Improved visual sensitivity in the perihand space

Abstract

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.

Visuospatial attention and visual perception in peripersonal space: the impact of intrinsic hand representation and manual action goals

“…Conversely, brief presentation of stimuli improved the accuracy of onset detection for high contrast targets. We found that contrary to earlier findings (Dufour & Touzalin, 2008), there was no evidence of enhancements in luminance contrast sensitivity when hands were adjacent to compared with distant from the display. Despite the demonstrated enhancements in temporal shifts in attention for high/ contrast onsets and offsets near hands found by others, hand proximity for stimulus presentation < 250ms did not improve spatial shifts to such basic magnocellular inputs.…”

“…When considered in combination with the results of Dufour and Touzalin (2008), the current findings suggest that when stimuli were presented for 250ms or less, greater visual sensitivity is not apparent for luminance onsets near versus distant from the hand. By contrast, Dufour and Touzalin (2008) found that visual sensitivity improved near the hand for luminance onsets which were presented for longer stimulus durations (500ms). This suggests that near-hand magnocellular facilitation may occur later, perhaps as the result of top-down allocation of attention.…”

“…In particular, Dufour and Touzalin (2008) found greater accuracy and faster response times when observers detected the illumination of LED targets (presented for 500ms) presented near versus distant from one of the participants hands.…”

“…This is particularly likely in light of findings from Dufour and Touzalin (2008) that for longer stimulus presentations (+500ms), contrast sensitivity was enhanced near hands.…”

“…Specifically, there is associated enhancement in magnocellular processing and attenuation of parvocellular processing for visual objects that appear within perihand space. For example, Gozli and associates (2012) demonstrated that hand proximity enhances high temporal contrast of magnocellular neurons (sensitivity to object offsets/ onsets) when using temporal and spatial gap tasks designed to selectively recruit the magnocellular and parvocellular networks respectively (Carey, et al, 1996;Dufour & Touzalin, 2008;. The (magnocellular) temporal gap task required the observer to detect a rapid onset and offset or 'flicker' in the target (a circle with a small gap in one quadrant).…”