Study Pinpoints Part Of The Brain Responsible For Slow Wave Sleep

Chuck Bednar for – Your Universe Online
Researchers from the Harvard School of Medicine and the University at Buffalo School of Medicine and Biomedical Sciences have discovered a region of the brain responsible for causing people to fall into a deep sleep.
This slumber-promoting circuit, which is located deep in the primitive brainstem, is only the second such “sleep node” ever discovered in the brains of mammals, the study authors said. In research published online last month in Nature Neuroscience, they explain how this region is not only capable of but also necessary for producing what is known as slow wave sleep (SWS) in humans.
By using genetically targeted activation and optogenetically based mapping to examine the brain’s circuitry, the researchers found that half of all sleep-promoting activity originates from a region of the brainstem known as the parafacial zone (PZ). The brainstem is a primordial part of the brain and is responsible for regulating the basic functions necessary for survival, including breathing, body temperature, blood pressure and heart rate.
“The close association of a sleep center with other regions that are critical for life highlights the evolutionary importance of sleep in the brain,” said Caroline E. Bass, assistant professor of Pharmacology and Toxicology in the University of Buffalo School of Medicine and Biomedical Sciences and a co-author on the recently-published paper.
She and her colleagues found that a specific type of neuron in the PZ which produces the neurotransmitter gamma-aminobutyric acid (GABA) is responsible for producing SWS. Furthermore, using a set of innovative tools, they were able to precisely control those neurons remotely, essentially allowing them to turn the neurons on and off at will.
“These new molecular approaches allow unprecedented control over brain function at the cellular level,” said Christelle Ancelet of the Harvard School of Medicine. “Before these tools were developed, we often used ‘electrical stimulation’ to activate a region, but the problem is that doing so stimulates everything the electrode touches and even surrounding areas it didn’t. It was a sledgehammer approach, when what we needed was a scalpel.”
“To get the precision required for these experiments, we introduced a virus into the PZ that expressed a ‘designer’ receptor on GABA neurons only but didn’t otherwise alter brain function,” added Patrick Fuller, assistant professor at Harvard and senior author on the Nature Neuroscience paper. “When we turned on the GABA neurons in the PZ, the animals quickly fell into a deep sleep without the use of sedatives or sleep aids.”
The research team, whose work was funded by the National Institutes of Health (NIH), said that the exact interactions between these neurons and other sleep and wake-promoting regions of the brain still need to be analyzed. However, they believe their findings could ultimately lead to the invention of new medications to treat insomnia and other sleep disorders, as well as the development of safer and more effective anesthetics.
“We are at a truly transformative point in neuroscience, where the use of designer genes gives us unprecedented ability to control the brain,” said Bass. “We can now answer fundamental questions of brain function, which have traditionally been beyond our reach, including the ‘why’ of sleep, one of the more enduring mysteries in the neurosciences.”