Default-mode network functional connectivity is closely related to metabolic activity

Area of Science:

• Neuroscience
• Brain Imaging
• Metabolic Imaging

Background:

• The brain's default-mode network (DMN) is crucial for cognition, but its functional connectivity mechanisms, particularly the blood-oxygen-level-dependent (BOLD) signal, remain unclear.
• Understanding the link between neural metabolism and DMN activity is essential for interpreting fMRI studies.

Purpose of the Study:

• To investigate the association between local glucose metabolism, glutamatergic neurotransmission, and DMN functional connectivity during rest.
• To elucidate the underlying mechanisms of the BOLD signal in the DMN.

Main Methods:

• Combined 2-deoxy-2-[(18)F]fluoroglucose positron emission tomography (FDG-PET), proton magnetic resonance spectroscopy ((1)H-MRS), and resting-state functional magnetic resonance imaging (rs-fMRI).
• Analyzed correlations between FDG-uptake, glutamatergic activity, and BOLD signal fluctuations in DMN regions, using the dorsal posterior cingulate cortex (dPCC) as a seed region.

Main Results:

• Spatial similarities were observed between FDG-uptake and BOLD signal fluctuations in DMN areas (inferior parietal lobe, angular gyrus, precuneus, medial frontal gyrus).
• Local glucose consumption in the medial frontal gyrus, PCC, and left angular gyrus was significantly associated with DMN functional connectivity.
• No significant relationship was found between glutamatergic neurotransmission and DMN functional connectivity.

Conclusions:

• Local metabolic activity, specifically glucose consumption, is closely associated with functional connectivity within the brain's default-mode network.
• These findings support the link between metabolism and BOLD signals, offering insights into the neurobiological underpinnings of resting-state fMRI.
• Glutamatergic neurotransmission did not show a direct association with DMN functional connectivity in this study.