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FSL  September 2011

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Subject:

Re: Fisher's transform and Higher-level FEAT analysis

From:

Stephen Smith <[log in to unmask]>

Reply-To:

FSL - FMRIB's Software Library <[log in to unmask]>

Date:

Fri, 30 Sep 2011 02:28:42 -0500

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (36 lines)

Hi

I'm afraid what you're doing doesn't make sense- copes are (contrasts between) regression coefficients not correlation coefficients. 

Also, if you are using one of the non-ols group-level options the varcope is used to feed into the higher level calculations, so you need to leave the cope as it is. 

Cheers. 

--------------------
Stephen M. Smith,  Professor of Biomedical Engineering
Associate Director,   Oxford University FMRIB Centre

FMRIB, JR Hospital, Headington,
Oxford. OX3 9 DU, UK
+44 (0) 1865 222726  (fax 222717)
[log in to unmask]
http://www.fmrib.ox.ac.uk/~steve
----------------------

On 29 Sep 2011, at 22:30, Aaron Kucyi <[log in to unmask]> wrote:

> Hi there,
> 
> I ran a first-level resting state fMRI seed-based correlation analysis for a group of subjects using FEAT, and I obtained individual-level correlation maps. If I feed my COPE files into a higher-level group analysis using FLAME, I obtain nice zstat images that look like canonical resting state networks. However, I also tried taking my first-level COPEs and performing Fisher's r-to-z transform on these files before feeding them into a higher-level FEAT (with the intent of ensuring that the correlations are normally distributed). If I do this and select "inputs are 3D cope images" and Mixed Effects Simple OLS, my resulting COPE images are not in correlation units and the zstat images are blank.
> 
> So I have the following questions:
> a) Am I running the higher-level FEAT on Fisher's transformed cope files correctly?
> b) If so (a), is there a way to convert the higher-level stats output files (cope, tstat, zstat) into correlation units? 
> c) If so (b), would I expect to see zstat images that are similar to the ones I had obtained with FLAME (without Fisher's transform)?
> 
> Thank you
> 
> Kind regards,
> 
> Aaron  
> 

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