Shifting attention in visual space: the effects of peripheral cueing on brain cortical potentials

The effects of attentional shifts following peripheral cues were studied in humans using event-related potentials (ERPs) and reaction times. Subjects released a key following the presentation of a target preceded by a predictive cue in the same (valid) or the opposite (invalid) visual field, or a bilateral, non-predictive cue. The stimulus onset asynchrony (SOA) separating cue and target was either 200 or 600 ms. Subjects were faster and more accurate when responding to validly cued targets. Attentional modulation of the ERP was manifested as an enhancement of P1-N1 amplitude at posterior electrode sites following a validly cued target. Furthermore, the latencies of P1, N1 and P3 were significantly shorter in valid trials than in invalid trials. These results only reached significance with the longer SOA, since ERP refractoriness distorted the response evoked by the target when the SOA was only 200 ms. The findings are discussed in the context of previous behavioral and ERP cueing studies.