Prospective and retrospective memory in normal and pathological aging

This thesis aims to explore how prospective and retrospective memory are affected by health in old age. In this regard, we have focused on dementia disorders, depressive symptomatology, and thyroid functions. Prospective memory involves remembering to perform actions, such as paying bills or taking one s medication. Retrospective memory involves remembering previous events or previously learned information, such as the content of a book. The memory process can be divided into three stages: encoding (forming new memories), storage (consolidation of information), and retrieval (remembering what we have previously encoded). In Study I, three groups were included: persons with Alzheimer s disease, persons with vascular dementia, and healthy control persons. The groups were compared on prospective and retrospective memory tasks. The two dementia groups were impaired compared to controls on both prospective and retrospective memory, and the impairment was evident for all stages of the memory process (i.e., encoding, storage and retrieval). However, there were no differences between the two dementia groups regarding the extent or pattern of memory deficits. Study II examined how prospective and retrospective memory were affected during the so called preclinical phase of Alzheimer s disease (i.e., before the disorder had progressed so much that it could be diagnosed). Both prospective and retrospective memory was impaired three years prior to diagnosis. In addition, the results showed that more people at risk of developing Alzheimer s disease could be identified when the combined results from the two memory tasks were taken into account, compared to using only one task at the time. The unique contributions of both memory measures indicate that they are, at least in part, separable entities. When studying retrospective memory in more detail, we found that the impairment in preclinical Alzheimer s disease was present across all three memory stages. Study III examined how depressive symptoms affected prospective and retrospective memory. Depressive symptoms refers to a continuum, ranging from states (such as mild dysphoria) that are common also among healthy persons to severe depressive disorders. The results showed that retrospective memory was negatively affected by depressive symptoms. The effect was evident for storage and retrieval, whereas there was a non-significant trend in the same direction for encoding. Prospective memory, however, was unaffected by depressive symptoms. If these results are valid, this can help us separate persons with depression from persons with early stage dementia, which in many cases is difficult. Study IV examined the effect of thyroid functioning on prospective memory. Thyroid function was measured through serum levels of two hormones: thyroid stimulating hormone (TSH) and thyroxine (T4). All participants were free from thyroid disorders. In spite of this, the results revealed that persons with higher TSH levels performed better on the prospective memory task. T4 levels were not related to memory performance. Previous research has shown a corresponding association between TSH and retrospective memory. The conclusion is that thyroid functioning has an impact on cognition, even in the absence of overt disease. To summarize, both prospective and retrospective memory are sensitive cognitive abilities, easily affected by disorders and other factors related to health. There are, however, some differences with regard to when, and how, these two forms of memory are affected. It is important to investigate this issue further, in order to gain a deeper understanding of the cognitive challenges that persons with different disorders or symptoms are facing. This can, in turn, lead to the development of new cognitive aids. In addition, cognitive psychology research can in some cases help us make faster and more accurate diagnoses

A naturalistic study of prospective memory function in MCI and dementia

Objective. Naturalistic measures of prospective memory (PM) show less age-related decline than laboratory measures. We investigated whether a naturalistic measure of PM differentiates between normal ageing, mild cognitive impairment (MCI), and dementia. Method. Ninety-eight older adults agreed to perform a time-based PM task in their everyday lives. Results. Despite a self-selection bias in task acceptance, dementia participants performed more poorly relative to both the MCI and control group. Performance on the naturalistic PM task showed good convergent validity with both a cognitive screening measure and a laboratory PM assessment. Conclusions. PM difficulties are experienced in the everyday lives of people with dementia and are related to laboratory-based assessments but do not appear to be evident on a naturalistic task for those with MCI

Prospective memory, retrospective memory, and individual differences in cognitive abilities, personality, and psychopathology.

Although individual differences in processing speed, working memory, intelligence, and other cognitive functions were found to explain individual differences in retrospective memory (RetM), much less is known about their relationship with prospective memory (ProM). Moreover, the studies that investigated the relationship between ProM and cognitive functions arrived to contradictory conclusions. The relationship between ProM, personality, and psychopathology is similarly unsettled. Meta-analytic reviews of the relationships of ProM with aging and personality suggest that the contradictory findings may be due to widespread methodological problems plaguing ProM research including the prevalent use of inefficient, unreliable binary measures; widespread ceiling effects; failure to distinguish between various ProM subdomains (e.g., episodic ProM versus vigilance/monitoring); various confounds; and, importantly, small sample sizes, resulting in insufficient statistical power. Accordingly, in a large scale study with nearly 1,200 participants, we investigated the relationship between episodic event-cued ProM, episodic RetM, and fundamental cognitive functions including intelligence, personality, and psychopathology, using reliable continuous measures of episodic event-cued ProM. Our findings show that (a) continuous measures of episodic event-cued ProM were much more reliable than binary measures, (b) episodic event-cued ProM was associated with measures of processing speed, working memory, crystallized and fluid intelligence, as well as RetM, and that such associations were similar for ProM and RetM, (c) personality factors did not improve prediction of neither ProM nor RetM beyond the variance predicted by cognitive ability, (d) symptoms of psychopathology did not improve the prediction of ProM although they slightly improved the prediction of RetM, and (e) participants' sex was not associated with ProM but showed small correlations with RetM. In addition to advancing our theoretical understanding of ProM, our findings highlight the need to avoid common pitfalls plaguing ProM research