Acquisition, retention, and discrimination reversal after hippocampal ablation in monkeys

The effect of hippocampal ablation on acquisition, retention, and learning-set formation in a simple auditory discrimination task was studied in rhesus monkeys. Hippocampal ablation was found to interfere with the retention of discriminations, those learned postsurgically being more affected than those learned presurgically. Successive postsurgical discrimination reversals resulted in the formation of discrimination reversal learning sets. It was concluded that while the hippocampus may subserve a facilitatory function in retention, its presence is not an essential condition for retention or for new learning.