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Abstract:
Previous event-related potential studies revealed an early
negative component (N170) that distinguished between human faces
and face components and any other stimulus types. Bentin et al.
(1996) suggested that this component is associated with exclusive
encoding of physiognomic information and the formation of a face's
sensory representation. Recently Sagiv & Bentin (1998) reported
that seeing schematic faces (smiley) is enough for eliciting a
normal N170. Hence the face-processing mechanisms to which the N170
is associated can apparently be activated by impoverished visual
input that is sufficient to elicit a face concept. The present
study tested this hypothesis. ERPs and fMRI measures of activation
were recorded during three stimulation blocks. In a first, the
stimuli were pairs of "X"s separated horizontally by 10 cm. In the
second, an ellipse encircled the same stimuli and with the addition
of "nose" and "mouth" formed a schematic face. The stimuli in the
third block were identical to the first. Isolated smiley eyes
elicited the N170 only in the third block. Bilateral fMRI
activation of face-areas (fusiform gyrus between collateral sulcus
and lateral occipitotemporal sulcus) was found in both first and
third blocks. In the first block only, cerebellar activation
(anterior lobe) occurred bilaterally in addition to the activation
of the face area. Together, these data suggest that conceptual
factors may change the manner in which visual input is processed by
visual association areas. The difference between fMRI and ERP
patterns requires further investigation.
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