[FieldTrip] ICA+frqanalysis questions
jdien07 at mac.com
Tue May 24 03:07:57 CEST 2011
I agree with David's reasoning. You may find the following article to be of help as well in understanding the issues involved:
Dien, J., Khoe, W., & Mangun, G. R. (2007). Evaluation of PCA and ICA of simulated ERPs: Promax versus Infomax rotations. Human Brain Mapping, 28(8), 742-763.
On May 23, 2011, at 11:57 AM, David Groppe wrote:
> Hi Odelia,
> When you use ICA (or any other spatial filter) to correct for EEG
> artifacts, you're going to distort your data some by removing true EEG
> activity in addition to the artifact (for an explanation, see:
> So to minimize distortion, it would be better not to apply ICA
> artifact correction to artifact-free data. However, if the frequency
> of the artifact differs across experimental conditions, it could
> confound your analysis. For example, I suspect people blink more
> often to targets in an oddball experiment than standards. Thus if you
> apply ICA only to blinky trials, you could find a difference between
> the EEG response to standards and targets that simply reflects the
> fact ICA removed more EEG activity in the target trials (i.e., it
> wouldn't reflect a true difference in neural processing).
> hope this helps,
> On Mon, May 23, 2011 at 1:44 AM, odelia nakar <odidodi at hotmail.com> wrote:
>> Hi all,
>> I'm troubled by the fact that when I use ICA for blinks\eyes movements
>> removal, I remove the relevant components also from trials that do not
>> contain blinks\eyes movements. In order to avoid this bias we thought to
>> combine the data before ICA ("data" structure) with the data after ICA
>> ("dataica" structure), only in specific trials, as follows:
>> blinks=[2 4 5 8 bla bla 156];
>> for ind=1:length(blinks)
>> To my first question: I just wanted to check that there is no problem with
>> that, or any reason not to use it.
>> Another issue- I use motor learning task, and I'm trying to understand what
>> happens through the process, in terms of power-frequency changes through the
>> process. How would you recommend that I'd use the ft_freqanalysis function?
>> What method to use (or what do I need to consider when choosing the method
>> Thanks a lot,
>> fieldtrip mailing list
>> fieldtrip at donders.ru.nl
> David Groppe, Ph.D.
> Postdoctoral Researcher
> Dept. of Cognitive Science
> University of California, San Diego
> fieldtrip mailing list
> fieldtrip at donders.ru.nl
E-mail: jdien07 at mac.com
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