Your brain juggles a lot of tasks at once, from critical thinking and managing your body's movements to regularly cleaning itself. But new research suggests that you may be able to support your brain’s waste clean-up process by doing something super simple: listening to noise while you sleep. There's a lot that happened in this study, including a very strategic use of pink noise to try to rid the brain of toxins and possibly even support deeper sleep.
This is also one small study, making it a stretch to say flipping on an ambient noise machine at night will make you smarter or healthier. But if you already enjoy listening to something like pink noise at night, it's helpful to know that there may be an added perk for your brain. Here's what the study found, plus why a sleep medicine specialist says more work is needed.
Meet the experts: Joshua Levitt, PhD, researcher and study co-author and Christopher Winter, MD, a sleep medicine specialist, neurologist, and author of The Sleep Solution: Why Your Sleep Is Broken and How to Fix It. For the study, which was published in the journal Science Translational Medicine, researchers from MIT recruited 14 healthy volunteers and monitored their brain activity while they napped in an MRI scanner. The researchers used closed-loop auditory stimulation, which is a brain modulation technique that detects changes in brain activity and then delivers a low-volume acoustic cue (in this case, pink noise) to enhance or reset brain activity.
For this study, participants were specifically subject to a 50-millisecond (or 0.05 second) burst of pink noise when their brains showed a peak in EEG slow waves. (EEG slow waves include delta waves, the slowest and highest-amplitude brain waves that are a defining characteristic of deep sleep.) The researchers discovered that the short burst of pink noise was linked to an increase in the amplitude of delta waves, along with the flow of cerebrospinal fluid, or the protective clear fluid surrounding the brain and spinal cord that’s thought to help get rid of waste. The findings can be "explored as a potential translational tool in clinical populations," the researchers wrote, which basically means there may be some health-boosting value to the general public, but exactly what isn’t clear yet. The study didn’t look into that, but there are some theories.
The EEG slow waves are probably the biggest factor, according to Joshua Levitt, PhD, researcher and study co-author. "They represent moments of widespread, cyclical activation and deactivation of the neurons in our brain," he says. "When parts of the brain are less active, they consume less oxygen, and the body shunts oxygen-supplying blood flow away from them." When this is widespread, which is what happens when there are slow waves, it means there's a large flow of blood away from the brain, Levitt says.
"Because our skull is a fixed volume at constant pressure, if one liquid flows out, another must flow in to take its place," Levitt says. "So, when blood flows out following deactivation, cerebrospinal fluid flows in." There, it can help deliver nutrition to your brain and clean out waste. Levitt says the findings are less about the pink noise itself and more about the technique of closed-loop auditory stimulation.
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