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Investigating the dependence of BOLD contrast on oxidative metabolism
Author(s) -
Schwarzbauer Christian,
Heinke Wolfgang
Publication year - 1999
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/(sici)1522-2594(199903)41:3<537::aid-mrm16>3.0.co;2-v
Subject(s) - oxidative metabolism , contrast (vision) , oxidative phosphorylation , chemistry , nuclear magnetic resonance , metabolism , biochemistry , computer science , physics , artificial intelligence
Most functional magnetic resonance imaging (fMRI) studies are based on measuring the changes in the blood oxygenation level–dependent (BOLD) contrast that arise from a complex interplay between cerebral hemodynamics and oxidative metabolism. To separate these effects, we consecutively applied two different stimuli: visual stimulation (black/white checkerboard alternating with a frequency of 8 Hz) and hypercapnia (inspiration of 5% co 2 ). Changes in cerebral blood flow (ΔCBF) and the effective transverse relaxation time ( T * 2 ) were measured in an interleaved manner by combining a previously described spin‐labeling technique with BOLD‐based fMRI. In six healthy volunteers, T * 2 was significantly longer during hypercapnia than during visual stimulation, whereas the corresponding ΔCBF values were the same at the given level of significance ( P < 0.01). This finding is explained by a significant increase in oxygen consumption under visual stimulation. The average T * 2 changes in the visual cortex related to cerebral hemodynamics and oxidative metabolism were 10.6 ± 3.0% and −4.7 ± 1.2%, respectively, resulting in a net increase of 5.9 ± 2.3%. Although the hemodynamic effect is dominant, the increase in oxidative metabolism gives rise to a significant decrease in BOLD contrast. The calculated average change in the cerebral metabolic rate of oxygen ( CMRo 2 ), 4.4 ± 1.1% ( N = 6), is in excellent agreement with previous results obtained by positron emission tomography. Magn Reson Med 41:537–543, 1999. © 1999 Wiley‐Liss, Inc.