SPACED TRAINING EFFECTS ON THE ACTIVITY OF STRIATAL AND HIPPOCAMPAL CIRCUITS

Although it is well established that information presented using spaced repetitions is better remembered than information presented via massed repetitions, still unexplored are the mechanisms contributing to the better stability of distributed learning at cellular and network level. To this purpose we compared in the Morris water maze (MWM) the effect of six training sessions distributed over three days with that of training massed in a single day. CD1 mice trained with the two training protocols did not differ in the ability to locate the platform 24hrs after the last training session. However, only the spaced-trained mice could efficiently remember the platform location 14-day after training. Analysis of learning revealed no difference in the learning curve or in the strategy used to acquire the task in the two groups. To explore the possibility that the two learning paradigms might involve different neural network we are using two experimental strategies: 1. TetTag mice to conduct a direct comparison between neuronal ensemble activated by learning and embedded into the memory trace in the two training protocols; 2. AMPA receptor blockade in different brain regions on memory retrieval. The results demonstrate increased neuronal activity in both the hippocampal and the striatal circuits after massed and distributed training. Moreover they suggest that AMPA receptor activity in the dorso-medial but not the dorso-lateral striatum is required for retrieval of spatial information acquired with massed training.