CA1 response entrained by sinusoidal current injection.

<p>(<b>A</b>) Sine current injection into a CA1 neuron at increasing peak to peak amplitude (y-axis) at 4 Hz, 40 Hz and 100 Hz (left to right). The APs have been clipped at 20 mV. Scale shown in the top left corner. Inset shows expanded views of the dashed box regions. The AP firing is entrained to the frequency of the sine wave especially with 4 Hz injection. Additionally, the cell spikes earlier in the cycle with increasing current amplitude. At 40 Hz, again the spikes are entrained to the frequency of the sine wave, but the cell goes into a quiet state after firing, possibly due to inactivation of active channels. In the 100 Hz case, it is difficult to make the cell fire even at high current amplitudes. (<b>B–D</b>) Average spikes per cycle as a function of peak-to-peak amplitude of current injected (N = 11 cells) in the 4, 40 and 100 Hz cases. The firing rate is entrained by the frequency of current injection. The increase in firing rate is sigmoidal in the 40 Hz case. (<b>E</b>) The latency of the first spike shows significant phase advancement only with the theta frequency current injection. Error bars represent SE.