the left occipitotemporal and inferior occipital sulci. Textures primarily activated portions of the collateral sulcus. In the left hemisphere, 9 of the 12 subjects showed a characteristic pattern in which faces activated a discrete region of the lateral fusiform gyrus, whereas letterstrings activated a nearby region of Cortex within the occipitotemporal and inferior occipital sulci. These results suggest that different regions of ventral Extrastriate Cortex are specialized for processing the perceptual features of faces and letterstrings, and that these regions are intermediate between earlier processing in striate and peristriate Cortex, and later lexical, semantic, and associative processing in downstream cortical regions.
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human Extrastriate visual Cortex and the perception of faces words numbers and colors
Cerebral Cortex, 1994Co-Authors: T. Allison, Gregory Mccarthy, Aina Puce, Anna C. Nobre, Aysenil BelgerAbstract:: Electrophysiological correlates of the processing of visual information were studied in epileptic patients with electrodes chronically implanted on the surface of striate and Extrastriate Cortex. In separate experiments patients viewed faces, letter strings (words and non-words), numbers, and control stimuli. A negative potential, N200, was evoked by faces, letter strings, and numbers, but not by the control stimuli. N200 was recorded bilaterally from discrete regions of the fusiform and inferior temporal gyri. These category-specific face, letter-string, and number "modules" vary in location. In most cases there was no overlap in the location of face and letter-string modules, suggesting a mosaic of functionally discrete regions. In some cases letter-string and number N200s were recorded from the same location, suggesting that these modules may be less spatially and functionally discrete. Face N200-like potentials can be recorded from temporal scalp, allowing the possibility of studying early face processing in normal subjects. Longer-latency face-specific potentials were recorded from the inferior surface of the anterior temporal lobe. Potentials evoked by colored checkerboards were recorded from a region of the fusiform gyrus posterior to the fusiform region from which category-specific N200s were recorded. These results suggest that there are several processing streams in inferior Extrastriate Cortex. In addition to object recognition systems previously proposed for faces and words, our preliminary results suggest a separate system dealing with numbers. Postulated systems dealing with larger manipulable objects and animals have not been detected.
