Evidence for Automatic On-Line Adjustments of Hand Orientation During Natural Reaching Movements to Stationary Targets

Abstract

Control of the spatial orientation of the hand is an important component of reaching and grasping movements. We studied the contribution of vision and proprioception to the perception and control of hand orientation in orientation-matching and letter-posting tasks. In the orientation-matching task, subjects aligned a "match" handle to a "target" handle that was fixed in different orientations. In letter-posting task 1, subjects simultaneously reached and rotated the right hand to insert a match handle into a target slot fixed in the same orientations. Similar sensory conditions produced different error patterns in the two tasks. Furthermore, without vision of the hand, final hand-orientation errors were smaller overall in letter-posting task 1 than in the orientation-matching task. In letter-posting task 2, subjects first aligned their hand to the angle of the target and then reached to it with the instruction not to change their initial hand orientation. Nevertheless, hand orientation changed during reaching in a way that reduced the initial orientation errors. This did not occur when there was no explicitly defined target toward which the subjects reached (letter-posting task 3). The reduction in hand-orientation errors during reach, even when told not to change it, suggests the engagement of an automatic error correction mechanism for hand orientation during reaching movements toward stationary targets. The correction mechanism was engaged when the task involved transitive actions directed at the target object. The on-line adjustments can occur without vision of the hand and even when target orientation is defined only by proprioceptive inputs.

Evidence for a Proprioception-Based Rapid On-Line Error Correction Mechanism for Hand Orientation during Reaching Movements in Blind Subjects

“…The performance of all blind subjects was no better than random. Nevertheless, the blind subjects wore a blindfold during the experiment to ensure conditions similar to those of the blindfolded normally sighted subjects (Gosselin-Kessiby et al, 2008) and to eliminate the effects of any residual luminescence sensitivity in a few of the blind subjects.…”

“…The experimental setup and tasks used in this study of blind subjects are identical to the proprioceptive sensory condition described previously for a study of normally sighted subjects (Gosselin-Kessiby et al, 2008). Figure 1 shows the experimental setup.…”

“…In contrast, few studies have investigated such mechanisms for spatial hand orientation (Glover and Dixon, 2001a,b,c;Tunik et al, 2005;Fan et al, 2006;Gosselin-Kessiby et al, 2008).…”

“…A limited number of studies have analyzed reaching and grasping movements when visual information was not available (Wing et al, 1986;Jakobson and Goodale, 1991;Darling and Miller, 1993;Hocherman, 1993;Gaunet and Rossetti, 2006;Coluccia et al, 2007;Gaunet et al, 2007;Gosselin-Kessiby et al, 2008). Some studies suggested that visual feedback or visual experience was not essential for the successful execution of reaching or grasping movements (Jeannerod, 1984;Castiello et al, 1993;Sergio and Scott, 1998;Ittyerah et al, 2007).…”

“…Recently, we showed that proprioceptive feedback alone about current and desired final hand orientation was sufficient to initiate and guide rapid on-line adjustments of hand orientation during reaching movements toward a target in blindfolded normally sighted subjects (Gosselin-Kessiby et al, 2008). An interesting question is whether prior visual experience is necessary for the development of rapid on-line correction mechanisms, which then generalize to the proprioceptive domain (Fiehler et al, 2009).…”