title: Changes in baseline cerebral blood flow in humans do not influence regional cerebral blood flow response to photic stimulation.
abstract: The effect of changes in baseline regional cerebral blood flow (rCBF) values on the cerebral blood flow response during neuronal activation was studied with functional magnetic resonance imaging (fMRI). Using a breath-holding challenge as a hypercapnic stimulus, rCBF alterations during photic stimulation under normo- and hypercapnia were determined in nine volunteers. With breath-holding, baseline rCBF in areas corresponding to the visual cortex significantly increased from 54 +/- 5 ml/100 g/min to 85 +/- 9 ml/100 g/min (P < 0.001). Despite this significant change in baseline flow values, the rCBF increase during visual stimulation was very similar under normo- and hypercapnic conditions (28 +/- 8 ml/100 g/min versus 26 +/- 8 ml/100 g/min, respectively). This study supports the notion that within wide physiologic variations, task-induced cerebral blood flow changes are independent of baseline rCBF values.
authors.affiliation: Department of Diagnostic Radiology, Lucas MR Imaging and Spectroscopy Center, Stanford University School of Medicine, Stanford, California 94305-5488, USA. tieli@princeton.edu
authors.forename: T Q
authors.initials: TQ
authors.lastname: Li
authors.forename: A
authors.initials: A
authors.lastname: Kastrup
authors.forename: M E
authors.initials: ME
authors.lastname: Moseley
authors.forename: G H
authors.initials: GH
authors.lastname: Glover
mesh_terms: D000328:Adult; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005260:Female; D006801:Humans; D006935:Hypercapnia / Q000503:physiopathology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D010775:Photic Stimulation / Q000379:methods; D012016:Reference Values; D012039:Regional Blood Flow; D012680:Sensitivity and Specificity