Maximizing negative correlations in resting-state functional connectivity MRI by time-lag.

Area of Science:

• Neuroscience
• Physiology
• Medical Imaging

Background:

• Resting-state functional connectivity MRI (r-fcMRI) is a key tool for mapping brain networks.
• The physiological meaning of negative correlations in r-fcMRI remains incompletely understood.
• Understanding negative correlations may reveal insights into brain circulation regulation.

Purpose of the Study:

• To investigate the physiological basis of negative correlations in r-fcMRI.
• To compare negative and positive functional connections in human and rat brains.
• To explore the relationship between connectivity valence and physiological parameters like cerebral blood flow and volume.

Main Methods:

• Calculated resting-state functional connectivity MRI (r-fcMRI) between anatomy-based brain regions in 18 humans and 18 rats.
• Analyzed connectivity with and without global signal correction and spatial smoothing.
• Used T-statistics to differentiate positive and negative connections and assessed significance with time-lags.

Main Results:

• Spatial smoothing and global signal correction influenced positive connections more than negative ones.
• Positive connections were predominantly between cortical regions; negative connections were mainly between cortical and non-cortical structures.
• Negative connections became more significant with time-lags, unlike positive connections, particularly without global signal correction.

Conclusions:

• The valence of r-fcMRI connectivity may indicate location-specific contributions of cerebral blood volume (CBV) and cerebral blood flow (CBF) to the BOLD signal.
• Negative correlations could arise from differing regulation of CBF and CBV between brain regions or inhomogeneous responses.
• r-fcMRI connectivity valence offers a potential window into neuronal regulation of brain circulation.