Negative dip in BOLD fMRI is caused by blood flow--oxygen consumption uncoupling in humans.
The sensitivity of MRI for local changes in the deoxyhemoglobin concentration is the basis of the blood oxygen level dependent (BOLD) effect. Time-resolved fMRI studies during visual activation show an early signal intensity (SI) decrease indicating a short lasting uncoupling of oxygen consumption and cerebral blood flow (CBF) before a SI increase due to the overcompensating hemodynamic response occurs. Normal neuronal activity may be preserved despite absent vascular responsiveness. Here we show that a negative BOLD effect occurs during motor activation in an asymptomatic patient with severely disturbed cerebral autoregulation due to extracranial artery disease. This is thought to be due to oxygen consumption in the absence of a hemodynamic response. This rare case of a persisting uncoupling of oxygen metabolism and CBF serves as a model that supports changes of the cerebral blood oxygen saturation as the major contributor of the BOLD effect.
Röther
Joachim
J
Department of Neurology, University Hospital Hamburg Eppendorf, Hamburg, Germany.
Knab
Rene
R
Hamzei
Farsin
F
Fiehler
Jens
J
Reichenbach
Jürgen R
JR
Büchel
Christian
C
Weiller
Cornelius
C
D000368:Aged; D001921:Brain / Q000098:blood supply / Q000503:physiopathology*; D001931:Brain Mapping; D016893:Carotid Stenosis / Q000175:diagnosis / Q000503:physiopathology; D002540:Cerebral Cortex / Q000098:blood supply / Q000503:physiopathology; D006454:Hemoglobins / Q000378:metabolism*; D006706:Homeostasis / Q000502:physiology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D002546:Ischemic Attack, Transient / Q000175:diagnosis / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D010101:Oxygen Consumption / Q000502:physiology*; D012039:Regional Blood Flow; D014715:Vertebrobasilar Insufficiency / Q000175:diagnosis / Q000503:physiopathology
D006454:Hemoglobins; C100003:deoxyhemoglobin