Localization of FFA using SSVEP-based binocular rivalry
In binocular rivalry, a subject views two incongruent stimuli through each eye but consciously perceives only one stimulus at a time, with a switch in perceptual dominance every a few seconds. To locate the fusiform face area (FFA) which is a face-selective region, thirteen subjects are recorded with a 64-channel electroencephalograph while experiencing binocular rivalry. A face image flickering at one frequency is presented to one eye and a non-face image flickering at the same frequency is presented to the other eye. Steady state evoked potential (SSVEP) at the frequency is used as tags for the two stimuli. This paper uses an algorithm called standardized shrinking LORETA-FOCUSS (SSLOFO) to reconstruct face-selective sources from the EEG data. The sources are selected by comparing signal strength at the stimulus frequency during face dominance and face suppression. The results demonstrate that the face-selective region identified in this paper is consistent with FFA, as has been confirmed to be activated about twice as strongly in fMRI experiments when people view faces as when they view other kinds of objects. The present study also suggests that the method has the potential advantage of investigating neural correlates.
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