Surface location has priority over distal and local cues for place learning in translational problems in the rat: a behavioural and neurobiological assessment

Horne, Murray R. (2006) Surface location has priority over distal and local cues for place learning in translational problems in the rat: a behavioural and neurobiological assessment. Masters thesis, Memorial University of Newfoundland.

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Abstract

A cognitive map is considered to be a representation of relationships between distal cues in the environment. Support for the cognitive map theory has come from behavioural, lesion, and electrophysiological studies. Recently place field data have suggested that place cells are more closely tied to local, apparatus cues, than to distal cues. This was shown in a series of studies in which an apparatus was translated 33-120 cm. Earlier translational place studies, of which there are very few, are consistent with these place cell recording studies. The present thesis extends the examination of place learning on a moveable apparatus in a larger environment to better understand the interaction between location on an apparatus and location in a room, highlighting which conditions are necessary for an animal to shift from a surface dominated strategy to a strategy based on distal cues. In the present thesis, success and failure on the translational place problem was observed. The only difference between success and failure was the presence of multiple discriminable start points when rats were successful. It is suggested that multiple start points provide positional information that allows the rats to notice different directions to the goal, and therefore shift from a surface dominated strategy to a distal cue dominated strategy. Qualitative changes in surface texture did not facilitate this shift from a surface to a distal cue strategy. Hippocampal and sham lesioned rats were trained on the same translational place problem in the presence of multiple start positions. Lesions of the hippocampus disrupted place learning on this problem suggesting that simpler orientation mechanisms were not involved. Theoretical models and future directions are discussed.

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