Effects of attention and stimulus probability on ERPs in a Go/Nogo task. Biol Psychol 35:123–138

Event-related potentials were measured to letters presented either to the left or the right of a fixation point that were preceded by a precue that indicated the position of the upcoming letter either correctly (valid trials) or incorrectly (invalid trials). One letter required a response (Go stimulus), while the other letter required no response (Nogo stimulus). In experiment I, Nogo letters occurred only on 25 % of the trials, while in experiment II, Go and Nogo letters were equiprobable. In both experiments, Nogo stimuli elicited larger N2 components and P3s with a more anterior topography than did Go stimuli. The N2 enhancement elicited by Nogo stimuli showed a frontal maximum (most markedly-when Go and Nogo stimuli were equiprobable) and was significantly influenced by precue validity. These results are discussed in terms of “Response Mismatch ” and action inhibition processes