Picture provided by Science News. Depicts colored tracers penetrate more deeply into a mouse’s brain when it’s asleep (left, red tracer) than awake (right, green tracer). |
Sleep has always been a significant
biological process that has intrigued people from ancient to modern times.
Ancient cultures held different views on sleep depending on their nomadic or
sedentary lifestyle and survival needs. Sleep is an important part of our
circadian rhythm and holds natural rejuvenating qualities. Many of the benefits
of sleep are being revealed with the aid of new technologies. Dr. Maiken Nedergaard,
from the University of Rochester Medical Center, is a pioneer in the
scientific community. Her research team recently conducted a study to determine
if during sleep the brain cleanses itself by flushing out unwanted toxins that
accumulate during active hours. In order to study this, the research team
injected dye into mice’s cerebrospinal fluid, which is the clear liquid that
surrounds the brain and spinal cord, to observe the travel route of the dye
through the brain. The data showed that the dye flowed when the mice were asleep
or unconscious and remained stagnant when the mice were awake. This helped
support their hypothesis because the cell structure must have shifted during
sleep creating space between the brain cells, which allowed the dye to be
flushed out. The increase in space between the brain cells is most likely
controlled by the glymphatic system, which regulates the flow of cerebrospinal
fluid in the brain. To further investigate the increased space between the
brain cells, the researchers tested it with electrodes. They inserted the electrodes
into both alert and unconscious mice’s brain and measured the distance. The scientists compared the results and the
space increased by 60% in sleeping mice. Additional support of this is that the
glia cells control the shrinking and swelling of the glymphatic system. When
noradrenaline, an arousal hormone responsible for increasing the control cell
volume, is blocked it induces asleep or unconsciousness and increases fluid
flow and brain cell spacing. Lastly, researchers conducted a test to see if there
is a connection between the glymphatic system and neurodegenerative disorders.
They injected beta-amyloid, which is a protein associated with Alzheimer’s
disease, into the brain to measure how long it remained in the brain when
asleep or awake. Scientists observed that the beta-amyloid was flushed out
quicker when the mice were asleep. This outcome supports that the brain
normally clears out toxic molecules from the brain. The glymphatic system could
be the new target for treating disorders and be a major breakthrough in the
medical field. There are many aspects and complex workings of the brain we have
not discovered yet but we are slowly gaining more understanding of the
biological processes.
Saey,
Tina Hesman. Sleep allows brain to wash out junk. Science News. Science News Magazine of the Society for Science and
the Public, 17 Oct. 2013. Web. 23 Oct. 2013.