Single unit and evoked potential responses in cat optic tract to paired light flashes

Summary

Single unit responses and gross evoked potentials were recorded in the optic tract of cats under barbiturate anesthesia in response to single and paired flashes of light. Parallels were drawn between the evoked potentials recorded in this study and those recorded in previous work in alert, behaving cats during perceptual discrimination of paired from single flashes. Comparability of the evoked potentials under the two conditions served as justification for correlating patterns of single unit responses and perceptual responses to pairs of flashes. Under light adaptation, unit recovery to paired flashes at various interflash intervals was comparable to evoked potential recovery and, hence, to the perceptual responses in only about one-half of the units tested. In contrast, under dark adapted conditions, only one-third of the units paralleled the evoked potentials. Thus, a large number of retinal units apparently fail to play a significant role in temporal discrimination of paired from single flashes. The discussion focuses upon the relationship between unit and perceptual responses and considers alternative ways in which information necessary for discrimination of paired from single flashes may be coded.