title: Sustained negative BOLD, blood flow and oxygen consumption response and its coupling to the positive response in the human brain.
abstract: Most fMRI studies are based on the detection of a positive BOLD response (PBR). Here, we demonstrate and characterize a robust sustained negative BOLD response (NBR) in the human occipital cortex, triggered by stimulating part of the visual field. The NBR was spatially adjacent to but segregated from the PBR. It depended on the stimulus and thus on the pattern of neuronal activity. The time courses of the NBR and PBR were similar, and their amplitudes covaried both with increasing stimulus duration and increasing stimulus contrast. The NBR was associated with reductions in blood flow and with decreases in oxygen consumption. Our findings support the contribution to the NBR of (1) a significant component of reduction in neuronal activity and (2) possibly a component of hemodynamic changes independent of the local changes in neuronal activity.
authors.affiliation: Center for Magnetic Resonance Research, University of Minnesota Medical School, Minneapolis, MN 55455, USA. amirs@cmrr.umn.edu
authors.forename: Amir
authors.initials: A
authors.lastname: Shmuel
authors.forename: Essa
authors.initials: E
authors.lastname: Yacoub
authors.forename: Josef
authors.initials: J
authors.lastname: Pfeuffer
authors.forename: Pierre Francois
authors.initials: PF
authors.lastname: Van de Moortele
authors.forename: Gregor
authors.initials: G
authors.lastname: Adriany
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Hu
authors.forename: Kamil
authors.initials: K
authors.lastname: Ugurbil
mesh_terms: D000328:Adult; D000465:Algorithms; D001931:Brain Mapping; D002560:Cerebrovascular Circulation / Q000502:physiology*; D015350:Contrast Sensitivity / Q000502:physiology; D004734:Energy Metabolism / Q000502:physiology*; D005074:Evoked Potentials, Visual / Q000502:physiology; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D009474:Neurons / Q000502:physiology; D010101:Oxygen Consumption / Q000502:physiology*; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation; D011930:Reaction Time / Q000502:physiology; D014793:Visual Cortex / Q000033:anatomy & histology / Q000502:physiology*