Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
6 Pt 1
pubmed:dateCreated
1999-7-28
pubmed:abstractText
Blood oxygenation level-dependent (BOLD) fMRI signals often exhibit pronounced over- or undershoot upon changes in stimulation state. Current models postulate that this is due to the delayed onset or decay of perfusion-dependent attenuating responses such as increased cerebral blood volume or oxygen consumption, which are presumed to lag behind the rapid adjustment of blood flow rate to a new steady-state level. If this view is correct, then BOLD overshoot amplitudes in a specific tissue volume should be correlated with steady-state increases in perfusion, independent of stimulus type. To test this prediction, we simultaneously recorded BOLD and relative perfusion signals in primary visual cortex while inducing graded perfusion increases with three types of visual stimulus. Two of these, a diffuse chromatic stimulus with no luminance variation and a very high spatial frequency luminance grating, did not produce detectable BOLD overshoot (or undershoot) when an equal mean luminance baseline was used. Radial checkerboard stimuli, however, caused pronounced over/undershoot of both BOLD and perfusion signals even when temporal mean luminance was held constant and stimulus contrast was adjusted to produce the same steady-state blood flow increases evoked by the other stimuli. Transient amplitudes were relatively invariant in spite of large changes in steady-state response, demonstrating nonlinear BOLD and perfusion step responses in human V1. These findings suggest that, rather than a purely tissue-specific biomechanical or metabolic phenomenon, BOLD overshoot and undershoot represent transient features in the perfusion signal whose effects may be amplified by slowly evolving blood volume changes.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jun
pubmed:issn
1053-8119
pubmed:author
pubmed:copyrightInfo
Copyright 1999 Academic Press.
pubmed:issnType
Print
pubmed:volume
9
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
573-85
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
1999
pubmed:articleTitle
Stimulus-dependent BOLD and perfusion dynamics in human V1.
pubmed:affiliation
McConnell Brain Imaging Centre, Montreal Neurological Institute, McGill University, Montreal, Quebec H3A 2B4, Canada.
pubmed:publicationType
Journal Article, Clinical Trial, Randomized Controlled Trial, Research Support, Non-U.S. Gov't