Conditioning and recovery of functions lost by brain damage.

The muscle spindle is a receptor apparatus in striated muscle that is necessary for voluntary muscle movement. Paralysis victims lose the feedback of this receptor and cannot initiate motor responses. Four hemiplegic patients were trained to use auditory feedback from electromyographic recordings to initiate activity in paretic limbs. With the addition of visual feedback and the use of the auditory signal as a reinforcing stimulus, the patients' muscle activity was then shaped to approximate normal movement.