The Impact Of Sleep Deprivation On Working And Emotional Memory

Memory is a core aspect of one’s cognitive processes and is used by everyone daily to ensure they retain what was taught in school, to remember to walk the dog, or just to remember a pleasant event that will make them feel good whenever it is recalled. Not having the capacity to remember would be detrimental to learning and everyday activities; it would be extremely difficult to live a normal life.

A routine, but the essential activity that is closely related to a strong memory is sleep. Sleep is critical to how well one’s memory functions; when someone is sleep-deprived, their memory has been found to worsen (LeWine, 2014). This leads me to ask how it is impacted by sleep deprivation (SD). There are many different types of memory, but two that are very important are working memory and emotional memory. I will seek to answer the question, “what is the impact of sleep deprivation on working and emotional memory?”

I think that sleep deprivation hurts memory, and to determine whether this is true, I will review a sample of relevant psychological research on the topic. I will first consider working memory by examining three studies that focus on the impact of sleep deprivation on this type of memory. I will then review three additional studies to explore the impact of sleep deprivation on emotional memory. Throughout the essay, I will refer to these studies to draw plausible conclusions in response to my research question.

All six of the studies used to answer the research question were retrieved from an online database from the University of Waterloo. The studies are all peer-reviewed studies related to my topic, conducted by psychologists from universities around the world, primarily the United States. The three studies involving working memory are those conducted by: Pasula et al. (2018); Hagewoud et al. (2009); and Drummond, Anderson, Straus, Vogel, and Perez (2012). The three studies looking at emotional memory were carried out by Fernandes-Santos et al. (2012); Tempesta, Socci, Ioio, Gennaro, and Ferrara (2017); and Kaida, Niki, and Born (2015). All of these studies used experimental methods to test their hypotheses about the impact of sleep deprivation on memory.

Many people today do not get enough sleep for various reasons, including having overly busy schedules and over-using electronic devices, often right before bed. Evidence for the negative impacts on memory of lost sleep will be examined throughout this essay to allow for a more detailed understanding of how memory functions, which is a topic that is still debated among psychologists and neuroscientists, and how important sleep is to optimal memory functioning.

The concept of working memory was first proposed by Baddeley and Hitch (1974) in their discussion of short-term memory. They proposed the working memory model which consists of a set of interacting components that process information from the environment. The working memory model argues that short-term memory is made up of multiple parts, each with a specific function. The model has five main parts, the phonological loop (auditory information processing section), the visual-spatial sketchpad (visual information processing section), the episodic buffer (processes what information is important), the central executive (the one that is essentially the control center of the working memory), and finally the long term storage (Baddeley and Hitch, 1974).

More recently, Pasula et al. (2018), examined the impact on the information processing components of working memory. Their study included a sample of 31 younger adults and 33 older adults who had two appointments two weeks apart. In both appointments, the participants took part in a test; however, the first time, they had a full night of sleep while the second time they were totally sleep deprived (TSD). The participants took part in the continuous recognition memory test (CRMT) which involved showing them a stimulus for three seconds. Participants were then presented with the same stimulus, but also three other items, and were required to recognize the original item (Pasula et al., 2018). In this study, the participants took part in a verbal CRMT (VBScript) as well as a visuospatial CRMT (vsCRMT). For the VBScript, the participants were shown a five-letter nonsense word that is pronounceable (Pasula et al., 2018). For the vsCRMT, the participants were shown a nonsense drawing of lines that did not resemble any shape (Pasula et al., 2018). The results for the verbal memory test revealed that all the participants performed worse on the vbCRMT after TSD than after regular sleep. However, the younger adults performed slightly better than the older adults. For the visuospatial task, the results were similar except that TSD affected the verbal encoding slightly more than the visuospatial displacement; there was also no significance in the results for the visuospatial task after TSD for older adults (Pasula et al., 2018). These results show that TSD negatively affects verbal encoding and visuospatial displacements; however, TSD did not affect the episodic memory of the participants. Total sleep deprivation was shown to negatively impact component processes of working memory to a greater extent in older adults than younger adults. Pasula et al. (2018) found that total sleep deprivation caused a decline in the memory of the younger adults to the degree of older adults without sleep deprivation, supporting the idea that sleep deprivation negatively affects working memory in a similar way that aging does.

This study is important because it was the first to examine how sleep deprivation affected both the verbal and visuospatial components of working memory together. The study’s value to the field, and the validity of its findings, were strengthened as it extended and supported similar studies carried out by Turner et al. (2007) and Chee et al. (2006) (Pasula et al., 2018). Despite this value, the study did have some limitations. First, Pasula et al. (2018) could have verified whether all the participants had regular sleep patterns. This would have allowed them to control for other possible influences on the participants’ memory tasks. Furthermore, they could have examined individual participant performance in all component processes of working memory to examine possible reasons for inconsistencies and to further the implications of the research (Pasula et al., 2018).

Sleep deprivation also affects visual working memory. Hagewoud et al. (2009) looked at how SD affected the memory of mice, both biologically and cognitively. Mice were used because they have similar genes to humans so it was assumed that the gene expression, and other processes that occur during sleep, might be similar to that of humans and so would be affected by SD in similar ways (“Why mouse matters”, 2010). Hagewoud et al. performed two experiments on three mice each. One mouse was the control, another had 6 hours of SD and the third had 12 hours of SD (Hagewoud et al., 2009).

The first experiment was a novel arm recognition task to test their spatial working memory. The mice were put into a Y-shaped maze with one arm of the maze blocked, then taken out for two minutes, and then returned to the maze with all arms available (Hagewoud et al., 2009). Good spatial working memory would mean the mice would explore the new unblocked arm the second time more than the other two arms (Hagewoud et al., 2009). The second experiment tested the hippocampal AMPA receptors and GluR1 protein levels by using western blotting (Hagewoud et al., 2009). In the first experiment, the sleep-deprived mice spent the same amount of time in the new arm like the previous arms, but the control mice spent more time in the new arm, showing that sleep deprivation negatively affected the spatial working memory of the mice.

The second experiment showed that sleep deprivation did not affect GluR1 proteins, but did affect AKAP150 protein levels and negatively affected the AMPA receptors (Hagewoud et al., 2009). These results show that sleep deprivation negatively affects spatial working memory by reducing hippocampal AMPA receptors, likely because of a decrease of APAP150 protein levels and supporting the idea that there is a biological explanation for the effect that sleep deprivation has on memory.

The Hagewoud et al. (2009) study does have some limitations. First of all, the study is correlational., meaning that the researchers could not establish a cause and effect relationship between the variables they studied. This means that the results may not actually prove that sleep deprivation directly affects visual working memory; however, it is still valid evidence of a relationship. The researchers also did not find lower levels of a protein that would explain the reduced AMPA levels; so there is a missing piece that does not explain exactly how sleep deprivation impaired visual working memory. Apart from these limitations, the study provides an important opportunity to consider both biological and cognitive approaches to understanding the effect of sleep deprivation on working memory. By researching more than one area of psychology, it increases the validity of the research because it allows for observations from more than one perspective.

In contrast to the previous studies, Drummond et al. (2012) suggested that there is actually the very little effect of sleep deprivation on memory. Drummond et al.’s 2012 study examined the effects of sleep deprivation on the capacity and filtering efficiency of visual working memory. Capacity refers to the number of pieces of information that can be held simultaneously for short periods, and filtering efficiency is how efficiently the visual working memory can filter out non-relevant information from the working memory since the capacity is limited (Drummond et al., 2012).

The participants in Drummond et al.’s study included forty-four young adults. They were all observed in a well-rested condition, as well as in either a partial sleep deprivation (PSD) condition or in a total sleep deprivation (TSD) condition. All participants’ sleep was monitored while in the laboratory to ensure they had the assigned amount of sleep each night (Drummond et al., 2012). Following the PSD or TSD, the participants performed two tasks, one for capacity and one for filtering efficiency. For the capacity task, the participants were shown four to eight colored squares, then shown a blank screen, followed by the same number of colored squares. The participants were instructed to say if the new image was the same or different from the original colored squares. The filtering efficiency task had six different trial types. The first was the same as the capacity task, but it only had one square, the second had two squares, and the final trial types had two target squares as well as four distractor rectangles. The participants were supposed to remember the squares and ignore the rectangles. To do so, their visual working memory had to filter out the irrelevant rectangles (Drummond et al., 2012). The results of this study reveal that both PSD and TSD did not decrease the capacity of the participants’ visual working memories. However, TSD did decrease the filtering efficiency, but PSD did not. Unlike other studies, this study showed that total sleep deprivation had an impact on the filtering efficiency of working memory, although the impact was small. TSD had no significant effect on the capacity.

Drummond et al.’s (2012) study involve several limitations which may explain why their results differed from other studies. They only examined one level of PSD, instead of examining different levels to give a greater understanding of their effects. The researchers also only administered the tasks at one time of day instead of at multiple times as done by Hagewoud et al. (2009). It is possible that different intervals would produce differing effects on working memory. The participants’ sleep patterns were not controlled before coming into the lab which means some participants could have had more or less sleep before participating in the experiment. Another possible explanation for the contrasting results of this study is the limited number and diversity of the sample size (forty-four participants all from the same region in the United States). Consequently, there may have been an unusual number of participants who were resilient to the effects of sleep deprivation on their visual working memory (Drummond et al., 2012). A larger and more diverse sample would have also allowed for better generalization of the findings.

Sleep deprivation has been shown to negatively impact multiple aspects of working memory. Studies conducted by Pasula et al. (2018) and Hagewoud et al. (2009) which examined the impact of SD on working memory found a significant association. Drummond et al. (2012), however, found little to no effect of SD on working memory. This latter study, however, involved limitations that weakened its validity, and which may account for the different results. Therefore, despite some contradictory evidence, sleep deprivation can be considered to have a significant negative impact on the component processes of working memory. Overall, these results suggest that avoiding sleep deprivation will support a well-functioning working memory, enabling optimal decision-making, information processing, and learning.

Another type of memory that is affected by sleep deprivation is emotional memory. Emotional memories are memories of events or stimuli that have a strong emotional connection (IB psychology, n.d.). For example, the memory of a photo that portrayed something happy would prompt, not only a memory of the appearance of the photo, but also the feeling associated with the photo. Often, emotional memories involve a deep connection, which is very strong and difficult to forget (IB psychology, n.d.).

Fernandes-Santos et al. (2012) looked at how TSD affected retrieval of emotional memory in male and female mice. Seventy-four male mice and seventy-five female mice were split into two conditions, TSD for six hours or a control condition involving regular sleep (Fernandes-Santos et al., 2012). TSD was achieved by gently tapping the cage or gently brushing the mice if they started to fall asleep. Immediately after sleep deprivation or regular sleep, the mice were tested in one of three ways.

The first test involved contextual fear conditioning (CFC), which is where the mice were placed in a dark chamber, where, before sleep, foot shocks were administered at regular intervals (Fernandes-Santos et al., 2012). After sleep, the mice were placed in the same dark chamber without the foot shocks and the amount of movement of the mice was measured (Fernandes-Santos et al., 2012).

The second test involved the passive avoidance task (PAT), where the mice were placed in a box with two rooms and a sliding door between them. One room was illuminated and the other was dark. The mice were placed in the lightroom and when they entered the darkroom, the door would close and foot shocks would be applied. For the test after TSD or regular sleep, the mice were placed in the same room except the darkroom did not have foot shocks. The hesitation of the mice to enter the darkroom was measured by timing how long it took them (Fernandes-Santos et al., 2012).

The third test involved the plus-maze discriminative avoidance task (PM-DAT), where for the training session, the mice were placed in a chamber with two arms. When the mice entered the second arm, a bright lamp would turn on and a cold wind would be produced. The mice were tested in the same chamber, but the light and wind would not turn on when they entered the second arm. The researchers measured how much time was spent in each arm in the test session. For the CFC test, the mice moved more when they were sleep-deprived than when they experienced regular sleep. This demonstrates impairment in the retrieval of emotional memory in the mice (Fernandes-Santos et al., 2012).