Possible sources of reduction in photic cortical evoked potential amplitude due to conditioning aversive stimulation (ESB) of central gray were examined. Macropotential recordings were led simultaneously from lateral geniculate body (lgb), area 17, and area 18 of albino rat. Conditioning aversive ESB of central gray reduced potential amplitudes in 1 gb and throughout visual cortex, in addition to producing intense ECoG activation. Paralysis and barbiturate sedation abolished effects in lgb; these data implicated peripheral factors. However, only sedation abolishes ESB effects on cortex. Furthermore, central gray ESB subliminal for escape but not for ECoG activation, as well as ESB applied to neutral reticular sites, also reduced cortical amplitudes in a manner similar to the effect of aversive ESB. Therefore, it is more likely that the activating properties of ESB, rather than the aversive quality, are responsible for the amplitude reductions.
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