The images show that the junctions between neurons, known as synapses, strengthen and grow during waking hours, then shrink by almost 20 percent during sleep, which opens up more room for them to grow, and learning to take place, when waking the next day.

In an effort to test their "synaptic homeostatis hypothesis (SHY)," which proposes that sleep is the price we pay for the plasticity of our brains, Drs. Chiara Cirelli and Giulio Tononi from the Wisconsin Center for Sleep and Consciousness used serial scanning 3D electron microscopy to capture images of the cerebral cortex of the mouse brain with extremely high spatial resolution.

The research project took four years and involved photographing, reconstructing and analyzing two areas of a mouse brain's cerebral cortex and ultimately resulted in the research team reconstructing 6,920 synapses and measuring their size so as to provide some visual proof of the SHY.