Figure 2. Repetitive firing properties of presubicular cells.

A, repetitive firing in response to step depolarizations (+40, +60 and +100 pA injected current). B, plotting the neuronal firing frequency as a function of the injected current showed a sigmoid input–output relation (n= 8). C, instantaneous firing frequency varies little during long current injections. The different colours show values for a series of five levels of current injection (ranging from +60 to +140 pA) into the same cell. D, frequency increases with current strength in a similar fashion for the 1st, 2nd and 4th action potential and at steady state (mean of the following action potential frequencies), indicating the relative lack of spike-frequency adaptation at different degrees of depolarization. E, cumulative probabilities of instantaneous spike frequencies for a +60 pA current injection gave steep curves for n= 8 cells examined (different colours for different cells), attesting to the relative absence of accommodation in presubicular neurons.