Fig. 9.

Neural modification induced by contingent reinforcement. A, The phase relationship of the discharge in the closure motor neuron B8 relative to the burst of activity in I2 n. can vary from one pattern to another. In some B8 bursts at least 50% of the activity occurred after termination of burst in I2 n. In this case the majority of activity in B8 was out of phase with activity in I2 n. B, The number of occurrences of bursts in B8 characterized in A and that were associated with expression of pattern I significantly increased in the contingent-reinforcement group (black bar), as compared with the control (white bar;p < 0.001) and yoke-control groups (gray bar; p < 0.05). No significant difference (N.S.) was observed between the control and the yoke-control groups. The contingent reinforcement specifically enhanced the discharge of B8 during the retraction phase (i.e., after the burst in I2 n. terminated).