Fig. 4.

Estimated timing of amacrine contribution to ganglion cell activity. (A, Top Left) Amacrine cell potential response to a uniform field visual stimulus. Stimulus duration was 300 s. (A, Top Right) Linear transmission filter between the amacrine cell and a ganglion cell. (A, Middle Left) Linear prediction of amacrine transmission g_T(t), computed by convolving the membrane potential recorded without current injection with the transmission filter measured using white noise current injection (Fig. 1), and then deconvolving with the measured membrane time constant of the amacrine cell. Ticks indicate the value of the predicted transmission g_T(t) at the times of ganglion cell spikes. Because the amplitude of the transmission filter was normalized, the predicted transmission is displayed in units of SD. (A, Bottom) The spiking response of the ganglion cell, recorded without current injection simultaneously with the response of the amacrine cell. (B) Cross-correlation function between g_T(t) and the spiking response of the ganglion cell. The cross-correlation was normalized by the SD of g_T(t). Because the filter has a negative peak, values of the predicted transmission below the mean represent inhibition, and values above the mean represent disinhibition. (C) The peak timing of the cross-correlation function in B for 10 amacrine cells and 30 ganglion cells. (D) The average ganglion cell firing rate displayed as a function of the amacrine cell predicted transmission g_T(t). The dotted line indicates the point corresponding to one-half of the maximal firing rate.