IMPAIRED SPATIAL-LEARNING AFTER SATURATION OF LONG-TERM POTENTIATION

If information is stored as activity-driven increases in synaptic weig hts in the hippocampal formation, saturation of hippocampal long-term potentiation (LTP) should impair learning. Here, rats in which one hip pocampus had been lesioned were implanted with a multielectrode stimul ating array across and into the angular bundle afferent to the other h ippocampus. Repeated cross-bundle tetanization caused cumulative poten tiation. Residual synaptic plasticity was assessed by tetanizing a nai ve test electrode in the center of the bundle. Spatial learning was di srupted in animals with no residual LTP (<10 percent) but not in anima ls that were capable of further potentiation, Thus, saturation of hipp ocampal LTP impairs spatial learning.