Comparison of electrophysiological characteristics of the retino-collicular and retino-thalamo-cortical parts of the visual system of the monkey Macaca rhesus.

In chronic experiments and in acute experiments with nembutal narcosis, photic-driven evoked potentials (EP's) were studied in the superior colliculi (SC) and in the cerebral visual cortex (VC, Area 17). In chronic experiments it was found that the EP's in SC and VC have similar latency periods (LP's) equal, respectively, to 12 +/- 1 and 12 +/- 2 msec (p less than 0.05); refractory periods during application of paired flashes are 50 and 70 msec for SC and VC, respectively. The critical frequencies for imitation of rhythmic flashes in both visual centers also coincide, reaching 20-25/sec. EP's with short LP's, equal to the LP's of evoked potentials in the VC, were found also in the frontal and motor cortex and the hippocampus. The problem regarding telencephalization of the retino-tectal channel of the visual system is discussed.