The dynamics of primate M retinal ganglion cells.
The retinal ganglion cells (RGCs) of the primate form at least two classes--M and P--that differ fundamentally in their functional properties. M cells have temporal-frequency response characteristics distinct from P cells (Benardete et al., 1992; Lee et al., 1994). In this paper, we elaborate on the temporal-frequency responses of M cells and focus in detail on the contrast gain control (Shapley & Victor, 1979a,b). Earlier data showed that the temporal-frequency response of M cells is altered by the level of stimulus contrast (Benardete et al., 1992). Higher contrast shifts the peak of the frequency-response curve to higher temporal frequency and produces a phase advance. In this paper, by fitting the data to a linear filter model, the effect of contrast on the temporal-frequency response is subsumed into a change in a single parameter in the model. Furthermore, the model fits are used to predict the response of M cells to steps of contrast, and these predictions demonstrate the dynamic effect of contrast on the M cells' response. We also present new data concerning the spatial organization of the contrast gain control in the primate and show that the signal that controls the contrast gain must come from a broadly distributed network of small subunits in the surround of the M-cell receptive field.
Benardete
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The Rockefeller University, New York, NY, USA.
Kaplan
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D000818:Animals; D015350:Contrast Sensitivity / Q000502:physiology; D004594:Electrophysiology; D005829:Geniculate Bodies / Q000502:physiology; D016014:Linear Models; D008252:Macaca fascicularis / Q000502:physiology*; D008297:Male; D008839:Microelectrodes; D010775:Photic Stimulation; D012165:Retinal Ganglion Cells / Q000166:cytology / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology