Genetic variation, hippocampal mossy fibres distribution, novelty reactions and spatial representation in mice.

It is now well established that variation in hippocampal circuitry correlates with various behavioural measures. In order to formulate more precise hypotheses about the functional role of the supra (SP-MF) and intra-infra mossy fibres (IIP-MF) layers, we investigated their covariation with a large number of behavioural measures in the classic and the spatial open-field taken from a genetically heterogeneous population composed of subjects from 12 isogenic mice groups (9 inbred strains and 3 F1's). The hippocampus-behaviour intercorrelation matrix reveals that behavioural reactions and inferred psychological processes only correlate with IIP-MF. Detailed analysis of correlates shows that IIP-MF positively correlate with locomotor activity, rearings and central sector crossings in the classic open-field and correlate negatively with the short-term habituation index to the objects in the spatial open-field. Surprisingly the memory of the spatial arrangement of a set of objects does not correlate with any hippocampal measure.