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Abstract:
Abstract: Faces are processed in a specialised area of the
right fusiform gyrus. Face-related ERPs peak at about 200 ms after
stimulus onset (N170, N200). We investigated whether this early
face-related activity is selectively modulated by focussing
attention either on faces or on another class of ecologically
relevant stimuli (houses). In normal subjects MEG and EEG were
recorded simultaneously (planar 49-channel MEG-system centered over
T6 and 9 EEG electrodes at T3/4, T5/6, O1/2, Fz, Cz, Pz). Grey tone
images of houses and faces were presented for 500 ms and masked for
1.5 s. Using a block design either a face or a house was the
attended target (press button). ERPs in the attended and unattended
condition were subtracted for non-targets in each stimulus class.
For houses MEG/EEG difference curves consistently showed
significant negative deflections between 250 and 350 ms; for faces
these differences already started between 150 and 200 ms. In some
subjects a second peak at 300 ms occurred, similar to houses. The
results show that early face-related activity can be selectively
modulated by attention implying category-specific top-down
influences imposed onto the right inferotemporal cortex. That
attentional effects occurred earlier for faces than for houses
suggests a preferential access of top-down influences to the
processing of stimuli with higher socioecological valence.
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