Sleeping Brain Waves Draw a Healthy Bath for Neurons

Sleeping Brain Waves Draw a Healthy Bath for Neurons

Elena Renken

For years, scientists have suspected that the harm caused by disturbed sleep has something to do with an overaccumulation of waste products or toxins in the brain. Studies showed that sleep is important for waste clearance, but the specifics were foggy. In 2012, research in the laboratory of Maiken Nedergaard, a neuroscientist at the University of Rochester Medical Center,  identified what appears to be the brain’s waste clearance pathway, the glymphatic (glial-lymphatic) system. This is a thin set of channels formed by the brain’s glial cells that can conduct fluid within the brain. The problem was that no plausible mechanism seemed to connect the neurological signs of sleep with the glymphatic system or even with movements of the cerebrospinal fluid (CSF) more generally. “We just weren’t sure what was changing, or how,” Lewis said.

“There are lots of detailed questions that still aren’t settled, but this is a huge step forward,” said Jeffrey Tithof, an assistant professor of mechanical engineering at the University of Rochester. His team studies the glymphatic system, and some of their recent unpublished findings mesh well with the alternation of blood and CSF seen in this human imaging. “We’re all pretty excited about it.”

Scientists have observed a relationship between sleep and Alzheimer’s: Sleep disruptions often precede the disease, which in turn appears to further disrupt sleep. The biology behind this connection is unknown, but a plausible explanation is that, by changing blood flow in the brain, electrical signals associated with sleep trigger waves of CSF to wash away toxic amyloid plaque around neurons. Anything that interferes with sleep might allow the plaque to accumulate and cause Alzheimer’s. “One of the reasons why I think a study like this is so exciting is that it provides one possible explanation that really might fit,” Iliff said. “But we have to test that.”