Figure 3.

The postsynaptic response of thalamocortical neurons depends on the preceding interspike interval. CSD profiles generated by selected spikes of the same LGNd neuron presented in Figure 1. A, The left profiles were generated by LGNd spikes with preceding interspike intervals of 5–20 ms (n = 5390 spikes). B, Profiles on the right were generated by LGNd spikes with preceding interspike intervals of 500–3000 ms (n = 1087 spikes). Gain settings and color intensities for both CSD profiles are identical. Note that the postsynaptic response but not the axonal response (arrow) is greatly reduced at the shorter interval. C, The spike-triggered field potential from the peak channel generated from selected spikes with different preceding interspike intervals. D, The amplitude of the axon terminal response (left) and the amplitude of the initial 1 ms of the postsynaptic current sink (right) plotted through the depth of the cortex for different preceding interspike intervals.