Independence of mechanisms for short-term and long-term memory in spatial contextual learning in the Morris water maze

Abstract

Aim. The dependence of long-term memory formation on short-term memory was studied to evaluate mechanisms for in teraction of different memory forms. Methods. Rats were trained in the Morris water maze using the spatial contextual model of learning. We compared results of the test (time to reaching the hidden platform) on the first training day (short-term memory) and the first attempts on the next three days, which reflected stages in the consolidation of long-term memory. The comparison was performed using a statistical method of splitting animals into quartiles based on their learning ability. Results. The rats showing a good learning ability at all stages of training constituted only a small part of the trained animals while most animals showed different abilities to formation of short-term memory and consolidation of long-term memory. The rats were identified, which 1) although showed weak abilities at one or both stages of the first-day training showed good abilities to consolidate the long-term memory on the next days and, on the contrary, 2) showed good abilities to form the short-term memory while the memory consolidation was impaired. Conclusions. The study results clearly indicated a lack of dependence between mechanisms of short-term and long-term memory.