[Eeglablist] topic 4 of eeglablist Digest, Vol 77, Issue 26

[Sarah Loree]

I'm able to open the CNT file in ASA just fine. I'm more asking a
theoretical question. The only problem I can foresee (with my little
knowledge of EMG) is that the EOG sampling rate was only 256 Hz instead of
the 1000 Hz that EMG usually uses.

Thanks again,
Sarah

2011/3/28 <eeglablist-request at sccn.ucsd.edu>

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> Today's Topics:
>
>   1. Subtracting conditions and statistics (Veronique Boulenger)
>   2. EEG fMRI analysis (Thai Vinh Nguyen)
>   3. ASA import GUI interface gone?! (ondrej lassak)
>   4. VEOG versus EMG (Sarah Loree)
>   5. Extracting data from study (Robin Mi)
>   6. Problem with pop_rejepoch (Peter Murphy)
>   7. mother wavelet (Marc)
>   8. Re: remove DC offset (Baris Demiral)
>
>
> ---------- Forwarded message ----------
> From: Veronique Boulenger <Veronique.Boulenger at ish-lyon.cnrs.fr>
> To: eeglablist at sccn.ucsd.edu
> Date: Fri, 25 Mar 2011 18:16:22 +0100
> Subject: [Eeglablist] Subtracting conditions and statistics
>  Dear EEGLab users,
>
> I am new to EEGlab so I apologize in advance if answers to my questions are
> obvious. I ran an MMN experiment and would like to subtract 2 conditions to
> compute a difference waveform (i.e. the MMN). I managed to plot the MMN
> using Sum/Compare ERPs from the Plot menu but I don't know how to save it as
> a "new condition" (to do some stats afterwards). Can anyone help?
>
> Also, I would like to do an ANOVA to compare MMN latency and amplitude
> between 2 types of contrasts and 2 groups of subjects (2x2 design). For
> this, I'd like to extract numerical values for peak latency and peak
> amplitude in a given time-window. Does anyone know how to do it with EEGlab?
>
> Many thanks in advance for your help!
>
> Cheers,
> Veronique Boulenger
>
> --
> Véronique Boulenger, PhD
> Chargée de Recherches CNRS
> Laboratoire Dynamique du Langage – UMR 5596
> Institut des Sciences de l’Homme
> 14 avenue Berthelot
> F69363 Lyon Cedex 07
>
> (33) 04.72.72.79.24
> (33) 04.72.72.65.90
> veronique.boulenger at ish-lyon.cnrs.fr
> http://www.ddl.ish-lyon.cnrs.fr/Annuaires/Boulenger
>
>
>
>
>
> ---------- Forwarded message ----------
> From: Thai Vinh Nguyen <thaivinhnguyen at gmail.com>
> To: eeglablist at sccn.ucsd.edu
> Date: Fri, 25 Mar 2011 09:45:22 +1000 (EST)
> Subject: [Eeglablist] EEG fMRI analysis
> Dear all,
>
> I am trying to combine single trial EEG with fMRI analysis using the
> integration by prediction approach. I'm just wondering how to build the
> design matrix using the EEG information. Suppose my experiment has two
> stimuli (A and B), so I will have a vector of EEG amplitudes for stimulus
> type A and another vector for B in each session. Which of the following
> design is correct to integrate EEG amplitudes with the fMRI analysis?
>
> 1. The design matrix has two predictors, one for each stimulus. The
> predictor is the convolution of the single trial amplitudes with the hrf
> function. Suppose I don't use hrf with time derivatives.
>
> 2. The design matrix has four predictors. The first predictor is the
> convolution of the stimulus type A onset with the hrf function (conventional
> fMRI analysis). The second predictor is the convolution of the EEG amplitude
> from stimulus A with the hrf function. The 3rd and 4th predictors are
> similar to the first two predictors, except they are for stimulus type B.
>
> Kind regards,
> Vinh.
>
>
>
> ---------- Forwarded message ----------
> From: ondrej lassak <tehuberpro at gmail.com>
> To: eeglablist at sccn.ucsd.edu
> Date: Sun, 27 Mar 2011 21:54:05 +0200
> Subject: [Eeglablist] ASA import GUI interface gone?!
> Hi
>
> has the asa CNT file direct support in the GUI been removed?
>
> thx
>
>
>
> ---------- Forwarded message ----------
> From: Sarah Loree <skloree at gmail.com>
> To: eeglablist at sccn.ucsd.edu
> Date: Fri, 25 Mar 2011 23:20:04 -0400
> Subject: [Eeglablist] VEOG versus EMG
> Hello there,
>
> I've been trying to analyze the data of a previous PPI experiment done in
> the lab I recently joined. A 64-channel EEG cap and bipolar VEOG and HEOG
> channels were used. The VEOG was recorded from supraorbital and suborbital
> sites and all recording was done using ANT's ASA system. The purpose of the
> experiment seems to have been to simply test startle reflex. (The EEG cap
> was also used in a second task after the PPI.) Would it be possible to use
> the VEOG channel in place of the usual EMG in measuring startle?
>
> Thanks,
> Sarah
>
>
>
>
> ---------- Forwarded message ----------
> From: Robin Mi <robin.mi at duke.edu>
> To: eeglablist at sccn.ucsd.edu
> Date: Fri, 25 Mar 2011 15:44:04 -0400
> Subject: [Eeglablist] Extracting data from study
> Hello,
>
> I have done the precomputing and plotted the spectra to a study.
> However, I am trying to figure out how to extract the individual
> channel values from the figure/study so that I can perform statistical
> testing on this, could someone help me with doing this? A previous
> person in my lab achieved this by using:
> std.changrp(128).specdata{1}), but I can't see a std variable in
> matlab and my STUDY.changrp does not contain specdata.
>
> Thanks,
> Robin Mi
> Woldorff Lab
>
>
>
> ---------- Forwarded message ----------
> From: Peter Murphy <murphyp7 at tcd.ie>
> To: eeglablist at sccn.ucsd.edu
> Date: Mon, 28 Mar 2011 13:19:26 +0100
> Subject: [Eeglablist] Problem with pop_rejepoch
> Dear all,
>
> I'm having an issue with the pop_rejepoch function and associated artefact
> rejection functions (pop_eegthresh, etc). Whenever I attempt to apply these
> to particular datasets as part of a script, they consistently appear to
> tamper with the latency information contained in the EEG.epoch.eventlatency
> substructure. Specifically, they seem to shift the latency of each trigger
> in each epoch by a very small amount of time (sub-millisecond). While this
> is a very small difference, it interferes substantially with my further
> attempts to automate the analysis of these data. Further, there's always the
> worry that some other aspects of the dataset, latency or otherwise, are
> being affected by use of these functions but I just havn't noticed it yet.
>
> Has anyone come across a similar issue before, and possibly have any
> causes/solutions? Any advice would be much appreciated.
>
> Thanks,
>
> Peter Murphy
>
>
>
>
> ---------- Forwarded message ----------
> From: Marc <maarcc at gmail.com>
> To: eeglablist <eeglablist at sccn.ucsd.edu>
> Date: Sun, 27 Mar 2011 21:05:27 +1000
> Subject: [Eeglablist] mother wavelet
> Hi.
>
> Which mother wavelet is most suitable to use for analyzing eeg signals less
> than 40 Hz from
> visual stimuli?
>
> Thanks.
> Marc
>
>
> ---------- Forwarded message ----------
> From: Baris Demiral <demiral.007 at googlemail.com>
> To: "Søren K. Andersen" <skandersen at ucsd.edu>
> Date: Thu, 24 Mar 2011 17:37:30 +0000
> Subject: Re: [Eeglablist] remove DC offset
> Hi Andrew, Soren,
>
> Let me clarify what I was trying to ask earlier. When you open the Channel
> Data Scroll on the EEGLAB interface, you are given an option in Display
>  "Remove DC offset". I tested this option with taking the mean of each
> channel as well as detrend function. It looked to me as if (whatever Remove
> DC offset is calling as a function), it does better job than the detrend and
> mean subtraction do. So, which function is it calling for?
>
> Recently, Bradley Voytek suggested doing the following on the continuous
> data at the beginning (even in the biosig import function if you are using
> that function):
>
> % remove *real* channel mean
>      for numChans = 1:size(EEG.data,1);
>      EEG.data(numChans, :) = single(double(EEG.data(numChans, :)) -
> mean(double(EEG.data(numChans, :))));
>     end
>
> And here is the reason as he put it:
> "Converting to double is important. If there is significant drift or DC
> offset, the "mean" function (which sums across all points) can cause
> an overflow error, leading to inaccurate results."
>
>
> Previously I was happy with only high-pass filtering (FIR filter) with
> value say 0.1 to eliminate/minimize slow drifts on the continuous raw EEG.
> But recently,  I started to do the following: Again on the raw EEG, first
> take the mean value from each channel out as discussed above, then detrend
> the continuous EEG with detrend function, and then high-pass filter (but now
> I have some problems with IIR versus FIR filters, IIR does not work on the
> continuous EEG data). Then I epoch he data and do other things. I never do
> dc correction on the epoched data so far and thanks Soren for clarifying
> possible artefacts of doing so.
>
>
> 2011/3/24 "Søren K. Andersen" <skandersen at ucsd.edu>
>
>>  Hi Andrew and Baris,
>>
>> if you only want to remove DC-offset, subtracting the mean of each epoch
>> is the best:
>>
>> EEG.data=EEG.data-repmat(mean(EEG.data,2),[1 EEG.pnts 1]);
>>
>> Detrending also removes linear drifts. This is often a good idea for
>> time-frequency analysis. However, detrending can cause major distortions
>> when analyzing ERPs, especially if epochs are short!
>>
>> Best,
>> Søren
>>
>>
>>
>> On 23-Mar-11 5:35 PM, Andrew Hill wrote:
>>
>> Hi Baris,
>>
>>  I'm not 100% sure what you are asking, but I use "detrend" to eliminate
>> drift that's left in my DC recorded BDF files even after I convert them to
>> EDF.
>>
>>  e.g.:
>>
>>  EEG.data = detrend(EEG.data);
>>
>>  Best,
>> Andrew
>>
>>   On Mar 21, 2011, at 4:50 AM, Baris Demiral wrote:
>>
>> Hi everyone,
>>
>>  Do you know which function is the "Remove DC offset" in the Display call
>> for?
>>
>>  I was not able to track it out.
>>
>>  Thanks,
>> Baris
>>
>> --
>> SB Demiral, PhD.
>> Department of Psychology
>> 7 George Square
>> The University of Edinburgh
>> Edinburgh, EH8 9JZ
>> UK
>> Phone: +44 (0131) 6503063
>>  _______________________________________________
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>>
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>>
>>
>> --
>> Søren K. Andersen, Ph.D.
>> Department of Neurosciences
>> University of California San Diego
>> La Jolla, CA 92093
>> Phone:(858) 534-1389
>> Fax:  (858) 534-1566
>> Email: skandersen at ucsd.edu
>>
>>
>
>
> --
> SB Demiral, PhD.
> Department of Psychology
> 7 George Square
> The University of Edinburgh
> Edinburgh, EH8 9JZ
> UK
> Phone: +44 (0131) 6503063
>
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