Hello,
most likely, the absolute analysis treshold (point 3) is too low;
could raise it stepwise to e. g. 0.20.
Low tresholds - especially with strongly smoothed data - may lead
to the mask being relatively large.
Also check the mask by using it as background, best, before
and after changing the threshold value.
It may also be useful to use your DARTEL template as background;
esp. the "too" low orbitofrontal clusters would need some checking,
if they lie within the GM area.
Hope this helps,
Philipp
At 21:12 12.11.2008 +0000, Muhammad A Parvaz wrote:
>Hi,
>
>We are using DARTEL to perform VBM. After following the DARTEL manual, when
>we are doing following Statistical Analysis:
>
>1. a two-sample T-Test between control and diseased groups
>2. gray matter volumes as covariate
>3. Absolute Threshold equals 0.05
>4. explicit masking using apriori/brainmask.nii
>5. Contrast [-1 1]
>6. threshold p = 0.01
>7. voxel threshold = 50
>
>Now, what can explain these out of brain 'activations'? What can be done to
>avoid or reduce this effect?
>
>Thanks
>-Muhammad
>
>
>Attachment Converted: "H:\EUDORA3\ATTACH\T-map.jpg"
>
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