Unveiling functional-metabolic synergy in the healthy brain: multivariate integration of dynamic [¹⁸F]FDG-PET and...

Despite accounting for only 2% of body weight, the human brain requires significant amounts of glucose, even at rest, underscoring the importance of functional-metabolic relationships. Previous studies revealed moderate associations between resting-state fMRI functional connectivity (FC) and local metabolism via [¹⁸F]FDG-PET, yet much remains to be understood, particularly regarding their coupling between functional and metabolic networks.

To this end, we employed multivariate Partial Least Squares Correlation (PLSC) to investigate the functional-metabolic relationship at both nodal and network level. From dynamic [¹⁸F]FDG-PET data we estimated parameters describing glucose metabolism -delivery rate ( $K_1$ ), phosphorylation rate ( $k_3$ ), and fractional uptake ( $K_{\text{i}}$ )- and generated within-individual metabolic connectivity (MC) networks. FC was derived from fMRI data filtered into two frequency bands and summarized as region-wise strength to capture nodal characteristics.

Our findings revealed that glucose delivery is linked with FC strength, particularly when fMRI signal frequencies include greater hemodynamic contributions. Even stronger functional-metabolic coupling occurs at the network level in the low-frequency fMRI band, with higher MC between sensory/attention and transmodal networks supporting stronger FC within sensory/attention areas.

By leveraging PLSC, this work deepens our understanding of the functional-metabolic synergy in the healthy brain, providing new insights into its organization.