Simulation of Retinal Contrast Gain Control Mechanisms

I present a simulation of contrast gain control mechanisms operating among transient M cells in the monkey s retina in order to investigate the spatial consequences of this interaction The simulation stages include a realistic viewing model non linear receptor model linear spatial ltering and a saturating output function Contrast gain control is introduced by pooling recti ed signals from on and o centred units over a signi cant spatial region and then using the resultant to provide gain modulation by divisive inhibition at the ganglion cell site Both feed forward and feedback models are considered Results show that local response linearity is preserved and therefore spatial signal distortion is avoided using this gain control scheme even though cell outputs appear to have a compressive response to contrast when tested with gratings The primary e ect is to reduce the contrast dynamic range across the image as a whole while keeping a high contrast sensitivity M cells therefore communicate useful undistorted information at both high and low contrasts Response maps for P and M cells are compared