Significance of different feedbacks for the transient processes of the discharges of single motor units during step-like voluntary movements.

Studies are made of the transient processes of the discharges of single tonic low-threshold and phasic high-threshold motor units (MUs) during step-like voluntary movements performed in case of visual feedback by the result of the movement and in case of artificial auditory feedback by the sound of the MU impulses, as well as in cases of absence of exteroceptive feedback. The studies comprise isometric and isotonic flexion and extension in the elbow joint, the MUs studied being from m. biceps brachii. The previously observed differences of the transient processes in tonic and phasic MUs are found to exist not only during movements taking place under visual control but also under other conditions studied. Under conditions of articicial auditory feedback the subjects may or may not use this feedback for control of the motor response.