The non-visual impact of eye orientation on eye—hand coordination

Abstract

When a peripheral visual stimulus is briefly presented in an empty surround, and an observer is required, after a delay of a few seconds, to point toward the remembered location of that target, the responses are strongly influenced by eye orientation at the time of pointing. Remembered locations, as indicated in total darkness, are typically more precise (more reproducible across trials) when the subject's eyes are aimed toward the target before pointing, than when initial fixation (straight ahead) is maintained during pointing. Furthermore, when the eyes are aimed toward the target, the indicated directions are usually biased toward less eccentric locations than those indicated with eyes aimed straight ahead. These differences in scatter and in bias arise regardless of whether the eye movement toward target location, which precedes pointing, is made while the target is visible or occurs thereafter in total darkness, thus demonstrating that non-visual stimuli associated with eye orientation affect the spatial memory used by the skeletal muscle system.

Multisensory spatial representations in eye-centered coordinates for reaching

“…First, we confirmed the findings of earlier studies for remembered visual targets (Enright, 1995;Henriques et al, 1998). In the static condition, subjects overshot the targets proportionally to the retinal eccentricity (Fig.…”

“…The overshoot illustrated in this figure has been amplified for visual clarity -actual overshoots are of the order of a few degrees. The same overshoot has been found when subjects point to the remembered location of the target suggesting that the position of targets for pointing is memorized in eye-centered (retinal) coordinates (Enright, 1995;Henriques et al, 1998). (C) An eye movement (dotted arrow) is intervened between the offset of the target and the onset of pointing, such that the target is presented at 08 on the retina (left plot) but its updated position is 2108 by the time pointing is initiated (right plot, the gray square indicates the extinguished target).…”

“…Beyond that range, the amplitude of the bias was found to saturate. Subsequently, Enright (1995) and Henriques, Klier, Smith, Lowy, and Crawford (1998) have shown that the same overshoot is observed when a delay is introduced between the offset of the target and the onset of the pointing movement. This suggests that the spatial location of visual targets for reaching is stored in an eye-centered representation since the amplitude of the overshoot depends on the retinal eccentricity of the target.…”

“…R 1 2 E 1 (see Westheimer, 1957 for details). To determine whether spatial memory performs a similar remapping, Enright (1995) and Henriques et al (1998) asked subjects to perform a saccade between the offset of the target and the onset of the pointing. The overshoot was found to reflect the retinal location of the stimulus after the saccade, demonstrating that spatial memory updates the eye-centered coordinates of the stimulus (Fig.…”

Visual motion due to eye movements helps guide the hand

“…For example, previous studies have shown that a stationary or moving textured background can influence smooth pursuit (Yee et al 1983;Collewijn and Tamminga 1984;Keller and Khan 1986;Howard and Marton 1992;Masson et al 1995;Mohrmann and Thier 1995;Niemann and Hoffmann 1997;Schwarz and Ilg 1999), and additional studies have shown that gaze position can influence reaching (Bock 1986;Enright 1995;Henriques et al 1998;van Donkelaar and Staub 2000;Neggers and Bekkering 2001;Soechting et al 2001;Admiraal et al 2003).…”