Hi Nicky and SPM'ers

There is evidence that it is possible to detect activation in white matter (some example references below) but because it is so controversial, it's very important to verify that your registrations were OK. You might want to look at the activation at the individual subject level, overlaid on the subjects' brains, without performing any standard space registration.

Erin



Neuroimage. 2010 Apr 1;50(2):616-21. Epub 2010 Jan 4.
Confirming white matter fMRI activation in the corpus callosum: co-localization with DTI tractography.
Mazerolle EL, Beyea SD, Gawryluk JR, Brewer KD, Bowen CV, D'Arcy RC.

Neuroimage. 2009 Mar 1;45(1):83-8. Epub 2008 Nov 21.
Optimizing the detection of white matter fMRI using asymmetric spin echo spiral.
Gawryluk JR, Brewer KD, Beyea SD, D'Arcy RC.

PLoS One. 2009;4(1):e4257. Epub 2009 Jan 23.
BOLD correlates of trial-by-trial reaction time variability in gray and white matter: a multi-study fMRI analysis.
Yarkoni T, Barch DM, Gray JR, Conturo TE, Braver TS.

J Neurophysiol. 2002 Aug;88(2):1051-8.
Interhemispheric transmission of visuomotor information in humans: fMRI evidence.
Tettamanti M, Paulesu E, Scifo P, Maravita A, Fazio F, Perani D, Marzi CA.

________________________________________
From: SPM (Statistical Parametric Mapping) [[log in to unmask]] On Behalf Of Marko Wilke [[log in to unmask]]
Sent: May 11, 2010 3:58 AM
To: [log in to unmask]
Subject: Re: [SPM] corpus callosum activity in older adult sample

Hi Nicole,

In your population, the assumption of the common space (defined by young
and healthy adults) likely does not hold true, so I would not be too
worried about that (but then again, I have never been a strong believer
in the idea that coordinates will always tell you the truth :)

What I would do is to write out the normalized T1 (using the same seg_sn
parameters you used to normalize your EPIs) and then average them. If
you then overlay your activation on this average image, it should tell
you where your cluster actually is with respect to your group average.
Also, remember that smoothing will always blur the images so that parts
of a cluster may well be in CSF, WM, or air, so some inclusion of non-GM
is not too uncommon.

Hope this helps,
Marko

Nicole Kochan wrote:
> Dear SPMers,
>
> I have done an experiment with older adults aged 70-85 years (2 groups:
> cognitively well and Mild Cognitive Impairment). I normalized EPIs to
> MNI template by first coregistering and segmenting to individual T1s.
>
> I obtained a significant group x working memory load interaction at
> cluster-corrected threshold. When I looked up the co-ordinate for the
> global maxima it corresponded to the corpus callosum. The cluster also
> included anterior cingulate. A ROI analysis in anterior cingulate
> confirmed suprathreshold voxels.
>
> I expect that because my sample had a fair degree of atrophy including
> enlarged ventricles that when warped to the standardised template based
> on young healthy that the corpus callosum was stretched anteriorly and
> so that is why it "looks" like the activation is in this area.
>
> Would it be helpful to convert the co-ordinates back to native space to
> get the true co-ordinates for the activity in this sample? Can this be
> done at the group level?
>
> Alternatively, has anyone got suggestions on how I would report this
> finding? Is the convention to ignore regions of WM and report to nearest GM?
>
> Many thanks for your suggestions.
>
> Nicky Kochan
>
> PhD student, School of Psychiatry, University of New South Wales
>

--
=====================================================================
Marko Wilke (Dr.med./M.D.)
                 [log in to unmask]

Universitäts-Kinderklinik University Children's Hospital
Abt. III (Neuropädiatrie) Dept. III (Pediatric neurology)
             Hoppe-Seyler-Str. 1, D - 72076 Tübingen
Tel.: (+49) 07071 29-83416 Fax: (+49) 07071 29-5473
=====================================================================