Fig. 2.

Effects of variance on current-to-spikes transformation. The static nonlinearity model was used to characterize the transformation between injected current and the firing rate. Gaussian current fluctuations (bandwidth, 0–50 Hz) with variances of 16 and 144 pA² were injected into a ganglion cell. The model parameters were calculated from 100 sec of recording.A, Linear filters for the two injected current variances. B, Static nonlinearities for the two current variances. The nonlinearity describes the relationship between the output of the filters (A) and the measured firing rate. C, Histograms of local voltage maxima for each current variance. Maxima were defined as data points with amplitudes larger than those of surrounding points, including both action potential peaks (> 0 mV) and subthreshold maxima (less than −20 mV). Bin size was 0.76 and 1.19 mV for low and high variance. Theinset plots the cumulative distribution of subthreshold maxima. The change in threshold was estimated from the voltages at which the cumulative distributions reached 0.99.