Which finger? Early effects of attentional selection within the hand are absent when the hand is viewed.

The sight of a hand can bias the distribution of spatial attention, and recently it has been shown that viewing both hands simultaneously can facilitate spatial selection between tactile events at the hands when these are far apart. Here we directly compared the electrophysiological correlates of within-hand and between-hands tactile-spatial selection to investigate whether within-hand selection is similarly facilitated by viewing the fingers. Using somatosensory event-related potentials, we have shown that effects of selection between adjacent fingers of the same hand at early somatosensory components P45 and N80 were absent when the fingers were viewed. Thus, we found a detrimental effect of vision on tactile-spatial within-body part (i.e. hand) selection. In contrast, effects of tactile-spatial selection between hands placed next to each other, which were first found at the P100 component, were unaffected by vision of the hands. Our findings suggest that (i) within-hand and between-hands selection can operate at different stages of processing, and (ii) the effects of vision on within-hand and between-hands attentional selection may reflect fundamentally different mechanisms.