ELECTROPHYSIOLOGICAL CORRELATES TO CUED ATTENTIONAL SHIFTS IN THE VISUAL AND AUDITORY MODALITIES

Reaction time (RT) is usually speeded and slowed to correctly and inco rrectly cued target stimuli, respectively, in experiments on attention shift (Posner, 1988). When targets occur in a spatial location differ ent from the cue, shifting attention from the cued location to the tar get location involves interrupt of ongoing activity, move attention to the new location, and reengage attention. The present study investiga ted whether the cognitive operations involved in cued vs uncued attent ional shifts also were detectable in the event-related potentials (ERP s). Two experiments are reported, one with visual and one with auditor y stimuli. In the visual modality, the cue and target were a lit-up sq uare and an asterisk, respectively, shown on a computer screen. In the auditory modality, the cue was a tone in either the left or right ear , followed by the target noise in either the same or the opposite ear. The results from the visual experiment showed shorter RTs to correctl y cued (Valid) targets and longer RTs to incorrectly cued (Invalid) ta rgets. Invalidly cued targets elicited enhanced P3 amplitudes, with a frontocentral distribution. Reduced P3 amplitudes were observed on Val id trials, largest reduction for parietooccipital leads. The auditory experiment showed P3 enhancement frontally and reduced amplitudes at t emporal and parietal leads. No RT differences were seen to Valid and I nvalid trials. The existence of an anterior attention system involved in interrupt and disengage of attention, and a posterior attention fac ilitation system related to cue presentation is discussed. (C) 1994 Ac ademic Press, Inc.