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Abstract:
The present study investigated hemispheric differences and
face-processing stages. Event-related potentials (ERPs) were
recorded during a face-matching task for four types of centrally
presented faces: Bisymmetric faces, comprised of a person's
hemiface and its mirror image; Chimeric faces, which joined the
hemifaces of two different people; and two types of Hemifaces, in
which a person's half-face to the right or left was joined to a
low-contrast, standard half-face in the opposite visual field. The
faces were presented in randomized order for 45 ms followed by a
pattern mask. A white stripe along the vertical midline of all
faces concealed the discrepancy between the two halves, such that
subjects were unaware that some faces were not bilaterally
symmetric. Despite a higher level of performance for Hemi-left than
Hemi-right faces and higher frequency of left than right
hemispatial matches for Chimeric faces, ERPs revealed no difference
between Hemi-left and Hemi-right faces or between left and right
hemispatial matches of Chimeric faces. The N170 component was
larger over the right than the left temporal cortex for all types
of faces. Interestingly, ERPs to Bisymmetric faces diverged from
those to Hemifaces at 200 ms poststimulus and from those to
Chimeric faces at 400 ms. These findings reveal that basic facial
properties that are absent in Hemifaces are discriminated earlier
in processing than information about facial identity.
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