A new "sleep node" discovered deep within the primitive brainstem reveals how humans fall into a deep sleep, and it is only the second discovered node that is essential to the process.
The study shows that half of all of the brain's sleep-promoting activity takes place in the parafacial zone (PZ) located in the brain stem, the University at Buffalo reported. The brain stem is responsible for the body's most essential functions such as breathing 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 UB School of Medicine and Biomedical Sciences and a co-author on the paper.
The team found the neurotransmitter gamma-aminobutyric acid (GABA) was essential for the process of falling into a deep sleep; the team members made their findings using tools that gave them the ability to switch certain neurons on and off and masterfully control brain function at the cellular level.
"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," said Christelle Ancelet, postdoctoral fellow at Harvard School of Medicine.
To create this stunning precision the researchers introduced a virus called PZ that expressed a "designer" receptor on GABA neurons without altering other types of brain function, according to Patrick Fuller, assistant professor at Harvard and senior author on the paper. Turning on the GABA neurons in the PZ caused animal subjects to fall into a deep sleep without the aid of sedatives or other drugs.
"We are at a truly transformative point in neuroscience," Bass said, "where the use of designer genes gives us unprecedented ability to control the brain. 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."
The findings were published Aug. 9 in the journal Nature Neuroscience and was funded by the National Institutes of Health.
