The organization of memory in the brain : role of caudate nucleus and hippocampus

• Main Author: Packard, Mark G.
• Format: Others
• Language: en
• Published: McGill University 1990
• Subjects: Memory.; Caudate nucleus.; Hippocampus (Brain)
• Online Access: http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74684

The present experiments were designed to examine the hypothesis that the hippocampus and caudate nucleus are parts of independent memory systems which differ in the type of memory they mediate. In experiment 1, the mnemonic functions of the hippocampus and caudate were doubly dissociated; lesions of the caudate nucleus impaired acquisition of the "habit memory" component of the 4 x 4 radial maze task, but had no effect the "cognitive memory" component of the task. Lesions of the fimbria-fornix produced the opposite behavioral dissociation. In experiment 2, lesions of the caudate nucleus produced a transient deficit in cognitive win-shift radial maze behavior when rats were allowed to obtain food from maze arms on an unlimited basis prior to win-shift training. In contrast, lesions of the caudate had no effect on win-shift acquisition when rats were allowed to explore an empty maze prior to win-shift training. These results suggest that reinforcement contingencies may be important in determining the type of memory process initiated by a training experience. In experiments 3ab, systemic post-training injection of the dopamine (DA) agonist D-amphetamine (D-AMP) and the DA D2 receptor agonist LY 171555, but not the DA D1 receptor agonist SKF-38393, improved acquisition on both a habit memory win-stay radial maze task, and a cognitive memory win-shift radial maze task. In experiments 4ab, the mnemonic functions of the hippocampus and caudate nucleus were doubly dissociated using post-training intracerebral injections of these same DA agonists. Post-training intracaudate injection of D-AMP, LY 171555, and SKF-38393 improved acquisition of win-stay, but not win-shift radial maze behavior. Post-training intrahippocampal injection of these DA agonists produced the opposite behavioral dissociation. Taken together, the results are consistent with the hypothesis that the caudate nucleus mediates the acquisition of habit memory, while the hippocampus mediates the acquisition