Sleep-Deprived Brains May Sacrifice Attention To Cleanse Themselves, Study Finds

Attention lapses from lack of sleep could be the brain’s way of catching up on waste removal, a new study suggests. Normally, this cleansing process occurs during sleep, but researchers found evidence that the brain may try to perform it while awake, potentially at the cost of focus.

Cerebrospinal fluid (CSF), which cushions the brain and spinal cord and removes accumulated waste, plays a crucial role in maintaining brain health. During sleep, waves of CSF wash through the brain, clearing out metabolic byproducts built up during the day.

"If you don't sleep, the cerebrospinal fluid waves start to intrude into wakefulness where normally you wouldn't see them. However, they come with an attentional tradeoff, where attention fails during the moments that you have this wave of fluid flow," said Laura Lewis, associate professor of electrical engineering and computer science at MIT and senior author of the study published in Nature Neuroscience.

Sleep is essential for everyday cognitive function. Deprivation can impair memory, focus, and other mental processes, and previous research has linked impaired waste clearance in the brain to a higher risk of dementia.

In the study, 26 participants were tested on their ability to pay attention following a night of sleep deprivation and again after a full night of rest. Two tasks were used: a visual test, in which participants pressed a button when a cross changed into a square, and an auditory test, where they responded to a beep.

Brain activity was recorded using electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI). Sleep-deprived participants showed slower reaction times, and in some cases, failed to register changes—classic signs of attention lapses.

Researchers observed that during these lapses, CSF flowed outward from the brain and returned once attention was regained.

The findings indicate that "at the moment that attention fails, this fluid is actually being expelled outward away from the brain. And when attention recovers, it's drawn back in," Lewis explained.

The team suggests that when sleep-deprived, the brain may prioritize cleaning itself over maintaining alertness.

"One way to think about those events is because your brain is so in need of sleep, it tries its best to enter into a sleep-like state to restore some cognitive functions," said Zinong Yang, lead author and postdoctoral associate at MIT.

Other physiological changes during attention lapses included reduced heart and breathing rates and pupil constriction, underscoring that the effects of sleep deprivation extend throughout the body.

The researchers concluded that attentional failures following sleep deprivation are part of a coordinated cascade of brain-body changes, combining shifts in neuronal activity, pupil constriction, and CSF flow. They noted this points to "a coupled system of fluid dynamics and neuromodulatory state."

With PTI inputs