Carlin, Sean

Near-hand benefits are seen when individuals are able to process targets more quickly, accurately, and with greater precision when a hand is placed near, rather than far from a target. One possibility is that near-hand stimuli recruit visual-tactile bimodal cells. Research reports that placing a hand near a target delayed immediate saccade onset and speeded delayed saccade onset. Study 1 examined saccade onset to targets appearing near a real hand, a realistic fake hand, or a non-hand visual cue. Immediate saccades were facilitated and delayed saccades were slowed with a real hand in the display, in comparison to a fake hand and no-hand. To establish the link between near-hand effects and bimodal cells, Study 2 used repetitive transcranial magnetic stimulation (rTMS) to depress cortical activity in PMd. RTMS did not induce a reversal of interference induced by near-hand, congruent targets. However, a reversal of the hand effect was found in the stimulation group; a real hand in the display may delay immediate saccades and improve delayed saccades post-stimulation. This finding may double dissociate the effect of the real hand from the fake hand and may be inconsistent with the hypothesis that the hand is attracting attention.

Author Keywords: multisensory integration, near-hand effects, PMd, premotor cortex, rTMS, visual-tactile bimodal neurons