Topographic ERP changes due to displacements of visuo-spatial attention

Abstract

In order to explore the cerebral processes of visuo-spatial attention shifts, the spatio-temporal characteristics of ERPs to targets following a spatial cue were examined topographically. Subjects were asked to respond selectively to a target presented 200 ms after offset of a spatial cue. Valid targets (75%) appeared at cue position; invalid targets (25%) were presented at a different position than the cue. In valid trials, an anterior negative deflection of Nd and a single-peaked P3 were observed with shorter reaction time. In invalid trials, a posterior N2–P3 complex was observed with delayed reaction time. Spatio-temporal patterns of brain electric fields (BEF) to valid and invalid trials differed between 240 and 280 ms after target presentation. Regardless of target locations, the BEF in valid trials was characterized by anterior negative/posterior positive distribution. On invalid trials, where subjects were forced to shift their visuo-spatial attention from the cue to the target, the BEF was characterized by an anterior positive/posterior negative distribution for all cue-target pairs except those presented in the upper visual field. Therefore, the BEF within 240–280 ms after the target presentation might be concerned with cerebral processes of visuo-spatial attention shift, i.e., with recapturing/evaluating target.