[Eeglablist] (Too) long of an explanation and questions at the end

Sharon Jalene sharonjalene at gmail.com
Sun Feb 16 23:53:44 PST 2014


Lipstick on a pig, eh? I can't stop laughing. Hopefully I can get enough
interest with this project to get a better looking pig. Thanks for the link!


On Sun, Feb 16, 2014 at 11:27 PM, Tom Campbell
<tom_campbell75 at hotmail.com>wrote:

>  Hi,
>
> The most serious noise issue concerns the electrodes. So the electronics
> are rather good at putting lipstick on a pig! The device has built-in
> filters, though additional offline filtering is an option.  People use this
> device for BCI without offline filtering.  It is possible to customise with
> better electrodes:
> https://github.com/SmartphoneBrainScanner/smartphonebrainscanner2-hardware/blob/master/easycap/build_instructions.md
>
> These may be of interest:
>
>
> Debener, S., Minow, F., Emkes, R., Gandras, K. & de Vos, M. How about
> taking a low-cost, small, and wireless eeg for a walk?. *Psychophysiology*
> *49* 1617-1621 doi:http://dx.doi.org/10.1111/j.1469-8986.2012.01471.x (
> 2012)
>
>
>
>
> T.
>
>
>
>
>
> ------------------------------
> From: arno at salk.edu
> Date: Fri, 14 Feb 2014 20:44:45 -0800
> To: sharonjalene at gmail.com
> CC: eeglablist at sccn.ucsd.edu
> Subject: Re: [Eeglablist] (Too) long of an explanation and questions at
> the end
>
>
> *1.    **Should I epoch the data before statistical analyses even though
> I am looking at the differences between the Grand Average - within
> subjects?*
>
> Yes, you need to extract data epochs to compute the grand average ERP. If
> you are computing the spectrum (based on the rest of your message), then
> epoch extraction is not necessary.
>
> *2.    *I am HP filtering at 1Hz and using Cleanline, automatic artifact
> rejection, visual artifact rejection.  I have played with ICA component
> rejection, but am not sure I have enough good data to do so. (I recorded
> pilot data on one subject - I have 3 minutes of data for each condition and
> 14 electrodes).   *Is there an optimal filtering method since I am using
> the EMOTIV?*
>
> This is a very noisy system. To extract meaningful ICA components, the
> more filtering the better.
>
> *a.     *One of my committee said I should NOT filter the data or remove
> artifacts since I am just looking for the Grand Average of certain freq
> bands.  Although I see his logic, I believe I should still remove
> spurious data so that the mean is not skewed by muscle and other artifacts...
> right?
>
> Yes, if you have strong drifts in your data or DC shifts, you will need to
> filter. Otherwise, it will ruin the whole spectrum.
>
> *3.    *I was able to create a STUDY.  I saved separate data sets with
> the electrodes of interest. I was able to run power spectrum channel stats
> as a 3 (conditions) X 2(Left and Right) ANOVA.  I saw the t-tests between
> conditions and the interaction.
> *a.     *Is the power spectrum giving me the average of the specified
> freq range?
>
> Yes
>
> *b.    *If I epoch the data, can I use Bootstrapping instead of
> parametric or permutation?
>
>
> No, this is independent.
>
> *c.     *How can I get the actual values, including the p values, of the
> stats?  I see the option to show a table with statistics containing the
> median, mean, mode, etc., but it rarely populates and is inconsistent. IS
> that statcond - on?
>
> Look at the history and add output to the function that plot the STUDY
> spectrum (the function name is std_spec). This function will return the
> statistics (which are computed by statcond).
>
> *d.    *If I show results from a bootsrap, what statistical test was used
> to obtain the results?
>
> The t-value (paired or unpaired) or the F-value is computed. The bootstrap
> procedure randomly samples the data and allow EEGLAB to obtain confidence
> intervals for these values under the null hypothesis.
>
> *e.     *Would I be better off using a ratio of Grand Average subtraction
> of the control from the FOCUS conditions. or pwelch in MATLAB  -then
> dropping the data into SPSS for some non parametric analysis (WIlcoxon rank
> ordered)?
>
> Sure. You should try what you are comfortable with. The results should be
> similar.
>
> Arno
>
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-- 
Sharon Jalene

www.youregettingverysleepy.com
office: 702-966-3010
mobile: 303-908-8441

*If one dream should fall and break into a thousand pieces, never be afraid
to pick one of those pieces *
*and begin again.*
*Flavia Weedn*
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