[Eeglablist] EEGLAB Orientation

Thu Dec 5 13:10:10 PST 2024

I think it's an empirical question.  If you're using a median, you are 
in effect relying on a single data point (albeit a median one) and it 
will have some amount of noise too.  The question then is whether the 
noise you throw out with the rest of the points outweighs the signal 
that you throw out with the rest of the points.  Or to put it another 
way, median is a great way to eliminate high amplitude noise, but not 
necessarily low amplitude noise.  A graphic example that comes from my 
non-systematic observations of median averaging for ERPs (using my EP 
Toolkit), at least, is that it can give rise to sharp discontinuities in 
the waveform.  I imagine a similar effect could happen in 
frequency-space.  For robust ANOVAs, the developers (Wilcox, Keselman, 
Lix, Algina, et al) generally also recommend a 20% trim, but after 
mucking around with ERP data (again using my EP Toolkit), I came to the 
conclusion that a modest 5% trim was the better way to go (assuming n>= 
20).  Still unsystematic, though.

Definitely worth looking at!

Joe

On 12/5/24 11:30, Makoto Miyakoshi via eeglablist wrote:
> Hi Cedric,
>
> If you decide not to perform any signal processing for so called data
> cleaning, do you think 20% trimming is trustworthy enough? I know it
> is an empirical question. But in theory, median's breakdown point is 50%.
> Since 50%>20%, why not?
>
> Cyril once told me that if people assume Gaussian distributions everywhere
> anyway, why not use median? Good point.
>
> Makoto
>
> On Thu, Nov 28, 2024 at 7:50 AM Cedric Cannard via eeglablist <
> eeglablist at sccn.ucsd.edu> wrote:
>
>>> I have long thought that the averaging process in Welch's method should
>> be replaced with median because EEG recordings can contain pretty bad
>> outliers.
>>
>> I recommend 20% trimmed mean :)
>>
>>
>> Cedric
>>
>>
>>
>> On Monday, November 25th, 2024 at 12:25 PM, Makoto Miyakoshi via
>> eeglablist <eeglablist at sccn.ucsd.edu> wrote:
>>
>>> Hi Arno and all
>>>
>>> Thanks for your input.
>>> I recommend people posted here try that plugin and tell me what it does.
>>>
>>> eegfiltnew() and fir_filt() are close enough, if you just
>>> need band-specific powers.
>>>
>>> Makoto
>>>
>>> On Sun, Nov 24, 2024 at 12:43 AM Arnaud Delorme via eeglablist <
>>> eeglablist at sccn.ucsd.edu> wrote:
>>>
>>>> For extracting brainwaves at specific frequencies, I would advise using
>>>> the eegstats EEGLAB plugin.
>>>>
>>>> Best wishes,
>>>>
>>>> Arno
>>>>
>>>>> On Nov 22, 2024, at 22:09, Meha Fatima via eeglablist <
>>>>> eeglablist at sccn.ucsd.edu> wrote:
>>>>>
>>>>> Hi. Thank you for this opportunity. I'd like to join in, too. Can you
>>>>> please share the Zoom link?
>>>>>
>>>>> On Fri, 22 Nov 2024 at 23:34, Makoto Miyakoshi via eeglablist <
>>>>> eeglablist at sccn.ucsd.edu> wrote:
>>>>>
>>>>>> Hi Devvarta,
>>>>>>
>>>>>>> Could you please open this zoom session for others as well?
>>>>>> Sure, gather as many participants as you want and let them ask as
>> many
>>>>>> questions as necessary.
>>>>>> I'll be available after 7:00 am in New York time (EST) which is
>> 5:30 pm
>>>>>> in
>>>>>> Bangalore. I prefer it in the morning rather than the
>> evening/night.
>>>>>> I notice that there has been a large and constant need for
>> extracting
>>>>>> EEG
>>>>>> power using EEGLAB, which is only partially supported by GUI.
>>>>>> After our discussion, maybe I can summarize the requested
>>>>>> functionalities
>>>>>> into a solution in the form of EEGLAB plugin. It should be pretty
>> easy.
>>>>>> What I want to know is the type of output format you need most. Is
>> it
>>>>>> ascii
>>>>>> or Excel? Do you want a result in linear scale (microV^2) or in
>> dB? Do
>>>>>> you
>>>>>> want a mean power within a frequency band (with SD across sliding
>>>>>> windows)
>>>>>> or full freq bin resolution (which is already available in EEGLAB
>>>>>> spectopo)
>>>>>> etc..
>>>>>>
>>>>>> I like the idea of robust PSD proposed by Melman and Victor (2016)
>> so
>>>>>> that
>>>>>> you do not need to worry too much about data cleaning.
>>>>
>> https://urldefense.com/v3/__https://pmc.ncbi.nlm.nih.gov/articles/PMC4903894/__;!!Mih3wA!Hc_qvUxHKj94lakBpoAoDLDmyqzks4elWCUSSecAgiLfWsompHx83bc4_GJA8f1FYPh9Rceqb8iycYCC-UFVaSR4uL8$
>>>>>> I have long thought that the averaging process in Welch's method
>> should
>>>>>> be
>>>>>> replaced with median because EEG recordings can contain pretty bad
>>>>>> outliers. At least, outcomes from Welch's method by mean and
>> median can
>>>>>> be
>>>>>> compared to evaluate the window-mean PSD's deviation from the
>>>>>> window-median
>>>>>> PSD.
>>>>>>
>>>>>> Grace, if this selection of time does not work for you, we can set
>> a
>>>>>> separate Zoom meeting. Tell me what time zone you are in.
>>>>>>
>>>>>> Makoto
>>>>>>
>>>>>> On Fri, Nov 22, 2024 at 3:42 AM Devvarta Kumar <
>>>>>> devvarta.k at nimhans.ac.in>
>>>>>> wrote:
>>>>>>
>>>>>>> Hi Mokoto
>>>>>>> I assume many of us would be interested in understanding the
>> process of
>>>>>>> calculating power in different bands in raw EEG. Could you
>> please open
>>>>>>> this
>>>>>>> zoom session for others as well?
>>>>>>> Regards
>>>>>>>
>>>>>>> Devvarta Kumar, Ph.D.
>>>>>>>
>>>>>>> Professor
>>>>>>> Department of Clinical Psychology
>>>>>>> M. V. Govindaswamy Building
>>>>>>> National Institute of Mental Health and Neurosciences,
>>>>>>> Hosur Road,
>>>>>>> Bangalore,
>>>>>>> Karnataka-560029
>>>>>>> India
>>>>>>>
>>>>>>> Ph: +91-80-26995188
>>>>
>> https://urldefense.com/v3/__http://www.nimhans.ac.in/users/dr-devvarta-kumar__;!!Mih3wA!E8Vsq9Vu8Q4ZAl8UIb5elP9m72UAtG-_h15RsH4N7qURhjnEctf1NKia1NpntFgQlL_UtZbHh_sQjnDjaxBj7B3Oazg$
>>>>>>> ResearchGate:
>>>>
>> https://urldefense.com/v3/__https://www.researchgate.net/profile/Devvarta_Kumar/contributions__;!!Mih3wA!E8Vsq9Vu8Q4ZAl8UIb5elP9m72UAtG-_h15RsH4N7qURhjnEctf1NKia1NpntFgQlL_UtZbHh_sQjnDjaxBj8leJO1o$
>>>>>>> ----- Original Message -----
>>>>>>> From: eeglablist at sccn.ucsd.edu
>>>>>>> To: eeglablist at sccn.ucsd.edu
>>>>>>> Sent: Friday, November 22, 2024 1:51:05 AM
>>>>>>> Subject: Re: [Eeglablist] EEGLAB Orientation
>>>>>>>
>>>>>>> Hi Grace,
>>>>>>>
>>>>>>> If your group wants to Zoom with me, I'll be available. Which
>> time zone
>>>>>>> are
>>>>>>> you in?
>>>>>>>
>>>>>>> Makoto
>>>>>>>
>>>>>>> On Thu, Nov 21, 2024 at 2:50 PM Grace Bang via eeglablist <
>>>>>>> eeglablist at sccn.ucsd.edu> wrote:
>>>>>>>
>>>>>>>> Hello!
>>>>>>>>
>>>>>>>> We are 3rd year medical students trying to conduct research
>> where we
>>>>>>>> collect brain wave activity data using the CGX Patch 2-channel
>> EEG.
>>>>>>>> We've
>>>>>>>> been having a lot of issues trying to navigate how to use
>> EEGLAB to
>>>>>>>> process
>>>>>>>> the data. We just want to be able to quantify the number of
>> alpha and
>>>>>>>> beta
>>>>>>>> waves present in the raw data. The resources we've read online
>> have
>>>>>>>> been
>>>>>>>> somewhat helpful, but we are looking for someone who can jump
>> on a
>>>>>>>> Zoom/phone call to help fill some gaps of knowledge. Neither
>> of us
>>>>>>>> have a
>>>>>>>> background in more complicated softwares/coding/EEGs so any
>> guidance
>>>>>>>> would
>>>>>>>> be greatly appreciated!
>>>>>>>>
>>>>>>>> - Grace Bang, OMS-3
>>>>>>>> _______________________________________________
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>>>>> --
>>>>>
>>>>> * Dr. Meha Fatima BSMT, Ph.D.*
>>>>> Assistant Professor
>>>>> Dow Institute of Medical
>>>>> Technology
>>>>> Dow University of Health Sciences
>>>>> mehafatima1 at gmail.com
>>>>> mehafatima1 at gmail.com.
>>>>> _______________________________________________
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-- 
--------------------------------------------------------------------------------

Joseph Dien, PhD
Senior Research Scientist
Department of Human Development and Quantitative Methodology
University of Maryland, College Park
https://urldefense.com/v3/__http://joedien.com__;!!Mih3wA!EGE2-zRkTBdtoncXH2B0SBkrfuhEPiKTJPw7napVfD_D5-0MyWNtH5yenPuXhv2sO8ypc5xF69eVQxHXlPw$ 