A recent study published in Experimental Brain Research has shed new light on how total sleep deprivation impacts the brain’s ability to process and integrate multiple stimuli presented in quick succession. The researchers found that a complete day without sleep significantly impairs both attentional and temporal integration mechanisms. In other words, going without sleep for a whole day seriously hinders our ability to pay attention and process information quickly, which is crucial for reacting correctly to fast changes around us.
Humans have a limited ability to process several events when they occur simultaneously or in quick succession. This limitation is evident in a phenomenon known as the attentional blink. The attentional blink is the difficulty people have in identifying the second of two stimuli presented closely together in time. The study aimed to explore how total sleep deprivation affects this phenomenon, given the known effects of sleep loss on various aspects of attention and perception.
“Initially, as a student, I was interested in studying the brain. After joining the Laboratory of Psychophysiology, I had the opportunity to delve into other topics that were very interesting to me, such as biological rhythms and sleep, or the limits in human neuropsychological capacities like attention and memory,” said study author Carlos Gallegos of the Autonomous University of Nuevo León.
To understand how total sleep deprivation affects attention, the researchers designed an experiment involving 22 undergraduate students. These students, aged around 17 years, had no health or sleep disorders. The study ensured they followed a regular sleep schedule before participating. They stayed at a laboratory for six consecutive days, undergoing different conditions to test their attention under various levels of sleep.
The experiment was divided into three main phases: For two nights, participants slept at least 8 hours to establish their normal level of attention. On the fourth day, 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 the Rapid Serial Visual Presentation (RSVP) to measure attention. In this task, participants had to identify two target numbers mixed among a series of distractor letters shown 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, participants’ ability to accurately identify the target numbers dropped significantly. This decline in performance was restored after the participants had two nights of unrestricted sleep, indicating that sleep is crucial for maintaining attention.
Sleep deprivation extended the time during which participants struggled to identify the second target number. Normally, the attentional blink occurs at intervals of 200-500 milliseconds, but sleep-deprived participants had difficulty even at 600 milliseconds. This extension suggests a significant impairment in the brain’s ability to process successive stimuli quickly.
“The main takeaway is that skipping a night of sleep can increase the risk of making errors,” Gallegos told PsyPost. “While some errors are harmless (such as misreading a word while studying), others can be fatal (like pressing the accelerator instead of the brake while driving). It’s important to emphasize that when we push capacities like attention and memory to their limits (as it occurs in the Attentional Blink), there’s always a chance of error, even during the day or without sleep deprivation.”
The magnitude of the attentional blink, which measures how much the accuracy of identifying the second target drops during the attentional blink interval, was reduced during sleep deprivation. This reduction was primarily due to an overall drop in accuracy for both targets, particularly the second one. The attentional blink magnitude returned to normal levels after the 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 sparing. However, this effect disappeared during sleep deprivation, indicating impaired temporal integration mechanisms. This means the brain’s ability to process and integrate information presented in quick succession was compromised.
Participants also made more errors by identifying the target numbers in the wrong order during sleep deprivation, especially within the intervals up to 400 milliseconds. This increase in order reversals suggests that sleep deprivation extends the period during which the brain integrates multiple stimuli, leading to confusion.
“In our task to measure the Attentional Blink, stimuli were presented rapidly, individually, and successively, and participants had to identify two numbers (targets) among letters (distractors),” Gallegos explained. “When stimuli appear in direct succession (without distractors in between), people often identify the first stimulus as the second and vice versa. This inversion in reporting the order of stimuli is even greater with sleep deprivation. This result suggests that there are some perceptual alterations that could lead to errors in selecting (attending) the correct stimulus.”
These findings have significant implications for individuals who frequently experience sleep deprivation, such as medical professionals, 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 responses.
“Pushing functions like attention and memory to their limits can be dangerous during the day, even with adequate sleep,” Gallegos noted. “The risk increases during the night and with sleep deprivation. Nowadays, it’s very common, especially with the use of technology, for people to multitask. This is a very common way of pushing our processes to the limit.”
“During the research on the limits of attention, we have learned that there are limits in other fundamental processes that operate simultaneously, such as perception and memory. I would like to further study the limits in these capacities and gain a better understanding of how these functions relate to each other.”
“Hopefully in the future, society will place more value on these two topics that are quite common,” Gallegos added. “On one hand, sleep, which is a necessity that we often neglect to meet the demands of daily life. On the other hand, the limit of cognitive capacities, which we also frequently push when engaging in various activities simultaneously.”
The study, “Total sleep deprivation effects on the attentional blink,” was authored by Carlos Gallegos, Candelaria Ramírez, Aída García, Jorge Borrani, and Pablo Valdez.
