SPONTANEOUS EXPLORATION, RESPONSE PLUS POSITION LEARNING AND HIPPOCAMPAL MOSSY FIBER DISTRIBUTION - A CORRELATIONAL STUDY

Forty-eight mice from twelve isogenic groups were tested in two different behavioral tests. The first test was a non-reinforced exploration of a Y-maze and the second was a response plus position learning followed by reversal learning in a T-maze. Behavioral results were correlated with the size of the area occupied by the various mossy fibre synaptic sub-fields in the hippocampus as revealed by Timm staining. The analysis of results showed that mice with a large suprapyramidal mossy fibre area tended to use a somewhat rigid motor response strategy during the initial exploration of the Y-maze, that they easily learned the response plus position task in the T-maze, but proved unable to quickly inhibit that learned response during the reversal task. On the other hand, mice with a large intra-infrapyramidal synaptic field displayed greater ability to cope with a situation including novelty or constraint elements.