Figure 5.

Temporal summation is nonlinear in NM neurons. A, NM neurons were stimulated as in Figure 4, but the amplitude of subthreshold responses was recorded. When EPSC interstimulus interval was short but outside the coincidence summation window, the amplitude of postsynaptic potentials (black traces) did not reach the simple linear summing model (gray traces). B, When normalized to the amplitude of a response to a single input, temporal summation was less than additive across a broad range of interstimulus interval for NM neurons (n = 13; mean ± SEM). Depolarizing inhibition lessened this effect, likely because responses to the initial single input were smaller. C, Temporal summation was also nonlinear for smaller EPSCs.