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Morris Water MazeIn neuroscience, the Morris water maze is a behavioral procedure designed to test spatial memory. It was developed by neuroscientist Richard Morris in 1981, and is commonly used today to explore the role of the hippocampus in the formation of memories about space. Overview In the typical paradigm, a rat is placed into a small pool of opaque water which contains a escape platform hidden a few millimeters below the water surface. Visual cues, such as colored shapes, are placed around the pool in plain sight of the rat. When released, the rat swims around the pool in search of an exit while various parameters are recorded, including the time spent in each quadrant of the pool, the time taken to reach the platform (latency), and total distance traveled. The rat's escape from the water reinforces its desire to quickly find the platform, and on subsequent trials (with the platform in the same position) the rat is able to locate the platform more rapidly. This improvement in performance occurs because the rat has learned where the hidden platform is located relative to the salient visual cues. Pharmacological manipulation Various drugs can be applied to test subjects before, during, or after maze training, which can reveal information about spatial learning and its underlying mechanisms. For example rats treated with the NMDA receptor blocker APV perform poorly in the Morris water maze, suggesting that NMDA receptors play a vital role in spatial learning http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=1345945. And since long-term potentiation -- a potential biological mechanism for behavioral learning -- also requires NMDA receptors, spatial learning may require LTP. Liang et al reported in 1994 that spatial learning requires both NMDA and AMPA receptors, consolidation requires NMDA receptors, and the retrieval of spatial memories requires AMPA receptors http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=7796636. References - Davis S, Butcher SP, Morris RG. "The NMDA receptor antagonist D-2-amino-5-phosphonopentanoate (D-AP5) impairs spatial learning and LTP in vivo at intracerebral concentrations comparable to those that block LTP in vitro." J Neurosci. 1992 Jan;12(1):21-34. PMID 1345945
- Liang KC, Hon W, Tyan YM, Liao WL. "Involvement of hippocampal NMDA and AMPA receptors in acquisition, formation and retrieval of spatial memory in the Morris water maze." Chin J Physiol. 1994;37(4):201-12. PMID 7796636
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