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Dynamics of visual feature analysis and object-level processing in face versus letter-string perception
Neurones in the human inferior occipitotemporal cortex respond to specific categories of images, such as numbers, letters and faces, within 150-200 ms. Here we identify the locus in time when stimulus-specific analysis emerges by comparing the dynamics of face and letter-string perception in the sam...
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Published in: | Brain (London, England : 1878) England : 1878), 2002-05, Vol.125 (Pt 5), p.1125-1136 |
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Main Authors: | , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | Neurones in the human inferior occipitotemporal cortex respond to specific categories of images, such as numbers, letters and faces, within 150-200 ms. Here we identify the locus in time when stimulus-specific analysis emerges by comparing the dynamics of face and letter-string perception in the same 10 individuals. An ideal paradigm was provided by our previous study on letter-strings, in which noise-masking of stimuli revealed putative visual feature processing at 100 ms around the occipital midline followed by letter-string-specific activation at 150 ms in the left inferior occipitotemporal cortex. In the present study, noise-masking of cartoon-like faces revealed that the response at 100 ms increased linearly with the visual complexity of the images, a result that was similar for faces and letter-strings. By 150 ms, faces and letter-strings had entered their own stimulus-specific processing routes in the inferior occipitotemporal cortex, with identical timing and large spatial overlap. However, letter-string analysis lateralized to the left hemisphere, whereas face processing occurred more bilaterally or with right-hemisphere preponderance. The inferior occipitotemporal activations at approximately 150 ms, which take place after the visual feature analysis at approximately 100 ms, are likely to represent a general object-level analysis stage that acts as a rapid gateway to higher cognitive processing. |
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ISSN: | 0006-8950 1460-2156 |
DOI: | 10.1093/brain/awf112 |