Abstracts Category : Other

Brain networks in healthy ageing and psychiatric conditions.

by Alistair Perry

Conceptualising the human brain upon its large-scale interactions has led to the realisation of integrativeneural processes as critical to cerebral functioning. This thesis sought to elucidate the brain patterns offunctional integration and segregation that are associated with the cognitive and behavioural changes inhealthy ageing and psychiatric conditions. The network features expressed with age-related cognitivechanges are poorly understood within a healthy older population. Th e brain network disturbances inindividuals at high-genetic risk for bipolar disorder (BO) are also unknown.Study 1 (Chapter 2) leveraged advances in diffusion-tractography to derive the features of structuralbrain networks in healthy older adults. The integrative features of the core backbone are observed in theconnectomes of both young and older adults, reflecting ongoing patterns of efficient brain communication.Study 2 (Chapter 3) leveraged multivariate analysis to examine in healthy older adults the complexrelations between age, functional connectivity, and cognitive performance. A functional sensorimotorsubnetwork was identified whose expression is opposed by age against core cognitive processes such asattention and processing speed. Modifiable factors such as increased education are associated with distinctfunctional networks.Lastly, study 3 (Chapter 4) investigated the structural networks in patients and also unaffectedrelatives at high-genetic risk for BO. Relative to matched-controls, alterations to fronto-limbic circuitshousing key emotional and cognitive centers were identified within both patient and high-risk groups.The present works illustrate the expression of large-scale brain network features are associated withphenotypic differences in healthy older adults and psychiatric conditions. Inter-individual differences in theintegration of cerebral information processing is strongly implicated here for the respective changes infunctioning: Sensorimotor networks supporting lower-order processes are most sensitive to healthy ageing,whilst fronto-limbic disturbances in patient and high-risk groups are consistent with the emotional liabilityin BO. The integrative features of key-hub regions are also demonstrated throughout these studies ascritical to brain communication capacity. This thesis hence contributes as an important body of work in ourability to understand and predict human brain functioning and behaviour.Advisors/Committee Members: Wen, Wei, Psychiatry, Faculty of Medicine, UNSW.