title: Reliability of the depth-dependent high-resolution BOLD hemodynamic response in human visual cortex and vicinity.
abstract: Functional magnetic resonance imaging (fMRI) often relies on a hemodynamic response function (HRF), the stereotypical blood oxygen level dependent (BOLD) response elicited by a brief (<4s) stimulus. Early measurements of the HRF used coarse spatial resolutions (≥3mm voxels) that would generally include contributions from white matter, gray matter, and the extra-pial compartment (the space between the pial surface and skull including pial blood vessels) within each voxel. To resolve these contributions, high-resolution fMRI (0.9-mm voxels) was performed at 3T in early visual cortex and its apposed white-matter and extra-pial compartments. The results characterized the depth dependence of the HRF and its reliability during nine fMRI sessions. Significant HRFs were observed in white-matter and extra-pial compartments as well as in gray matter. White-matter HRFs were faster and weaker than in the gray matter, while extra-pial HRFs were comparatively slower and stronger. Depth trends of the HRF peak amplitude were stable throughout a broad depth range that included all three compartments for each session. Across sessions, however, the depth trend of HRF peak amplitudes was stable only in the white matter and deep-intermediate gray matter, while there were strong session-to-session variations in the superficial gray matter and the extra-pial compartment. Thus, high-resolution fMRI can resolve significant and dynamically distinct HRFs in gray matter, white matter, and extra-pial compartments.
authors.affiliation: Department of Neuroscience, Core for Advanced MR Imaging, Baylor College of Medicine, Houston, TX 77030, USA. Electronic address: junghwan.kim@bcm.edu.
authors.forename: Jung Hwan
authors.initials: JH
authors.lastname: Kim
authors.affiliation: Department of Neuroscience, Core for Advanced MR Imaging, Baylor College of Medicine, Houston, TX 77030, USA.
authors.forename: David
authors.initials: D
authors.lastname: Ress
mesh_terms: D000328:Adult; D001931:Brain Mapping / Q000379:methods*; D005260:Female; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D015203:Reproducibility of Results; D014793:Visual Cortex / Q000000981:diagnostic imaging* / Q000502:physiology*; D055815:Young Adult
chemical_list: D010100:Oxygen
keywords: Brief stimulus-evoked neural activity; Cerebral hemodynamic response function; Cortical thickness; Pial vascular hemodynamic response; Signed-distance function; White matter hemodynamic response