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closeRapid Assessment of Shape Category -- Ernest Greene, Academic Editor
Posted by egreene on 05 Jan 2009 at 17:06 GMT
It has been the general belief that image processing in the occipital cortex provides rather elementary discrimination of contour properties, e.g., orientation, length, and curvature. These encoding operations were thought to require time intervals of 100 ms or more, after which the information was passed into the temporal lobe where shape-selective discriminations took place in another 70-100 ms. However, a number of studies have found category specific discriminations at shorter time intervals, and the present study joins that chorus. These investigators used MEG recordings to monitor brain areas that provided selective responses to face, house and body shapes (presented with or without inversion). The recordings provide millisecond-level resolution of brain activation, and selective response was observed to occur between 70-100 ms for each of the categories. This argues for especially fast category-specific processing routes, and/or new principles for encoding the shape information that would support these very rapid discriminations.