Vascular coupling in resting-state fMRI: evidence from multiple modalities

Area of Science:

• Neuroimaging
• Physiology
• Medical Physics

Background:

• Resting-state functional magnetic resonance imaging (rs-fMRI) is used to study intrinsic brain connectivity.
• The influence of vascular effects on rs-fMRI signals remains incompletely understood.

Purpose of the Study:

• To investigate the extent to which vascular effects contribute to rs-fMRI signals.
• To evaluate the impact of common preprocessing techniques on vascular signal components in rs-fMRI.

Main Methods:

• Utilized multi-modal imaging to assess vascular signal fluctuations and their coupling with physiological parameters (arterial pressure, CBF velocity, brain tissue oxygenation) below 0.08 Hz.
• Analyzed blood oxygen level-dependent (BOLD) signals from six regions of interest (ROIs).
• Applied preprocessing steps including global, white-matter, and CSF signal regression, along with low-pass filtering (<0.08 Hz).

Main Results:

• Marked vascular signal fluctuations were observed, tightly coupled with physiological parameters below 0.08 Hz.
• BOLD signals in ROIs exhibited similar spectral power distributions to physiological signals.
• Preprocessing significantly reduced BOLD signal spectral power (55.6%-64.9%) and inter-ROI coherence (9.9%-37.3%).
• Global signal regression demonstrated the most substantial reduction in both spectral power and coherence.

Conclusions:

• A significant portion of rs-fMRI signal variance may be attributable to vascular and hemodynamic changes.
• Standard rs-fMRI preprocessing methods can substantially attenuate these vascular contributions.
• Findings necessitate critical re-evaluation of the neurogenic interpretation of rs-fMRI connectivity data.