This Sleep Circuit In The Brain Can Turn You Off Like A Switch
A sleep circuit in the brain has been identified in the brainstem of mammals that, once stimulated, causes test animals to quickly fall asleep regardless of the time of day.
Researchers at Harvard School of Medicine and the University at Buffalo School of Medicine and Bio-medical Sciences found this so-called sleep node (the second ever found) in the brain stem of the mammalian brain. The brain stem is the communication hub of the brain being connected directly to your spine and relaying signals from your gray matter through and down your spinal cord. Much more importantly though, it is the life support system that handles low-level but kinda important functions like breathing, heart-rate, body temperature, blood pressure, and sleeping.
As much as I’d love to do away with delicious yet wasteful sleep, the fact that it is an integral part of the brain stem and its suite of vital functions can only mean that evolution placed great importance on the value of sleep. The destructive power of insomnia and other sleep disorders then gains some perspective for the unfortunate millions of people (including my mom and brother) who suffer from this debilitating condition. Anything we can learn about it then would not only prove fascinating but could prove tremendously beneficial to many people.
Identifying this sleep circuit is actually the mundane aspect of this discovery. Controlling it is where things get seriously cool. In the past, this would be accomplished by simple electrical stimulation. This has drawbacks however since it is very imprecise. Any part of the brain touching the electrode gets stimulated including nearby tissue and unwanted cell types. This is where the truly revolutionary science of optogentics comes in.
Optogenetics uses optics and genetics (Duh) to monitor and control cells (in this case neurons) anywhere in the body. Scientific American described it well this way:
“What excites neuroscientists about optogenetics is control over defined events within defined cell types at defined times—a level of precision that is most likely crucial to biological understanding even beyond neuroscience. “
How this level of control is achieved may sound a little sketchy but stick with me. Scientists (and engineers) use the specific genetic code from other organisms (algae, fungi etc) that codes for a light-sensitive protein called opsin. This code is inserted into a virus (a viral vector) that is injected into the brain such that the protein is expressed only on the surface of the specific cells that you want to control. You then shine light of a specific wavelength onto the neurons using a surgically inserted optical fiber or perhaps light that can penetrate the skull. This light activates the protein causing the specific neurons to fire at the precise time you need them to.
Using this technique to activate the sleep node in the brainstem, test animals quickly fell into a deep sleep. In the future, we need to tease out what the interaction is between this sleep node and other areas of the brain that serve similar functions. The hope of course is that this will eventually lead to new and powerful ways to help people with sleep disorders.
Image Credit: Leighton, Frederic: Flaming June (1895)
brainstem image: http://www.neurosurgerypa.com/anatomy/neuro_br_brainstem.html