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Functional MRI of somatosensory activation in rat: Effect of hypercapnic tip‐regulation on perfusion‐ and BOLD‐imaging
Author(s) -
Bock Christian,
Schmitz Bernd,
Kerskens Christian M.,
Gyngell Michael L.,
Hossmann KonstantinAlexander,
HoehnBerlage Mathias
Publication year - 1998
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/mrm.1910390316
Subject(s) - perfusion , functional magnetic resonance imaging , somatosensory system , magnetic resonance imaging , functional imaging , stimulation , perfusion scanning , oxygenation , blood oxygen level dependent , medicine , nuclear medicine , neuroscience , nuclear magnetic resonance , chemistry , cardiology , psychology , radiology , physics
Functional activation of somatosensory cortex was studied in α‐chloralose anesthetized rats by functional magnetic resonance imaging (fMRI), using both perfusion–weighted and T 2 *–weighted (blood oxygenation level dependent, BOLD) imaging. The sensitivity of functional activation was altered by ventilating animals for 3 minutes with 6% CO 2 . Before hyper–capnic conditioning, electrical stimulation of the left forepaw at a frequency of 3 Hz led to an increase of signal intensity (relative to the unstimulated baseline condition) in the right somatosensory cortex by 6 ± 2% (means ± SD) in T 2 *–weighted images and by 45% ± 48% in perfusion–weighted images. After hypercapnic conditioning the signal intensity increase in perfusion–weighted images doubled to 91% ± 62% ( P = 0.034), whereas that of T 2 *–weighted images only marginally increased to 7 ± 4% (not significant). This different behavior in both imaging modalities is interpreted as evidence for an increased flow response in combination with a higher oxygen extraction. Thus, the fMRI data reflect hypercapniainduced resetting of the functional–metabolic coupling of the tissue during activation.