Info requested on Neuroimaging

Harm-Jan Wieringa wieringa at
Tue Nov 3 10:38:00 EST 1998

Hello Luke,

> A neuroradiologist told me once that sometime in the next few years,
>fMRI is going to be done by imaging intracellular vs. extracellular
>sodium ions, which will remove this time lag.  It's a lot easier to get
>a strong signal from protons, and it is probably very difficult to
>distinguish intra- and extra-cellular from chemical shift (when it's
>chemical shift coming from atoms that aren't even in the same molecule),
>so my uninformed speculation is that the techniques they come up with
>might require high-budget specialized magnets, not the kind you find in
>most hospitals.  One thing of interest is that this technique would
>directly image neural activity, not blood oxygenation levels or
>something thought to correlate with neural activity...

If you can image those directly then, naturally, the hemodynamic time delay
is out of the picture. But you need high-resolution functional imaging, and
that takes time and probably a high-field. I know that in Japan they have 8T
scanners and will get a 14T one.
Normal ones can do anatomical scans up to about 1 mm. resolution (NOT

>> There are efforts on the way to combine both techniques. They may
>> each other. Some go even so far as to measure the EEG in the MRI scanner,
>> during an fMRI experiment.
> I've heard of that, but I didn't realize they did them both at the same
>time.  I wonder how they keep the two from interfering with each other?
See for instance

Duringt the RF pulse you do have distortion of the EEG, but that is usually
no problem. For instance for Epilepsy, you see the spike-wave in the EEG,
then start the fMRI scan and catch that brain activity in the fMRI (thanks
to the delay of the hemodynamic response).


More information about the Neur-sci mailing list