The relationship between autobiographical memory an executive functions in older adults

Abstract

Autobiographical memory is considered the most durable memory component in the human memory system. This thesis aimed to examine the characteristics of autobiographical memory performance and its relationship with executive functioning in normal and pathological ageing. The particular focus was on two aspects of autobiographical memory - recall specificity and fluency - that have been little investigated in cognitive ageing research to date.
The literature reviewed included the domains of cognitive and clinical psychology, neuropsychology, and gerontology. It is clear from the review of the literature that considerable uncertainty exists regarding the status of autobiographical memory in healthy ageing and dementia. Moreover, little is known about the involvement of executive processes in the retrieval of personal remote memories in old age.
A series of cross-sectional quasi-experimental studies is reported. The autobiographical memory and executive functioning of 136 participants were assessed by utilising a variety of neuropsychological instruments, and a range of statistical techniques were used in the analysis of the interactions between these two cognitive systems. The findings are discussed in terms of theoretical and practical implications for cognitive, ageing, and clinical research.
To the author's knowledge, no research to date has attempted to investigate the specificity of autobiographical recall in a sample of Alzheimer's patients - an aspect this study addressed, thus providing an original contribution to knowledge. In addition, it has been established that the autobiographical memory overgenerality identified in Alzheimer's Disease was expressed through an excess of categoric memories.
These findings were followed by an attempt to establish whether autobiographical memory performance is influenced by age-associated changes in executive functions in healthy ageing. The thesis adopted as its main theoretical framework the executive decline hypothesis, the proposal that a subtle decline in executive functions could account for age-related decreases in memory (Troyer, Graves & CulIum, 1994; Crawford, Bryan, Luszcz, Obonsawin & Stewart, 2000). For the first time, the investigation of this hypothesis has been extended to autobiographical memory recall. The results indicated that the executive functions, when indexed by a composite score, failed to mediate ageassociated retrieval of personal memories in older adults. However, a specific executive function - verbal fluency - predicted a significant amount of age-related
variance of autobiographical memory recall. These findings were interpreted in terms of the mediator-specificity requirements in mediational models.
Further, the thesis examined the impact of verbal fluency strategic mechanisms, clustering and switching, on autobiographical memory retrieval. The results indicated that the strategic mechanisms employed in verbal fluency failed to
predict autobiographical memory recall in older adults, as opposed to the original measure of total words generated across the verbal fluency tasks. This finding supported previous research questioning the sensitivity of the new verbal fluency
scoring methodology (Troyer, Moscovitch & Winocur, 1997). An additional factor that has not been fully explored in previous research is the possibility that certain aspects of executive function could be important for different components of autobiographical memory. By analysing the existence of different subcomponents within the two cognitive systems and their association, this thesis provided additional evidence for the debate over the unity and diversity of executive functions.
To summarise, it has been established that verbal fluency mediates age-related autobiographical memory recall in older adults, manifested through autobiographical fluency. This finding is explained in terms of the common source proposal, referring to the processes of strategic search underlying performance on both tasks. Further investigation is needed to clarify these issues and examine the age effects on intra-individual variability in executive functioning and autobiographical memory.