For brain cleaning.
Study finds that spinal fluid pumps around the brain of sleeping mice, flushing out waste products.
Science 18 October 2013:
Vol. 342 no. 6156 pp. 373-377
Sleep Drives Metabolite Clearance from the Adult Brain
"The conservation of sleep across all animal species suggests that sleep serves a vital function. We here report that sleep has a critical function in ensuring metabolic homeostasis. Using real-time assessments of tetramethylammonium diffusion and two-photon imaging in live mice, we show that natural sleep or anesthesia are associated with a 60% increase in the interstitial space, resulting in a striking increase in convective exchange of cerebrospinal fluid with interstitial fluid. In turn, convective fluxes of interstitial fluid increased the rate of β-amyloid clearance during sleep. Thus, the restorative function of sleep may be a consequence of the enhanced removal of potentially neurotoxic waste products that accumulate in the awake central nervous system. "
Are there other states of being where this occurs - in humans ?
Does zazen, upright sitting, also have a function like this?
What of the cleansing of body-mind practice like tonglen in Vajrayana Buddhism or Hakuin's naikan?