Fig. 8.
Enhancement of correlation detection by background synaptic noise. Probability that an action potential indicated the presence of a transient input of 10 ms (top), 20 ms (middle) or 30 ms (bottom) as a function of the amplitude of the input. In all panels, open symbols represent experiments with synaptic background noise (Ge0=14 nS, Gi0=22.5 nS, σe=5 nS, σi=12.5 nS). In these experiments, inputs consist in a short (10 ms, 20 ms or 30 ms) increase in the S.D. of the background noise. In this condition, the spontaneous firing rate was about 1 Hz. Crosses represent experiments without synaptic background noise. In these experiments, the cell was depolarized to a resting level equivalent to the mean membrane potential with point-conductance clamp, and inputs consisted in short (10 ms, 20 ms or 30 ms) current pulses of varying amplitude. In this condition, the cell did not have a spontaneous firing rate. The curves are sigmoid fits of the data points. Each point is computed from 120 trials. In the case where synaptic background noise was included, the detection of the input signal (P>0.5; dashed lines) occurred for inputs amplitudes smaller than when no synaptic background noise was included (filled arrows and opened arrows respectively).