COVARIATIONS BETWEEN HIPPOCAMPAL MOSSY FIBERS AND WORKING AND REFERENCE MEMORY IN SPATIAL AND NONSPATIAL RADIAL MAZE TASKS IN MICE

Male mice from nine inbred mouse strains were tested at the age of 3 m onths in either a spatial or a non-spatial version of the radial maze. Only four out of eight arms contained food rewards, permitting simult aneous assessment of working and reference memory in both situations. Other animals from the same strains were processed histologically to e stimate the strain-specific extents of the mossy fibre projections. No significant between-task correlations were obtained for either workin g or reference memory. However, measures of working and reference memo ry correlated with each other within tasks. This suggests that these c oncepts may perhaps not be validly used in the mouse. Large, positive correlations of the size of the intra- and infrapyramidal mossy fibre projection with both working and reference memory were obtained in the spatial radial maze task, but not in the non-spatial one. We conclude that heritable variations of the hippocampal intra- and infrapyramida l mossy fibre projection influence processes related to spatial learni ng capabilities in radial mazes.