HEALTH – December 2014

The sleeping brain: the importance of sleep

We have all felt the fatigue that comes from a night without sleep but we rarely pay attention to the underlying reason behind this seemingly useless activity. A series of recent advances in the field of neurobiology complements what has long-captivated poets and philosophers- the purpose of sleep. A research study done in 2012 at the Center for Translational Neuromedicine in the University of Rochester, New York, shows some interesting results. In the same way that a kitchen or a room becomes progressively dirty the more we use it, every cell in our body, generates undesirable substances, some of which become toxic when they accumulate. Our lymphatic system collects and cleanse the body of this cellular waste. One of the researchers involved in the study, Dr. Jeffrey Iliff, notes the fact that the brain, our body’s most metabolically active organ, does not have a lymphatic system. The research group, led by Dr. Maiken Nedergaard, proposes an alternate mechanism by which the brain cleanses itself. A key finding is that it only happens while we sleep.

With little room to expand, many blood vessels and millions of neurons and other cells, it appears that there is no extra space for lymphatic vessels in the brain. So what is the brain’s solution? It uses one of its intrinsic resources- cerebrospinal fluid (CSF). Until recently, it was thought that the sole function this was to provide buoyancy and protect the brain from impacts with the skull. Thanks to two-photon microscopy, the researchers were able to observe inside a rat’s brain-, which is markedly similar to a human’s-, what appears to be a complex system of waste management, similar to the lymphatic system.

From the brain’s surface, CSF uses the interstitial space between the cell and the arteries where waste is accumulated- to travel deep into the brain. This is very important because the cells here are extremely sensitive to minor changes in their chemical surroundings. This process also plays a key role in neurodegenerative diseases, since the accumulation of interstitial waste is linked to their development, as is the case of amyloid-beta and Alzheimer’s. “The brain has only a limited energy at its disposal and it appears that it must choose between two different functional states awake and aware or sleep and cleaning up”, said Dr. Nedergaard. “You can think of it like having a house party. You can either entertain the guests or clean up the house, but you can’t really do both at the same time”.

In this study there is, perhaps, a convincing reason to try and better our sleeping habits. There is no doubt that each new study generates more questions but for now, each time you go to bed, thank your brain, for it is probably working quietly at cleaning itself while your mind wonders off to a land of dreams.

Bibliography

Iliff, J. J., M. Wang, Y. Liao, B. A. Plogg, W. Peng, G. A. Gundersen, H. Benveniste, G. E. Vates, R.
Deane, S. A. Goldman, E. A. Nagelhus, and M. Nedergaard. “A Paravascular Pathway Facilitates
CSF Flow Through the Brain Parenchyma and the Clearance of Interstitial Solutes, Including Amyloid .” Science Translational Medicine 4.147 (2012): 147ra111. Web.
“To Sleep, Perchance to Clean.” – News Room. University of Rochester, 17 Oct. 2013. Web. 23 Nov. 2014.

André Renaldo Fernández was born and raised in Puerto Rico and is currently a first-year medical student at the University of Rochester, where he is also a member of the Latino Student Medical Association (LMSA). He received his bachelor’s degree in Biology from the College of William & Mary in Williamsburg, Virginia, where he was heavily involved with the Latino community. He will like to continue this interest through LMSA by raising awareness of the health issues surrounding the Latino population in the United States. In his free time, he enjoys playing the piano, swimming, and going for long walks.