Does this mean we can all rest easy now?
Scientists have finally answered the question of how toxins are cleared from the brain during sleep, according to a Boston University study published Friday in the journal Science.
They now hope to apply the newfound knowledge for treatments and prevention of neurodegenerative diseases, such as Alzheimer’s and dementia.
Biomedical engineer Laura D. Lewis led a team of BU researchers investigating non-REM sleep — a deep phase of dreamless slumber. Previous studies found that when rodents sleep, toxins, which can lead to the development of neurodegenerative diseases, are cleared during non-REM unconsciousness.
Non-REM sleep has also been associated with memory retention and is known to generally happen earlier in the night.
“We had a sense each of these metrics was important, but how they change during sleep and how they relate to each other during sleep was uncharted territory for us,” Lewis tells Wired of the brain’s blood oxygen and fluid levels.
During non-REM sleep, researchers found that waves of cerebrospinal fluid — a water-like substance — slowly wash over the brain and neurons begin to synchronize, switching on and off simultaneously.
“You would see this electrical wave where all the neurons would go quiet,” Lewis tells the outlet. The turned-off, non-firing neurons mean less blood flow to the brain, creating a space for the fluid to fill — and flush out — accumulated metabolic byproducts such as beta-amyloid.
If not cleared, this protein — or “brain plaque” — can lead to “a cascade of biochemical activities culminating in the destruction of synapses,” Stanford scientists previously reported. This damage can lead to neurodegenerative diseases.
To reach their breakthrough findings, BU researchers had study participants sleep in an MRI machine while wearing EEG caps, and tracked participants’ brains for electrical currents and other metrics.
They now hope to discover clinical applications, but, first, they need some rest. Lewis says the project has left the study’s authors quite exhausted.
“It’s this great irony of sleep research. You’re constrained by when people sleep.”