Butters, E.; Collins-Jones, L.; Mesquita, R. C.; Acharya, D.; McKiernan, E.; Laurell, A. A.; Low, A.; Srinivasan, S.; O'Brien, J. T.; Su, L.; Bale, G.

Dementia is associated with altered resting state connectivity, measures of which could aid in its early detection and monitoring. High-density diffuse optical tomography (HD-DOT) is well-suited to detect these alterations at scale due to its numerous practical advantages, but it has not yet been applied to dementia. In this study, we investigated resting state functional connectivity across the prefrontal cortex in individuals with Mild Cognitive Impairment (MCI, n = 22), Alzheimer\'s Disease (AD, n = 21), and in healthy controls (n = 22). A graph theoretical approach was taken to characterise both global and local patterns of connectivity over a five-minute resting period. We found that individuals with AD and MCI exhibited denser and stronger networks, with shorter path lengths, as well as a loss of consistent key network hubs with worsening cognitive impairment. These results indicate that networks in dementia are more globally connected, albeit in a disorganised manner, perhaps reflecting the recruitment of additional connections for short-term stability which may be ultimately damaging in the long-term. Following the demonstration of HD-DOT\'s capacity to detect differences between healthy ageing and dementia, this work opens up new possibilities for the use of optical imaging in the study of this clinical population and HD-DOT\'s potential for scalable clinical use.