Back to PLS HelpPosted on 05/30/07 19:03:54
Number of posts: 0
I have a few questions for you concerning a block fMRI analysis in PLS.
First, my design is a block design in which the subjects' behaviour determines the nature of a given block. Because of this, some conditions of some runs for some subjects are empty--in cases when the subject did not judge any block in a run to fall into a certain condition. PLS does not like it when I try to leave a condition for a run blank, however. It will not create a datamat when you leave a condition blank, and it will not run a PLS on a subject with a condition in which a block length is 0. Does anyone have an idea for dealing with these empty conditions?
Second, what is the difference between correlation overview and behaviour LV overview for a seed voxel analysis? And what does it mean when all conditions in the correlation plot have very similar magnitudes and the same direction (negative)? Thanks in advance,
-Alan Gordon
Replies:
I'm Online
Posted on 05/31/07 12:25:30
Number of posts: 291
First, my design is a block design in which the subjects' behaviour determines the nature of a given block. Because of this, some conditions of some runs for some subjects are empty--in cases when the subject did not judge any block in a run to fall into a certain condition. PLS does not like it when I try to leave a condition for a run blank, however. It will not create a datamat when you leave a condition blank, and it will not run a PLS on a subject with a condition in which a block length is 0. Does anyone have an idea for dealing with these empty conditions?
I wish that he following answer from:
http://www.rotman-baycrest.on.ca/pls/FAQ.txt
might help:
Q: I have more than one runs in my MRI study. However, for some runs, I do not have all the conditions. How should I fill out the onset field?
A: If you want to exclude certain conditions for certain runs, you can simply put a -1 for the onset field, (and put a 1 for the length of Blocked fMRI). Then choose "Merge data of each condition: across all runs" to create a datamat. Please ignore the command line message saying "Scans -01 not included due to out of bound". You can not choose "Within each run only", since you do not have all the conditions filled for every runs. In additon, for each condition, you must have at least one valid onset (not -1) in one of your runs.
Second, what is the difference between correlation
overview and behaviour LV overview for a seed voxel analysis?
correlation overview is the correlation between behavior data and brain scores;
behavior LV overview is the plot of behavior LV.
And what does it mean when all conditions in the correlation plot have very similar magnitudes and the same direction (negative)? Thanks in advance,
that probably means that conditions are differentiated easily for this particular LV.
I'm Online
Posted on 05/31/07 12:27:50
Number of posts: 291
First, my design is a block design in which the subjects' behaviour determines the nature of a given block. Because of this, some conditions of some runs for some subjects are empty--in cases when the subject did not judge any block in a run to fall into a certain condition. PLS does not like it when I try to leave a condition for a run blank, however. It will not create a datamat when you leave a condition blank, and it will not run a PLS on a subject with a condition in which a block length is 0. Does anyone have an idea for dealing with these empty conditions?
I wish that he following answer from:
http://www.rotman-baycrest.on.ca/pls/FAQ.txt
might help:
Q: I have more than one runs in my MRI study. However, for some runs, I do not have all the conditions. How should I fill out the onset field?
A: If you want to exclude certain conditions for certain runs, you can simply put a -1 for the onset field, (and put a 1 for the length of Blocked fMRI). Then choose "Merge data of each condition: across all runs" to create a datamat. Please ignore the command line message saying "Scans -01 not included due to out of bound". You can not choose "Within each run only", since you do not have all the conditions filled for every runs. In additon, for each condition, you must have at least one valid onset (not -1) in one of your runs.
Second, what is the difference between correlation
overview and behaviour LV overview for a seed voxel analysis?
correlation overview is the correlation between behavior data and brain scores;
behavior LV overview is the plot of behavior LV.
And what does it mean when all conditions in the correlation plot have very similar magnitudes and the same direction (negative)? Thanks in advance,
that probably means that conditions are differentiated easily for this particular LV.
...that probably means that conditions are not differentiated easily for this particular LV.
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