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Abstract:
Abstract: Visual symmetry is important for discriminating
living from inanimate objects, identifying face orientation and
mate selection. Its importance is expressed in its ubiquity as a
design principle in objects of human construction (e.g., Persian
rugs). We used functional magnetic resonance imaging (fMRI) to
identify occipital cortical areas activated by the presence of
simple bilateral or multiple symmetries in fields of otherwise
random dots. Human fMRI responses were recorded using a multislice,
spiral acquisition sequence. Observers fixated the center of
stimuli that alternated between sets of symmetric and statistically
matched noise patterns, updated every 1.5 sec. Fourier analysis
identified voxels activated at the alternation rate at p <
0.001. A variety of translational or reflection symmetries
preferentially activated the middle occipital gyrus (MOG)
bilaterally. These stimuli produced little or no differential
activation of the early, retinotopic visual areas, the V5/MT motion
area, parietal cortex or the cerebellum. Moreover, the symmetry
stimuli did not activate the lingual and fusiform gyri at the base
of the brain (known to show activation to objects and faces vs
non-object textures). Since symmetry is a common property of
objects and faces, we suggest that activation of the dorsal MOG is
attributable to the symmetry of these object stimuli, whereas the
more ventral activation sites may reflect their epistomological
properties.
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