The effects of dorsal hippocampal or CA3 lesions on spatial reference and working memory in two spatial tasks

Glover, Lucas

The effects of dorsal hippocampal or CA3 lesions on spatial reference and working memory in two spatial tasks

Persistent URL

http://hdl.handle.net/10456/7986

Author(s)

Glover, Lucas

Date Issued

April 17, 2009

Abstract

The rodent dorsal hippocampus is necessary for normal spatial memory, where dorsal lesions produce an impairment in this mnemonic function. It is not known which specific subregions within the dorsal hippocampus mediate spatial memory. In the present study, rats were trained in the radial maze before bilateral neurotoxic lesions of dorsal CA3 (dCA3) or dorsal hippocampus (dHPC). Post-operative testing showed that both groups were impaired on reference and working memory. The same rats were then tested for spatial acquisition in the Morris Water Maze (MWM) and later tested on retrieval. All groups acquired the task equally but only the dHPC, and not dCA3, group showed impaired retrieval. Upon subsequent testing of working memory ability in the MWM, dHPC rats, but not dCA3, showed deficits. Analysis of behavioral data followed histological confirmation of lesion placement showing selective dCA3 and dHPC lesions made by ibotenic acid and colchicine, respectively. These behavioral results suggest that encoding of a reference memory may only depend upon the tissue available within the hippocampus, where the ventral portion may compensate for the lost dorsal section. Upon retrieval of this information, however, the dHPC is required and may utilize a larger neural network for successful retrieval. As for spatial working memory, the dCA3 is differently involved in working memory where compensatory mechanisms can act depending on delay and/or task-specific demands that recruit other areas besides the dCA3.

Honors

Neuroscience, 2009

Psychology, 2009

First Reader(s)

Cross, Jeffrey