Predominantly extra-retinotopic cortical response to pattern symmetry

Symmetry along one or more axes is a key property of objects and

biological organisms. We report on a bilateral visual region of occipital

cortex that responds strongly to the presence of multiple symmetries in

the viewed image. The stimuli consisted of random dots organized in

fourfold and onefold mirror-symmetric patterns, against random

control stimuli. The contrast between symmetric and random patterns

produced negligible or inconsistent activation of the primary visual

projection area V1 or of other medial occipital projection areas.

However, there was strong symmetry-specific activation in extraretinotopic

lateral occipital cortex. The high level of activation in this

region of cortex may represent part of a general class of computations

that require integration of information across a large span of the visual

field.