The value of slow wave sleep in flushing the brain of toxins was discovered when they discovered the glymph system in 2012 that is that drain for flushing the toxins. During slow wave sleep, the neurons shrink 40% in size. That space allows the glymph system to dilate or open up allowing the toxins to flow to the cerebral spinal fluid to be expelled. The glymph system is a very fine sheath over the vascular structure that opens up to a minute level to allow flow. Doctors and researchers had been looking for this drain system for decades.