Neural mechanisms involved in the critical flicker frequency of the cat

Abstract

Summary The role of various neural structures in flicker perception was explored by testing the effect of lesions on the critical flicker frequency (CFF) threshold of the cat. Ten cats were trained to discriminate between a flickering and a steady light, after which the frequency of the former was increased until the discrimination was no longer apparent. Repeated testing and control runs with the light masked confirmed the determination of a stable CFF. After subtotal lesions in the visual cortex, lateral geniculate body, nucleus posterior, puivinar, or lateralis posterior, or a combination of these (System I), the CFF decreased. After subtotal lesions in the tectal region (superior and inferior colliculi), the CFF increased, even in two cats with depressed CFFs due to prior lesions in System I. Our results suggest that the posterior nucleus, pulvinar, and lateralis posterior, in series with the geniculo-striate system, comprise components of a high flicker-discrimination system. The superior colliculus, on the other hand, subserves a different role, possibly constituting a component of a system (system II) which mediates low flicker rates but which interacts with System I in determining the CFF. Evidence is presented that system II may also exert an inhibitory influence on System I, limiting the discrimination of high flicker rates.