Fig. 5.

Disinhibitory gating from amacrine cell transmission. (A) Simplified circuit of an amacrine cell with a linear synaptic terminal making a synapse on the rectifying synaptic terminal of a bipolar cell, or directly onto the ganglion cell. (B) Filters of bipolar, amacrine, and ganglion cells. Bipolar cell filters (dotted line) were not measured in this study, but have been shown to be biphasic (10). For purposes of illustration, the bipolar cell is taken to have similar time course as the ganglion cell, but advanced by 10 ms. Filters of amacrine and ganglion cells are taken from the time-reverse of the mean effective stimuli in Fig. 3B. (C) The stimulus is the mean effective stimulus of the ganglion cell. Bipolar, amacrine, and ganglion cell responses were computed by convolving the stimulus with the response filters in B. For the ganglion cell, an additional threshold was applied. The time course of inhibitory neurotransmitter was computed by convolving the amacrine cell response and the negative of the measured transmission filter to the ganglion cell. Thus, transmission is shown to represent inhibitory neurotransmitter, which decreases when the ganglion cell is active.