Increased blood flow detected by fMRI scans?

Brian zhil at online.no
Sat Oct 20 11:24:14 EST 2001


"Richard Norman" <rsnorman at mediaone.net> skrev i melding
news:qfh1ttofdui4h57qd8ed6uq2dmt1r5u9lo at 4ax.com...
> 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."

In other words, they said that the energy-usage by the cell reflects the
oxygen-flow through the blood, while spike(s) are _not_(no big surprise
there, I would be much more surprised if the oxygen-level correlated with
the spikes...).

Brian





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