Ultrastructural evidence for synaptic scaling across the wake/sleep cycle.
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.
Department of Psychiatry, University of Wisconsin-Madison, 6001 Research Park Boulevard, Madison, WI 53719, USA.
Luisa
L
de Vivo
Department of Psychiatry, University of Wisconsin-Madison, 6001 Research Park Boulevard, Madison, WI 53719, USA.|Department of Experimental and Clinical Medicine, Section of Neuroscience and Cell Biology, Università Politecnica delle Marche, Ancona, Italy.
Michele
M
Bellesi
Department of Psychiatry, University of Wisconsin-Madison, 6001 Research Park Boulevard, Madison, WI 53719, USA.
William
W
Marshall
National Center for Microscopy and Imaging Research, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.
Eric A
EA
Bushong
National Center for Microscopy and Imaging Research, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.|Department of Neurosciences, School of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.
Mark H
MH
Ellisman
Department of Psychiatry, University of Wisconsin-Madison, 6001 Research Park Boulevard, Madison, WI 53719, USA. ccirelli@wisc.edu gtononi@wisc.edu.
Giulio
G
Tononi
Department of Psychiatry, University of Wisconsin-Madison, 6001 Research Park Boulevard, Madison, WI 53719, USA. ccirelli@wisc.edu gtononi@wisc.edu.
Chiara
C
Cirelli
D000818:Animals; D001369:Axons / Q000648:ultrastructure; D007858:Learning / Q000502:physiology*; D017774:Long-Term Potentiation / Q000502:physiology*; D051379:Mice; D008854:Microscopy, Electron; D009044:Motor Cortex / Q000648:ultrastructure; D012890:Sleep / Q000502:physiology*; D013003:Somatosensory Cortex / Q000648:ultrastructure; D013131:Spine / Q000648:ultrastructure; D013569:Synapses / Q000648:ultrastructure*; D014851:Wakefulness / Q000502:physiology*