Memory And Episodic Memory

It is well known that as people age that various aspects of memory and sleep are altered. What is more elusive is whether these changes occur independently or whether changes in patterns of sleep influence changes in performance in memory and decision making tasks in older age. In order to attempt to elucidate this hypothesis, a brief overview of the nature of episodic memory followed by a review of some of the more recent adult sleep literature is necessary before considering how the relationship between sleep and episodic memory may change across adulthood.

Episodic memory is a form of declarative memory in which a person encodes and recalls inputs which are subjective and relate to one’s own personal experiences and life events (Tulving,

In one of the few neuroimaging studies pertaining to patterns of retrieval in episodic memory, Polyn and colleagues (2005) found that patterns of activity were similar when subjects actively viewed faces, places, and objects as when subjects attempted to reactivate memories of these specific images. This degree of similarity between encoding and retrieval was found to predict how much information about the images subjects were able to retrieve, with greater degrees of similarity predicting greater information recall (Polyn et al.,

Younger adults exhibit decreased performance on measures of working memory such as the N-back (Smith, McEvoy, and Gevins, 2002), digit span (Frey, Badia, and Wright, 2004), and Sternberg verbal working memory task (Mu et al., 2005), as well as decision making tasks (Killgore, Balkin, and Wesensten, 2006), and on measures of long term memory such as memory search (McCarthy and Waters, 1997), and paired word learning (Forest and Godbout, 2000). At the neurobiological level, Chee and Choo (2004) found that after a day of total sleep deprivation, younger adults showed similar patterns of activation and deactivation as is commonly seen in healthy older adults on memory tasks. Areas of the medial parietal and occipital lobes showed a decrease in BOLD signal, increased BOLD signal in the left prefrontal region, and complete deactivation of the anterior medial frontal and posterior cingulate regions (Chee and Choo, 2004). While it is tempting to conclude that similar mechanisms are at play during sleep deprivation in young adults and in healthy cognitive aging in older populations, research to date has often been contradictory and riddled with methodological issues, making it difficult to draw any clear