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

James Jones-Rounds jj324 at cornell.edu
Thu Feb 13 08:05:40 PST 2014

Thank you Mikolaj! Yes, I simultaneously discovered the EEG.CAT.Conn
fields, which contain the data I am seeking. However, I don't know of an
easy way to plot it.

What I've succeeded in doing is kind of a hack-path work around: I just
take a duplicate version of one the datasets I'm using to generate the
difference coherence, and overwrite the EEG.CAT.Conn.Coh (because in my
case right now I'm looking at Complex Coherence) with the matrix-subtracted
EEG.CAT.Conn.Coh 4-D matrix I just created. In other words (in case anyone
else needs to do this)

coh_diff_Condition1_minus_Condition2 = EEG(2).CAT.Conn.Coh -

%%% This assumes both coherence matrices have the same dimensions, i.e.
same number of windows.

%%% Then I take one of those EEG datasets, duplicate it as EEG(3).

EEG(3).CAT.Conn.Coh = coh_diff_Condition1_minus_Condition2;

%%% This I can then plot using the Time-Frequency Grid process in SIFT, and
it works like a charm, although beware that any other connectivity measures
that haven't been modified will still look the same as in the dummy dataset
that I used to hold this difference coherence matrix, unless you replace
those, too, with difference/subtraction values.



On Wed, Feb 12, 2014 at 7:40 AM, Mikołaj Magnuski <imponderabilion at gmail.com
> wrote:

> Hi James,
> You can find all computed connectivity measures in EEG.CAT.Conn (although
> I am not sure why the field is named 'CAT' - it would be nice to know :) ).
> The matrices that reside there have the same names as method names that
> can be chosen in SIFT connectivity measures gui.
> For example EEG.CAT.Conn.nPDC contains a 4-d matrix of normalized partial
> directed coherence.
> The dimensions are component-component-time-frequency (the last two may be
> the other way around, I don't remember now).
> (BTW "obliterate the putative "difference coherence" due to destructive
> interference." sounds really cool. :) Would make for good lyrics for a SIFT
> theme song maybe? )
> 7 lut 2014 22:32 "James Jones-Rounds" <jj324 at cornell.edu> napisał(a):
>> 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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James Jones-Rounds
Laboratory Manager
Human Development EEG and Psychophysiology (HEP) Laboratory,
Department of Human Development,
Cornell University | Ithaca, NY
eeg at cornell.edu
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