Combined spatial and temporal imaging of brain activity during visual selective attention in humans

VISUAL-SPATIAL attention is an essential brain function that enables us to select and preferentially process high priority information in the visual fields^1,2. Several brain areas have been shown to participate in the control of spatial attention in humans^3-5, but little is known about the underlying selection mechanisms. Non-invasive scalp recordings of event-related potentials (e.r.ps) in humans have shown that attended visual stimuli are preferentially selected as early as 80-90 ms after stimulus onset^6,7, but current e.r.p. methods do not permit a precise localization of the participating cortical areas. In this study we combined neuroimaging (positron emission tomography) with e.r.p. recording in order to describe both the cortical anatomy and time course of attentional selection processes. Together these methods showed that visual inputs from attended locations receive enhanced processing in the extrastriate cortex (fusiform gyrus) at 80-130 ms after stimulus onset. These findings reinforce early selection models of attention^8-10.