A recent study published in Experimental Brain Research has shed new light on how complete sleep deprivation affects the brain’s ability to process and integrate multiple stimuli presented in sequence. Researchers found that a full day without sleep significantly impairs attentional and temporal integration mechanisms. In other words, being without sleep for an entire day seriously hinders our ability to pay attention and quickly process information, which is essential for responding appropriately to the rapid changes around us.
Humans have a limited ability to process several events when they occur simultaneously or in rapid succession. This limitation is evident in a phenomenon known as attentional bias. The attentional blink is the difficulty people have in identifying the second of two stimuli presented close 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.
“At first, 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, “said the author of the study Carlos Gallegos. University Autonomous of Nuevo Leon.
To understand how total sleep deprivation affects attention, researchers set up an experiment involving 22 university students. These students, aged about 17, had no health or sleep problems. The study ensured they followed a regular sleep schedule before participating. They stayed in a laboratory for six consecutive days, undergoing different conditions to test their attention under different levels of sleep.
The experiment was divided into three main phases: For two nights, the participants slept 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 Rapid Serial Visual Presentation (RSVP) to measure attention. In this task, participants had to identify two target numbers intermixed among a series of distracting letters rapidly displayed on a computer screen. The accuracy of identifying these numbers at different time intervals helped measure the attentional flash.
After 24 hours without sleep, the participants’ ability to accurately identify target numbers dropped significantly. This decline in performance was restored after participants had two nights of unrestricted sleep, indicating that sleep is crucial for maintaining attention.
Sleep deprivation prolonged the time during which participants struggled to identify the second target number. Normally, the attentional blink occurs at intervals of 200-500 milliseconds, but the sleep-deprived participants had difficulty even at 600 milliseconds. This extent suggests a significant impairment in the brain’s ability to rapidly process successive stimuli.
“The bottom line is that skipping a night of sleep can increase the risk of making mistakes,” Gallegos told PsyPost. “While some mistakes are harmless (such as misreading a word while studying), others can be fatal (such as hitting the accelerator instead of the brakes while driving). It’s important to note that when we push capacities like attention and memory to their limits (as in Mindful Blink), there’s always a chance for error, even during the day or without sleep deprivation.”
Attentional flash size, which measures how much the accuracy of identifying the second target drops during the attentional flash interval, was reduced during sleep deprivation. This reduction was mainly due to a general decrease in accuracy for both targets, especially the second. The magnitude of the attentional flare 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 quickly (within 100 milliseconds) after the first, both are usually correctly identified – a phenomenon known as lag-1 sparing. However, this effect disappeared during sleep deprivation, indicating impaired mechanisms of temporal integration. This means that the brain’s ability to process and integrate rapidly presented information is compromised.
Participants also made more errors identifying target numbers in the wrong order during sleep deprivation, especially within intervals of up to 400 milliseconds. This increase in order switching suggests that sleep deprivation lengthens 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 sequentially, and participants had to identify two numbers (targets) between letters (distracters),” Gallegos explained. “When stimuli are presented consecutively direct (with no distractors in between), people often identify the first stimulus as the second and vice versa. This reversal in the reporting of the stimulus order is even greater with sleep deprivation. This result suggests that there are some perceptual changes that can lead to errors in selecting (attending) the appropriate stimulus.”
These findings have important 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 being awake, 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 enough sleep,” Gallegos noted. “The risk increases at night and with lack of sleep. Nowadays, it is very common, 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 the limits of attention, we have learned that there are limits to other fundamental processes that operate simultaneously, such as perception and memory. I would like to further study the limits on these capacities and gain a better understanding of how these functions relate to each other.”
“We hope that in the future, society will place more value on these two topics that are quite common,” Gallegos added. “On the 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 often push when we engage in different activities simultaneously.”
The study, “Effects of Total Sleep Deprivation on Attentional Ignorance,” was authored by Carlos Gallegos, Candelaria Ramírez, Aída García, Jorge Borrani, and Pablo Valdez.