On Fri, 19 Oct 2001 15:16:56 +1000, "Andrew Gyles"
<syzygium at alphalink.com.au> wrote:
>Blood oxygen level dependent functional magnetic resonance imaging (BOLD
>fMRI) scans show active regions of the brain. It has been assumed that the
>excess of oxygen detected in an active region is brought there by increased
>blood flow.
>>Has this assumption of increased blood flow been proved correct by
>experiment?
>>Andrew Gyles
Try looking in places like
http://www.fmrib.ox.ac.uk/fmri_intro/physiology.html
or
http://www.sciam.com/2001/1001issue/1001scicit6.html
The specific experimental work you want is
Logothetis NK, Pauls J, Augath M, Trinath T, Oeltermann A.
Neurophysiological investigation of the basis of the fMRI signal.
Nature. 2001 Jul 12;412(6843):150-7.
The relation to oxygenation is quite certain, since we know
just what molecular properties produce the MRI signal -- it
is the oxygenation state of hemoglobin. What Logothetis
et al. did was relate it to neurophysiological recordings.
They found that the BOLD fMRI (blood-oxygen-level-dependent)
signals were correlated mostly with the local field potentials, not
the single unit or multiunit spike recordings. They say "These
findings suggest that the BOLD contrast mechanism reflects the input
and intracortical processing of a given area rather than its spiking
output."
