Scientific abstract
Aging is associated with changes in brain structure and declining cognitive functioning. Yet, the age trajectories differ among individuals. Considerable attention has recently been given to the effects of various forms of cognitive-enrichment in aging (Hertzog, Kramer, Wilson, & Lindenberger, 2008). Memory training may be important in this regard. At the starting point of the present ph.d.-research project, however, it remained unknown whether improving cognitive performance through memory training is accompanied by measureable changes in the adult and aging brain itself.
The goal of the present project was to study how memory training is related to structural characteristics of the adult brain. We studied two aspects of a novel memory training intervention: 1) is training accompanied with measureable changes in the brain? And 2) is training-benefit in adults with memory problems related to structural features of the brain––before intervention?
As described in the two first papers, we undertook a randomized controlled magnetic resonance (MR) imaging study of an intensive two-months memory-training program in healthy adults (mean age 60.3). Assessment of cognitive performance and MR-imaging was performed before and after training. Structural changes in cerebral grey and white matter were assessed using MR-protocols optimized for reliable longitudinal analysis. Following intervention, the training group improved task-specific memory performance. A unique finding is that training was accompanied by regional increases in cerebral cortical thickness and white matter integrity compared with controls. We found significant relationships between the changes in performance and brain structure characteristics, suggesting a link between the two levels of enquiry. The current assessment-interval spanned less than three months, and follow-up studies are needed to conclude on the long-term effects of the present memory training on brain and cognition.
A second objective of the present thesis was to assess the feasibility of memory training in a clinical setting. Earlier research had indicated positive effects of cognitive intervention for adults with memory concerns, but evidence regarding who might benefit from training was lacking. We offered the same training program for 19 memory clinic outpatients with subjective memory impairment, but with no objective signs of memory loss, and studied predictors of training benefit. The results showed that training was feasible for this patient group, including high participation rates and low dropout rates. Left hippocampal volumes before training were found to predict memory-training benefit. Sub-region analysis suggested that the effects were selective to the left cornu ammonis (CA) sectors CA2/3, and CA4 and dentate gyrus, which are of known importance for episodic memory. The finding implicate that structural imaging could serve useful in future trials evaluating treatment potential and in selecting candidates for intervention.