Conditioned and unconditioned aversive stimuli enhance light-induced Fos expression in the primary visual cortex

Studies in rats indicate that photic responses within the dorsal lateral geniculate nucleus can be enhanced in response to stimuli known to induce negative emotional arousal.(2-4,12,24) Little is known, however, about the effect of such stimuli on photic responses within primary visual cortex, the principal projection area of the dorsal lateral geniculate. Here, we examined the effect of unconditioned and conditioned aversive stimuli on photic responses within the primary visual cortex in rats using expression of the transcription factor Fos as a functional marker of neuronal activation.(16) In previous studies carried out within the circadian visual system,we found that photic induction of Fos within the principal target area of the circadian visual pathway, the suprachiasmatic nucleus of the hypothalamus, was attenuated when the light stimulus was given concurrently with an aversive footshock or was made an aversive conditioned stimulus through previous pairings,vith footshock.(5) In addition, we found that photic stimulation of Fos expression in the suprachiasmatic nucleus was attenuated in a context made aversive through previous pairings with footshock.(6) We now report that in these same animals, unlike what was seen,within the suprachiasmatic nucleus, Fos expression in the primary visual cortex is significantly elevated. These findings support the view that emotional arousal can enhance the response of cells in the,visual cortex to photic input, and point to the differential effect of aversive emotional events on photic responses within pathways underlying visual perception and those involved in circadian regulation. (C) 1998 IBRO. Published by Elsevier Science Ltd.