Motor commands and the perception of movement patterns.

Electrophysiological experiments have shown that during voluntary movement, the activity of kinesthetic receptors relevant to actively contracting muscles is modified. Furthermore, efferent motor commands interact with the central transmission and processing of kinesthetic sensory input. This article addresses itself to the question of whether the efferent motor commands of voluntary movement influence the perception and processing of kinesthetic spatial information. In two experiments, subjects moved around unfamiliar and unseen criterion stencil patterns with their right hands. In the first experiment subjects were required to concurrently track the constrained movements with their left hands. In the second experiment, following movement around a criterion pattern, the subjects had to recall it with their right hands. Tracking and recall movements in the two experiments showed a systematic spatial bias in the direction in which the right-hand constrained movements were commanded. It is argued that when a limb movement is contrained, the interaction between the efferent command pattern and the returning kinesthetic sensory input results in its position being perceived with a constant error in the direction in which the movement was commanded.