The overall objective of this dissertation was to increase scientific understanding of brain reserve. Chapter 1 describes how brain reserve has come to be viewed in two distinct ways: differential expression of brain injury on the basis of individual differences in gross brain properties (neurological), or on the basis of lifespan patterns of complex mental activity (behavioural). Evidence in the Alzheimer???s disease and ageing literature has been extensive, yet with conflicting reports. In order to better evaluate this evidence, a systematic review of cohort studies is the focus of Chapter 2. Complex mental activity was found to be associated with reduced incidence of dementia and slowed rate of cognitive decline. Neurological brain reserve evidence was limited. A major task of this dissertation was to develop a more standard and complete behavioural brain reserve instrument. Chapter 3 relates the development of the Lifetime of Experiences Questionnaire (LEQ) in a group of 86 healthy elderly. The LEQ had adequate levels of internal consistency and reliability. In a validation test, higher LEQ scores were also found to predict attenuated cognitive decline over 18 months independent of covariates including premorbid IQ. Chapter 4 describes how both LEQ (as a measure of behavioural brain reserve) and intracranial volume (as a measure of neurological brain reserve) significantly predicted cognitive decline over three years in a sample of 70 aged subjects. Total LEQ was furthermore significantly correlated with hippocampal volume independent of intracranial volume, and this association mediated the relationship with cognitive decline. Behavioural brain reserve may therefore work by protecting individuals from hippocampal atrophy. The fifth chapter explores therapeutic and neurobiological aspects of behavioural brain reserve in a preliminary fashion. A randomized-control mental activity trial was run with 20 healthy elderly who received repeat magnetic resonance spectroscopy. Mental activity subjects were found to have selective and sustained upregulation of phosphocreatine metabolism in the hippocampal region, a finding of potential neuroprotective significance. Experience-dependent neuroplasticity is proposed as a unifying framework in the final chapter, allowing synthesis of the present findings and reconciliation of the neurological and behavioural approaches to brain reserve.
| Identifer | oai:union.ndltd.org:ADTP/230336 |
| Date | January 2005 |
| Creators | Valenzuela, Michael J., Psychiatry, Faculty of Medicine, UNSW |
| Publisher | Awarded by:University of New South Wales. School of Psychiatry |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | Copyright Michael J. Valenzuela, http://unsworks.unsw.edu.au/copyright |
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