Dissociation of function within the hippocampus.

Abstract Hooded rats with damage to the posteroventral hippocampus (Group VH) lapped more at a pipette to obtain water than animals with damage to the anterodorsal hippocampus and neocortex. The increased frequency of lapping on the part of Group VH was apparent under a number of different conditions. Some of these conditions included: (a) following prolonged adaptation to 23-hr and 47-hr deprivation schedules; (b) following different intensities of mouth-shock. Despite their enhanced lapping Group VH did not consume more water in doing so. Neither did they drink more when water was available for short periods in the home cage, but only consumed more over 24-hr periods following extended exposure to the deprivation schedule. On the basis of these findings it was concluded that the changes in drinking behavior of animals with posteroventral hippocampal lesions was secondary to a general loss of their ability to inhibit behavioral responsiveness. Rats with anterodorsal hippocampal lesions performed like animals of Group VH when they suffered additional damage that involved the posterior septal area, suggesting some functional equivalence between the posterior septum and posteroventral hippocampus.