Academic journal article Canadian Journal of Experimental Psychology

Sensory Integration in the Learning of an Aiming Task

Academic journal article Canadian Journal of Experimental Psychology

Sensory Integration in the Learning of an Aiming Task

Article excerpt

Abstract

Results of recent research on motor control indicate that in an aiming task, visual information remains of primary importance for optimal accuracy even after extended practice. One of the points that is yet unclear is whether it is solely the dynamic visual information about the moving limb that is important for movement control. To shed some light on this issue, subjects practiced an oscilloscope aiming task. In a transfer test, the dynamic information regarding the displacement of the to-be-moved object could be withdrawn without altering the static visual information that had been available during the learning of the task. The results indicated that, after 200 trials of practice, withdrawing dynamic visual information regarding the displacement of the to-be-moved object produced a deterioration in the accuracy of the subjects' responses. This indicates that the role played by the dynamic visual information for aiming control does not diminish with practice. Moreover, although visual cues available before or after movement execution have been shown to help better plan an upcoming movement, the static cues available during movement execution do not appear to play an important role in the movement representation thought to develop through practice.

It is generally agreed that motor control is achieved by an interplay between central planning and the processing of afferent information (see Schmidt, 1988). However, relatively little is known regarding the role played by different sources of afferent information for movement control, as well as their mode of intervention early and late in the learning of movements. A possible strategy to study these questions is to have subjects practice, for example, a manual aiming task while the sources of afferent information which are of interest are available. Then, following different amounts of practice, the subjects are asked to perform the same task, but this time while one particular source of afferent information is no longer available. If performing in this transfer test results in an increase in aiming error, then one must conclude that the removed source of afferent information was important for movement control. If, on the contrary, the withdrawal of that information does not cause any increase in aiming error, then one must conclude thatit was not used for control purposes.

The results of the studies in which an aiming task and this experimental design were used (see Proteau, 1992, for a review) showed that withdrawing vision of the moving limb and of the surrounding environment in a transfer condition (performed while only the target to be reached was visually available), caused a severe decrease in the spatial accuracy of the subjects' movement. Moreover, in some studies, this decrease in accuracy became more severe as the number of acquisition trials performed under a normal vision condition increased (Adams, Goetz, & Marshall, 1972; Proteau, Marteniuk, Girouard, & Dugas, 1987). Both these observations suggest that visual information was useful for movement control even after extensive practice.

One of the points that remains unclear is whether it is solely the dynamic visual information associated with the moving limb or the pointing object, that is important for movement control as practice progresses. In past aiming studies, the transition to the transfer condition involved withdrawal of both the dynamic and the static visual cues available during the ongoing movement. It is reasonable that, with practice, an individual learns to correlate the position taken by his or her limb to the visual and kinesthetic sensory information available. Therefore, the withdrawal of the visual scene in which the movement normally unfolds could have caused the above reported effects (MacKenzie & Marteniuk, 1985). Alternatively, it can also be argued that a large part of the effect was caused by postural sway resulting from visual occlusion. …

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