Role of the hippocampus in configural learning

Contemporary theories of animal learning propose that memory for a specific event can be based upon either an elemental network of associations, a configural associative network or a hybrid of these possibilities. The two aims of this thesis were (1) to assess whether rats form configural representations of the spatiotemporal features of specific cues, and (2) to test the hypothesis that the hippocampus plays a critical role in configural representations that encode the spatiotemporal properties of an event, more commonly known as episodic memory. Chapter 2 investigated rats' ability to represent the spatiotemporal context in which objects were presented. These experiments failed to find robust evidence for such an ability. Chapter 3 discusses the development of a novel task, based on a sensory preconditioning procedure, that demonstrated configural memory for the spatiotemporal features of auditory cues in normal rats. In addition, it was shown that excitotoxic lesions of the hippocampus disrupted such configural memories. The experiments reported in Chapter 4 used the procedure developed in Chapter 3 to show that temporary inactivation of the hippocampus during memory retrieval disrupted configural, but not elemental memory retrieval. The results presented in this thesis support the hypothesis that normal rats are able to form elemental and configural representations involving the spatiotemporal properties of cues, and that the hippocampus has a role in configural but not elemental associative memory.