Ciara Treacy

The development of effective preventative intervention to counter or slow age-related cognitive decline (ARCD), thereby supporting functional independence as people age, is limited by an inadequate understanding of the neural mechanisms underpinning normal cognitive ageing. Both sustained attention and inhibition represent two incompletely understood executive functions, requiring closer examination in the context of healthy ageing. These executive functions are crucial for successful goal pursuit, meeting the demands of everyday life and maintaining autonomy, with attentional/inhibitory disengagement having considerable social and health-related consequences. Despite the ubiquitous demands placed on sustained attention and inhibition, there is not a consensus among research findings linking healthy ageing to performance decrements. Importantly, sustained attention requires top-down regulation, such that behavioural inhibition may influence this attentional capacity. Thus, by considering the different aspects of inhibition and sustained attention together, we may better reveal their relationship to ageing. An additional consideration is that there are several independent, sub-component processes of inhibition, yet still, the multifaceted nature of inhibition is often an overlooked factor in experimental design. From a neurobiological perspective, whilst the neural activation patterns of sustained attention and inhibition have been well-documented in healthy populations via functional MRI (fMRI), evidence linking these executive functions with brain structure and/or neurochemistry are comparatively lacking. These neurobiological insights may help explain the disparities prevailing across the age-attention and age-inhibition literature, in addition to the aforementioned behavioural factors. Thus, the aim of this thesis was to investigate the MRI-assessed neurobiology subserving sustained attention and inhibitory sub-components in medically/cognitively healthy older adults (as well as assessing their behavioural interplay), utilising structural magnetic resonance imaging (sMRI) and magnetic resonance spectroscopy (MRS) to advance current understandings.