Dear Matthew,
>On the other hand the height correction will be fairly
>accurate - although you should correct for the smoothness within the
>ROI itself.
How does one correct for smoothness in ROI? I was simply comparing the
smoothness (number of resels per voxels in the search volume) in the ROI
relative to the average smoothness of the whole image. Is there a
statistical procedure in SPM99 that allows correcting for smoothness in ROI
during SVC? Sorry, i'm not an expert, so would really appreciate your help.
many thanks and best wishes
Elena
At 12:37 22/02/2005 -0800, Matthew Brett wrote:
>Hi,
>
>> If I am to understand the discussion, applying SVC to VBM is
>> (relatively) valid if an explicit assumption is made about
>> stationariness in relation to the smoothness of the regions undergoing
>> SVC relative to the average smoothness of the image (grey matter
>> partitions smoothed with 8-12mm kernel).
>
>I know this is terribly obvious, but the assumption of stationarity
>doesn't make the image any more stationary, and so does not make the
>analysis any more valid.
>
>I think what Satoru is saying is that there can still be significant
>non-stationarity in VBM analyses even at 12mm smoothing, and for this
>reason, the cluster statistic will be unreliable in SPM (but not
>fmristat). >
>Is that fair Satoru?
>
>Best,
>
>Matthew
>
------------------------------------------------------------
Ms Elena Antonova
Post Doctoral Research Worker
PO78 Department of Psychology
Institute of Psychiatry
King's College London
De Crespigney Park
Denmark Hill
London SE5 8AF
UK
tel: +44 (0) 207 919 3048
fax: +44 (0) 207 919 2116
email: [log in to unmask]
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