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The effect of transient hypercapnia on task‐related changes in cerebral blood flow and blood oxygenation in awake normal humans: a functional magnetic resonance imaging study
Author(s) -
Schwarzbauer Christian,
Hoehn Mathias
Publication year - 2000
Publication title -
nmr in biomedicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.278
H-Index - 114
eISSN - 1099-1492
pISSN - 0952-3480
DOI - 10.1002/1099-1492(200011)13:7<415::aid-nbm662>3.0.co;2-3
Subject(s) - hypercapnia , cerebral blood flow , functional magnetic resonance imaging , blood flow , hemodynamics , magnetic resonance imaging , anesthesia , nuclear magnetic resonance , perfusion , oxygenation , haemodynamic response , chemistry , medicine , neuroscience , psychology , blood pressure , acidosis , physics , heart rate , radiology
It has recently been reported in α‐chloralose anesthetized rats that the hemodynamic response to somatosensory stimulation almost doubled following transient hypercapnia (THC). In principle, this effect could be employed to enhance the sensitivity of perfusion‐based fMRI experiments. To investigate whether a comparable effect was detectable in awake normal humans, changes in cerebral blood flow (ΔCBF) and the effective transverse relaxation time (Δ T 2 *) induced by a visual search task were measured in 10 healthy volunteers before and after THC. Concerning Δ T 2 * no significant differences were found, whereas in four subjects ΔCBF was significantly decreased ( p < 0.01) following THC. These results demonstrate no increase in the CBF response following THC for awake humans. We conclude that the most likely explanation for this discrepancy with the earlier results obtained with animals is an as yet unknown mechanism of modulation of the cholinergic system by the anesthesia. Copyright © 2000 John Wiley & Sons, Ltd.Abbreviations used: ΔCBF change in cerebral blood flowfMRI functional magnetic resonance imagingGE gradient echo, MDEFT, modified driven equilibrium fourier transformSE spin echoSIDE simultaneous detectionTE se spin‐echo timeTE ge gradient‐echo timeTI inversion timeTR recovery timeΔ T 2 * effective transverse relaxation time.