[Eeglablist] Induced power from wavelet

[Lundin, Nancy B.]

Hello Makoto and Matt,


Makoto, actually my question was related specifically to calculating induced/non-phase locked activity rather than dealing with ERSP in general.


And Matt, I agree that EEGLAB is performing the time frequency transform prior to trial averaging. However, it is my understanding that this gives us the total power, including both phase-locked (evoked) and non-phase locked (induced) activity combined together. I was wondering how to specifically get the values for the induced activity, which it seems would involve a subtraction of total power minus evoked power.


One suggestion I have received is to subtract the average ERP in the time domain from the data of each individual trial in the time domain, and then run a wavelet decomposition on this data to get the induced activity. I will try this unless anyone has any other suggestions.


Thank you for your time,

Nancy


Nancy Lundin
Doctoral Student, Clinical Psychology & Neuroscience
Indiana University Bloomington
Department of Psychological & Brain Sciences
1101 East 10th St.
Bloomington, IN 47405
________________________________
From: matt schalles <matt.schalles at gmail.com>
Sent: Wednesday, January 25, 2017 8:45 PM
To: mmiyakoshi at ucsd.edu
Cc: Lundin, Nancy B.; eeglablist at sccn.ucsd.edu
Subject: Re: [Eeglablist] Induced power from wavelet

Hi Nancy, et al.

It is my understanding that the way EEGlab calculates ERSPs, the time-frequency transform is done prior to temporal averaging of trials, which should give you the induced activity, without having to do additional subtractions.

cheers,

Matt Schalles, Ph.D.
Cognitive Neuroscientist, VA Health System
Visiting Assistant Professor, Mills College

On Tue, Jan 24, 2017 at 6:00 PM, Makoto Miyakoshi <mmiyakoshi at ucsd.edu<mailto:mmiyakoshi at ucsd.edu>> wrote:
Dear Nancy,

I don't quite understand the question, but I guess that you want to know how you deal with ERSP most straightforwardly? I think you use newtimef() function, and visualize the first output as

figure
imagesc(output); axis xy

The basic figure is this. Then you change xaxis labels, yaxis labels, etc. Do not forget to use eegh(); you perform an operation from GUI first, then type eegh() to obtain the code executed.

Makoto

On Sun, Jan 22, 2017 at 3:01 PM, Lundin, Nancy B. <nlundin at indiana.edu<mailto:nlundin at indiana.edu>> wrote:

?Hello list,


I would like to calculate the induced ERSP in my data. I planned to run the wavelet decomposition on my data to calculate total power, and then separately run a wavelet over the averaged data to get the evoked activity, and then subtract the evoked from the total to get induced activity. However, when I manually average the trials, I get an error message when attempting to save my EEG datasets saying that the number of epochs in the data structure is not the same as the number of epochs in the data (which makes sense, since I averaged).


I was wondering if there was a more direct way to calculate induced ERSP in EEGLAB rather than this manual subtraction method?


Thank you,

Nancy


Nancy Lundin
Doctoral Student, Clinical Psychology & Neuroscience
Indiana University Bloomington
Department of Psychological & Brain Sciences
1101 East 10th St.
Bloomington, IN 47405

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--
Makoto Miyakoshi
Swartz Center for Computational Neuroscience
Institute for Neural Computation, University of California San Diego

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