Sustained negative BOLD, blood flow and oxygen consumption response and its coupling to the positive response in the human brain.
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.
Shmuel
Amir
A
Center for Magnetic Resonance Research, University of Minnesota Medical School, Minneapolis, MN 55455, USA. amirs@cmrr.umn.edu
Yacoub
Essa
E
Pfeuffer
Josef
J
Van de Moortele
Pierre Francois
PF
Adriany
Gregor
G
Hu
Xiaoping
X
Ugurbil
Kamil
K
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*