The effect of anterior thalamic and cingulate cortex lesions on object-in-place memory in monkeys

Six Macaque monkeys (Macaca mulatta) were trained in an object-in-place memory task, designed to capture the 'whole scene' nature of episodic memory. In this task the correct, rewarded, response in each scene was to a particular object of a pair, which always occupied a particular position in a unique background which had been generated using randomly chosen colours and shapes. In each session, the monkey learned a new list of these unique scenes. The animals then underwent surgical ablation of either the anterior thalamic nuclei or the cingulate cortex. It was found that the animals with anterior thalamic lesions showed a substantial impairment, whereas the monkeys with cingulate cortex ablations were not significantly impaired at the task. These results confirm the importance of the anterior thalamic nuclei in episodic memory, and suggest that the cingulate gyrus is not a region which is crucial in the type of episodic memory task used in the present experiment.