Latent mechanisms of plasticity are upregulated during sleep.

Sleep is thought to serve an important role in learning and memory, but the mechanisms by which sleep promotes plasticity remain unclear. Even in the absence of plastic changes in neuronal function, many molecular, cellular, and physiological processes linked to plasticity are upregulated during sleep. Therefore, sleep may be a state in which latent plasticity mechanisms are poised to respond following novel experiences during prior wake. Many of these plasticity-related processes can promote both synaptic strengthening and weakening. Signaling pathways activated during sleep may interact with complements of proteins, determined by the content of prior waking experience, to establish the polarity of plasticity. Furthermore, precise reactivation of neuronal spiking patterns during sleep may interact with ongoing neuromodulatory, dendritic, and network activity to strengthen and weaken synapses. In this review, we will discuss the idea that sleep elevates latent plasticity mechanisms, which drive bidirectional plasticity depending on prior waking experience.