We’ve all been there – waking up on the wrong side of the bed after a poor night of sleep. What should have been alertness has instead been unwittingly replaced by brain fog and attention deficit, but why does this happen?
Scientists from the Massachusetts Institute of Technology (MIT) have now uncovered exactly what occurs inside the tired brain during those lapses in judgment, in a new study published in the Nature Neuroscience journal.
The study found that during these moments of brain fog, a wave of cerebrospinal fluid (CSF) is released out of the brain – a process which normally occurs whilst we are sound asleep, and helps to wash away waste products built up during the day.
This cleanse is believed to be essential for maintaining a normal, healthy functioning brain and helping the body to regenerate.
However, when someone is lacking a good night’s rest, this process is interrupted and the body attempts to catch up on those natural functions by emitting pulses of CSF in the day. This, in turn, comes at the expense of significantly impairing one’s ability to pay attention.
Researchers from MIT in the US recruited 26 volunteers and tested them twice – once after a night of sleep deprivation in a laboratory, and then another after a well-rested night.
They then measured the brain function of these participants and their ability to perform tasks, while simultaneously monitoring how much CSF flowed in and out of the brain.
The activities included a visual task, which involved staring at a cross and pressing a button when it turned into a square, and an auditory task requiring them to press a button when they heard a beeping sound.
As expected, sleep-deprived participants performed worse than well-rested participants, with slower response times. Some didn’t even register a change at all for some of the stimuli.
During these moments of distraction, the researchers found a flux of CSF expelled out of the brain at the very moment those lapses in attention occurred, and found CSF flowing back into the brain after each moment.
They also discovered that their breathing and heart rate decreased, and their pupils constricted 12 seconds before the CSF flowed out of the brain, only to dilate again after the attention lapse.
Laura Lewis, senior author of the study, said: “What’s interesting is it seems like this isn’t just a phenomenon in the brain, it’s also a body-wide event.
“These results suggest to us that there’s a unified circuit that’s governing both what we think of as very high-level functions of the brain — our attention, our ability to perceive and respond to the world — and then also really basic fundamental physiological processes like fluid dynamics of the brain, brain-wide blood flow, and blood vessel constriction.”
Lewis previously conducted a study in 2019, which discovered that CSF flow in and out of the brain during sleep follows a rhythmic pattern, and these are linked to changes in brain waves. This is what led her to wonder what might happen to CSF after sleep deprivation.
