Background of the Literature
Memory is a critical cognitive function that is important in everyday cognitive processes. However, memory performance may not always be the same, given the capacity for various factors to affect memory performance. The literature involves previous work on memory under neuropsychology and the factors affecting memory. The literature has different findings that help shape the review, giving comparative and contrasting opinions. Neuropsychology aims to explain how the brain achieves learning and accomplishes memory. Memory is a significant area of neuropsychology; hence, the literature review scrutinizes how sleep, alongside other factors, affects memory, cognitive tasks of testing memory, gaps and limitations of previous work, and solutions to setbacks.
Several studies on memory highlight sleep as the primary determinant of brain performance and memory. The common analogy that points sleep to memory performance influences various theories on memory. Marr’s theory of memory consolidation holds that the transfer of information in the brain occurs while one is asleep or in quiet rest (Sattari et al., 2019). Sleep is a primary psychological function necessary for human life. Sleep has been proven to serve multiple functions, including facilitating memory recall and reducing mental fatigue (Chennaoui et al., 2019). Cognition, the general term for cognitive processes concerning the acquisition, storage, manipulation, and manipulation of information, is closely related to sleep. A body of literature emphasizes the role of sleep in maintaining and enhancing cognitive performance (Chennaoui et al., 2019). New memories acquired before sleep get preserved, improved, and stabilized when one sleeps.
Apart from sleep, scholars identify various factors that can affect memory. According to literary research findings, certain illnesses can affect the cognitive system, such as COVID-19 (Guo et al., 2022). Several people infected with the virus were reported to have developed neurological symptoms and prolonged models of cognitive deficits (Guo et al., 2022). People diagnosed with Alzheimer’s are prone to developing poor memory compared to their age mates without the disease (Sheffler et al., 2022). Therefore, infection with certain illnesses may cause adverse effects on the cognitive system and affect patient memory.
Additionally, scholars have found that age has a natural degenerative effect on memory. Older persons under cognitive tests performed poorer than younger persons despite all healthy subjects (Fan et al., 2019). Diffusion tensor imaging indicated a variation in white matter where older persons had less white matter (Fan et al., 2019). Sattari et al. (2019) suggest that certain higher-order functions decline with age. While some scholars associate sleep with positive improvements in working memory among older adults, others find no relationship, indicating that sleep may not improve short-term memory performance in older people (Sattari et al., 2019). Additionally, further research shows that age affects memory, given the vulnerability of older person’s frontal white matter fibers caused by normal aging (Fan et al., 2019). Thus, cognitive aging leads to lower memory capacity, whereas sleep may not help improve memory performance.
Scholars have developed a strong link between sleep and memory, arguing that sleep affects memory. Research studies have identified multiple positive effects of extra sleep, such as naps, on learning and memory (Chennaoui et al., 2019; Sattari et al., 2019). The efficiency of naps and short rests has forced scholars to question the efficiency of sleep quality over quantity. Finding time to nap during the day seems to be an efficient way of reducing mental fatigue and improving an individual’s quality of sleep, hence enhancing memory capacity. Cases of insomnia and sleep deprivation affect memory, as scholarly evidence shows a decline in working memory performance after a night of sleep deprivation among young adults (Sattari et al., 2019). Given that sleep facilitates reduced mental fatigue, insufficient sleep may have adverse effects on memory, such as reduced cognitive performance (Chennaoui, 2019). Therefore, poor sleep may affect memory. Hence, young people need to get more sleep to reduce mental fatigue.
Various theories explain the significance of sleep in enhancing memory performance. Marr’s memory consolidation theory argues that information gets transferred between the hippocampus and narcotex in periods of quiescence, for instance, during sleep and quiet rest (Sattari et al., 2019). Emerging literary evidence suggests a possible connection between sleep, brain plasticity, and hippocampus efficiency. Sleep allows the growth hormones to be more effective, which plays into neurogenesis. Any change in neurogenesis may affect hippocampus-dependent functions such as learning and memory (Chennaoui et al., 2019). Therefore, sleep provides time for the brain to transfer information and enhance memory while one sleeps.
Cognitive Tasks for Testing Memory Under Neuropsychology
Cognitive tests for memory capacity have often been used in studying working memory. Working memory is a significant aspect of cognitive performance, making it the most studied construct in cognitive psychology. Studies have found that working memory is a mental skill highly susceptible to acute sleep deprivation (Ling et al., 2020). The digit span test and N-Back test are two cognitive tests commonly used in testing memory span and how much people can retain in their short-term memories. Working memory is a crucial determinant of various higher cognitive functions such as problem-solving, reasoning, and intelligence (Sattari et al., 2019, Ling et al., 2020). In some research studies, youth with insomnia performed poorly in the digit span task (Ling et al., 2020). However, research findings seem to have mixed results on the effect of sleep on working memory, particularly when subjected to cognitive tests.
Mixed research findings indicating a gap in research shows the effects of insomnia on working memory. Previous research showed the harmful effects of insomnia on working memory when measured in the N-back task (Ling et al., 2020). Other results showed no impact of insomnia on N-back and digit span task performance (Ling et al., 2020). Mixed research findings among scholars call for further research on the possible effects of insomnia and sleep deprivation on memory. Thus, cognitive tests help determine various aspects that may affect memory, including age, illness, and sleep.
Gaps in Previous Work
Whereas several literature sources have indicated a link between sleep and memory, other scholarly sources find no relationship between sleep and memory. The existing gap causes a debate on whether sleep stabilizes memory since some literature shows the same memory performance after a period of rest, similar to a period of waking (Zhang et al., 2022). Existing literature fails to address whether sleep can improve memory performance in older persons. Moreover, the literature leaves a gap in the subject matter of the biological activity of the brain while one sleeps. Follow-up studies should efficiently implement new research methods to dissect the lacunas for conclusive findings in future studies.
Limitations of Previous Work
While this review provides insight into memory, it suffers various limitations. Limitations on understanding memory as an aspect of neuropsychology include a lack of sufficient understanding of mechanisms underlying working memory improvement. Although literature agrees on the effectiveness of sleep in improving memory, research that integrates rest with memory efficiency remains marginal. First, few studies have examined the effects of sleep deprivation and insomnia in adolescents and older people (Ling et al., 2020, Sattari et al., 2019). Moreover, there is a need for further exploration into the effects of sleep on memory in uncontrolled environments for diverse and reliable findings.
Additionally, a significant limitation to a wholesome understanding of the effects of sleep on memory is that most researchers overlook certain factors that affect sleep. First, some have been medically proven short-sleepers (Ling et al., 2020, p. 7). Secondly, for adolescents and young adults, school start time requires them to wake up early hence may not meet the recommended sleep duration for their age (Ling et al., 2020). Additionally, sleep loss may result from medical conditions, travel schedules, or work schedules, especially among night shift workers (Chennaoui et al., 2019). Therefore, more consideration of multiple existing variables is needed, which may lead to inconsistent research findings.
Solutions to the Limitations on Memory in Neuropsychology
Sleep that has been shown to improve long-term memory may enhance working memory among young adults (Sattari et al., 2019). Therefore, given the literary evidence of sleep deprivation and insomnia symptoms among adolescents and young adults, the highlighted group needs to engage in healthy sleep patterns. The literature has established the need for further studies on the effectiveness of sleep quality over quantity, given the marginal evidence around the subject. Additionally, given the mixed findings on the effect of sleep on memory, there is a need to incorporate neuroimaging and neurophysiological techniques to understand the elusive nature of insomnia-related memory performance (Ling et al., 2020). Moreover, further research is needed to understand the mechanisms of sleep and its effects on memory for reliable findings.
Summary
The literature has indicated that while sleep significantly influences memory, other factors, such as age and diseases, also affect memory. Various scholarly evidence shows a strong link between sleep and excellent memory, while other researchers present conflicting information that offers no special relationship between sleep and memory. Sleep enhances learning and, therefore, memory by reducing mental fatigue. The literature has indicated various limitations of previous research on memory and calls for future research in conducting research outside controlled environments and more studies on mechanisms that integrate sleep with memory.
References
Chennaoui, M., Leger, D., & Merino, D, G. (2019). Sleep and the GH/IGF-1 axis: Consequences and countermeasures of sleep loss/disorders. Elsevier, pp.1-42. Web.
Fan, Y. T., Fang, Y. W., Chen, Y. P., Leshikar, E. D., Lin, C. P., Tzeng, O. J., Huang, H. W., & Huang, C-M. (2019). Aging, cognition, and the brain: Effects of age-related variation in white matter integrity on neuropsychological function. Aging andMental Health, 23(7), pp. 831- 839. Web.
Guo, P., Ballesteros, A. B., Yeung, A. P., Liu, R., Saha, A., Curtis, L., Kaser, M., Haggard, M., & Cheke, L. G. (2022). COVCOG 2: Cognitive and memory deficits in long COVID: A second publication from the COVID and cognition study. Frontiers in Aging Neuroscience, 14. Web.
Ling, J., Sun, W., Chan, N, Y., Zhang, J., Lam., S.P., Li, A. M., Chan, J. Y., Kyle, S. D., & Li, S. X. (2020). Effects of insomnia symptoms and objective short sleep duration on memory performance in youths. Journal of Sleep Research, 00, pp 1-10. Web.
Sattari, N., Whitehurst, L. N., Ahmadi, M., & Mednick, S. C. (2019). Does working memory improvement benefit from sleep in older adults? Neurobiology of Sleep and Circadian Rhythms, 6. Web.
Sheffler, J. L., Meynadasy, M., Taylor, D., Kiosses, D. N., & Hajcak, G. (2022). Subjective, neuropsychological, and neural markers of memory in older adults. International Psychogeriatrics, 34(12). Web.
Zhang, J., Whitehurst, L. N., & Mednick, S. C. (2022). The role of sleep for episodic memory consolidation: Stabilizing or rescuing? Neurobiology of learning and memory. Elsevier, pp. 191. Web.