Sleep and wake at cortical synapses

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 wakefulness, the continuous interaction with the external environment leads to strengthening of neuronal 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. de Vivo and Dr. Bellesi will discuss molecular and electrophysiological evidence from experiments performed over the last years, which supports this hypothesis. In addition, they will talk about their latest morphological study describing the ultrastructural changes occurring at cortical synapses across the sleep and wake cycle and after sleep loss.