[Eeglablist] Help with LIMO ANCOVA/Regression and STUDY cluster analysis
Dr Cyril, Pernet
wamcyril at gmail.com
Tue Feb 2 03:04:29 PST 2021
Hi Deniz
> I have a STUDY design with 2 independent groups, and each subject has a single EEG file that consists of 2 conditions recorded during the same session. So I have 2 factors for the variable group (between subject) and 2 factors for the variable condition (within subject).
> So far with my Study design and using LIMO, I am able to run a repeated measure ANOVA with condition as the repeated variable and group as the between subject factor, and groupxcondition as the interaction term.
>
> My goal is to test the correlation between ERP components and the behavioral outcome of my task
> 1)ANCOVALIMO  I would like to explore the relationship between the main effects and a potential covariate.
the 'best' thing to do would be to compute contrasts, i.e. [1 1 0] for
each subject which is your main effect, then ANCOVA 2 gp and covariates
[...] What I tried was (after precomputing channel measures for ERPs,
power spectrum and ERPimage):
> 1)First level analysis: Estimate model parameters (beta files), with interaction term, OLS, and selected timeframe.
> no interaction  you do group statistics (anyway there should be any
to compute given 2 conditions only ie your design should have 3 columns,
if so no need to recompute)
> 2)Second level analysis:
> Choose channel file, and work folder
> Run ANCOVA—> Full scalp analysis —> How many independent group?—>enter 2—>Load beta or con files? —> load beta files for each group separately (gp1 and gp2)_—> Which parameters to test?—> Enter [1 2] for my repeated conditions (n=2) —> Here I see the error:
yes my bad  there should a message preventing you to do that ; you
cannot do rep. measures here (will include in the next patch)
as explained above, use contrasts from 1st level instead.
> 2)RegressionLIMO
> I also thought that if ANCOVA did not work, I could run a regression model separately for each independent group.
> In the tutorial it gives an example of creating a first level contrast for each subject, and then run asample ttest to create the con files which would be used in the regression model along with the regressor variable. I was wondering if there is a way to use parameters from the repeated measure ANOVA model as they would account for the noise better, or maybe it would not differ much since I used OLS?
well see above  if you split the ANCOVA covariates (ie use
XXXXXX000000 and 00000XXXXX with values) say for age, then you model
separately the effect of age for each group  which allws you to test [1
1] if group differ, [0 0 1 1] if the effect of age differ, [0 0 1 1]
the common effect of age

Dr Cyril Pernet,
Centre for Clinical Brain Sciences (CCBS)
Neuroimaging Sciences
wamcyril at gmail.com
https://urldefense.com/v3/__https://cpernet.github.io/__;!!Mih3wA!SnAfzFWSPbHfADvSa3Og6H9jrUCox2t6UeGKSyD4tlE7mxL4X4RsqEyaqH6yA0saiR2Q$
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