Hi: We're trying to do a correlation analysis between BOLD % Signal Change and behavioral performance. The fMRI data is being analyzed using freesurfer (specifically, the program roisummary-sess, see https://surfer.nmr.mgh.harvard.edu/fswiki/roisummary_2dsess? action=highlight&value=roisummary-sess). This program outputs a couple values (detailed on that page), notably, the number of voxels in the area, the number that were active above statistical threshold, and the "mean functional baseline offset". Unfortunately, since I am a novice in Freesurgfe, it's unclear to me how to get a % signal change from this data. Presumably, the offset value says something about the difference in activity between the on and off periods, but I don't know the exact meaning of this value, and how to get a % signal change from it.
We get a single output file per run (~280s) and have 12 runs total (8 on day 1, 6 on day 2). We have various behavior metrics corresponding to each of these.
I'm attaching one of the output files here. Thanks a lot! Lucia
n002-task-3-008 98 32 1093.3451 8.9397 76.000000 3.300000 0.000000 1 1 7.8309
Hi Lucia,
if you look at that wiki page, there is an example of your file below. The exact meaning of the fields depends upon your design, but basically you should divide the BOLD amplitude by the mean functional baseline offset to get the percent signal change. There will be a BOLD amplitude for each condition. From your file it looks like there is only one condtion, so it's percent signal change would be 100*7.8309/1093.3451 = 0.72%, which is pretty reasonable.
doug
Lucia Maria Vaina wrote:
Hi: We're trying to do a correlation analysis between BOLD % Signal Change and behavioral performance. The fMRI data is being analyzed using freesurfer (specifically, the program roisummary-sess, see https://surfer.nmr.mgh.harvard.edu/fswiki/roisummary_2dsess? action=highlight&value=roisummary-sess). This program outputs a couple values (detailed on that page), notably, the number of voxels in the area, the number that were active above statistical threshold, and the "mean functional baseline offset". Unfortunately, since I am a novice in Freesurgfe, it's unclear to me how to get a % signal change from this data. Presumably, the offset value says something about the difference in activity between the on and off periods, but I don't know the exact meaning of this value, and how to get a % signal change from it.
We get a single output file per run (~280s) and have 12 runs total (8 on day 1, 6 on day 2). We have various behavior metrics corresponding to each of these.
I'm attaching one of the output files here. Thanks a lot! Lucia
n002-task-3-008 98 32 1093.3451 8.9397 76.000000 3.300000 0.000000 1 1 7.8309
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Doug Greve -
Lucia Maria Vaina