Investigation of BOLD signal dependence on cerebral blood flow and oxygen consumption: The deoxyhemoglobin dilution model

Abstract

The relationship between blood oxygenation level-dependent (BOLD) MRI signals, cerebral blood flow (CBF), and oxygen consumption (CMR O 2 ) in the physiological steady state was investigated. A quantitative model, based on flow-dependent dilution of metabolically generated deoxyhemoglobin, was validated by measuring BOLD signals and relative CBF simultaneously in the primary visual cortex (V1) of human subjects (N ‫؍‬ 12) during graded hypercapnia at different levels of visual stimulation. BOLD and CBF responses to specific conditions were averaged across subjects and plotted as points in the BOLD-CBF plane, tracing out lines of constant CMR O 2 . The quantitative deoxyhemoglobin dilution model could be fit to these measured iso-CMR O 2 contours without significant (P I 0.05) residual error and yielded MRI-based CMR O 2 measurements that were in agreement with PET results for equivalent stimuli. BOLD and CBF data acquired during graded visual stimulation were then substituted into the model with constant parameters varied over plausible ranges. Relative changes in CBF and CMR O 2 appeared to be coupled in an approximate ratio of D2:1 for all realistic parameter settings. Magn Reson Med 42:849

Global Cerebral Oxidative Metabolism during Hypercapnia and Hypocapnia in Humans: Implications for BOLD fMRI

“…In this study, we continuously monitored and minimized changes in PETO 2 through the use of computerized targeting facilitated by RespirAct, and were therefore able to achieve the isolation of CO 2 effects, which is a key requirement for the experiment at hand, and constitutes a basic assumption in numerous fMRI experiments using CO 2 challenges. Our results suggest that there are no significant alterations in global CMRO 2 due to these challenges, consistent with predictions obtained using the deoxyhemoglobin dilution model (Hoge et al, 1999). Although the current measurements show an absence of substantial global CMRO 2 modulation by low levels of PETCO 2 modulation, they do not preclude the possibility of spatial heterogeneities in the CMRO 2 response to capnic challenges.…”

Human Cerebral Blood Flow and Metabolism in Acute Insulin-Induced Hypoglycemia

“…The flow and transverse relaxation data have been incorporated into a model of deoxyhemoglobin concentration, oxygen extraction, and consumption by numerous workers (Ogawa et al, 1993;Davis et al, 1998;Hoge et al, 1999;Oja et al, 1999) expressed in equation (1). The blood susceptibility-induced transverse relaxation rate, R 2 0 , is calculated from the time reversible gradient echo relaxation rate, R 2 *, and time irreversible spin echo intrinsic relaxation rate, R 2intrinsic , corrected by the loss of signal from B o homogeneity (An and Lin, 2002;Yablonskiy, 2002).…”

“…These coupling ratios are consistent with several recent estimates of flow metabolism coupling during task activation. For example, using MR, Hoge et al (1999) reported fM/fP ratio of 0.52 for graded visual stimulation while Davis et al (1998) reported an fM/fP ratio of 0.35 using a 12 Hz visual stimulation paradigm. Using PET, Marrett and Gjedde (1997) report an fM/fP ratio of 0.37 with a 4 Hz visual stimulation protocol, while Fox and Raichle (1986) report an fM/fP ratio of 0.1 using somatosensory stimulation in their early PET studies.…”

A component based noise correction method (CompCor) for BOLD and perfusion based fMRI

“…When utilized together, the BOLD and perfusion signals can provide a quantitative understanding of the metabolic response to neural activity and provide insight into neurovascular coupling mechanisms (Hoge et al 1999). However, as the fMRI community has moved to higher field strengths, physiological noise has become an increasingly important confound limiting the sensitivity and the application of fMRI studies (Kruger and Glover 2001;Liu et al 2006).…”