What Does Your Brain Do While You Sleep?

Now we know, thanks to a Boston University sleep research study published in the journal Science. The results underline how vital sleep is for keeping our brains healthy, actually clearing toxins from our brains while we sleep. This new research may help provide new avenues for treating (and preventing) neurodegenerative brain diseases like Alzheimer’s.

What the study focused on:

  • When we sleep, our brains go through several unique phases, from a light slumber to a deep REM (rapid eye movement) sleep.
  • The Boston University study focused on non-REM sleep, that deep phase which happens earlier in the night and has been associated with memory retention.
  • Scientists knew from a 2013 study on mice that toxins like beta amyloid, which can contribute to Alzheimer’s disease, were swept away during this sleep stage.
  • Boston University researchers were curious how those toxins were cleared out and why that process only happened during sleep.
  • Researchers suspected that cerebrospinal fluid, a clear, water-like liquid that flows around the brain, might be involved, but didn’t understand why sleep was required to make the detox happen.

How the study worked:

There were several hurdles to navigate past. Study participants had to be able to fall asleep inside an MRI machine – no small task! Then, in order to get realistic sleep cycles, researchers had to run the tests at midnight, asking that subjects stay up late the night before so they would be sleepy enough to drift off once the test began.

  • Participants were outfitted with an EEG cap so researchers could look at naturally occurring electrical currents flowing through their brains during sleep. These currents showed which stage of sleep the person was in while the MRI measured blood oxygen levels in their brains and how much cerebrospinal fluid was flowing.
  • What researchers discovered was that during non-REM sleep, large, slow waves of cerebrospinal fluid were washing over the brain. The EEG readings showed that during non-REM sleep, neurons start to synchronize, turning on and off at the same time. Because the neurons stopped firing in unison, they didn’t need as much oxygen, which meant less blood would flow to the brain. The team then observed that cerebrospinal fluid would then rush in, filling in the (blood flow) space left behind.

Maiken Nedergaard, the neuroscientist at the University of Rochester who led the 2013 study that described how sleep can clear out brain toxins in mice said, “I don’t think anybody in their wildest fantasy has really shown that the brain’s electrical activity is moving fluid. So (this new study) is really exciting.”

“We know that the function of sleep is not just to relax,” says Leanne O’Neil of INDY Neurofeedback, “but is actually a very important brain health function. Since our neurons don’t all turn off at the same time when we’re awake, sleep is the only time brain blood levels allow waves of cerebrospinal fluid to circulate around the brain and clear out any metabolic byproducts that accumulate, like beta amyloid.”

What does this mean for treating Alzheimer’s?

Instead of targeting medications that act on one particular molecule (like beta amyloid) in the brain, new treatments might focus on increasing the amount of cerebrospinal fluid that washes over the brain. After all, brain aging is not just about just one type of toxin, but many.

The brain is endlessly fascinating, says O’Neil, and there is much to learn and put to good use in maximizing brain efficiency, dexterity, and high functioning. That’s why we are excited about our anti-aging protocol and all we do here at INDY Neurofeedback.