Improvement of learned behavior through cholinergic stimulation of the caudate nucleus

To test the hypothesis that cholinergic activity of the head of the caudate nucleus (CN) is involved in the processes underlying instrumental performance, the effects of microinjections of several doses of choline into this structure on lever pressing behavior were assessed. A dose-dependent modification of performance was found: small doses improve and large doses impair level pressing, while choline applications into the parietal cortex were without effect. The facilitatory effects were reproduced by microinjections of acetylcholine into the CN. These data further support our working hypothesis.