Visual Neuroscience



The dynamics of primate M retinal ganglion cells


ETHAN A.  BENARDETE a1c1p1 and EHUD  KAPLAN a1p2
a1 The Rockefeller University, New York

Abstract

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.

(Received January 9 1998)
(Accepted September 2 1998)


Key Words: Primate; Retina; M cell; Dynamics; Contrast gain control.

Correspondence:
c1 Correspondence and reprint requests to: Ethan A. Benardete, Department of Neurosurgery, New York University Medical Center, 550 First Avenue, New York, NY 10016.
p1 Current address: Department of Neurosurgery, New York University Medical Center, 550 First Avenue, New York, NY 10016, USA.
p2 Permanent address: Department of Ophthalmology, Mount Sinai Medical Center, New York, NY 10029, USA.