RT Journal Article SR Electronic T1 How retinal microcircuits scale for ganglion cells of different size JF The Journal of Neuroscience JO J. Neurosci. FD Society for Neuroscience SP 7673 OP 7683 DO 10.1523/JNEUROSCI.15-11-07673.1995 VO 15 IS 11 A1 CK Kier A1 G Buchsbaum A1 P Sterling YR 1995 UL http://www.jneurosci.org/content/15/11/7673.abstract AB Ganglion cell receptive field centers are small in central retina and larger toward periphery. Accompanying this expansion, the distribution of sensitivity across the centers remain Gaussian, but peak sensitivities decline. To identify circuitry that might explain this physiology, we measured the density of bipolar cell synapses on the dendritic membrane of beta (X) and alpha (Y) ganglion cells and the distribution of dendritic membrane across their dendritic fields. Both central and peripheral beta cells receive bipolar cell synapses at a density of approximately 28/100 microns2 of dendritic membrane; central and peripheral alpha cells receive approximately 13/100 microns2. The distribution of dendritic membrane across the dendritic field is dome- like; therefore, the distribution of bipolar cell synapses is also dome- like. As the dendritic field enlarges, total postsynaptic membrane increases with field radius, but only linearly. Consequently, density of postsynaptic membrane in the dendritic field declines, and so does density of synapses within the field. The results suggest a simple model in which the receptive field center's Gaussian profile and peak sensitivity are both set by the density of bipolar cell synapses across the dendritic field.