IUBio

Increased blood flow detected by fMRI scans?

Brian zhil at online.no
Sat Oct 20 14:39:59 EST 2001


"Richard Norman" <rsnorman at mediaone.net> skrev i melding
news:lmd3ttgv1s43jeda5eqjforg38t8e4ilh4 at 4ax.com...
> >> 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?

Yes, it would be nice if I could answer these questions, but I'd say that as
they were measuring in monkeys that were unconscious, they would not have
measure the real energy usage.
Protein production for growth of the synapses are probably the greatest user
of oxygenated blood.
Recycling (as they said) would in part be accounted for by anaerobic burning
of glucose.
The rest would in be used by the cell for homeostasis.
As for action potentials, they would be the small increase of the oxygenated
blood.
That is; recycling from cyclic AMP to ATP.
I'd guess that the phosphorylation should be the next step, although I have
no idea how they would accomplish that.
But for percentages...............that is the main question.

Brian





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