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Abstract:
Abstract: The N170 occipito-temporal scalp potential is
elicited by a variety of objects, but is typically larger for
faces. Recently, we suggested that the amplitude of the N170 is
unlikely to encode the "faceness" of a stimulus because (1)
amplitude differences can be as large between object categories
(e.g., cars and shoes) than between faces and these categories, and
(2) the N170 amplitude is even larger for inverted faces. In
contrast, a 10 ms delay for inverted images is observed only for
faces, being a candidate to reflect a process uniquely dedicated to
faces. However, given behavioral and neuroimaging evidence that
experts can process objects in a similar manner and in the same
neural substrate as faces, we predicted that expertise would
modulate the N170 inversion-related delay. ERPs were recorded to
upright and inverted faces and Greebles in a sequential-matching
task, for ten subjects before and after expertise training with
Greebles. A N170 inversion-related delay was always obtained for
faces, but it was observed for Greeble stimuli only in Greeble
experts. An inversion effect in amplitude was also obtained for
experts only, in the left hemisphere. In general, expertise effects
were larger in the left hemisphere. The N170 can be modulated by
expertise and is thus unlikely to reflect a process uniquely
dedicated to faces.
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