A recent study from the Massachusetts Institute of Technology (MIT) offers new insights into the biological mechanisms underlying the cognitive impairment experienced after a night of inadequate sleep. Many individuals can relate to the feeling of a foggy mind and diminished focus following restless nights. This research unveils that during these lapses in attention, the brain engages in critical maintenance activities typically conducted during sleep.
The study highlights the role of cerebrospinal fluid (CSF), which cushions the brain and assists in eliminating metabolic waste accumulated throughout the day. Previous research led by Dr. Laura Lewis, an MIT electrical engineering and computer science professor, indicated that CSF flows rhythmically in synchronization with brain wave changes during a typical sleep cycle. To investigate the effects of sleep deprivation on this CSF flow, Dr. Lewis and her team assessed 26 volunteers’ cognitive performance under both sleep-deprived and well-rested conditions. Utilizing advanced imaging techniques, including electroencephalograms and functional magnetic resonance imaging, they monitored various physiological responses, including heart rate, pupil diameter, and CSF dynamics, while participants engaged in simple cognitive tasks.
The findings were telling: participants who had not slept adequately exhibited significantly poorer performance, with slower reaction times and, in some cases, a complete failure to respond to stimuli. Notably, the research team observed a correlation between lapses in attention and the movement of CSF out of the brain, which returned as attention was regained. “In a state of sleep deprivation, the brain seems to initiate bursts of CSF flow in an effort to recover some cognitive functions, albeit at the expense of attentiveness,” explained Zinong Yang, the lead author of the study. Additionally, physiological responses such as reduced heart and breathing rates, along with pupil constriction, were documented, with pupil changes occurring prior to the CSF flow shifts. Dr. Lewis emphasized that these lapses in attention are not merely subjective experiences but are indicative of broader physiological events occurring throughout the brain and body. The study points towards a unified neural circuit that integrates high-level cognitive functions, like attention, with fundamental physiological processes. While the researchers did not delve into the specific nature of this circuit, they suggested that the noradrenergic system, which is known to regulate various cognitive and bodily functions through the neurotransmitter norepinephrine, could be a likely candidate for further exploration.
Source: Secrets of the sleep-deprived brain via MIT Technology Review