Headed in the right direction: start point orientation and direction learning in rats

Peckford, Genieve (2012) Headed in the right direction: start point orientation and direction learning in rats. Masters thesis, Memorial University of Newfoundland.

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Abstract

When trained to locate a hidden platform in a T-maze moved between two positions, rats appear to adopt a conditional strategy based on start point. To determine if location cues or orientation cues at the start point underlie this discrimination rats were trained from two maze positions to swim in a consistent direction from the choice point to the platform. When the maze was later moved to two new positions, rats required to make the same response based on start point orientation showed no disruption in performance while rats required to make the same response based on start point location did show an initial disruption in performance (Experiment 1). Animals explicitly trained to use start point location cues in Experiment 2 took significantly longer to solve a spatial task than rats trained explicitly to use orientation cues. When the start point location cues were masked, by making the room dark prior to placing the rats in the maze, performance did not deteriorate if rats were required to respond based on orientation of the start point but was disrupted if they were required to respond based on start point location cues (Experiment 3). This sense of direction requires exposure to the room cues to get oriented, as rats brought into an already darkened room (Experiment 4) were disrupted regardless of whether responses were tied to orientation cues or location cues. These findings are consistent with views of spatial learning that attribute a strong role to a rats' sense of direction. However, lesions to the anterior dorsal nucleus of the thalamus, a component of the head direction cell circuit, produced only transient deficits in direction learning in the water maze and small errors in heading on a foraging task.

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