One prominent theory of hippocampal function is that it is involved in relational memory, or the binding of multiple distinct elements into a coherent representation in memory. Here, we investigated the role of the hippocampus in relational memory by examining eye movements. Across three experiments, four rhesus monkeys viewed naturalistic, complex scenes that were novel, repeated, or manipulated. In the manipulated scenes, a change was introduced in one item which changed in its location or its replacement with a new item. In Experiment 1, normal monkeys made fewer fixations when scenes were repeated without a manipulation and spent more time looking at the altered region in manipulated scenes. Consistent with previous studies in humans, the monkeys' eye movements differed depending on the viewing history of the scene suggesting successful memory formation. In Experiment 2, a hippocampal-lesioned monkey displayed deficits in this task that revealed a significant lesion by manipulation type interaction. This is consistent with findings from human amnesic patients and suggests that the hippocampus is critical for relational memory. In Experiment 3, we studied the role of context in relational memories. Three normal and one hippocampal-lesioned monkey viewed scenes with and without a background. We found that control monkeys displayed better memory when the scenes were presented in a context, i.e., with a background. Interestingly, the hippocampal-lesioned monkey demonstrated significant relational memory, only when the scenes were presented without a background. These data suggest that the presence of a background context normally acts as an aid to relational memory formation, but this requires an intact hippocampus.
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About this Honors Thesis
|Committee Chair / Thesis Advisor|
|Hippocampal Dependence for Relational Memory and Context Rich Scenes in Rhesus macaques ()||2018-08-28||