According to a recently published study, Experimental Brain Research New light has been shed on how sleep deprivation affects the brain's ability to process and integrate multiple stimuli presented in rapid succession. Researchers found that a full day without sleep significantly impairs both attention and temporal integration mechanisms. In other words, a full day without sleep significantly impairs our ability to pay attention and process information quickly, which is essential for us to respond correctly to rapid changes in our surroundings.
Humans have a limited ability to process multiple events when they occur simultaneously or in rapid succession. This limitation is manifested in a phenomenon known as the attentional blink, which is the difficulty in identifying the second of two stimuli presented closely spaced in time. Given the known effects of sleep deprivation on various aspects of attention and perception, this study aimed to explore how complete sleep deprivation affects this phenomenon.
“As a student, I was interested in studying the brain. Since joining the Psychophysiology Institute, I have had the opportunity to delve deeper into other topics that are of great interest to me, such as biological rhythms, sleep and the limits of human neuropsychological capacities such as attention and memory,” said study author Carlos Gallegos from the Autonomous University of Nuevo Leon.
To understand how complete sleep deprivation affects attention, researchers designed an experiment with 22 undergraduate students. These students, around 17 years old, had no health or sleep disorders. The study made sure they followed a regular sleep schedule before participating. They stayed in the lab for six consecutive days and experienced different conditions to test their attention at different sleep levels.
The experiment is divided into three main phases: On two nights, participants get at least eight hours of sleep to establish their normal level of attention; On the fourth day, participants are kept awake for 24 consecutive hours; Participants are allowed to sleep freely for two nights to see if their level of attention has returned to normal.
To measure attention, the researchers used a task called Rapid Serial Visual Presentation (RSVP), in which participants had to identify two target numbers interspersed among a series of distractor letters that were rapidly displayed on a computer screen. Their accuracy in identifying these numbers over different time intervals served to measure the attentional blink.
After 24 hours of sleep deprivation, subjects' ability to accurately identify the target digits was significantly reduced. This performance decline was reversed after subjects had two nights of unrestricted sleep, indicating that sleep is crucial for maintaining attention.
Sleep deprivation increased the time that subjects struggled to identify the second target digit. The attentional blink normally occurs between 200 and 500 milliseconds, but sleep-deprived subjects had difficulty even at 600 milliseconds. This prolongation suggests a significant impairment in the brain's ability to rapidly process successive stimuli.
“The key takeaway is that not getting a full night's sleep increases your risk of making mistakes,” Gallegos told PsyPost. “Some mistakes are harmless (like misreading a word while studying), while others can be deadly (like pressing the gas instead of the brake while driving). It's important to emphasize that when we push capacities like attention or memory to their limits (as happens with the attentional blink), mistakes are always possible, even during the day and when we're not sleep-deprived.”
Attentional blink volume, which measures the degree to which accuracy in identifying the second target decreases during the attentional blink interval, decreased during sleep deprivation. This decrease was primarily due to an overall decrease in accuracy for the two targets, especially the second target. Attentional blink volume returned to normal levels after recovery sleep, revealing a temporary but profound effect of sleep deprivation.
Under normal conditions, if a second target appears shortly after the first (within 100 milliseconds), both are usually correctly identified – a phenomenon known as lag-1 sparing. However, this effect disappeared during sleep deprivation, indicating that temporal integration mechanisms are impaired, meaning that the brain's ability to process and integrate information presented in rapid succession is impaired.
Participants also made more mistakes when they were sleep-deprived, identifying target digits in the wrong order, especially within 400 milliseconds of each other. This increase in order reversals suggests that sleep deprivation gives the brain more time to integrate multiple stimuli, leading to confusion.
“In our task measuring the attentional blink, stimuli were presented quickly, individually, and sequentially, and subjects had to identify two numbers (targets) among letters (distractors),” explains Gallegos. “When stimuli appear in succession (without any intervening distractors), people often identify the first stimulus as the second, and vice versa. This reversal in reporting the order of stimuli is even more pronounced with sleep deprivation. This result suggests that there are perceptual changes that may lead to errors in selecting the correct stimulus (attention).”
These findings have important implications for people who are frequently sleep-deprived, such as healthcare workers, pilots, and others in critical jobs. The research suggests that even staying awake for 24 hours significantly reduces our ability to process rapid changes in our environment. This impairment increases the risk of making errors in tasks that require rapid reaction times.
“Even if you get enough sleep, it's dangerous to push functions like attention and memory to their limits during the day,” Gallegos says. “The risks are higher at night or if you don't get enough sleep. Multitasking is common today, especially with the use of technology, and it's a very common way to push our processes to their limits.”
“In our research into the limitations of attention, we found that there are also limitations in other fundamental processes that operate simultaneously, such as perception and memory. We would like to further study the limitations of these abilities and improve our understanding of how these functions are interconnected.”
“I hope that in the future, society will place more value on these two very common themes,” Gallegos adds. “On the one hand, sleep, a necessity that is often neglected in order to meet the demands of daily life, and on the other hand, the limits of cognitive capacities, which are also often exceeded when engaged in different activities at the same time.”
The study, “Effect of complete sleep deprivation on the attentional blink,” was written by Carlos Gallegos, Candelaria Ramirez, Aida Garcia, Jorge Bollani, and Pablo Valdés.
