Vision enhances selective attention to body-related information

Viewing ones' own hands while directing attention to one of the hands leads to earlier attentional modulations of somatosensory processing than when hands are not visible. This effect of vision on tactile-spatial selection could be explained by vision providing additional information about the location of the hands in external space. The present study investigated whether vision of the hands also affected tactile-attentional mechanisms when the relative locations of the hands were irrelevant. Participants silently counted infrequent tactile or auditory deviants in an alternating stream of tactile and auditory stimuli while ignoring stimuli in the other modality, when their hands were either visible or covered from view. Modality-selective attentional modulations of ERPs to tactile stimuli (when touches vs. tones were attended) were already present for the time range of the N80 component when hands were visible, but there were only later modulations (starting at N140) when hands were covered. This suggests that, rather than being restricted to tasks requiring spatial selection between body parts, vision of the hands can facilitate attention toward the body in far more general terms. In contrast to tactile stimuli, attentional modulations of ERPs to auditory stimuli (when tones vs. touches were attended) were not reliably affected by viewing the hands. This suggests that the primary purpose of visual facilitation may be to enhance the processing of body-related information only.