Improved visual sensitivity in the perihand space.

Studies in monkeys and humans suggest a dissociation between the visual fields near and far from the hand. In this study, we investigated visual detection and spatial discrimination in near- and far-hand fields using the stimulus of a flashing light emitting diode placed near (1 cm) and/or far (40 cm) from the hand. We found that there was greater accuracy (i.e., fewer errors) in the near-hand field. Control experiments indicated that (a) the superior near-hand detection performance was not due to response strategies, (b) the hand did not serve as a spatial reference, (c) the greater accuracy in the near-hand field did not reflect within-hemisphere or within-hemispace facilitation and (d) the effect appeared to be essentially due to viewing of the hand but not proprioceptive information. The results suggest there is an interconnected system for integrated (visual-tactile) coding of peripersonal space centered on body parts and comprising bimodal visuo-tactile cells.