title: Cortical lamina-dependent blood volume changes in human brain at 7 T.
abstract: Cortical layer-dependent high (sub-millimeter) resolution functional magnetic resonance imaging (fMRI) in human or animal brain can be used to address questions regarding the functioning of cortical circuits, such as the effect of different afferent and efferent connectivities on activity in specific cortical layers. The sensitivity of gradient echo (GE) blood oxygenation level-dependent (BOLD) responses to large draining veins reduces its local specificity and can render the interpretation of the underlying laminar neural activity impossible. The application of the more spatially specific cerebral blood volume (CBV)-based fMRI in humans has been hindered by the low sensitivity of the noninvasive modalities available. Here, a vascular space occupancy (VASO) variant, adapted for use at high field, is further optimized to capture layer-dependent activity changes in human motor cortex at sub-millimeter resolution. Acquired activation maps and cortical profiles show that the VASO signal peaks in gray matter at 0.8-1.6mm depth, and deeper compared to the superficial and vein-dominated GE-BOLD responses. Validation of the VASO signal change versus well-established iron-oxide contrast agent based fMRI methods in animals showed the same cortical profiles of CBV change, after normalization for lamina-dependent baseline CBV. In order to evaluate its potential of revealing small lamina-dependent signal differences due to modulations of the input-output characteristics, layer-dependent VASO responses were investigated in the ipsilateral hemisphere during unilateral finger tapping. Positive activation in ipsilateral primary motor cortex and negative activation in ipsilateral primary sensory cortex were observed. This feature is only visible in high-resolution fMRI where opposing sides of a sulcus can be investigated independently because of a lack of partial volume effects. Based on the results presented here, we conclude that VASO offers good reproducibility, high sensitivity and lower sensitivity than GE-BOLD to changes in larger vessels, making it a valuable tool for layer-dependent fMRI studies in humans.
authors.affiliation: Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany. Electronic address: renzo@cbs.mpg.de.
authors.forename: Laurentius
authors.initials: L
authors.lastname: Huber
authors.affiliation: Institute of Neuroscience and Psychology, University of Glasgow, Glasgow, UK; Max Planck Institute for Biological Cybernetics, Tübingen, Germany.
authors.forename: Jozien
authors.initials: J
authors.lastname: Goense
authors.affiliation: Signal Processing in Neuroimaging and Systems Neuroscience, University of Sheffield, Sheffield, UK.
authors.forename: Aneurin J
authors.initials: AJ
authors.lastname: Kennerley
authors.affiliation: Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Trampel
authors.affiliation: Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany.
authors.forename: Maria
authors.initials: M
authors.lastname: Guidi
authors.affiliation: Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany.
authors.forename: Enrico
authors.initials: E
authors.lastname: Reimer
authors.affiliation: Maastricht Brain Imaging Centre, Maastricht University, Maastricht, The Netherlands.
authors.forename: Dimo
authors.initials: D
authors.lastname: Ivanov
authors.affiliation: Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany.
authors.forename: Nicole
authors.initials: N
authors.lastname: Neef
authors.affiliation: Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany.
authors.forename: Claudine J
authors.initials: CJ
authors.lastname: Gauthier
authors.affiliation: Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Turner
authors.affiliation: Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany.
authors.forename: Harald E
authors.initials: HE
authors.lastname: Möller
mesh_terms: D000328:Adult; D000465:Algorithms; D000818:Animals; D001808:Blood Vessels / Q000033:anatomy & histology; D001810:Blood Volume / Q000502:physiology*; D001921:Brain / Q000033:anatomy & histology*; D002540:Cerebral Cortex / Q000033:anatomy & histology* / Q000098:blood supply / Q000502:physiology*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D004525:Efferent Pathways / Q000033:anatomy & histology / Q000502:physiology; D005260:Female; D005290:Ferric Compounds; D005385:Fingers / Q000294:innervation / Q000502:physiology; D000882:Haplorhini; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D009044:Motor Cortex / Q000033:anatomy & histology / Q000502:physiology; D009068:Movement / Q000502:physiology; D010100:Oxygen / Q000097:blood; D051381:Rats; D059629:Signal-To-Noise Ratio; D055815:Young Adult
chemical_list: D005290:Ferric Compounds; C000499:ferric oxide; D010100:Oxygen
keywords: 7Tesla MRI; Cerebral blood volume; Cortical profiles; Layer-dependent fMRI; Negative BOLD response; SS-SI-VASO; Vascular space occupancy