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Title: Proton MRS studies in ageing : investigating relaxation, concentration, and correlation with resting-state activity in the PCC
Author: Rusiak, Karolina W.
ISNI:       0000 0004 5993 5425
Awarding Body: Prifysgol Bangor University
Current Institution: Bangor University
Date of Award: 2016
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The human brain undergoes changes over its lifespan, which may appear in the form of cognitive decline or disease. As such, it is necessary to investigate the ageing process at the neurochemical level as normal and pathological processes may overlap. The thesis examines metabolite transverse (T2) relaxation times as well as metabolite concentrations in relation to cognitive performance and functional connectivity across age. A systematic review of the T2 relaxation literature offers consensus T2 relaxation values for N-Acetyl Aspartate (NAA), creatine, and choline across tissue content at 1.5 and 3 Tesla for accurate quantification of metabolite concentration levels. Building on these findings, the first empirical study investigates T2 relaxation values across age in healthy younger and typically ageing older adults. The results suggest a significant difference in NAA apparent T2† relaxation values between the younger and older cohort. The findings from the systematic review and first empirical study are used for accurate quantification of metabolite concentration levels in the second and third empirical studies. The second empirical study examines the relation of the major excitatory (glutamate) and inhibitory (GABA) neurotransmitters to cognitive performance across age. The outcome suggests age and reduced glutamate concentration levels to be predictors of cognitive performance on selective cognitive tests. In the third empirical study, glutamate and GABA concentrations are assessed in relation to functional connectivity between the posterior cingulate cortex and hippocampus, brain regions that are affected in mild cognitive impairment and Alzheimer’s disease. The findings, considered with caution, suggest that higher glutamate concentrations are associated with increased functional connectivity between posterior cingulate cortex and hippocampus. Taken together these studies shed light into the ageing process by characterising neurochemical mechanisms in relation to cognitive performance and functional connectivity. The utilization of proton magnetic resonance spectroscopy as well as functional magnetic resonance imaging can provide underpinnings of healthy ageing along with pathologies.
Supervisor: Mullins, Paul Sponsor: European Regional Development Fund (ERDF) ; Ireland Wales Territorial Co-operation (INTERREG 4A) Programme 2007-2013
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available