Regional differences in the coupling of cerebral blood flow and oxygen metabolism changes in response to activation: Implications for BOLD-fMRI

• Published in: NeuroImage (Orlando, Fla.) Fla.), 2008-02, Vol.39 (4), p.1510-1521
• Main Authors: Ances, Beau M., Leontiev, Oleg, Perthen, Joanna E., Liang, Christine, Lansing, Amy E., Buxton, Richard B.
• Format: Article
• Language: English
• Subjects: Adult; Algorithms; Arterial spin labeling (ASL); Blood oxygenation level dependent (BOLD) effect; Brain; Brain - anatomy & histology; Brain research; Calibration; Carbon Dioxide - blood; Cerebral blood flow; Cerebral metabolic rate of oxygen consumption; Cerebrovascular Circulation - physiology; Corpus Striatum - anatomy & histology; Corpus Striatum - blood supply; Data Interpretation, Statistical; Female; fMRI; Humans; Hypercapnia; Hypercapnia - pathology; Image Processing, Computer-Assisted; Lentiform nuclei of the basal ganglia; Magnetic Resonance Imaging - methods; Male; Metabolism; Middle Aged; Neurovascular coupling; NMR; Nuclear magnetic resonance; Oxygen - blood; Oxygen Consumption - physiology; Visual Cortex - anatomy & histology; Visual Cortex - blood supply
• ISSN: 1053-8119; 1095-9572
• DOI: 10.1016/j.neuroimage.2007.11.015

Functional magnetic resonance imaging (fMRI) based on blood oxygenation level dependent (BOLD) signal changes is a sensitive tool for mapping brain activation, but quantitative interpretation of the BOLD response is problematic. The BOLD response is primarily driven by cerebral blood flow (CBF) changes, but is moderated by M, a scaling parameter reflecting baseline deoxyhemoglobin, and n, the ratio of fractional changes in CBF to cerebral metabolic rate of oxygen consumption (CMRO 2). We compared M and n between cortical (visual cortex, VC) and subcortical (lentiform nuclei, LN) regions using a quantitative approach based on calibrating the BOLD response with a hypercapnia experiment. Although M was similar in both regions (∼ 5.8%), differences in n (2.21 ± 0.03 in VC and 1.58 ± 0.03 in LN; Cohen d = 1.71) produced substantially weaker (∼ 3.7x) subcortical than cortical BOLD responses relative to CMRO 2 changes. Because of this strong sensitivity to n, BOLD response amplitudes cannot be interpreted as a quantitative reflection of underlying metabolic changes, particularly when comparing cortical and subcortical regions.