[FieldTrip] Regression of behavioral data against EEG data

[Burcu Bayram]

Dear FieldTrip community,

I'm new to regression analysis of EEG data and unsure which regression 
outputs to use. Beta-coefficients give a very different pattern of 
results compared to r squared values or p-values, although all of them 
(to my understanding) should express a form of relation between the two 
datasets. We are looking for help regarding the interpretation of those 
data and which one to select for our analysis. In our model, behaviour 
is the predictor and EEG activity is the outcome. The datapoints for 
each are single experimental trials (~2000 per subject).
So far, we just used simple linear regression, but the plan is to use 
multiple linear regression at a later stage.
The idea is to plot and interpret the regression results as if they were 
EEG amplitudes. So we get a time course and a topography of regression 
results, that help us to determine where and when in the brain behavior 
predicts neural activity. Our main questions are:

1. Which value makes most sense to use as an indication of brain/ 
behavior relationship? The betas should provide the quality/ direction 
of the relationship, but don't say anything about how large or important 
that relationship is. The r squared or also the t or p values for each 
coefficient tell something about the strength of the relationship. The 
issue is, that they give really different activity patterns. You can see 
the topographies of beta values, r squared values and p-values in the 
attached images.

2. The second question is which of the single-subject regression outputs 
actually can be used for group level plots and statistics: Is it 
possible to average over e.g. betas or p-vales across subjects, and also 
do group level statistics with (e.g. compare group-level p-values or 
betas between two conditions)?

Thank you so much in advance!

Best regards,
Burcu
-------------- next part --------------
A non-text attachment was scrubbed...
Name: beta_av_postmean.png
Type: image/png
Size: 60341 bytes
Desc: not available
URL: <http://mailman.science.ru.nl/pipermail/fieldtrip/attachments/20221210/cd830c53/attachment-0003.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: p_values_av_postmean.png
Type: image/png
Size: 108560 bytes
Desc: not available
URL: <http://mailman.science.ru.nl/pipermail/fieldtrip/attachments/20221210/cd830c53/attachment-0004.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: r_squared_av_postmean.png
Type: image/png
Size: 118310 bytes
Desc: not available
URL: <http://mailman.science.ru.nl/pipermail/fieldtrip/attachments/20221210/cd830c53/attachment-0005.png>