title: Neurochemical and BOLD responses during neuronal activation measured in the human visual cortex at 7 Tesla.
abstract: Several laboratories have consistently reported small concentration changes in lactate, glutamate, aspartate, and glucose in the human cortex during prolonged stimuli. However, whether such changes correlate with blood oxygenation level-dependent functional magnetic resonance imaging (BOLD-fMRI) signals have not been determined. The present study aimed at characterizing the relationship between metabolite concentrations and BOLD-fMRI signals during a block-designed paradigm of visual stimulation. Functional magnetic resonance spectroscopy (fMRS) and fMRI data were acquired from 12 volunteers. A short echo-time semi-LASER localization sequence optimized for 7 Tesla was used to achieve full signal-intensity MRS data. The group analysis confirmed that during stimulation lactate and glutamate increased by 0.26 ± 0.06 μmol/g (~30%) and 0.28 ± 0.03 μmol/g (~3%), respectively, while aspartate and glucose decreased by 0.20 ± 0.04 μmol/g (~5%) and 0.19 ± 0.03 μmol/g (~16%), respectively. The single-subject analysis revealed that BOLD-fMRI signals were positively correlated with glutamate and lactate concentration changes. The results show a linear relationship between metabolic and BOLD responses in the presence of strong excitatory sensory inputs, and support the notion that increased functional energy demands are sustained by oxidative metabolism. In addition, BOLD signals were inversely correlated with baseline γ-aminobutyric acid concentration. Finally, we discussed the critical importance of taking into account linewidth effects on metabolite quantification in fMRS paradigms.
authors.affiliation: 1] Department of Radiology, Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, USA [2] Division of Endocrinology, Department of Medicine, University of Minnesota, Minneapolis, Minnesota, USA [3] Multimodal and Functional Neuroimaging Research Group, CEITEC-Central European Institute of Technology, Masaryk University, Brno, Czech Republic.
authors.forename: Petr
authors.initials: P
authors.lastname: Bednařík
authors.affiliation: Department of Radiology, Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, USA.
authors.forename: Ivan
authors.initials: I
authors.lastname: Tkáč
authors.affiliation: 1] MARBILab, Museo storico della fisica e Centro di studi e ricerche Enrico Fermi, Rome, Italy [2] Fondazione Santa Lucia IRCCS, Rome, Italy.
authors.forename: Federico
authors.initials: F
authors.lastname: Giove
authors.affiliation: 1] MARBILab, Museo storico della fisica e Centro di studi e ricerche Enrico Fermi, Rome, Italy [2] Fondazione Santa Lucia IRCCS, Rome, Italy.
authors.forename: Mauro
authors.initials: M
authors.lastname: DiNuzzo
authors.affiliation: Department of Radiology, Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, USA.
authors.forename: Dinesh K
authors.initials: DK
authors.lastname: Deelchand
authors.affiliation: FMRIB Centre, University of Oxford, Oxford, UK.
authors.forename: Uzay E
authors.initials: UE
authors.lastname: Emir
authors.affiliation: Division of Biostatistics, School of Public Health, University of Minnesota, Minneapolis, Minnesota, USA.
authors.forename: Lynn E
authors.initials: LE
authors.lastname: Eberly
authors.affiliation: Department of Radiology, Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, USA.
authors.forename: Silvia
authors.initials: S
authors.lastname: Mangia
mesh_terms: D000328:Adult; D005260:Female; D005947:Glucose / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism; D006801:Humans; D019344:Lactic Acid / Q000378:metabolism; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood*; D010775:Photic Stimulation; D014793:Visual Cortex / Q000502:physiology*; D055815:Young Adult; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D019344:Lactic Acid; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D005947:Glucose; D010100:Oxygen