[Eeglablist] Use single trials (when available)

[Arnaud Delorme]

Dear Makoto,

When single trials are used, the ERP is simply averaging all single trials from all subjects, which is different from the subject average (unless all subjects have the same number of trials). Typically single trials should be used when performing statistics on a single subject.

Arno

> On Oct 27, 2016, at 7:35 PM, Makoto Miyakoshi <mmiyakoshi at ucsd.edu> wrote:
> 
> Dear Laura and Arno,
> 
> Hmm, you are right, they look differ!
> Arno, why do ERP results with and without 'use single trial' differ? Does it concatenate, when 'on', all single trials and perform average, rather than average trials for each subject?
> 
> Makoto
> 
> On Thu, Oct 27, 2016 at 11:28 AM, Laura Dubreuil Vall <laura.dubreuil at neuroelectrics.com <mailto:laura.dubreuil at neuroelectrics.com>> wrote:
> Dear Makoto,
> 
> Thanks for your reply. I was thinking that when using the “Use single trials” option, the average of each subject would be subtracted from each subject before averaging all the trials (or something similar). For example, something like this:
> 
> for i=1:Nsubjects
> 	s(i)=mean of subject i;
> 	for j=1:Ntrials of subject i
> 		trial_j=trial_j - s(i);
> 	end
> end
> 	
> In any case, there is definitely a difference between plotting ERPs with this option enabled or disabled, see attached. So I was just wondering what is the difference between both of them.
> 
> Thanks a lot!
> 
> <Not using single trials.png><Using single trials.png>
> 
> Laura Dubreuil Vall | Technical Manager
> Neuroelectrics (www.neuroelectrics.com <http://www.neuroelectrics.com/>)
> cell: +1 617 390 6447 <tel:%2B1%20617%20390%206447>
> __________________________________________________
> US offices:						Europe offices:
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> 
> 
> 
>> On 24 Oct 2016, at 19:58, Makoto Miyakoshi <mmiyakoshi at ucsd.edu <mailto:mmiyakoshi at ucsd.edu>> wrote:
>> 
>> Dear Laura,
>> 
>> > What does it imply in terms of plotting the average ERPs?
>> 
>> To compute average event-related potentials, this option should not make any difference at all, if I understand it correctly... I have never used this option.
>> 
>> Makoto
>> 
>> 
>> 
>> On Tue, Oct 18, 2016 at 5:19 PM, Laura Dubreuil Vall <laura.dubreuil at neuroelectrics.com <mailto:laura.dubreuil at neuroelectrics.com>> wrote:
>> Hello,
>> 
>> I would like to ask a question regarding the “Use single trials (when available)” option for a STUDY when plotting ERPs (apologies if it has already been answered before).
>> 
>> What does it imply in terms of plotting the average ERPs? Does it subtract the mean from each subject (like a random intercept)? Or is it just averaging all the single trials of the STUDY, regardless of the subject?
>> 
>> Thank you very much in advance.
>> 
>> Kind regards,
>> 
>> Laura Dubreuil Vall | Technical Manager
>> Neuroelectrics (www.neuroelectrics.com <http://www.neuroelectrics.com/>)
>> cell: +1 617 390 6447 <tel:%2B1%20617%20390%206447>
>> __________________________________________________
>> US offices:						Europe offices:
>> 210 Broadway, Suite 201			Av. Tibidabo, 47 bis
>> Cambridge, MA, 02139			08035, Barcelona, Spain
>> Phone: +1 617 682 0770 <tel:%2B1%20617%20682%200770>			Phone: +34 93 254 03 63 <tel:%2B34%2093%20254%2003%2063>
>> 
>> 
>> 
>> 
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>> 
>> 
>> 
>> -- 
>> Makoto Miyakoshi
>> Swartz Center for Computational Neuroscience
>> Institute for Neural Computation, University of California San Diego
> 
> 
> 
> 
> -- 
> Makoto Miyakoshi
> Swartz Center for Computational Neuroscience
> Institute for Neural Computation, University of California San Diego

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