Fig. 7.

Background firing correlations declined as a function of increasing center-to-center distance. (a) Synchrony (mCCH peak relative to baseline, averaged over all GC pairs) of model ganglion cells as a function of center-to-center distance. Synchrony declined rapidly with increasing separation. A similar decline with increasing center-to-center separation is exhibited by the background correlations between cat alpha cells (Mastronarde, 1983). (b) Top: Raster plot showing the spontaneous firing activity of a line of ganglion cells stretching across the model retina. Bottom: Instantaneous firing rate of all ganglion cells. Background gamma-band oscillations are evident, as in physiological data (Neuenschwander et al., 1999). (c) Top: Raster plot of ganglion cell activity after reducing synaptic weights by 95%. Long-range synchrony mediated by gap junctions is clearly apparent. Bottom: The instantaneous firing rate of all ganglion cells shows very strong synchronization. Blocking synaptic transmission produces qualitatively similar effects in salamander retina (Brivanlou et al., 1998).