How Sleep Deprivation Affects Cognitive Functions

Simply put, sleep deprivation occurs when an individual fails to get an appropriate amount of sleep according to their biological need. The amount of sleep required varies by person, but in general, adults need seven to eight hours and teenagers need about nine hours per night. In our busy world, many people fail to get enough sleep and suffer the consequences. According to the American Academy of Sleep Medicine, sleep deprivation has many negative consequences both physiologically and psychologically including the increased risk of serious medical conditions; lack of motivation, attention, and competency; and poor performance (2008). In this paper, I will explore the effects of sleep deprivation on cognitive functions, specifically from the cognitive and biological psychological perspectives.

Cognitive Perspective

In their article, Effects of Sleep Deprivation on Procedural Errors, Michelle Stepan, Kimberly Fenn, and Erik Altmann (2018) explore the cognitive effects that sleep deprivation has on procedural tasks that require memory. Stepan et al. note the proven effects that lack of sleep has on attention and vigilance but stress the need for more research on how sleep deprivation affects higher-order cognitive processes. The authors explain how their research is the largest known study on the impact of sleep deprivation on higher-order cognition. This study mainly focuses on how sleep deprivation affects memory and whether the effects are localized to cognitive deficits as a whole or solely memory processes. Acknowledging that sleep deprivation impacts ability and willingness, Stepan et al. hypothesize that deprivation most significantly affects memory maintenance above other cognitive processes.

In order to test this hypothesis, Stepan et al. selected 234 men and women Michigan State University undergraduates. The participants had no sleep or memory disorders, no morning or evening preference, and no major sleep disturbances. First, subjects completed a procedural task that consisted of a series of seven steps where subjects identified a different two-alternative forced-choice decision rule to apply to a randomly generated stimulus. The test provided no details about which step to do next, making the participants recall where they were in the sequence. While taking the test, the participant is interrupted every few trials for about 20 seconds. The participant then must continue the sequence with the right step and answer. In order to answer the question correctly, the participant must remember the last step completed before the interference. All participants completed the first part of the experiment together where they all took this same test one time. Then, they were randomly assigned to the control group who received a normal night of sleep and the experimental group who faced 24 hours of sleep deprivation before the second test. The participants took the same test again in the morning, and that was the conclusion of the experiment.

Results showed that sleep deprivation participants failed the second test at a higher rate than the participants who received sleep. The experiment group had a 15% fail rate, while the control group had a 1% fail rate. This shows that sleep deprivation caused 15% of participants to lose the ability or willingness to complete the same task they had successfully performed the day before. However, the researchers already concluded at the beginning of the study that sleep deprivation affects attention and ability as a whole. The researchers further analyzed the results to determine the effects on memory. The experiment had isolated the effects on memory by having two different trial type errors: one being after a regular step in the sequence and the other being after an interruption. Committing an error after an interruption indicated that the error was made because of a memory deficit, not from a general cognitive mistake. The data shows that sleep deprived participants made significantly more post interruption errors than the control group and made more post interruption errors as the second test progressed. The baseline sequence errors showed little deviation across both groups and progression throughout the test. This led the researchers to deduce that baseline sequence errors were not related to sleep deprivation and that sleep deprivation contributed mostly to post interruption errors. They concluded that the underlying factor is memory maintenance and that sleep deprivation impairs the mechanisms that manage the buildup of proactive interference (Stepan et al., 2018).

Biological Perspective

Also exploring the effects of sleep deprivation, Christopher Asplund and Michael Chee examined the biological aspect of the brain in their article, Time-on-task and sleep deprivation effects are evidenced in overlapping brain areas (2013). As in the cognitive perspective, the authors of this article also recognize that sleep deprivation is proven to degrade performance in tasks that require attention. The central focus of this research was to examine the effects of sleep deprivation on extended task engagement (time-on-task) and to determine if they overlap in areas of the brain. Time-on-task refers to the amount of time spent involved in a certain task. The researchers hypothesized that sleep deprivation worsens time-on-task because the two correlate and share overlapping areas in the brain.

To test this hypothesis, Asplund et al. selected 20 male and female participants from the National University of Singapore. All of the participants had regular sleeping habits, had no morning or evening preference, and had no psychiatric or sleep disorders. The experiment consisted of two parts: in the first, subjects had normal sleep and in the second, they were sleep deprived (meaning they stayed awake for 24 hours straight). First, the subjects completed an attention-demanding test after a normal night of sleep. The test required the participants to search for the letters J or K among a rapid stream of letters as fast as possible. Their brains were scanned throughout the test to measure cerebral blood flow. Secondly, the subjects had their brains scanned as they completed the same test again, only this time they were sleep deprived.

The results showed that cerebral blood flow changes in task-related neural activation in those sleep deprived versus those not sleep deprived. Consistent with the hypothesis, both sleep deprivation and time-on-task overlapped in a decrease of blood flow to the frontal and parietal cortices (specifically the attention regions) and the ventral visual cortex, which processes visual information. Because the two overlap in the brain, cerebral blood flow is drastically decreased when sleep deprivation is paired with time dependent situations. A decrease in blood flow to a certain area of the brain means decreased activation in that area. This causes a worsened time-on-task performance. Therefore, sleep deprivation worsens the performance of time-dependent evaluations from a biological perspective because the two are proven to overlap in the brain (Asplund et al., 2013).

Sleep deprivation is a serious, underlying issue that affects many individuals and societies today. In our world, busyness and being active have taken priority over sleep and rest, creating a nationwide sleep deprivation epidemic. This has negative impacts on productivity in the workplace and in the classroom. Although this problem is so prevalent, there is only one real solution for it: sleep. According to the American Academy of Sleep Medicine, The only sure way for an individual to overcome sleep deprivation is to increase nightly sleep time to satisfy his or her biological sleep need; there is no substitute for sufficient sleep (2008). Sleep cannot be replaced by caffeine or other stimulants or even naps. Only a good night of sleep will provide the best results.

Although making time to get more sleep can be very difficult, it is very important in order to improve learning. Research shows that sleep enhances memory of what was learned during the day, promotes creativity related to previous learning, and, overall, improves cognitive functions. One study found in Weiten's Psychology: Themes and variations supports these claims of how sleep improves learning. In the study, participants were first shown how to accomplish a perceptual-motor task and then retested 12 hours later. Those who slept during the 12-hour break proved to have significant improvement in performance compared to those who did not sleep (Weiten, 2017). These benefits of sleep have important implications for those wanting to maximize their productivity and overall success in the workplace or the classroom.

Conclusively, sleep deprivation is a serious issue affecting our society today. It has become a nationwide epidemic with detrimental side effects.

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