Behavioral studies using genetically defined mice--a bibliography (August 1979-July 1980)

Using genetically-defined rodent strains for the identification of hippocampal traits relevant for two-way avoidance behavior: a non-invasive approach

Genetically-defined rodent strains permit the identification of hippocampal traits which are of functional relevance for the performance of two-way avoidance behavior. This is exemplified here by analyzing the relationship between infrapyramidal mossy fibers (a tiny projection terminating upon the basal dendrites of hippocampal pyramidal neurons) and two-way avoidance learning in about 800 animals. The necessary steps include 1) identification of structural traits sensitive to selective breeding for extremes in two-way avoidance, 2) testing the robustness of the associations found by studying individual and genetical correlations between hippocampal traits and behavior, 3) establishing causal relationships by Mendelian crossing of strains with extreme structural traits and studying the behavioral consequences of such structural 'randomization', 4) confirming causal relationships by manipulating the structural variable in inbred (isogenic) strains, thereby eliminating the possibility of genetic linkage, and 5) ruling out the possibility of spurious associations by studying the correlations between the hippocampal trait and other behaviors known to depend on hippocampal functioning. In comparison with the classical lesion approach for identifying relationships between brain and behavior, the present procedure appears to be superior in two aspects: it is non-invasive, and it focuses automatically on those brain traits which are used by natural selection to shape behaviorally-defined animal populations, i.e., it reveals the natural regulators of behavior.

Radial maze performance in three strains of mice: role of the fimbria/fornix

Three strains of mice were tested on an 8-arm radial maze, an index of hippocampus-dependent spatial memory. Levels of performance differed between strains with C57Br/cj greater than Balb/cj greater than C57Bl/6j. Lesions of the fimbria/fornix disrupted performance in the C57Br and Balb strains: the C57Bl mice never performed better than chance before or after surgery. Choline acetyltransferase activity in hippocampus was not correlated with radial maze performance. These findings suggest a possible genetic contribution towards radial maze behavior.