Comment by DoreenMichele

Striking electron microscope pictures from inside the brains of mice suggest what happens in our own brain every day: Our synapses – the junctions between nerve cells – grow strong and large during the stimulation of daytime, then shrink by nearly 20 percent while we sleep, creating room for more growth and learning the next day.

https://neurosciencenews.com/sleep-brain-reset-6047/

Sleep Shrinks the Brain--and That's a Good Thing

Without a nighttime reset, synapses could burn out like an outlet with too many appliances plugged in

https://www.scientificamerican.com/article/sleep-shrinks-the...

The sleeping and the anesthetized mice had a 60% increase in the volume of fluid, apparently because brain cells actually shrink to allow more space in the channels. When the researchers woke the mice up, the flow of fluid into the brain abruptly slowed.

http://m.nautil.us/blog/sleep-when-brain-cells-shrink--neuro...