Journal Article

Ultrastructural evidence for synaptic scaling across the wake/sleep cycle

de Vivo, Luisa, Cirelli, Chiara, Bushong, Eric A., Marshall, William, Ellisman, Mark H., Tononi, Giulio, Bellesi, Michele

2017

Overview

It is assumed that synaptic strengthening and weakening balance throughout learning to avoid runaway potentiation and memory interference. However, energetic and informational considerations suggest that potentiation should occur primarily during wake, when animals learn, and depression should occur during sleep. We measured 6920 synapses in mouse motor and sensory cortices using three-dimensional electron microscopy. The axon-spine interface (ASI) decreased ~18% after sleep compared with wake. This decrease was proportional to ASI size, which is indicative of scaling. Scaling was selective, sparing synapses that were large and lacked recycling endosomes. Similar scaling occurred for spine head volume, suggesting a distinction between weaker, more plastic synapses (~80%) and stronger, more stable synapses. These results support the hypothesis that a core function of sleep is to renormalize overall synaptic strength increased by wake.

• Publisher: American Association for the Advancement of Science,The American Association for the Advancement of Science
• Subject: Animals / Axons - ultrastructure / Data processing / Electron microscopy / Endosomes / Genetics / Glutamate receptors / Head / Information processing / Learning / Learning - physiology / Long-Term Potentiation - physiology / Mice / Microscopy / Microscopy, Electron / Motor Cortex - ultrastructure / Noradrenaline / Norepinephrine / Potentiation / Protein turnover / Rodents / Scaling / Scanning electron microscopy / Sleep / Sleep - physiology / Sleep and wakefulness / Somatosensory Cortex - ultrastructure / Spine / Spine - ultrastructure / Strengthening / Synapses / Synapses - ultrastructure / Synaptic depression / Synaptic strength / Wakefulness - physiology / Wakes