The hippocampus is not necessary for a place response but may be necessaryfor pliancy

Rats with kainate-colchicine hippocampal lesions (HL) and controls (C) were initially trained in the Morris water maze with procedures that deterred t heir prepotent thigmotaxic response. Training began with an escape platform that occupied nearly the entire pool. The area to which the rats could esc ape was made smaller by substituting smaller platforms as training progress ed. In contrast to standard procedures, HL rats and C rats showed comparabl e performance during acquisition and preferentially searched the goal quadr ant on probe trials during which the platform was removed. In a follow-up e xperiment, the platform was moved to a random position along the wall, whic h required a switch to a thigmotaxic response far most effective escape. HL rats that were thigmotaxic before place training did not switch to a thigm otaxic response as readily as did controls, behavior consistent with the vi ew that hippocampal damage reduces pliancy.