A recent study published in Experimental brain research has shed new light on how total sleep deprivation affects the brain’s ability to process and integrate multiple stimuli presented in rapid succession. The researchers found that going a full day without sleep significantly impairs both attention and temporal integration mechanisms. In other words, going a whole day without sleep seriously hinders our ability to pay attention and process information quickly, which is crucial for responding correctly to rapid changes around us.
People have a limited ability to process different events when they occur simultaneously or in rapid 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 close in time. The study aimed to investigate 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 of human neuropsychological capacities such as attention and memory,” says study author Carlos Gallegos from the Autonomous University of Nuevo León.
To understand how total sleep deprivation affects attention, the researchers designed an experiment involving 22 students. These students, approximately 17 years old, had no health or sleep disorders. The study made sure they followed a regular sleep schedule before participating. They stayed in a laboratory for six consecutive days and underwent different conditions to test their attention under different sleep levels.
The experiment was divided into three main phases: Over two nights, participants slept for at least 8 hours to establish their 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 the Rapid Serial Visual Presentation (RSVP) to measure attention. This task required participants to identify two target numbers mixed in a series of distractor letters that were quickly displayed 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 targets dropped significantly. This performance drop was restored after participants had two nights of unrestricted sleep, indicating that sleep is crucial for maintaining attention.
Sleep deprivation increased the time during which participants struggled to identify the second target number. Normally, attentional blinks occur at intervals of 200-500 milliseconds, but sleep-deprived participants had problems even at 600 milliseconds. This expansion suggests a significant deterioration in the brain’s ability to rapidly process successive stimuli.
“The main conclusion is that skipping a night of sleep can increase the risk of errors,” Gallegos told PsyPost. “While some mistakes are harmless (such as misreading a word while studying), others can be fatal (such as pressing the accelerator instead of the brake while driving). It is important to emphasize that when we push abilities like attention and memory to their limits (as happens with the Attentional Blink), there is 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 decreases during the attentional blink interval, was reduced during sleep deprivation. This reduction was mainly due to an overall decrease in accuracy for both targets, especially the second. The magnitude of attentional blinks returned to normal levels after recovery sleep, highlighting the temporary but serious 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 that the brain’s ability to process and integrate information presented in rapid succession is impaired.
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 reversals suggests that sleep deprivation lengthens the period in which the brain integrates multiple stimuli, leading to confusion.
“In our task to measure Attentional Blink, stimuli were presented quickly, individually and sequentially, and participants had to identify two numbers (targets) among letters (distractors),” Gallegos explained. “When stimuli appear directly one after the other (with no distractors in between), people often identify the first stimulus as the second and vice versa. This reversal in reporting the order of stimuli is even greater under sleep deprivation. This result suggests that there are some perceptual changes that can lead to errors in selecting (viewing) the correct stimulus.”
These findings have significant implications for individuals who often suffer from 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 limitation increases the risk of errors on tasks that require quick responses.
“Pushing functions like attention and memory to their limits during the day can be dangerous, even if you get enough sleep,” Gallegos noted. “The risk increases during the night and with lack of sleep. Nowadays it is very common, especially with the use of technology, for people to multitask. This is a common way to push our processes to the limit.”
“While researching the limits of attention, we learned that there are limits to other fundamental processes that occur simultaneously, such as perception and memory. I would like to further explore the limits of these capabilities and better understand how these functions relate to each other.”
“Hopefully, in the future, society will place more importance on these two topics, which are quite common,” Gallegos added. “On the one hand, sleep, a necessity that we often neglect to meet the demands of daily life. On the other hand, the limit of cognitive capacities, which we often push when we undertake different activities at the same time.”
The study, “Total sleep deprivation effects on the attentional blink,” was authored by Carlos Gallegos, Candelaria Ramírez, Aída García, Jorge Borrani and Pablo Valdez.