Event-related potential correlates of transient attention shifts to color and location.

Effects of selectively attending to specific combinations of stimulus location and color were measured by means of event-related brain potentials in a trial-by-trial cueing paradigm. A symbolic precue was presented at the beginning of each trial indicating the response-relevant position and color of an upcoming imperative stimulus. Responses were required to infrequent target stimuli of the relevant color appearing at the cued location. Stimuli at attended locations elicited enhanced posterior N1/components as well as enhanced negativities at midline electrodes. No P1 enhancement was found for stimuli at the attended location. Attended color stimuli elicited a broad negativity starting about 220 ms that tended to be larger for stimuli presented at attended locations. These results show that transient attention shifts to non-spatial features like color are reflected by event-related potential (ERP) effects comparable to the effects measured under sustained attention conditions. Transient spatial attention yields earlier and larger ERP effects than transient attention to color and may modulate the ERP effects of non-spatial attention.