Dissociations between glucose metabolism and blood oxygenation in the human default mode network revealed by simultaneous PET-fMRI
Proceedings of the National Academy of Sciences of the United States of America June 30, 2021 L. Stiernman, F. Grill, A. Hahn et al.
Negative fMRI signals in the brain's default mode network (DMN) during cognitive control do not reflect a relative increase in synaptic activity during rest periods. Using hybrid PET-MRI, the study found that task-positive BOLD responses in attention and control networks align with increased glucose metabolism during cognitive control, but metabolism in the DMN remained high during both rest and task despite negative BOLD responses. This dissociation indicates that DMN BOLD responses are not simply the inverse of metabolic activity, challenging common interpretations and suggesting distinct neurovascular coupling in this network.