DIFFERENTIAL-EFFECTS OF DORSAL AND VENTRAL HIPPOCAMPAL-LESIONS

Several studies have demonstrated that dorsal, but not ventral, hippoc ampus is critical for spatial memory. The mnemonic role of the ventral hippocampus remains unclear. The existence of relatively direct conne ctions between hypothalamic nuclei and ventral hippocampus suggests th at the ventral hippocampus may be involved in acquisition of informati on regarding internal cues (e.g,, hunger). Male Long-Evans rats receiv ed ibotenic acid-induced lesions of either dorsal or ventral hippocamp us or underwent sham surgeries. After a 3 week recovery, subjects were tested on delayed alternation in a T-maze and on a task in which food -deprivation state was used as a contextual cue (Davidson and Jarrard: 1993). Rats with dorsal, but not ventral, lesions were impaired in de layed alternation, consistent with previous findings, but both groups were impaired in the learning of the internal state-shock association task.