Dissociating top-down attentional control from selective perception and action.

Research into the neural mechanisms of attention has revealed a complex network of brain regions that are involved in the execution of attention-demanding tasks. Recent advances in human neuroimaging now permit investigation of the elementary processes of attention being subserved by specific components of the brain's attention system. Here we describe recent studies of spatial selective attention that made use of positron emission tomography (PET), functional magnetic resonance imaging (fMRI), and event-related brain potentials (ERPs) to investigate the spatio-temporal dynamics of the attention-related neural activity. We first review the results from an event-related fMRI study that examined the neural mechanisms underlying top-down attentional control versus selective sensory perception. These results defined a fronto-temporal-parietal network involved in the control of spatial attention. Activity in these areas biased the neural activity in sensory brain structures coding the spatial locations of upcoming target stimuli, preceding a modulation of subsequent target processing in visual cortex. We then present preliminary evidence from a fast-rate event-related fMRI study of spatial attention that demonstrates how to disentangle the potentially overlapping hemodynamic responses elicited by temporally adjacent stimuli in studies of attentional control. Finally, we present new analyses from combined neuroimaging (PET) and event-related brain potential (ERP) studies that together reveal the timecourse of activation of brain regions implicated in attentional control and selective perception.