Fig. 6.

Plasticity in electrical coupling. a Bursting in pairs of pattern-initiating neurons (here B63/B65) elicited by simultaneous depolarization while the contralateral B63 (B63c) was hyperpolarized to prevent wider CPG activity. In control (left) and non-contingent (right) preparations, burst onsets in the two activated neurons are weakly coordinated and the leading cell varies between cycles. However, in contingent preparations (middle), the onsets of now regularized bursts in the pattern-initiating cell pairs are strongly coordinated, with B63 bursts always slightly leading its partner. b The increased coordination of the pattern-initiating cell bursts is associated with a learning-induced enhancement of their electrical coupling. These connections (resistor symbols in schematics) were tested by injecting a fixed negative current (−10 nA) into a B30 or B65 to alter its membrane potential (VB30/B65) and that of the electrically coupled B63 (VB63). After contingent reinforcement, the electrical coupling of both B30 and B65 with B63 increased significantly as compared to control and non-contingent conditions