Behavioural Brain Research, 41 (1990) 251-259 251 Elsevier BBR 01130 No correlations between spatial and non-spatial reference memory in a T-maze task and hippocampal mossy fibre distribution in the mouse W.E. Crusio 1'*, J.-Y. Bertholet I and H. Schwegler 2 ~GOnOtique, Neurog~nOtique et Comportement, URA 1294 CNRS, Paris (France) and 2Anatomisches Institut, UniversitgitFreiburg, Freiburg (F.R. G.) (Received 28 May 1990) (Revised version received 4 October 1990) (Accepted 4 October 1990) Key words." Hippocampus; Intra- and infrapyramidal mossy fibre; Reference memory; Spatial learning; Non-spatial learning; T-maze; Mouse Two reference memory tasks were tested in a T-maze, which was placed in a spatially richly structured environment and turned 180 ° between trials following a semi-random schedule. Male mice from 9 different inbred strains were either trained always to go to the same place (spatial task) or always to make the same turn (non-spatial task). Animals were subsequently processed for Timm's stain and the sizes of their intra- and infrahippocampal mossy fibre terminal fields (ipp-MF) were measured. Significant strain differences were found for this variable and in both learning tasks, but learning and hippocampal variation did not correlate. This disagrees with earlier findings in a radial maze, where significant correlations between the iipMF and spatial reference memory were obtained. Two hypotheses are brought forward to explain this discrepancy. First, in radial mazes (multiple choices) different memory capabilities might be used than in T-mazes (only two choices). Second, a considerable amount of stress appeared to be present in our subjects, possibly induced by the large size of the T-maze. This might have interfered negatively with acquisition. Further experiments will be needed to test these hypotheses. INTRODUCTION Subtle anatomical variations in the mouse hip- pocampus have been shown to co-vary with be- havioural variation in a number of tasks ~°. In particular, the size of the intra- and infra- pyramidal mossy fibre (iip-MF) projection has been shown to correlate with two-way active- avoidance learning23, water-maze learning 21,26, Y-maze discrimination 12, and exploration4,6 and habituation 3'13 in an open-field. Recently, we observed some very strong corre- lations between the iip-MF and learning in a num- ber of radial-maze tasks 5,19. Depending on the experimental set-up of the radial maze, spatial learning, non-spatial learning, working memory (storing trial-specific information; see ref. 17), re- ference memory (concerning information relevant over all trialsl7), or chaining responses can be tested. Our previous results showed a positive correlation between the iip-MF and spatial working memory (larger iip-MF being associated * Present address: Institut f'tir Humangenetik und Anthropologie, Universit~it Heidelberg, Im Neuenheimer Feld 328, 6900 Heidelberg, F.R.G. Correspondence." J.-Y. Bertholet, G6n6tique, Neurog6n6tique et Comportement, 45, rue des Saints-P6res, 75270 Paris cedex 06, France. 0166-4328/90/$03.50 © 1990 Elsevier Science Publishers B.V. (Biomedical Division)