English: (A. Responses of precentral cell and arm muscles during active movement. Successive lines from top to bottom show activity of flexor carpi radialis (F), extensor carpi radialis (E), biceps (B), triceps (T), cortical unit (U), and the position of the elbow (P). A single trial is shown at left, and the averages over 60 successive trials at right. This cell fired before active flexion of the elbow. Vertical calibration bar equals 50 impulses per second. (B. Dissociation of the correlation between cell and muscle activity by reinforcing bursts of cell activity with simultaneous suppression of all muscle activity (8). After approximately 15 minutes of reinforcing successively better approximations to the required pattern-involving about 100 reinforced response patterns and an equal number of unreinforced responsesthe monkey repeatedly emitted bursts of cortical cell activity without any measurable EMG activity