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help > RE: Changes in rsFC from pre to post scan: how to determine directionality?
Dec 8, 2019 05:12 PM | Alfonso Nieto-Castanon - Boston University
RE: Changes in rsFC from pre to post scan: how to determine directionality?
Dear Laila,
If I am understanding correctly you would like to evaluate whether the changes in connectivity between the first and second sessions are correlated with PTSD symptom scores in your sample. To do that you would typically:
1) in Setup.Covariates (2nd level) define and/or load a covariate (e.g. named 'ptsd') containing the PTSD symptom scores for each subject
2) in the Second-level Results tab
select 'AllSubjects' and 'ptsd' in the 'subject effects' list, and enter a [0 1] between-subjects contrast (to look at associations with ptsd symptoms)
select 'rest1' and 'rest2' in the 'conditions' list, and enter a [-1 1] between-conditions contrast (to look at changes in connectivity)
Hope this helps
Alfonso
Originally posted by Laila Franke:
If I am understanding correctly you would like to evaluate whether the changes in connectivity between the first and second sessions are correlated with PTSD symptom scores in your sample. To do that you would typically:
1) in Setup.Covariates (2nd level) define and/or load a covariate (e.g. named 'ptsd') containing the PTSD symptom scores for each subject
2) in the Second-level Results tab
select 'AllSubjects' and 'ptsd' in the 'subject effects' list, and enter a [0 1] between-subjects contrast (to look at associations with ptsd symptoms)
select 'rest1' and 'rest2' in the 'conditions' list, and enter a [-1 1] between-conditions contrast (to look at changes in connectivity)
Hope this helps
Alfonso
Originally posted by Laila Franke:
Dear Alfonso, dear All,
In a ROI-to-ROI analysis, I am interested in the change between two resting-state sessions: rest1 (-1) & rest2 (1). My research question is whether participants who show an increase in amygdala-anterior insula connectivity in rest2 relative to rest1, will show higher posttraumatic stress disorder (ptsd) symptoms. Thus my connectivity scores are a predictor for PTSD symptoms (I do this calculation outside of CONN).
I already read elsewhere (https://www.nitrc.org/forum/forum.php?th...) that :
The standard way to present this would be as a conjunction of two contrasts, one contrast (for example) could be defined as [1,1] (for selecting only those areas that show positive correlations on average across both conditions), and the second contrast could be defined as [1,-1] (for selecting those areas that show higher connectivity in the first condition compared to the second condition). The conjunction of the two (those areas that show significant one-sided effects in *both* of these individual contrasts) will inform you which areas show higher positive connectivity in the first condition compared to the second condition (similarly, for example, the conjunction of [-1,-1] and [-1,1] will tell you which areas show higher negative connectivity in the first condition compared to the second)
Yet, I have troubles finding out how to define this conjunction contrast; I basically want to extract values indicating how much each individual showed higher amygdala-anterior insula connectivity in rest2 vs. rest1. At the conditions tab I thus thought to input following contrast: [1 1; -1 1]; However, when I do this, I get two different correlations for each individual, which I don't entirely understand. What would the first correlation represent - the positive connectivity strength between amygdala and insula across both conditions? And would the second correlation indicate the increase of positive correlation strength from rest1 to rest2?
Sorry for these basic questions, just started working with rsfMRI analyses in CONN, and would be really grateful for your thoughts on this.
Thank you in advance!
Best,
Laila
In a ROI-to-ROI analysis, I am interested in the change between two resting-state sessions: rest1 (-1) & rest2 (1). My research question is whether participants who show an increase in amygdala-anterior insula connectivity in rest2 relative to rest1, will show higher posttraumatic stress disorder (ptsd) symptoms. Thus my connectivity scores are a predictor for PTSD symptoms (I do this calculation outside of CONN).
I already read elsewhere (https://www.nitrc.org/forum/forum.php?th...) that :
The standard way to present this would be as a conjunction of two contrasts, one contrast (for example) could be defined as [1,1] (for selecting only those areas that show positive correlations on average across both conditions), and the second contrast could be defined as [1,-1] (for selecting those areas that show higher connectivity in the first condition compared to the second condition). The conjunction of the two (those areas that show significant one-sided effects in *both* of these individual contrasts) will inform you which areas show higher positive connectivity in the first condition compared to the second condition (similarly, for example, the conjunction of [-1,-1] and [-1,1] will tell you which areas show higher negative connectivity in the first condition compared to the second)
Yet, I have troubles finding out how to define this conjunction contrast; I basically want to extract values indicating how much each individual showed higher amygdala-anterior insula connectivity in rest2 vs. rest1. At the conditions tab I thus thought to input following contrast: [1 1; -1 1]; However, when I do this, I get two different correlations for each individual, which I don't entirely understand. What would the first correlation represent - the positive connectivity strength between amygdala and insula across both conditions? And would the second correlation indicate the increase of positive correlation strength from rest1 to rest2?
Sorry for these basic questions, just started working with rsfMRI analyses in CONN, and would be really grateful for your thoughts on this.
Thank you in advance!
Best,
Laila
Threaded View
| Title | Author | Date |
|---|---|---|
| Laila Franke | Dec 7, 2019 | |
| Alfonso Nieto-Castanon | Dec 8, 2019 | |
| Laila Franke | Dec 8, 2019 | |