Effects of scopolamine and hippocampal lesions on negative patterning discrimination performance in rats

Rats were trained in operant chambers to perform an appetitive negative patterning successive discrimination. They were required to respond to the left in response to a tone or click and right to a tone-click compound. Scopolamine and methyl scopolamine impaired performance accuracy and increased response latency and response omissions. Subsequent hippocampal aspiration lesions initially impaired accuracy, which later improved. Lesions decreased response latencies. Finally, the effects of scopolamine and methyl scopolamine were shown to be similar in lesioned and control rats, suggesting that the hippocampus is not involved in the actions of these drugs on this task.