[Eeglablist] Correct for EGI latency error functions

[Isaiah Innis]

It is common to be unaware of this problem. To quote EGI: "These delay
values have not been effectively communicated to EGI customers . . ."

That aside, here are the advisory notices from EGI:
https://www.dropbox.com/s/60ecjesnp62lxjj/EGI%20advisory%20notice%20and%20update.docx?dl=0
Note that there are two notices - an initial warning followed by an update.

The filter causing the issue is the hardware filter (before analog to
digital conversion) within the amplifier. Filters applied offline are
unaffected.

For NetStation users, EGI released a stand alone "Anti Alias Filter
Alignment" utility to adjust files offline.  NetStation version 5.1.2 and
later include this utility as part of the installation and also allow for
online correction. Be aware that when using the tool offline, "data must be
adjusted in a state prior to segmentation, therefore you will have to
reprocess the data (personal communication w/EGI). "  Since this correction
must occur before segmentation anyway, we export our continuous data  to
.raw files then adjust the data and perform all pre-processing steps in
eeglab.


Let me know if anything above is unclear,

2015-10-11 21:11 GMT-04:00 chao wang <hnchaowang at gmail.com>:

> Hi Isaiah,
>
> Thank you for sharing this information. I am an EGI user, but I am not
> aware of such an issue. So, would you please tell the meaning of "Advisory
> Notice: Anti-Alias Filter Effects on EEG Timing"? Does the "Anti-Alias
> Filter" mean the filter in the recording phase, i.e. the hardware filter
> within the amplifiers? Or the FIR filter in the offline pre-processing
> phase? Besides, how can this effect be corrected with NetStation? I rely
> more on NetStation for pre-processing.
>
> I appreciate your help, thank you!
>
>
> Best,
> Chao
>
> On Mon, Oct 12, 2015 at 3:00 AM, <eeglablist-request at sccn.ucsd.edu> wrote:
>
>> ---------- Forwarded message ----------
>> From: Isaiah Innis <isainnis at umail.iu.edu>
>> To: EEGLAB List <eeglablist at sccn.ucsd.edu>
>> Cc:
>> Date: Fri, 9 Oct 2015 12:48:27 -0400
>> Subject: [Eeglablist] Correct for EGI latency error functions
>> Hello eeglab list:
>>
>> Those of us who use EGI hydro-cel systems received "Advisory Notice:
>> Anti-Alias Filter Effects on EEG Timing" warning that there is a fixed
>> latency delay present for any event codes sent to the EEG during recording.
>> The EEG is delayed with respect to the events, and needs to be corrected by
>> either shifting the EEG forward or the events back. While it is possible
>> to correct this within NetStation, since our lab analyzes data exclusively
>> using eeglab I wrote a series of functions to correct the delay within
>> eeglab. It is my hope that others may find this beneficial. However, I am a
>> matlab novice and would like to see if anyone on the list has any comments
>> or suggestions.
>>
>> You can download a .zip archive with the functions here: <
>> https://www.dropbox.com/sh/2udz5qrdb79b2b8/AAAS6Bws_O65gJnpnATS1azza?dl=0
>> >.
>>
>> If you have any questions or criticisms upon reviewing the functions,
>> please contact me at: isainnis at indiana.edu
>> If there is interest, I will make this a plugin for ease of use.
>>
>> Thank you,
>> --
>> Isaiah Innis
>> Indiana University '13
>> EEG Technician, IUB IRF
>>
>>
> ---------- Forwarded message ----------
>> From: Makoto Miyakoshi <mmiyakoshi at ucsd.edu>
>> To: Isaiah Innis <isainnis at indiana.edu>
>> Cc: EEGLAB List <eeglablist at sccn.ucsd.edu>
>> Date: Sat, 10 Oct 2015 14:52:48 -0700
>> Subject: Re: [Eeglablist] Correct for EGI latency error functions
>> Dear Isaiah,
>>
>> Thank you for sharing this info. I heard of it from Elise, one of
>> visitors here. EGI users, please pay attention!
>>
>> Makoto
>>
>> On Fri, Oct 9, 2015 at 9:48 AM, Isaiah Innis <isainnis at umail.iu.edu>
>> wrote:
>>
>>> Hello eeglab list:
>>>
>>> Those of us who use EGI hydro-cel systems received "Advisory Notice:
>>> Anti-Alias Filter Effects on EEG Timing" warning that there is a fixed
>>> latency delay present for any event codes sent to the EEG during recording.
>>> The EEG is delayed with respect to the events, and needs to be corrected by
>>> either shifting the EEG forward or the events back. While it is
>>> possible to correct this within NetStation, since our lab analyzes data
>>> exclusively using eeglab I wrote a series of functions to correct the delay
>>> within eeglab. It is my hope that others may find this beneficial. However,
>>> I am a matlab novice and would like to see if anyone on the list has any
>>> comments or suggestions.
>>>
>>> You can download a .zip archive with the functions here: <
>>> https://www.dropbox.com/sh/2udz5qrdb79b2b8/AAAS6Bws_O65gJnpnATS1azza?dl=0
>>> >.
>>>
>>> If you have any questions or criticisms upon reviewing the functions,
>>> please contact me at: isainnis at indiana.edu
>>> If there is interest, I will make this a plugin for ease of use.
>>>
>>> Thank you,
>>> --
>>> Isaiah Innis
>>> Indiana University '13
>>> EEG Technician, IUB IRF
>>>
>>>
>>> _______________________________________________
>>> Eeglablist page: http://sccn.ucsd.edu/eeglab/eeglabmail.html
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>>>
>>
>>
>>
>> --
>> Makoto Miyakoshi
>> Swartz Center for Computational Neuroscience
>> Institute for Neural Computation, University of California San Diego
>>
>


-- 
Isaiah Innis
Indiana University '13
EEG Technician, IUB IRF
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