Hi,
I am trying to compare the quality of fMRI data with different artifact inducing objects in the magnet. I ran expanding and contracting rings and followed the retinotopy fsfast analysis in FreeSurfer 5.1.0. I am trying to compare the data by looking at the sig.nii.gz (which from the website should correspond to the voxel-wise significances) with the different artifacts. I am not sure though how to interpret the negative values for a retinotopy analysis? Can someone clarify what the negative values represent. I would have expected the significance to only be positive, as there isn't a traditional contrast in the smoothly varying stimulus.
Thanks! Dan
Hi Dan, it just gets the sign of the contrast it was computed from. You can just take the absolute value. doug
On 05/24/2013 03:58 PM, dgw wrote:
Hi,
I am trying to compare the quality of fMRI data with different artifact inducing objects in the magnet. I ran expanding and contracting rings and followed the retinotopy fsfast analysis in FreeSurfer 5.1.0. I am trying to compare the data by looking at the sig.nii.gz (which from the website should correspond to the voxel-wise significances) with the different artifacts. I am not sure though how to interpret the negative values for a retinotopy analysis? Can someone clarify what the negative values represent. I would have expected the significance to only be positive, as there isn't a traditional contrast in the smoothly varying stimulus.
Thanks! Dan
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dgw -
Douglas N Greve