Figure 9.

Lack of dependence of the regularization of fictive biting on cycle frequency. A–C, Samples of simultaneous extracellular and intracellular recordings of radula motor output and B63 bursting, respectively, in different in vitro preparations from control (A), contingently trained (B), and noncontingently trained (C) animals during tonic current injection (intensities indicated below each recording panel) into the B63 neuron. In control and noncontingent preparations that expressed irregular fictive biting in the absence of current injection (A, C, middle), a 2 nA depolarization of B63 (A, C, top) increased the motor pattern frequency to a level similar to that expressed spontaneously by a contingent preparation (B, top) but without inducing a regularization of motor pattern generation. Conversely, in the contingent preparation that already spontaneously expressed regularized fictive biting (B, top), a 2 nA hyperpolarization of B63 (B, middle) decreased the cycle rate to a level close to the spontaneous frequencies of control and noncontingent preparations (A, C, middle) without affecting the overall regularity of motor pattern production. For all preparations, the injection of −5 nA into B63 completely suppressed motor pattern genesis (A–C, bottom).