Reconfiguration of metabolic connectivity in ageing

Information transfer across the brain has a high energetic cost and requires efficient glucose metabolism. Here we use recently developed high temporal resolution functional positron emission tomography (fPET) to create a timecourse of glucose metabolism for individual subjects and assess the relationship between metabolic connectivity and cognitive function in ageing. The metabolic connectomes of 40 younger (mean 27.9 years; range 20-42) and 46 older (mean 75.8; 60-89) adults were characterised by high connectivity in the frontal, temporal, motor, parietal and medial cortices. Older age was associated with lower global integration of metabolic hub regions. In younger adults, a high proportion of glucose was used to support hubs in the frontal regions. Older adults used a higher proportion of a smaller energy budget to support mostly posterior hub regions. This metabolic network topology of older adults was associated with worse cognitive performance. We conclude that ageing is associated with a high glucose cost in hub regions and disrupted information transfer across the metabolic network. Our results highlight the fundamental role that metabolism plays in supporting information transfer in the brain and the unique insights that metabolic connectivity provides into the ageing brain.