Lost in vision: ERP correlates of exogenous tactile attention when engaging in a visual task.

Behavioural studies have shown that when engaging in a visual task response facilitation to tactile stimuli at exogenously cued locations is diminished. Here we investigated behavioural and also neural correlates of tactile exogenous attention when participants either watched a visual stream (single task) or also detected targets in the visual stream (dual task). During the visual stream, tactile cues were presented to the left or right hand followed by tactile targets at the same or opposite hand. Behavioural results demonstrated slowed responses to tactile targets at cued locations (i.e., IOR) in the single whilst no attention effect in the dual task. Concurrently recorded EEG revealed multiple stages of tactile processing to be attenuated when engaging in a visual task: First, the amplitude of the cueelicited somatosensory P100 component was suppressed suggesting relative early cross-modality effects in the dual task. Second, correlates of cue-induced attentional control processes showed a reduced late somatosensory negativity (LSN) in the dual compared to the single task suggesting smaller preparatory processes. Finally, early attentional selection correlates of post-target ERPs (N80) were absent in the dual task. This study demonstrated for the first time that engaging in a visual task abolished behavioural IOR in touch. ERP analyses showed that early somatosensory processing as well as specific correlates of tactile attentional orienting and target selection are diminished under visual engagement. Our findings are in line with a supramodal account of attention.