Cortical layer-dependent arterial blood volume changes: improved spatial specificity relative to BOLD fMRI

Area of Science:

• Neuroimaging
• Functional Magnetic Resonance Imaging (fMRI)
• Hemodynamics

Background:

• Functional hemodynamic responses are crucial for understanding brain activity.
• Conventional BOLD (Blood Oxygen Level Dependent) signals have limitations in spatial specificity.
• Magnetization transfer (MT)-varied gradient-echo (GE) fMRI offers a novel approach to separate arterial blood and tissue signals.

Purpose of the Study:

• To examine the spatial specificity of functional hemodynamic responses.
• To simultaneously map BOLD changes and quantitative cerebral arterial blood volume (DeltaCBV(a)) changes across cortical depth.
• To compare the spatial localization of DeltaCBV(a) and BOLD signals.

Main Methods:

• Simultaneous mapping of BOLD and DeltaCBV(a) in cats using 9.4 T fMRI.
• Utilized a non-invasive MT-varied GE fMRI technique.
• Separated signals from arterial blood and tissue based on MT properties.

Main Results:

• Highest conventional BOLD signal changes were observed at the cortical surface.
• Highest DeltaCBV(a) changes occurred in the middle cortical layers.
• DeltaCBV(a) measurements showed better spatial localization to neural activity sites compared to BOLD signals.

Conclusions:

• Quantitative DeltaCBV(a) measurement provides superior spatial specificity in high-resolution fMRI.
• MT-varied GE fMRI is valuable for precise localization of hemodynamic responses.
• Findings suggest DeltaCBV(a) is a more accurate marker for neural activity localization than conventional BOLD.