The Link between Slow-Wave Sleep and Episodic Memory Changes from Younger to Older Adults

Introduction

Memories of human beings do not remain static but undergo a steady restructuring process which is scientifically known as memory consolidation as a person ages. A number of studies have pointed out that memory consolidation is largely facilitated by sleep which plays a critical role in the whole process. This owes to the fact that it is during sleep when specific ectrophysiological and neuro-chemical activities takes place. Various authors have put forth a number of models among them including the synaptic homeostasis hypothesis, and the hippocampo-neocortical dialogue in an attempt to explain the role of sleep in memory consolidation processes. However, majority of studies that have been conducted on this issue have not been exclusive, while some have focused on young subjects.

Until recently, indeed the majority of the studies trying to establish a link between sleep and cognitive changes have only focused on younger adults. Stated differently, research establishing the link between memory and sleep in older adults have elicited low interest among scholars. Despite the fact that aging is characterized by memory impairment, alterations in sleep architecture alongside changes in neurochemical and brain process, the relation of these elements suggest that consolidation of sleep-dependent memory occurs and may be impaired at a different level, especially among older adults.

Though a study by Sculin (2012) focused on establishing the relationship between slow-wave sleep and episodic memory changes in both old and younger populations, this study had a number of limitations. Among these limitations include failure to conduct appropriate clinical screening for use of sleep-altering medicine and neurodegenerative disorders. Therefore, this study mainly focuses on leveraging this limitation by specifically ensuring that all participants are appropriately screened through both clinical interviews and neuropsychological testing to identify participants utilizing sleep-altering medicine and those with neurodegenerative disorders.

Literature Review

Scullin (2012) conducted a study to establish the linkage between slow-wave sleep and episodic memory alterations from younger to older individuals. In this study, participants who included both younger and older adults were required to encode word pairs two times a day, morning and evening hours. This procedure is then repeated after asleep or no sleep interval. The authors employed a home-stage monitoring system in obtaining sleep-stage scoring. Among the findings from this study is a positive correlation between the amount of SWS and word retention in the course of retention interval. On the other hand, the study did not find any positive correlation between SWS and memory among older adults. Instead, the study noted one peculiar negative correlation between SWS and memory. According to the authors, these findings offer a suggestion that the connection between SWS and episodic memory which is rife among younger adults may be altered among healthy older adults.

Nonetheless, the study by Scullin (2012) was faced with a number of limitations. For example, the screening process for sleep-altering medications and neurodegenerative disorders was through self-report and not through clinical interviews or neuropsychological testing. This according to the authors raised the possibility of including participants with conditions of mild cognitive impairment (MCI) which is related to REM and SWS sleep declines.

The current study will therefore leverage this limitation by conducting an appropriate screening process which includes the use of clinical interviews and neuropsychological testing so as to eliminate individuals with mild cognitive impairment. This way, we will be able to obtain results that are more accurate.

A study by Cherdieu et al (2014) was focused on finding out if there is any benefit for memory derived from sleep. The study procedure included testing episodic memory among 20 young adults (22.11.7 years) and another 20 older (between 60=90) volunteers. These participants were given a task that involved performing a two-dimensional visual patina object location. The researchers then evaluated retention capabilities after 12 hours of sleep or wakefulness. Performances prior to and after specific sleep and wakefulness intervals enabled the researchers to measure the rate of forgetfulness. The measurement of sleep architecture was by polysomnography (young adults:467 min and older adults = 410 min).

The study by Cherdieu et al (2014) established that the positive effect of sleep on memory consolidation was lower among the adult participants when related to the younger population. The study went on to note that among older adults, sleep did not harbor a positive effect in terms of improving memory consolidation when compared with being awake. Furthermore, sleep aided young adults from being forgetful while the rate of forgetfulness among older adults was still found to be significant after sleeping.