Back to PLS Helpinterpreting e.r. fmri pls results
Posted on 02/03/10 21:19:05
Number of posts: 6
Hello,
I apologize if this question has been addressed in a previous thread. I was just hoping to get some advice in interpreting my E.R. fMRI PLS results. I conducted a PLS analysis and ended up with one significant LV, with many positive and few negative voxels. In my experiment, I have four conditions. According to the design scores, one of the conditions has a positive value (witha high value) whereas the other 3 have (lower) negative values. Do I interpret this result to mean that the positive voxels in the brain LV image are acitve during the one condition in which there is a positive design score and the negative voxels are active in the conditions in which there is a negative design score?
Thanks in advance,
Paul
I apologize if this question has been addressed in a previous thread. I was just hoping to get some advice in interpreting my E.R. fMRI PLS results. I conducted a PLS analysis and ended up with one significant LV, with many positive and few negative voxels. In my experiment, I have four conditions. According to the design scores, one of the conditions has a positive value (witha high value) whereas the other 3 have (lower) negative values. Do I interpret this result to mean that the positive voxels in the brain LV image are acitve during the one condition in which there is a positive design score and the negative voxels are active in the conditions in which there is a negative design score?
Thanks in advance,
Paul
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Posted on 02/04/10 08:19:31
Number of posts: 229
Paul..
you have identified a "difference" in activity levels - it could map onto what is typically considered to be "activation/deactivation" but it does not have to be the case..
if you plot the actual response (response function plot) for a voxel in a region with positive saliences, you should see that the activity is higher in the first condition relative to the other three. For voxels with negative saliences, the reverse should be true - activity should be higher in those three conditions relative to the first.
cheers,
nancy
you have identified a "difference" in activity levels - it could map onto what is typically considered to be "activation/deactivation" but it does not have to be the case..
if you plot the actual response (response function plot) for a voxel in a region with positive saliences, you should see that the activity is higher in the first condition relative to the other three. For voxels with negative saliences, the reverse should be true - activity should be higher in those three conditions relative to the first.
cheers,
nancy
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