Revealing effects of noninformative spatial cues: an EEG study of inhibition of return.

Simple responses to noninformatively cued spatial stimuli can be delayed whenever a cue has been briefly presented at the location of the subsequent target. This phenomenon (inhibition of return) might be due to a mechanism that inhibits irrelevant information. However, with sustained cues no inhibition is observed. It has been hypothesised that in the latter, task inhibition is masked by an excitation process. ERP measures support the inhibition-excitation account: (a) P1 suppression, assumed to reflect inhibition, was observed for all targets presented at a cued location. (b) A later negative component (Nd250) was increased with sustained cues, and hence might reflect the excitation process. (c) A negative component at right parietal electrode sites (Nd310) appeared only when inhibition of return was observed. A second study confirmed the link between these ERP components and mechanisms involved in inhibition of return.