TY - JOUR
T1 - Baseline blood oxygenation modulates response amplitude
T2 - Physiologic basis for intersubject variations in functional MRI signals
AU - Lu, Hanzhang
AU - Zhao, Chenguang
AU - Ge, Yulin
AU - Lewis-Amezcua, Kelly
PY - 2008/8
Y1 - 2008/8
N2 - Although BOLD functional MRI (fMRI) provides a useful tool for probing neuronal activities, large intersubject variations in signal amplitude are commonly observed. Understanding the physiologic basis for these variations will have a significant impact on many fMRI studies. First, the physiologic modulator can be used as a regressor to reduce variations across subjects, thereby improving statistical power for detecting group differences. Second, if a pathologic condition or a drug treatment is shown to change fMRI responses, monitoring this modulatory parameter is useful in correctly interpreting the fMRI changes to neuronal deficits/recruitments. Here we present evidence that the task-evoked fMRI signals are modulated by baseline blood oxygenation. To measure global blood oxygenation, we used a recently developed technique, T 2 relaxation under spin-tagging (TRUST) MRI, which yielded baseline oxygenation of 63.7% ± 7.2% in the sagittal sinus with an estimation error of 1.3%. It was found that individuals with higher baseline oxygenation tend to have a smaller fMRI signal, and vice versa. For every 10% difference in baseline oxygenation across subjects, BOLD and cerebral blood flow (CBF) signals differ by -0.4% and -30.0%, respectively, when using visual stimulation. TRUST MRI is a useful measurement for fMRI studies to control for the modulatory effects of baseline oxygenation that are unique to each subject.
AB - Although BOLD functional MRI (fMRI) provides a useful tool for probing neuronal activities, large intersubject variations in signal amplitude are commonly observed. Understanding the physiologic basis for these variations will have a significant impact on many fMRI studies. First, the physiologic modulator can be used as a regressor to reduce variations across subjects, thereby improving statistical power for detecting group differences. Second, if a pathologic condition or a drug treatment is shown to change fMRI responses, monitoring this modulatory parameter is useful in correctly interpreting the fMRI changes to neuronal deficits/recruitments. Here we present evidence that the task-evoked fMRI signals are modulated by baseline blood oxygenation. To measure global blood oxygenation, we used a recently developed technique, T 2 relaxation under spin-tagging (TRUST) MRI, which yielded baseline oxygenation of 63.7% ± 7.2% in the sagittal sinus with an estimation error of 1.3%. It was found that individuals with higher baseline oxygenation tend to have a smaller fMRI signal, and vice versa. For every 10% difference in baseline oxygenation across subjects, BOLD and cerebral blood flow (CBF) signals differ by -0.4% and -30.0%, respectively, when using visual stimulation. TRUST MRI is a useful measurement for fMRI studies to control for the modulatory effects of baseline oxygenation that are unique to each subject.
KW - Basal state
KW - Blood oxygenation
KW - Brain
KW - TRUST
KW - fMRI
UR - http://www.scopus.com/inward/record.url?scp=49049089731&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=49049089731&partnerID=8YFLogxK
U2 - 10.1002/mrm.21686
DO - 10.1002/mrm.21686
M3 - Article
C2 - 18666103
AN - SCOPUS:49049089731
SN - 0740-3194
VL - 60
SP - 364
EP - 372
JO - Magnetic resonance in medicine
JF - Magnetic resonance in medicine
IS - 2
ER -