Disorienting the rat: do lesions to the DTN and LMN cause rats (Rattus norvegicus) to lose their way?

Ingram, Matthew L. (2013) Disorienting the rat: do lesions to the DTN and LMN cause rats (Rattus norvegicus) to lose their way? Masters thesis, Memorial University of Newfoundland.

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Abstract

The dorsal tegmental nucleus (DTN) and lateral mammillary nucleus (LMN), and the connections between them, are thought to produce the head direction cell signal, which is associated with animal navigation. Bilateral lesions to these structures disrupt head direction (HD) cell firing in downstream areas of the primary HD cell circuit. Rats with bilateral lesions to the DTN (Experiments 1 and 2) or LMN (Experiment 3) were compared to sham controls in a series of tasks where directional sense is thought to be important. The tasks included a directional water T-maze problem where rats were trained to travel in a constant direction from two different locations to locate a hidden platform and two variants of a foraging task where rats were trained to return to a home location after finding food. Rats with lesions to the DTN were impaired across all tasks. Rats with lesions to the LMN were impaired on the variable-hole version of the foraging task, but showed only transient deficits on the water maze task (However, only a small number of rats sustained an acceptable level of damage to the LMN). These data demonstrate the importance of the direction system on these tasks.

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