Sleep and synapses

Michele Bellesi
Università Politecnica delle Marche


We spent more than one third of our life sleeping and, yet, the role of sleep remains one of the most unsolved mystery of biology. Sleep is a universal phenomenon, as it seems to be present in all the species carefully studied so far. It is unknown when and why sleep emerged in evolution, but the simplest hypothesis is that sleep evolved to serve at least one core function in all species.

The synaptic homeostasis hypothesis (SHY) proposes that sleep is the price the brain pays for plasticity. During a waking episode, learning statistical regularities about the current environment requires strengthening connections throughout the brain. This increases cellular needs for energy and supplies, decreases signal-to-noise ratios, and saturates learning. During sleep, spontaneous activity renormalizes net synaptic strength and restores cellular homeostasis.

Dr. Bellesi will show molecular and electrophysiological evidence from experiments performed over the last years, which supports this hypothesis. In addition, he will talk about his latest morphological study describing the structural changes occurring at cortical synapses across the sleep and wake cycle.