Fig. 5.

Low-frequency minimal stimulation of stratum lacunosum-moleculare paces repetitive firing of pyramidal neurons.A₁, Seventy superimposed traces showing the effect of a 3 Hz train of minimal stimulation (arrows) on the firing of a CA1 pyramidal cell depolarized to threshold by steady current injection.A₂, The corresponding spike frequency histogram shows that the timing of low-frequency spiking in the pyramidal cell is paced throughout the train of minimal stimulation in stratum lacunosum-moleculare. On average, the firing of pyramidal cells was ∼180° out of phase with the minimal stimulation at 3 Hz.B, Increased rhythmicity of pyramidal cell firing (B₁) is reflected in autocorrelation functions of 2 sec recordings of membrane potential obtained just before (B₂) and during (B₃) the train of minimal stimulation.