[Eeglablist] Filtering issues

[Stephen Politzer-Ahles]

Hi Marianne,

ftp://sccn.ucsd.edu/pub/locfiles/neuroscan/ has a location file for a
64-channel cap. If the locations of the 32 channels in your cap are the
same as those (just with 32 channels missing), then you could edit that
file by removing the channels you don't have. I'm not sure if the locations
are the same, though, since I haven't used Quik-cap; if you do this, you
should try plotting the channel locations afterwards to make sure they're
correct.

You also might find some helpful information in a previous discussion on
this issue: http://sccn.ucsd.edu/pipermail/eeglablist/2011/004243.html

Best,
Steve

On Fri, Sep 28, 2012 at 3:05 AM, Marianne Løvstad <mar.lovstad at gmail.com>wrote:

> Hello
>
> We are currently using Quik-cap 32 channels to record eeg data on a
> Neuroscan system. Do anyomne know of a channel location file we can use in
> eeglab?
>
> Marianne Løvstad
>
>
> 2012/9/26 Andreas Widmann <widmann at uni-leipzig.de>
>
>> Hi,
>>
>> googling the list archives (
>> http://www.google.com/search?q=highpass+site:sccn.ucsd.edu/pipermail/eeglablist/)
>> gives you several threads discussing this problem, e.g.
>> http://sccn.ucsd.edu/pipermail/eeglablist/2008/002210.html
>>
>> In a nutshell: The filter order as suggested by EEGLAB is too high for
>> this extreme cutoff-frequency. Use higher cutoff or different filter type.
>> Transition band width is defined as cutoff * 0.15 for firls-based filters
>> in EEGLAB IIRC.
>>
>> Note:
>> I recommend upgrading to a more recent version of EEGLAB where fir1 is
>> used as default filter function (in case you did not select firls
>> explicitly). firls-based filtering does not give optimal results (
>> http://www.frontiersin.org/Perception_Science/10.3389/fpsyg.2012.00233/full
>> ).
>>
>> Best,
>> Andreas
>>
>> Am 21.09.2012 um 17:03 schrieb tmle at notes.cc.sunysb.edu:
>>
>> > Hi eeglablist,
>> >
>> > I have been attempting to apply a highpass filter to our 64-channel
>> data set. So far I have only resampled (to 256) and rereferenced (to
>> average reference) prior to this step. However, when I enter .01 for the
>> lower edge in the basic filter option, eeglab will run for about 20 minutes
>> then give me an out of memory error (eeglab error in function firls() at
>> line 150). Could you please let me know why this might be the case? I'm not
>> sure whether my laptop memory is a problem as it has 8G of RAM. Also,
>> eeglab says the eegfilt () - highpass transition band width is 0.001Hz.
>> Shouldn't this be .01 like I have entered for the lower edge?
>> >
>> > Thanks,
>> >
>> > Le
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>
>
>
> --
>
>
> Marianne Løvstad
> Psykologspesialist/Ph.d. student
> Sunnaas sykehus
> tlf: + 47 93 45 20 03
>
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-- 
Stephen Politzer-Ahles
University of Kansas
Linguistics Department
http://people.ku.edu/~sjpa/
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