Revealing layer-specific cortical activity in human M1 using high-resolution line-scanning fMRI

Area of Science:

• Neuroimaging
• Functional Magnetic Resonance Imaging (fMRI)
• Human Brain Activity

Background:

• Ultra-high field fMRI enables study of cortical activity at high spatiotemporal resolution.
• Laminar fMRI is crucial for understanding local brain circuits and function.
• Previous line-scanning fMRI in animals showed laminar differences, but human application faced challenges with safety limits and temporal resolution.

Purpose of the Study:

• To present a novel gradient-echo-based human line-scanning fMRI method.
• To achieve high spatiotemporal resolution for laminar fMRI in humans.
• To investigate laminar differences in the hemodynamic response during a motor task.

Main Methods:

• Developed a human line-scanning fMRI technique using four saturation regions.
• Achieved a narrow Full Width at Half Maximum (FWHM) of 3.9 mm and a repetition time (TR) of 250 ms.
• Acquired laminar fMRI data in the human motor cortex during a finger-tapping task.

Main Results:

• Demonstrated high spatiotemporal resolution (voxel size 0.39 x 3.0 x 3.0 mm³).
• Observed distinct temporal dynamics of the Blood-Oxygen-Level-Dependent (BOLD) response across cortical layers.
• Deeper layers showed an earlier BOLD response peak and faster return to baseline compared to superficial layers.

Conclusions:

• Line-scanning fMRI is a valuable tool for high-resolution human brain imaging.
• This method allows investigation of laminar differences in neural activity.
• Findings advance understanding of the mechanistic nature of the BOLD response across cortical layers.