[pymvpa] Questions about mvpa preprocessing...

Roberto Guidotti robbenson18 at gmail.com
Fri Apr 15 17:45:31 UTC 2011

Thank you, for the quick response and for the advice.

For the first question: in the review papers I've read this question is
never treated in depth, but only if the study is across-subject, thank you
for the paper you link to me. My study is preliminary, I want to check that
MVPA technique tells me something else... My analysis is firstly
within-subject and then I could "upgrade" to cross-subject!!

The second question: I know it were incomprehensible ;) now I'll explain
simply :D I have a task with two conditions plus resting, without resting
state (fds = fds[fds.sa.targets != 'Rest']) my accuracy is good, with the
full dataset I have bad results (no. of training examples for each class are
balanced) I don't know if I the independence conditions, with this dataset,
could be true. My question is the fact that my resting state is not
classified as resting state, or my conditions are misclassified, is it an
alarm bell?

Thank you.

2011/4/15 J.A. Etzel <jetzel at artsci.wustl.edu>

> I've often performed MVPA after spatial normalization. As with most things,
> whether it's a good idea depends on your analysis goals: if you will perform
> an across-subjects analysis some sort of spatial normalization is required;
> if only within-subjects, it's optional.
> As a plug, I wrote about some of these issues in my tutorial paper: Etzel
> JA, Gazzola V, Keysers C. 2009. An introduction to anatomical ROI-based fMRI
> classification analysis. Brain Research 1282:114-125. There are quite a few
> other introductory papers, too - check the citations.
> I'd need more details for the resting state question. It can be very nice
> to include a "control" (should be chance) classification in an analysis.
> good luck,
> Jo
> On 4/15/2011 9:40 AM, Roberto Guidotti wrote:
>> Dear all,
>> I'm not sure if this is the right place to ask these questions:
>> Is it right to coregister fMRI images to standard atlas and then perform
>> the MVPA analysis? If yes, there are some other issue to take care in
>> the post analysis operation?
>> Is important that the resting state, if included in classification, has
>> bad classifier accuracy?
>> I'm sorry if these are trivial question and if I'm off topic.
>> Thank you
>> RG
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