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David Pitcher, Brad Duchaine, Vincent Walsh, Nancy Kanwisher; TMS evidence for feedforward and feedback mechanisms of face and body perception. Journal of Vision 2010;10(7):671. doi: 10.1167/10.7.671.
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© ARVO (1962-2015); The Authors (2016-present)
Neuroscientists seeking to understand the cognitive mechanisms that underlie visual object perception have used functional magnetic resonance imaging (fMRI) to identify spatially distinct cortical regions in the human brain selective for different object categories. One such region, the occipital face area (OFA), shows a stronger response to faces than to other object categories and has been proposed to be the first stage in a cortical network specialized for face perception. We sought to more precisely establish when the OFA is engaged in face perception using transcranial magnetic stimulation (TMS). Ten subjects performed a delayed match to sample face discrimination task while double pulse TMS (separated by 10ms) was delivered over each subject's functionally localised OFA. Results showed that TMS disrupted task performance at two distinct latencies, 40–50 ms after stimulus onset and 100–110ms after stimulus onset. In a second experiment we investigated whether TMS delivered over an adjacent body-selective region, the extrastriate body area (EBA), would produce a similar temporal pattern of impairment. Ten subjects performed a delayed match to sample body discrimination task while double pulse TMS was delivered over each subject's functionally localised EBA. Results again showed two impairment windows, the first at 40–50ms and the second at 100–110ms after stimulus onset. The first impairment window at 40–50ms appears to reflect an early feed forward stage of face and body processing. The later impairment window at 100–110ms could reflect a second wave of feed forward information or task specific feedback mechanisms originating from higher cortical areas.
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