“Integrative learning” promotes learning but not memory in older rats

BACKGROUND: We had previously advanced the concept of “Integrative Learning”, that is, “under the role of ‘meta-learning self’, learners actively integrate learning materials to achieve rapid and in-depth understanding of knowledge”, and designed an animal behavioral model to compare the effects of “Integrative Learning” (IL) vs. “Progressive Learning” (PL) in young rats. It was found that IL is more advantageous than PL. Here, we aim to examine whether the same phenomenon persist in older rats. METHODS: Fifteen 12-month-old male Sprague-Dawley (SD) rats were selected as subjects and randomly divided into the IL group and the PL group, and a 14-unit integrative T-maze was constructed for the study. Training and testing procedures contained three stages: the learning stage, the memory retention test stage and the Gestalt transfer learning stage. Data on young rats (1-month-old) from the previous study were also drawn here for comparisons on learning performance. RESULTS: (1) The 12-session learning stage can be divided into three sub-stages as each sub-stage represented the new opening of one third of the whole path in the PL group. There were significant interactions in total errors made between groups and sessions: the PL group had significantly fewer errors during Sub-stage One due to a much shorter path to be learned, however, the IL group’s errors made sharply dropped as learning progressed into Sub-stage Two and Three, and were maintained at a significantly lower level than the PL group during Sub-stage Three. (2) When compared with young rats, age had a main effect on the number of errors made—the 1-month-old groups learned overall better and faster than the older groups, whereas the pattern of group differences between the IL and PL learning modes remained consistent across young and older groups. (3) Unlike young rats, during the memory retention test stage and the Gestalt transfer learning stage, the IL group did not perform better than the PL group in older rats. CONCLUSIONS: (1) “Integrative Learning” promotes learning but not memory in older rats. (2) Higher-order cognitive abilities that support meta-cognition, long-term retention and knowledge transfer might be deteriorating in older rats.