Hippocampus and Spatial Memory

O Keefe J. 1993. Hippocampus, theta, and spatial memory. Curr Opin Neurobiol 3(6) 917-924. 

Vanderwolf CH, Cain DP (1994) The behavioral neurobiology of learning and memory a conceptual reorientation. Brain Res Brain Res Rev 19 264-297 Villarreal DM, Do V, Haddad E, Derrick BE (2002) NMDA receptor antagonists sustain LTP and spatial memory active processes mediate LTP decay. Nat Neurosci 5 48-52 Walker DL, Ressler KJ, Lu KT, Davis M (2002) Facilitation of conditioned fear extinction by systemic administration or intra-amygdala infusions of d-cycloserine as assessed with fear-potentiated startle in rats. J Neurosci 22 2343-2351 Wallenstein GV, Eichenbaum H, Hasselmo ME (1998) The hippocampus as an associator of discontiguous events. Trends Neurosci 21 317-323 Wehner JM, Radcliffe RA, Bowers BJ (2001) Quantitative genetics and mouse behavior. Annu Rev Neurosci 24 845-867... 

Burgess N, Maguire EA, O Keefe J (2002) The human hippocampus and spatial and episodic memory Nemon 35 625-641... 

Chronic stress impairs the hippocampus-dependent spatial memory and blocks LTP in area CAl of the hippocampus possibly by interfering with the function of key signaling molecules involved in memory and LTP including reduction of phosphorylated CaMKII [P-CaMKII], PKCy, and calmodulin and increase in calcineurin levels [Table 47.2 244, 245]. These changes are prevented by chronic nicotine treatment during stress [245]. Another important signaling molecule that is markedly impacted by stress is BDNF. The expression of BDNF mRNA [256-258] and protein levels [245, 259] is decreased after stress. Chronic nicotine treatment restores the protein levels of BDNF in CAl area of the hippocampus of chronically stressed animals [245]. 

The hippocampus, which got its name from the Greek word for seahorse, due to its form, is a nucleus in the depth of the temporal lobe. The hippocampus is important for the integration of sensory information, for spatial orientation and for memory formation. The hippocampal formation contains the CA (cornu ammonis) regions, the dentate gyms and the subiculum. 

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It is striking that the behavioural consequences of an impairment of as GABAa receptors are opposite to those of a NMDA receptor deficit. While mice with a deficit in hippocampal NMDA receptors (NRI-CAl knockout) show a deficit in the formation of spatial and temporal memory (Tsien et al. 1996 Tang et al. 1999), the mice with a deficit in as GABAa receptors display an improvement in hippocampal spatial and temporal memory performance. Thus, it appears that these two receptor systems play a complementary role in controlling neuronal processing in the hippocampus. 

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Blum, S., Moore, A. N., Adams, F. and Dash, P. K., 1999, A mitogen-activated protein kinase cascade in the CA1/CA2 subfield of the dorsal hippocampus is essential for long-term spatial memory, J Neurosci, 19, pp 3535-44. 

Broadbent NJ, Squire LR, Clark RE. Spatial memory, recognition memory, and the hippocampus. Proc Natl Acad Sci USA 2004 101 14,515-14,520. 

Galani R, Weiss I, Cassel J-C, Kelche C. 1998. Spatial memory, habituation, and reactions to spatial and nonspatial changes in rats with selective lesions of the hippocampus, the entorhinal cortex or the subiculum. Behav Brain Res 96 1-12. 

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