[caret-users] fMRI mapping & t-values

Katja Umla-Runge k.umla-runge at mx.uni-saarland.de
Tue Jun 19 05:05:47 CDT 2007

Dear Caret users,

Mapping spmT*.img files (SPM99) to a surface in Caret, the resulting  
image seems (at first glance) to fit the data table I obtained from  
SPM. However, if I set the threshold to say t = 3,61 (metric -->  
settings --> threshold --> Pos User = 3,61 --> threshold type: User)  
which is the threshold I got from SPM for a given one-sample t-test,  
less activations remain as compared to the SPM data table. As an  
example, my results include an occipital activation with t = 4,67. If  
I want to see this structure activated on my Caret surface, I need to  
enter a threshold of about t = 1. Why do t-values and corresponding  
activations do not correspond between the two systems? How can make  
them correspond?
Thank you in advance.


Dipl.Psych. Katja Umla-Runge

Saarland University
Department of Psychology        phone: +49 - (0)681 - 302 4643
P.O.Box 151150                  fax:   +49 - (0)681 - 302 4049
D-66041 Saarbruecken            email: k.umla-runge at mx.uni-saarland.de


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