Autogenic and nonautogenic sensorimotor actions in the control of multiarticulate hand movements.

Human subjects were trained to generate rapid movements of the thumb and index finger and produce a controlled pinch contact force. When unanticipated loads were applied to oppose thumb flexion movements, the desired pinch contact force was achieved by compensatory adjustments of both the thumb and the index finger flexor muscles. The nonautogenic finger muscle responses were (1) at latencies of 60 to 90 ms, (2) manifest the first time a load was introduced, and (3) absent for thumb loads introduced during a task not requiring coordination of thumb-finger actions. These intermovement sensorimotor mechanisms may reflect a general task-dependent process contributing to coordination of multiarticulate movements.