[Eeglablist] Time-frequency analysis (subtraction first or analysis first)

[Arnaud Delorme]

Dear Hsu,

only your first statement is correct. The second one could be correct if 
you could pair the trials, but it would be very rare that you would want 
to do this (since trials are recorded at different times and are usually 
not paired between conditions). Look up the help of the newtimef 
function which allows computing differences between power between 
different conditions and newcrossf which allows computing difference 
between phase coherence images.

Best,

Arno

Hsu, Shen-Mou wrote:
> Dear list-memebers,
>
> Suppose that I am interested in comparing two conditions A and B in terms of their power and phase coherence. I was wondering which one of the following steps is more theoretically correct. 1. After segmentation, calculate the EEG differences between the condition A and B and then perform time-frequency analysis on the differences. 2. After segmentation, perform time-frequency analysis on the EEG data of the condition A and B respectively and then compute the power or phase coherence differences between two conditions. Any comments would be much appreciated.
>
> Many thanks,
>
> Shen-Mou Hsu
>