form perception

..This supports object-based theories of attention and demonstrates that perceptual grouping, which is usually conceived of as a purely stimulus-driven process, can also be governed by goal-directed mechanisms...

..These results indicate that the representations of faces and objects in ventral temporal cortex are widely distributed and overlapping...

..Our results indicate that a large amount of learning took place in object-specific mechanisms that are insensitive to image size...

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..Our results demonstrate that contextual interactions in V1 play a pivotal role in contour integration and saliency...

..Overall, the correlation between recognition performance and fMRI signal was highest in occipitotemporal object areas (the lateral occipital complex)...

..This may serve as a general neuronal mechanism of perceptual learning and reflect top-down mediated changes in cortical states...

..This region was found in the lateral occipitotemporal cortex in all subjects tested and apparently reflects a specialized neural system for the visual perception of the human body...

..Overall, these results indicate that the lateral occipital complex plays an important role in human object recognition...

..The results showed that mechanisms that adapt to 3-D shapes combine real and illusory 2-D orientation information over a range of spatial frequencies...

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..Together with previous theoretical work and human object perception experiments, we speculate that UTL may reflect the mechanism by which the visual stream builds and maintains tolerant object representations...

..5°. Later-developing, low-level integrative mechanisms of lateral connectivity and feedback appear not to be differentially impaired in the illness...

..Neural activity in the lateral prefrontal cortex reflected the category of visual stimuli, even when a monkey was retrained with the stimuli assigned to new categories...

..Commonalities of visual shape representation across hierarchical levels may reflect the replication of neural circuits used in generating complex shape representations at multiple spatial scales...

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..In both experiments we also found no differences between closed and open jagged contours detection in terms of element separation. The neuroanatomical implications of these findings relatively to area V1 are discussed...

..These latter areas appear to correspond to those associated with the perception of complex stimuli such as faces and places...

..1996). This implies that MT neurons make a different contribution to the two tasks. For the depth task, either the pool of neurons used is smaller or the correlation between neurons in the pool is larger...

..Moreover, a holistic-inclusive effect was correlated with changes in the right FFA. Face recognition may not be unique in its reliance on holistic processing, measured in terms of both behavior and brain activation...

..Evidence from psychophysics and physiology is converging towards the identification of an intermediate level of shape processing, where sensitivity to such global attributes emerge...

..These data favour a model of segmentation where boundary formation initiates surface filling-in...

..The results indicate that as children learned nouns, they also learned to attend to shape in the novel word task. At the same time, children showed an acceleration in new noun production outside of the laboratory...

..However, some children with WS can achieve similar performance to typically developing children on some tasks involving the dorsal stream although the strategies and processing may be different in the 2 groups...

..The two modes may work in parallel, with a graded balance changing according to the behavioral context. Determining whether or not these hypotheses are valid will require further studies...

..The results suggest that the encoding of faces and other complex patterns draws upon contrastive neural mechanisms that reference the central tendency of the stimulus category...

..The temporal sequence of the events suggests that the computation of illusory contours involves intercortical interaction, and that early perceptual organization is likely to be an interactive process...

..We suggest, based on these findings, that somatosensory representations of shape are computed by areas 3b, 1, 2, IPA, and ASM in this hierarchical fashion...

..These results demonstrate two spatially and temporally distinct stages of visual cortical processing, the first one limited to local features and the second one integrating information at a more global level...

..We suggest that the extraction of information of angles embedded within contour stimuli may start in area V2...

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..A strong left hemisphere dominance in visual form recognition was also revealed. The observed laterality may be a reflection that the left hemisphere is more important in symbolic and/or semantic coding of visual form information...

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..These findings have implications for computational models of face recognition and for competing neural theories of face and object recognition...

..7) Only some natural textures will provide sufficient monocular cues to support veridical shape inferences, and this can be predicted from their global Fourier transforms...

..These data indicate that the LOC represents not simple image features, but rather higher level shape information...

..Finally, it is concluded that the underlying functional architecture is not only dynamic and context dependent, but the pattern of connectivity depends as much on past experience as on actual stimulation...

..Our findings suggest that shape-selective adaptation is a general mechanism of visual object processing and its neural effects are primarily reflected in the N170 component of the ERP responses...

..Taken together, the results are consistent with the hypothesis that humans optimally combine the two cues to surface slant, with cue weights proportional to the subjective reliability of the cues...

..The results are consistent with the view that the right fusiform plays a greater role in processing specific visual form information about objects, whereas the left fusiform is also involved in lexical/semantic processing...

..Our results imply that crowding is distinct from ordinary masking, and is perhaps related to texture perception. Under crowded conditions, the orientation signals in primary visual cortex are pooled before they reach consciousness...

..Thus, our findings provide evidence that learning acts on distinct visual recognition processes and shapes feedforward interactions across brain areas to support performance in complex perceptual tasks...

..We must, therefore, conclude that there is no evidence from the current study that glossiness influences shape perception although to the observer matte and glossy objects look quite different...

..They further suggest that local texture skew, when available in an image, contributes significantly to perceptual estimates of surface orientation...

..A species-typical feature was identified in the perceptual processes associated with complex forms, such as those involved in individual recognition...

..These findings extend those of related studies by showing that CEs of this type actually correspond to the second phase of a bi-phasic pattern of specific perception-action interference...

..The existence of a case of non-face developmental visual agnosia would indicate that the development of normal face recognition mechanisms does not rely on the development of normal object recognition mechanisms...

..Our results suggest a general model of cortical function, whereby horizontal connections provide a broad domain of potential associations, and top-down inputs dynamically gate these linkages to task switch the function of a network...

..In particular, the model proposes that intrinsic properties of synchronization account for the increased salience of smooth, closed contours. Application of the model to real images is demonstrated...

..In addition, we show that identification of 3-D shapes from chromatic flows can be masked by luminance modulations, indicating that it is subserved by orientation-tuned neurons sensitive to both chromatic and luminance modulations...

..We show that coupling compressive nonlinearities in LGN neurons with expansive nonlinearities in cortical neurons can model the frequency-specific component of suppression...

..Our data confirm that different cues can disambiguate each other. Data from both experiments are well modeled by a Bayesian approach incorporating a prior for convexity...

..These findings are consistent with predictive coding models of vision that postulate that inferences of high-level areas are subtracted from incoming sensory information in lower areas through cortical feedback...

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..Thus, only object-load seemed to influence encoding and retention while feature-load played a crucial role during retrieval. Our results demonstrate that object-load and feature-load influence short-term memory at different stages...

..These results show that action makes an important contribution to depth perception, and argue for a revision of the rigidity hypothesis to incorporate the special case of stationary objects...

..H. Elder & R. M. Goldberg, 2002). The potential of hierarchically extended Bayes models for a better understanding of principles in cue integration is discussed...

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..Our findings imply that manipulating adaptation duration provides an opportunity to specifically adapt different neural processes of shape-specific coding and to investigate their stimulus selectivity...

..We conclude that task-dependent ERP differences fail to capture object processing speed, at least for some categories like faces. We discuss models of object processing that might explain our results, as well as alternative approaches...

..This pattern of deficits is consistent with the known properties of area V4 in nonhuman primates, indicating that AR's lesion affects a cortical region functionally homologous to macaque V4...

..We suggest that poorer recognition of other-race faces may reflect reduced perceptual expertise with such faces and perhaps reduced motivation to individuate them...

..Our results indicate that, in addition to other cortical regions, areas V5 and V1 are activated. Activity in area V1 was particularly prominent...

..This difference represents a substantial economy in cortical neuronal processing of peripheral visual information and may allow a recent theory of intercellular binding to be tested...

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..The aftereffects survived a size change between adaptation and test faces (Experiment 2), a result that rules out low-level adaptation as an explanation. These results provide strong evidence that face-shape coding is view-specific...

..Such results show that early processes in object recognition respond to category-specific visual information, and are associated with strong lateralization and orientation bias...

..The representation of shape in IT thus exceeds a mere faithful representation of physical reality, by emphasizing perceptually salient features relevant for essential categorizations...

..We find that these V1 modulations to shape change are correlated with low-level changes in orientation contrast rather than shape perception per se...

..The extraction of information about an object's color seems to occur relatively early in visual analysis as compared with the extraction of surface texture, perhaps because the latter requires more complex computations...

..These results provide further evidence for a nonhierarchical organization of the cortical face-processing network...

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..The detection of illusory contours by independently evolved visual systems argues that processing of edges in the absence of contrast gradients reflects fundamental visual constraints and not just an artifact of visual processing...

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..Thus, there is a growing empirical consensus that MLE provides a good quantitative account of cue combination and that sensory information is used in a manner that maximizes the precision of perceptual estimates...

..However, older subjects' performance was not affected by the orientation of the local elements. This indicates an age-related decline in contour integration...

..Each stream is composed of a mixture of magno, parvo, and konio geniculate signals. Further studies are required to elucidate how the patches and interpatches differ in the output they convey to extrastriate cortex...

..The grouping process was surprisingly fast: In a backward masking experiment we show that a stimulus duration of 30-60 ms is sufficient to perceive a contour and to identify its shape...

..Cancellation increased monotonically as the angle between two adapting views decreased, consistent with broadly tuned, view-specific coding of face shape...

..The significance of these differences and similarities between postreceptoral mechanisms is discussed...

..This indicates a common physiological processing stream for orientation-based contour integration of red-and-green and black-and-white elements...

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..Isotropic textures thus convey correct 3-D shapes of developable surfaces only in some conditions, and the same perceptual strategies lead to non-veridical percepts in other conditions...

..After training, discrimination thresholds for the incongruent stimuli are increased relative to thresholds for congruent stimuli, suggesting that subjects learned effectively to integrate the two formerly unrelated signals...

..In the reverse condition, detection of global form was not influenced by adding local deviations onto the structure. This suggests that local and global shape information can be detected independently within the human visual system...

..The remapping of visual processing, demonstrated here with form adaptation, may help to explain our impression of a smooth transition, with no temporal delay, of visual perception across glances...

..NAPs offer a striking advantage over MPs for object classification and are therefore more likely to play a central role in the representation of objects...

..The pattern of correlations among measures observed in the present study was consistent with previous reports, supporting the usefulness of the 400 picture set as a tool for cognitive research in different cultures and ages...

..We find stronger responses to circular patterns in areas V3/VP and V4. Our results suggest that extracting circular shape is an important step in intermediate shape processing...

..Independent behavioral measures confirmed that faces with averted gaze were more arousing, suggesting the activity in the central nucleus may be related to attention and arousal...

..We argue that the illusion arises owing to a convexity preference when the raw data have ambiguous interpretations. However, using a familiar object with typical orientation, shading, and pigmentation greatly enhances the effect...

..The results are interpreted in terms of a surface-based model of 3D shape representation, which proposes edge-bounded 2-dimensional polygons as basic primitives of surface shape...

..Overall, the results of the experiments reveal that older observers can effectively perceive 3-D shape from both vision and haptics...

..Here, we show that this failure actually originates from a combination of poor encoding of local orientation and abnormal processing of visual context...

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..This interaction between type of task and mode of presentation, may be due to the increased amount of correlation between test and standard figures of the encoding noise common to the two dimensions of each figure...

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..The theoretical approach within which we frame our discussion considers internal models of anticipatory control which may provide a suitable explanation of our results...

..The advantage of multi-tone over two-tone negatives can be attributed to preserved facial information carried by the high-spatial-frequency components of the image...

..A generic rendering engine grants access to a variety of element-drawing functions, including Gabors, Gaussians, letters, and polygons...

..neuronal populations in area V2 and whether neurons in V2 are directly implicated in specific aspects of form perception. A third project will study the representation of three-dimensional shapes in area V4...

..abstract_text> ..

..This is an area involved in form perception and visual attention. We will study how the organization of area V4 relates to form perception and attention...

..The face patch system offers a unique opportunity to dissect the neural mechanisms underlying form perception, because the system is specialized to process one class of complex forms, and because its computational ..

..discourse) and to study their relation to similar non-linguistic perceptual abilities such as motion and form perception, gesture comprehension, and aspects of spatial processing. (3)...

..We will examine the relationship between these phase anomalies and infants' phase sensitivity...

..The broad long-term objective of this research is to elucidate the mechanisms underlying visual form perception under its natural dynamic conditions...

..The proposed research is to conduct experimental and theoretical research on the problem of integrating form perception and the perception of motion...

..There are two compelling reasons to undertake the study of 3D form perception. The first is that 3D form perception is a paradigm of sensory integration in the brain...

The long-term goal of this work is to understand the neural mechanisms of visual form perception. The current project aims to study the processing of modestly complex visual stimuli such as smooth contours, junctions and texture ..

..of light adaptation (to the mean luminance and chromaticity in the stimulus); and (3) how color and form perception are influenced by adaptation to spatial stimuli...

..Taken together, the results of this program of research will test hypotheses that tie our understanding of visual search to our understanding of short and longer term visual memory. [unreadable] [unreadable]..

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..He will expand the Guided Search model to handle additional data (e.g. eye movements in visual search and the "attentional blink"). ..

..The workshop will be held at the University of Houston from November 1 through November 3, 2003. ..

..Thus techniques from cognition, perception, statistical learning theory, and physiology together will reveal what is computed where, in the brain, when an observer identifies an object. ..

..Knowing how the visual system computes SFM is not only essential for understanding the brain per se, but also important for finding psychophysical diagnostic tools for pinpointing potential areas of brain damage. ..

..It also should help to provide new ways to conceptualize debilitating memories in post-traumatic stress disorder (and some phobias) and to suggest new treatments for such afflictions. ..

..The methods developed here will be useful in identifying functional consequences of color vision deficits. PHS 398 (Rev. 05/01) Page 2 Principal Investigator/Program Director (Last, first, middle): ZAIDI, QASIM ..

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..The results of this research will be beneficial in understanding the increased accident risk associated with age. ..

..Understanding the cerebral basis of motor control and the body schema is likely to contribute substantially to the development of interventions that target these representations. [unreadable] [unreadable]..

..The relevance of this research to public health lies in its direct application of the results of this research program to achieve a better understanding of impairments found within and outside the autism spectrum. ..

..This study will also determine whether nasalward/temporal biases previously reported for large field uniform stimuli propagate to the figure/ground segmentation process. ..

..The second is that prosopagnosia results from deficits in form perception, and the third is that it results from deficits in texture perception...

..More generally, this knowledge will lead to improved tests of spatial cognition that will be useful in better understanding the deficits in knowledge and behavior resulting from diseases, such as Alzheimer's, and brain damage. ..

..Identifying early antecedents of later deficits has profound implications for intervention, assessment,and remediation, as well as for understanding the nature of the infant mind. ..

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..The knowledge to be gained from this research is essential for formulating effective physical therapies for the elderly or children with DCD, or for learning to use visual aids and prosthetic limbs. ..

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..Finally, we propose to use transcranial magnetic stimulation to identify specific brain regions that are necessary for normal temporal processing. ..

..This research may lead to technological advancement in the area of computer vision, as well as to better understanding of disorders of perceptual organization such as visual agnosia and dyslexia. [unreadable] [unreadable]..

..In all of the experiments, we will use a novel fMRI adaptation technique to characterize tuning functions in specified visual areas. ..

..The results will have manifold implications for understanding normal and impaired human function, for constructing artificial (including robotic) vision systems for probing the neural mechanisms of perception. ..

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..Developmental curves will be compared for cross-sectional and longitudinal samples and across domains (faces and objects). ..

..The experiments on spatial learning by preview compare the learning of a route by walking vs. auditory or haptic exposure. ..

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..Ultimately both the prehension and tactile exploration tasks have promise as diagnostic and therapeutic techniques to aid in rehabilitation medicine with stroke patients and patients with peripheral neuropathies. ..

..The potential clinical significance of this work is also clear. If, as hypothesized, the body schema is crucial to action, interventions targeting this representations may have important therapeutic implications. ..

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..A number of illusions which occur in vision will also be investigated when presented tactually. In addition, top down influences as well as context effects will also be studied. ..

..g., in the ventral "pattern processing stream" such as V4 and IT) and perception of global shape attributes. ..

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..Finally, as mental motor imagery tasks require minimal language capacity or abstract reasoning, we propose to investigate the use of these measures in subjects with cognitive impairment. ..

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..The INRSA component will fund exclusively fellows with U.S. residency certification while the other institutional components will fund both the remaining U.S. and non-U.S. fellows on an equal basis. ..

..Concentration on mouse behaviors, neurochemistry and behavior will advance studies aimed at kinetic applications. ..

..Finally, the results of this proposal will have important implications for our understanding and modeling of the relation between attention and overt orienting. ..

..Providing sensory feedback would clearly enhance the efficacy of brain-machine interfaces and these results will provide new information about the normal utilization of sensory inflow in the control of movements. ..

..Experimental and computational studies are outlined to determine the possible benefits of fading and explore their possible implications for neural-computational bases of learning. ..

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..Once validated, this technique will allow us to test hypotheses regarding the specific area of PRL in patients with ARMD. ..

..Thus, the major aim of the proposed study is to further examine the dynamic process of the neural substrates of emotional experience, including both time course and magnitude of the neural instantiation of affective processes. ..

..The training is at the graduate level, and usually lasts from 4 to 6 years. ..