Rapid elbow flexion in the absence of proprioceptive and cutaneous feedback.

Rapid goal-directed movements of elbow flexion were studied in normal human subjects and in patients deprived of proprioceptive and cutaneous feedback. All normal subjects showed a burst of electromyographic (EMG) activity in the extensor muscle (antagonist) that served to arrest the limb precisely in the target zone. The magnitude of this burst co-varied with the magnitude of the initial accelerating burst in the flexor muscle (agonist). In patients, there was a small decelerating burst poorly correlated with the agonist activity. All patients had difficulty to control the amplitude of their movements due to improper adjustment of the size and time of onset of the decelerating burst. It is concluded that the central nervous system can generate a sequence of commands to accelerate and decelerate a limb in the absence of peripheral feedback. However, information from the moving limb is required to adjust the magnitude and time of onset of deceleration.