Archive for 19 October, 2013

Sleep Cleanses Toxins, Gunk, Trash in Brains

What do our brains do while we sleep? Image courtesy of Katherine Streeter for NPR

Finally we have it folks. After millenia of having a crack at the mystery, with thousands of crackpot theories in vogue and spending exponentially more think-time and dollars on the research, theory, practicals and experiments on man, fish, insect and beast, 13 scientists of a melting-pot persuasion representing atleast 5 continents in their origins based in Rochester have some semblance of a partial explanation as to the function that sleep of the night-cap kind serves. Here is “Sleep Drives Metabolite Clearance from the Adult Brain”, Lulu Xie, Hongyi Kang, Qiwu Xu, Michael J. Chen, Yonghong Liao, Meenakshisundaram Thiyagarajan, John O’Donnell, Daniel J. Christensen, Charles Nicholson, Jeffrey J. Iliff, Takahiro Takano, Rashid Deane, and Maiken Nedergaard, Science, 18 October 2013: 342 (6156), 373-377. DOI:10.1126/science.1241224]

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.

Duh, I say. Is it huh, I hear you say? From a mish-mash of coverage of this seminal development and dissemination in various places (and counting) like NPR, Science Blog, Associated Press, Times of India and Zee News, allow me to plainspeak. Essentially, brains sweep hemselves clean of toxins during sleep. In mice, their brain cells shrink, allowing cerebrospinal fluid to flow easily around them. The fluid can then clear away toxins. The study reveals brain takes out the trash while we sleep in findings that give fresh meaning to the old adage that a good night’s sleep clears the mind for sleep gets rid of gunk that builds up while we’re awake which while explaining the function of sleep, may also provide new clues to treat Alzheimer’s disease and other disorders. These waste products included amyloid beta, a protein that when accumulated is a driver of Alzheimer’s disease. In order to help remove the waste, cerebral spinal fluid is pumped through brain tissue. The process is sped along during sleep because the brain’s cells shrink by about 60 percent, allowing the fluid to move faster and more freely through the brain. The whole operation takes place in what researchers call the glymphatic system, which appears to be nearly 10 times more active during sleep than while awake. The body does this sweeping only during sleep and not continuously during wakefulness for the sake of energy efficiency and performance in day activities.

I would not be much of a self-acclaimed scientist and card-carrying blogger if I did not put my spin on it now, would I? We may not have hundreds of mice lying about to dissect their brains about and 2-photon microscopes in the garage but this study appeals to us because this ‘cleaning trash’ theory is something we all innately have internalized to explain, if only to ourselves, why nature has made sleep mandatory that takes up roughly half of our lives (counting the sleep from when we are young and senile which is a lot). Life is short and then we have to sleep. Doh! Not to drill holes but there is a lot more to be explained about sleep, especially in humans who also sleep recreationally with naps, siestas, kunukus etc. and under stress when we are ill, hit on the head etc. What happens and what is the purpose of sleep in these situations? Seriousness apart, that sleep cleanses our brains of toxins makes one wonder about death which is but indefinite sleep. It seems to me that death is that one last big cleanse. It is nature cleansing the planet of our toxic insignificant existence in this mortal coil. Sweet dreams, bitter visions, sour nightmares et al.

19 October, 2013 at 14:48 Leave a comment


October 2013


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