[Eeglablist] How to "difference plot" of coherences from two different datasets or conditions in SIFT and/or EEGLAB

[James Jones-Rounds]

Hello all (and Tim),

I am a happy SIFT user and have found some exciting results measuring
event-related complex coherence in certain frequency bands, between
independent components, in a within-subject design using SIFT. My next step
is to generate "difference" plots, i.e. the coherence (between two
components) during one task (i.e. averaged epochs) subtracted from the
coherence (between those same two components within the dataset, or between
different components in another dataset) during another task.

I don't see an apparent way to do this in SIFT. Do you have any
suggestions?

One idea I had was that if the coherence data existed in a matrix or
structure field that SIFT generated, I could do a matrix-subtraction and
then plot that resulting matrix. I wouldn't want to just matrix-subtract
one set of raw frequency data from another, because I imagine that unless
they're perfectly phase-locked (unlikely), that would obliterate the
putative "difference coherence" due to destructive interference. I want to
just matrix-subtract the coherence values (coherence power at each
frequency, at each time point in the epochs) that's used to plot coherence
using the "Visualization > Time-Frequency Grid" menu item in SIFT.

Thanks for your advice in advance, to any and all who can think of some!

James

-- 
James Jones-Rounds
Laboratory Manager
Human Development EEG and Psychophysiology (HEP) Laboratory,
Department of Human Development,
--------------------------------------------
Cornell University | Ithaca, NY
607-255-9883
eeg at cornell.edu
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