Differential roles of sleep spindles and sleep slow oscillations in memory consolidation

摘要

Author summary We spend a third of our lives sleeping. During sleep, human and animal brains are decoupled from the external sensory input, however, brain activity remains high and varies across sleep stages. It is believed that one of the important sleep functions is the consolidation of recent memories to organize them for long-term storage. Two major sleep rhythms are observed during sleep spindles (during stage 2) and slow oscillations (during stage 3) and studies reported the importance of these rhythms in sleep-related memory consolidation. Nevertheless, the specific mechanisms of how these rhythms contribute to memory consolidation are poorly understood. Our new study predicts that sleep replay-repeatable sequences of neural cell firing, which are believed to be the neuronal substrate of memory consolidation-is organized within the patterns of the synchronous cell firing associated with these sleep rhythms. We found that for multiple interfering memories, sleep slow oscillations preferentially consolidate only the stronger memory traces, possibly leading to the weak memories extinction. In contrast, sleep spindles allow a slow but reliable consolidation of the multiple competing memories independently. Our study predicts how the basic structure of the natural sleep (where stage 2 precedes stage 3) provides an optimal environment for consolidation of multiple memories.