Localized, post-conditioning, electrical stimulation of the brain has been used in an attempt to determine specific neuroanatomical structures which may contribute to memory storage processes. Recently, data has accumulated implicating the involvement of the dorsal hippocampal formation in memory consolidation processes in the rat. The data, however, must be interpreted with caution. While data has suggested that intense hippocampal stimulation resulting in extrahippocampal spread of abnormal afterdischarge activity is a necessary condition for the production of memory deficits, other data suggests that memory deficits can be produced by low-level electrical stimulation which produces no discernible abnormal afterdischarge activity. The proposed research is an attempt to determine under what conditions the dorsal hippocampal formation contributes to memory consolidation processes by examining one variable, strength of conditioning, and its importance in the production of memory deficits produced by post-conditioning low-level hippocampal stimulation. Specifically, strength of conditioning will be varied by (a) varying reinforcement magnitude and (b) varying the relative contribution of classical and instrumental conditioning to response suppression. By employing low-level post-conditioning stimulation of the dentate gyrus region of the dorsal hippocampus, the proposed research will give more definitive conclusions on the role of this area in memory consolidation processes. It is also proposed that the analysis may present preliminary data which will have direct implications for the contribution of specific neuroanatomical loci to classical and instrumental conditioning processes.