EVENT-RELATED POTENTIALS TO AUDITORY-STIMULI FOLLOWING TRANSIENT SHIFTS OF SPATIAL ATTENTION IN A GO NOGO TASK

The effects of spatial attention on the human auditory event-related potential (ERP) were examined, while attention was oriented on a trial-by-trial basis. Additionally, it was investigated whether the ERP modulation to Nogo stimuli depends on attention. In four experiments, Go and Nogo stimuli were delivered 13.3-degrees from the left or right of fixation. In Experiments 1 and 2, subjects had to press a button whenever a Go stimulus was presented at the location previously indicated by a visual precue. In Experiments 3 and 4, the cue indicated the likely location of the upcoming stimulus but a button-press was required to Go stimuli at either location. Attended (correctly cued) as compared with unattended (incorrectly cued) stimuli elicited a bimodal negative deflection in the ERPs with a parietally distributed first and a frontocentrally distributed second part. Further, Nogo stimuli evoked differential ERP modulations in the N2 and in the P3 range. The former were dependent and the latter were independent of spatial attention.