What happens in between? Human oscillatory brain activity related to crossmodal spatial cueing

Abstract

Previous studies investigated the effects of crossmodal spatial attention by comparing the responses to validly versus invalidly cued target stimuli. Dynamics of cortical rhythms in the time interval between cue and target might contribute to cue effects on pefformance. Here, we studied the influence of spatial attention on ongoing oscillatory brain activity in the interval between cue and target onset. In a first experiment, subjects underwent periods of tactile stimulation (cue) followed by visual stimulation (target) in a spatial cueing task as well as tactile stimulation as a control. In a second experiment, cue validity was modified to be 50%, 75%, or else 251% to separate effects of exogenous shifts of attention caused by tactile stimuli from that of endogenous shifts, Tactile stimuli produced; 1) a stronger lateralization of the sensorimotor beta-rhythm rebound (15-22 Hz) after tactile stimuli serving as cues versus not serving as cues; 2) a suppression of the occipital alpha-rhythm (7-13 Hz) appearing only in the cueing task (this suppression was stronger contrateral to the endogenously attended side and was predictive of behavior success); 3) an increase of prefrontal gamma-activity (25-35 Hz, specifically in the cueing task. We measured cue-related modulations of cortical rhythms which may accompany crossmodal spatial attention, expectation or decision, and therefore contribute to cue validity effects. The clearly lateralized alpha suppression after tactile cues in our data indicates its dependence on endogenous rather than exagenous shifts of visuo-spatial attention following a cue independent of its modality. © 2008 Trenner et al.