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Point-spread function of the BOLD response across columns and cortical depth in human extra-striate cortex
Alessio Fracasso1, Serge O Dumoulin2, Natalia Petridou3
1University of Glasgow, Institute of Neuroscience and Psychology, Glasgow, Scotland, United Kingdom.
Progress in Neurobiology
|March 20, 2021
Summary
High-resolution functional MRI can now image brain columns and layers. This study measured the blood oxygen level dependent (BOLD) point-spread function (PSF) across cortical depth in human V2. The BOLD PSF was largest superficially and decreased with depth.
Area of Science:
- Neuroimaging
- Human Brain Anatomy
- Functional Magnetic Resonance Imaging (fMRI)
Background:
- Brain organization relies on fundamental units like columns and layers, exemplified by ocular dominance columns (ODCs) and V2 stripes.
- Conventional neuroimaging lacks the resolution to study these structures, but ultra-high field (UHF) magnetic resonance imaging (MRI) offers new possibilities.
- Blood oxygen level dependent (BOLD) fMRI is a key non-invasive technique for measuring brain activity indirectly through hemodynamic changes.
Purpose of the Study:
- To investigate the spatial characteristics of the BOLD response in relation to neuronal activity at the scale of cortical layers and columns.
- To estimate the BOLD point-spread function (PSF) across cortical depth in human V2 using high-resolution fMRI.
Main Methods:
- Utilized sub-millimeter anatomical and gradient-echo BOLD (GE BOLD) acquisitions at 7 Tesla (7T) in human participants.
- Leveraged the stripe-based organization of visual area V2 to obtain in-vivo PSF estimates along cortical depth.
- Acquired high-resolution fMRI data to resolve fine-scale brain structures.
Main Results:
- The BOLD point-spread function (PSF) was found to be maximal in the superficial layers of the cortex, measuring 1.78 mm.
- The BOLD PSF exhibited a decreasing trend with increasing cortical depth, reaching 0.83 mm near the white matter.
- These findings provide crucial information about the spatial resolution limits of BOLD fMRI in deep cortical layers.
Conclusions:
- High-resolution 7T GE BOLD fMRI can resolve fine-scale functional organization within the human cortex.
- The spatial spread of the BOLD response varies significantly across cortical depth, impacting the interpretation of high-resolution fMRI studies.
- Understanding the BOLD PSF across cortical depth is essential for accurately mapping brain activity at the columnar and laminar levels.
