Prior information of stimulus location: effects on ERP measures of visual selection and response selection.

This paper examines the effects of prior information of the location of an upcoming stimulus on event-related EEG potentials associated with the focusing of attention. Results of two tasks, reported in a previous publication (Praamstra, P., Boutsen, L., Humphreys, G.W., 2005. Frontoparietal control of spatial attention and motor intention in human EEG. J. Neurophysiol. 94, 764-774), were compared: one in which spatial attention was cued to the stimulus location and one in which the cue was non-informative. Only informative directional cues elicited directing-attention EEG potentials in the delay period between cue and target. Notwithstanding these electrophysiological signs of an attentional orientation prior to the occurrence of the target, there were no reaction time effects related to the presence of advance spatial information. By contrast, the advance information did have effects on EEG potentials following the target stimulus. The N2pc, reflecting an attentional selection mechanism in extrastriate cortex, was reduced in amplitude with advance spatial information. The N2cc, coinciding in time with the N2pc but measured over the motor cortex, was preempted by the advance spatial information. These results support that the N2cc is not due to overlap of the N2pc with movement execution-related activity. It is proposed that the neural activity underlying this EEG potential arises from the dorsal premotor cortex and serves an executive-attentional function that helps to ensure that the selection of a manual response is not biased by the direction of spatial attention.