Effects of Lesioned Red Nuclei on Spatial Navigation in Rats

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Running Head: Spatial Navigation in Rats

Effects of Lesioned Red Nuclei on Spatial Navigation in Rats
Through cerebellar research we have found that the cerebellum is involved in non-motor functions just as much as it is involved in motor functions. This study looked at the pathway from the cerebellum to the red nucleus to the thalamus into the cerebral cortex. Our hypothesis was that lesioning the red nucleus would show deficits like those seen in lesions of the cerebellum revealing that this pathway is crucial in visuo-spatial processing. Lesions of the red nucleus on four rats were tested against five controlled sham conditioned rats. We found that these lesions had some effect on the spatial navigations of the rats however the lesions were not found to be significant across training days. Our results imply that the red nucleus is involved in spatial navigation processes however there must be other pathways at work that allow for visuo-spatial information to be relayed.
Effects of Lesioned Red Nuclei on Spatial Navigation in Rats It was long thought that the cerebellum was only involved in motor tasks. However in the last decade research has shown that the cerebellum is involved in many non-motor tasks such as, emotional processing, learning and memory, linguistic processing, planning, and visuo-spatial processing. A summary of cerebral non-motor functions have been reported in a recent literature review by Rapaport, et al (2000) which points to the association between the cerebellum and schizophrenia. Since schizophrenic symptoms have mostly non-motor properties it would seem that the recent studies on non-motor functions in the cerebellum would be true. Further support on associations of the cerebellum and non-motor functions can be seen in studies such as conducted by Joyal, et al. (1996) who provided some evidence that there were spatial navigation strategy deficits following cerebellar lesions. They were looking at effects of motor and non-motor functions in rats after midline and lateral cerebellar lesions. Tasks that were used to evaluate effects of these lesions were; bridge test, grid test, wire suspension, spontaneous alternation, the Morris Water Maze test, and the visual discrimination test. Using results obtained from evaluations on each of the tests, Joyal et al (1996) found that the cerebellar lesions caused both motor and non-motor deficits in the rats. For purposes pertaining to this study we will concentrate on deficits observed in the Morris Water Maze. Joyal et al (1996) found that rats with midline cerebellar lesions were found to have deficits in the visual platform condition. Showing evidence that these deficits were pertaining to motor functioning. Rats with lateral cerebellar lesions only showed deficits in the invisible platform portion of the Morris Water Maze. Supporting evidence that the cerebellum is involved in processing spatial orientation information. An experiment conducted by Leggio, et al (2000) looked at learning of motor tasks through observation in rats. More specifically, rats were allowed to observe 200 trials of control rats in the Morris Water Maze. They were then surgically given a hemicerebellectomy and were put into the Morris Water Maze. The rats exhibited abilities of spatial navigation and escape latencies similar to those of control rats. However when hemicerebellectomy preceded the observation of control rats in the Morris Water Maze spatial navigation strategies and escape latencies were significantly impaired. These observations clearly indicate a strong relationship between the cerebellum and spatial procedures regardless of actually performing the task. The importance of finding that observations of tasks can be learned and replicated pre-hemicerebellectomy and that they are not learned and replicated post- hemicerebellectomy show that the cerebellum plays a vital role...
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