Firing coincidences between neighboring retinal ganglion cells: inside information or epiphenomenon?

Retinal ganglion cells often fire impulses in synchrony; is this synchronization an irrelevant byproduct of processing shared inputs, or does it encode information? We examined the rate of occurrence of coincident impulses from pairs of ganglion cells responding to stimuli that varied along several dimensions. We find that coincidences convey little if any additional information about simple static stimuli beyond what could be determined from the firing rates of the two cells considered separately. In fact, at least one of the separate cells generally provided a better information channel than the coincidence rate, implying that under these conditions ganglion cells do not employ a strategy of encoding by coincidences.