Fig. 10.

Central depolarization gates afferent activity in B51. Horizontal bars indicate current injection into B44. A, Centripetal spikes in B51 do not elicit PSPs in B8 when B8 is at its resting membrane potential. B, Current has been injected into the soma of B51, which has been depolarized by 15 mV. Centripetal spikes now elicit PSPs in B8.C, B51 is again at its resting membrane potential. The size of the current pulse injected into B44 is decreased inB so that the B44 firing frequency will remain relatively unchanged; i.e., because B51 and B44 are electrically coupled, some of the current injected into B51 in B is seen by B44. A smaller current pulse is, therefore, used to drive B44 when B51 is depolarized.