[FieldTrip] Behavior-power correlations

Xiaoming Du XDu at mprc.umaryland.edu
Mon May 2 23:54:48 CEST 2016

Hi Kaitlyn,
Which version of Fiedtrip you are using? 
I got similar error message when I used old version, but no error when I updated to latest version. 
Hope this will help.

>>> Arjen Stolk <a.stolk8 at gmail.com> 5/2/2016 4:41 PM >>>
Hi Kaitlyn,

My question is this: what is the appropriate design array for computing a correlation with ft_statfun_correlationT? Is the behavioral variable supposed to be part of the design or must it be part of a dummy structure designed to be similar in size and structure to the frequency data?

It's really as described on the page you referred to (http://www.fieldtriptoolbox.org/faq/how_can_i_test_for_correlations_between_neuronal_data_and_quantitative_stimulus_and_behavioural_variables)

n1 = 3;    % n1 is the number of subjects
design(1,1:n1)       = [0.6 0.9 0.1]; %here we insert our independent variable (behavioral data) in the cfg.design matrix, in this case reaction times of 3 subjects.

cfg.design           = design;
cfg.ivar             = 1; 
stat = ft_freqstatistics(cfg, data_brain{:});
where data_brain is a multiple subjects structure in case you're doing this at the second/group level (i.e. correlate a behavioral variable to a neural variable across subjects). Thus, a dummy variable is no longer needed.

Alternatively, is there a way to get, for every individual in the grand average, one value representing the average power for, e.g., 300-600ms in the 4-7Hz range?

You may want to use ft_freqdescriptives for that, per subject.

Best, Arjen

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