Sleep and spine loss

Sleep and waking modulate spine turnover in the adolescent mouse cortex

Maret et al 2011 (Nature Neuroscience)

This is an intriguing little paper just appeared in Nature Neuroscience, looking at spine turnover in sensorimotor (a bit of a vague word this) cortex of adolescent (P23-44) YFP-expressing mice. They imaged the same section of dendrite through the skull of the same mouse on two separate occasions - quite a technical achievement - at the end of a period of wakefulness, and then again after the mouse's next sleeping period. In this situation they found a net loss of spines after the sleeping period, whereas if they reversed the order, imaging after sleep first, then after waking, they found a net gain of spines. These differences disappeared in adults.

So sleep seems to be an important period of synaptic pruning in adolescent mice. I wonder if this applies to humans as well. Teenagers seem to go through these periodic bouts of excessive sleeping. Perhaps they're not being lazy after all - they're engaging in important synaptic pruning, remodelling their brain circuits in preparation for adult life?