Control of Retinal Sensitivity

Abstract

Both the "on" and the "on-off" ganglion cells in the mudpuppy retina generate graded responses over a narrow range of log test intensities. Sustained full field or surround backgrounds change the range of center log test intensities that elicits the graded response for both cell types. The on-off, but not the on ganglion cells are further affected by moving or flashing surround backgrounds. These cells are hyperpolarized, threshold is elevated, and the entire graded range of response is elicited by a higher range of log center test intensities. Depolarizing activity is elicited in amacrine cells by moving backgrounds that affect the on-off ganglion cells, but bipolar activity is unaffected. These results suggest that the amacrine cells at the inner plexiform layer mediate a third stage of sensitivity control in the retina, increasing threshold for response to change specifically in the on-off ganglion cells.

Sodium Channels in Transient Retinal Bipolar Cells Enhance Visual Responses in Ganglion Cells

“…The dynamic range was also narrower for this class of ganglion cell, and their responses to increments of illumination were larger than ganglion cells receiving TTX-insensitive input. This is in agreement with previous studies that have shown that the dynamic range of transient ganglion cells is narrower than that of sustained ganglion cells (Werblin and Copenhagen, 1974;Thibos and Werblin, 1978). The dynamic range of bipolar and ganglion cell responses to light has been attributed to GABA-mediated input from amacrine cells (Euler and Masland, 2000;Ichinose and Lukasiewicz, 2002).…”

The relationship between light‐evoked synaptic excitation and spiking behaviour of salamander retinal ganglion cells.

“…These earlier experiments, however, were performed with all lateral inhibitory mechanisms intact, while the present data were obtained with glycine and GABAA receptor-mediated inhibition blocked. Intensity spans measured here in ganglion cells matched well those reported by Thibos & Werblin (1978) for bipolar cells (2-1 log units), consistent with the idea that the major influence of inhibition on response range may occur at the level of the inner plexiform layer (Werblin & Copenhagen, 1974). This notion remains to be tested.…”

Glycinergic synaptic inputs to bipolar cells in the salamander retina

“…Since inputs from glycinergic amacrine cells apparently tend to be antagonistic to the photoreceptor inputs, it is possible that they contribute to the surround antagonism observed in bipolar cells. This might particularly be the case for antagonism generated by surround transients, since amacrine cells are thought to mediate such antagonism at the inner plexiform layer (Werblin & Copenhagen, 1974). At the same time, our finding that the inputs from glycinergic interplexiform cells are synergistic with the photoreceptor inputs to on-centre bipolar cells suggests that glycinergic interplexiform cells are probably not involved in the generation of surround antagonism, at least for on-centre bipolar cells.…”