Point-spread function of the BOLD response across columns and cortical depth in human extra-striate cortex

Area of Science:

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

Background:

• Brain organization relies on fundamental units like columns and layers.
• Conventional neuroimaging lacks the resolution to study these structures.
• Ultra-high field (UHF) MRI offers unprecedented in-vivo spatial resolution for human brain studies.

Purpose of the Study:

• To estimate the point-spread function (PSF) of the blood oxygen level dependent (BOLD) response across cortical depth.
• To assess the feasibility of high-resolution fMRI for resolving brain columns and layers.
• To investigate the spatial spread of the BOLD signal in relation to neuronal activity in human V2.

Main Methods:

• Utilized sub-millimeter anatomical and gradient-echo BOLD (GE BOLD) acquisitions at 7 Tesla.
• Leveraged the stripe-based organization of visual area V2 for PSF estimation.
• Acquired in-vivo, non-invasive fMRI data from human participants.

Main Results:

• The BOLD PSF was found to be maximal in the superficial cortical layers (1.78 mm).
• The BOLD PSF decreased with increasing cortical depth, reaching 0.83 mm near the white matter.
• Demonstrated depth-dependent spatial spread of the BOLD signal in human V2.

Conclusions:

• High-resolution 7T GE BOLD fMRI can resolve cortical layers and columns.
• Understanding the depth-dependent BOLD PSF is crucial for interpreting high-resolution fMRI data.
• This technique advances non-invasive in-vivo investigation of human brain functional and structural organization.