A recent study published in Experimental brain research shed new light on how complete sleep deprivation affects the brain’s ability to process and integrate multiple stimuli presented in rapid succession. Researchers have found that a whole day without sleep significantly disrupts the mechanisms of attention and temporal integration. In other words, going a whole day without sleep seriously hinders our ability to pay attention and process information quickly, which is key to properly reacting to the rapid changes around us.
Humans have a limited ability to process multiple events when they occur simultaneously or in rapid succession. This limitation is seen in a phenomenon known as the attentional blink. The attentional blink is a problem people have when identifying the second of two stimuli presented close together in time. The aim of the study was to investigate how overall lack of sleep affects this phenomenon, given the known effects of sleep loss on various aspects of attention and perception.
“I was initially interested in studying the brain as a student. After joining the Psychophysiology Laboratory, I had the opportunity to delve into other topics that interested me greatly, such as biological rhythms and sleep or the limits of human neuropsychological capacities, such as attention and memory,” said study author Carlos Gallegos of the Autonomous University of Nuevo León.
To understand how complete sleep deprivation affects attention, the researchers designed an experiment involving 22 college students. These students, aged around 17, had no medical or sleep disorders. The study ensured they followed a regular sleep schedule before participating. They stayed in the lab for six consecutive days and underwent different conditions to test their attention during different levels of sleep.
The experiment was divided into three main phases: Over two nights, the participants slept for at least 8 hours to establish a normal level of attention. On the fourth day, the participants stayed awake for 24 hours straight. Participants were allowed to sleep freely for two nights to see if their attention levels returned to normal.
The researchers used a task called Rapid Serial Visual Presentation (RSVP) to measure attention. In this task, participants had to identify two target numbers intermixed among a series of distractor letters displayed rapidly on a computer screen. The accuracy of identifying these numbers at different time intervals helped measure the attentional blink.
After 24 hours without sleep, the participants’ ability to accurately identify the target numbers decreased significantly. This decline in performance was restored after participants had two nights of unrestricted sleep, suggesting that sleep is essential for maintaining attention.
Sleep deprivation increased the time participants tried to identify the second target number. Normally, blinking occurs at intervals of 200-500 milliseconds, but the sleep-deprived participants had difficulty even after 600 milliseconds. This enlargement suggests a significant impairment in the brain’s ability to rapidly process successive stimuli.
“The main finding is that missing a night can increase the risk of making mistakes,” Gallegos told PsyPost. “While some mistakes are harmless (e.g. misreading a word while studying), others can be fatal (e.g. stepping on the gas instead of the brake while driving). It is important to emphasize that when we push capacities such as attention and memory to their limits (as occurs with the Attentional Blink), there is always the possibility of error, even during the day or without sleep deprivation.”
Attentional blink size, which measures how much the accuracy of identifying a second target drops during the blink interval, was reduced during sleep deprivation. This decrease was mainly due to an overall decrease in accuracy for both targets, especially the latter. Attentional blink size returned to normal levels after recovery sleep, highlighting the temporary but severe impact of sleep deprivation.
Under normal conditions, if the second target appears very shortly (within 100 milliseconds) after the first, both are usually identified correctly—a phenomenon known as lag-1 sparring. However, this effect disappeared during sleep deprivation, indicating impaired temporal integration mechanisms. This means that the brain’s ability to process and integrate information presented in rapid succession has been compromised.
Participants also made more errors by identifying target numbers in the wrong order during sleep deprivation, particularly at intervals of up to 400 milliseconds. This increase in sequence turnover suggests that sleep deprivation lengthens the period during which the brain integrates multiple stimuli, leading to confusion.
“In our attentional blink task, stimuli were presented rapidly, individually, and sequentially, and participants had to identify two numbers (targets) between letters (distractors),” Gallegos explained. “When stimuli appear in direct succession (with no distractors in between), people often identify the first stimulus as the second, and vice versa. This inversion in stimulus order reporting is even greater in sleep deprivation. This result suggests that there are some perceptual changes that could lead to errors in selecting (attending to) the correct stimulus.”
These findings have significant implications for individuals who often suffer from sleep deprivation, such as paramedics, pilots, and others in high-stakes jobs. The study suggests that even after 24 hours of wakefulness, people’s ability to process rapid changes in their environment is severely compromised. This impairment increases the risk of errors in tasks that require quick reactions.
“Pushing functions like attention and memory to their limits can be dangerous during the day, even with adequate sleep,” Gallegos noted. “The risk increases at night and with lack of sleep. It is very common these days, especially with the use of technology, for people to multitask. This is a very common way to push our processes to the limit.”
“In researching attentional limits, we discovered that there are limits in other fundamental processes that operate simultaneously, such as perception and memory. I would like to further study the limits of these capacities and better understand how these functions are related to each other.”
“We hope that in the future society will place more value on these two topics, which are quite common,” Gallegos added. “On the one hand, sleep, which is a necessity that we often neglect to meet the demands of everyday life. On the other hand, the limit of cognitive abilities, which we also often push when simultaneously engaging in various activities.”
The study, “Effects of Total Sleep Deprivation on Attentional Blinking,” was written by Carlos Gallegos, Candelaria Ramírez, Aída García, Jorge Borrani, and Pablo Valdez.