UBC Theses and Dissertations
Selective memory impairments produced by transient lidocaine-induced lesions of the nucleus accumbens Seamans, Jeremy Keith
Anatomical studies have identified major efferent pathways from the hippocampus to the nucleus accumbens (N.Acc.), but the functional significance of this interaction remains unclear. The delayed spatial win-shift radial arm maze task has been used as a selective behavioral measure of damage to the hippocampal system, whereas the cued win-stay version of this task is unaffected by hippocampal lesions, but is disrupted by lesions in the dorsal striatum. The present study utilized these two procedures, along with reversible lidocaine-induced lesions of the N.Acc., to determine whether the N.Acc. is part of the extra-hippocampal system that subserves efficient memory-based foraging behavior. These lesions impaired performance on the spatial win-shift but not the cued win-stay task. Pre-training lesions on the spatial win-shift task did not affect foraging for four pellets during either the training or test phases of the experiment. In contrast, lidocaine-induced lesions, given prior to the test-phase, significantly disrupted retrieval of four pellets on the 8-arm maze. Comparable deficits also were observed in animals trained to forage efficiently for four pellets on an 8-arm maze, without prior win-shift experience. State-dependent drug effects were ruled out by replicating the disruptive effects of lidocaine-infusions into the N.Acc. on spatial win-shift performance in animals receiving this treatment prior to both training and test phases. Collectively, these results indicate that the N.Acc. interacts with the hippocampus in guiding spatial win-shift behavior by allowing information about previously visited spatial locations to influence foraging in a complex radial arm maze environment.
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