Proposes that the mammalian hippocampus constitutes part of the neural machinery necessary for the generation of a brain process which is functionally equivalent to Pavlovian internal inhibition. Relevant neuroanatomical and electrophysiological data are presented in support of this proposal. The major behavioral effects of hippocampal lesions in situations in which internal inhibition is presumed to occur are discussed. These situations include habituation to novelty, discrimination reversal, overtraining, extinction, and spontaneous alternation.(69 ref.)(PsycINFO Database Record (c) 2016 APA, all rights reserved)