The timing of attentional modulation of visual processing as indexed by ERPs.

ABSTRACT The most debated matter in electrophysiological investigations of neural mechanisms governing atten tional selection of visual information is the 'timing of attentional modulation of processing in the visual pathways. Indeed, because of their high temporal res- olution (in the order of milliseconds), but their scarce spatial resolution in localizing neural processing, event-related potentials (ERPsj of the bmin have < on- tributed predominantly to determining the time at which a particular attentional manipulation affects visual processing, and to providing evidence for the debate on early versus late selection. After a review of our own ERP studies and in vivo cellular, ERPs/ERFs, and fMRI studies of other authors, we advance the opinion that although modulation of spatial attention processing might start after relatively longer latencies and in extrastriate areas, feature-directed attention affects striate cortical, if not subcortical, regions at a very early time point.