Mice brain images prove that synapses shrink every night

By Ursula Biba 

Various studies prove the importance of sleep, and as neuroscience progresses, there is increasingly more evidence to support that claim. Researchers at the Wisconsin Center for Sleep and Consciousness have proven the synaptic homeostasis hypothesis (SHY), which states that sleep is essential for the brain’s plasticity and learning, to be true with electron microscope images of mice brains. These images reveal that synapses, the spaces between nerve cells heavily involved in learning and memory, grow during the day and shrink 20% during sleep to provide room for growth the following day. Dr. Chiara Cirelli and Giulio Tononi used serial scanning 3-D electron microscopy to analyze reconstructed imaged of the cerebral cortex in mice. Over the course of four years, they analyzed the brain images with no knowledge of the specimens’ amounts of sleep, and correlated the images by amount of sleep after data collection’s conclusion. The team found that sleep led to an average 18% decrease in synapse size in both areas of the cerebral cortex. Although this occurred in 80% of synapses, the largest junctions did not shrink during sleep, leading researchers to believe these large synapses are integral to the most stable memory traces. When extrapolated to the human brain, Cirelli and Tononi’s findings reveal that trillions of cortical synapses shrink every night.


University of Wisconsin-Madison. "Sleep research high-resolution images show how the brain resets during sleep." ScienceDaily. ScienceDaily, 2 February 2017. <www.sciencedaily.com/releases/2017/02/170202141913.htm>.