IUBio

Increased blood flow detected by fMRI scans?

Richard Norman rsnorman at mediaone.net
Sat Oct 20 12:44:23 EST 2001


On Sat, 20 Oct 2001 18:24:14 +0200, "Brian" <zhil at online.no> wrote:

>"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

Yes, it is a tautology that oxygen use correlates with metabolism.
The question is what cellular processes of the neuron consume the most
energy?  Is it making action potentials?  Or is it synaptic
transmitter synthesis (and recycling)?  Or is it all the cell
processes that go along with neuromodulation, including up- and
down-regulation of membrane proteins?  Or just what?  





More information about the Neur-sci mailing list

Send comments to us at biosci-help [At] net.bio.net