[Eeglablist] Synchronization of EEG data with auditory stimulus

[Tarik S Bel-Bahar]

Hi Ali,

This process can be pretty tricky, and you're better off chatting with an
engineer hardware specialist, since the millisecond precision synchrony of
your experimental events in relation to the EEG recording are critical for
valid results in your case.
In situations where researchers seek extreme accuracy, they often rely on
precision instrumentation and displays, as well as important things that
allow accurate alignment of all signatures, ideally to to one main clock.
Timing issues and hardware are not often discussed though, and in some
cases sidestepped, so kudos to you.

Psychtoolbox and other matlab and python based tools (see also Kothe's Lab
Streaming Layer)
all have extensive documentation where one can learn how to use them. One
can also google for
specific things like "Psychtoolbox code for synching with eeg amplifier",
or similar searches. I think LSL might work well for you.
Perhaps an easier alternative is to simply find a way to translate your
"real clock time" into "EEG time" accurately. If you can just do that, load
the translated beep times into your EEG after recording as new events.
Here's perhaps something easier too: if your amp has the capability of
adding a sensor into it's output, the plug in an audio sensor and record it
with your amp. Your EEG recording software may also have an option for such
an integration.
Good luck with your EEG timing adventure. You may hear from some of the
timing folks on the list soon too.
When you have a solution, please share with the list so others can benefit
from your adventure.

On Fri, Apr 20, 2018 at 11:01 AM, ali zahedi <ali.zahedi.bham at gmail.com>
wrote:

> Dear Tarik,
>
> Thank you very much for the information you have provided, and sorry for
> my late reply.
> Can you please give me the detail on how I can use psychtoolbox and sync
> it up with my EEG amplifier?
> (I am really new in working with EEG hardware...).
>
>
> I tried to find GUI in psychtoolbox but I only found a demo to produce an
> audio.
> Actually I do not have any idea to work with psychtoolbox and use it to
> sync the beeps with my EEG data.
> My beep generator (written in c#) works in real clock time and I get the
> beep times in real clock time. However, my EEG data does not work with real
> clock time and it has its own timer starting from 0 anytime I start
> recording.
>
> I really appreciate your support and I would be very grateful if you could
> guide me to use psychtoolbox with more details.
>
> Thank you very much.
>
> Regards,
> Ali
>
>
> On Tue, 10 Apr 2018, 00:14 Tarik S Bel-Bahar, <tarikbelbahar at gmail.com>
> wrote:
>
>> Hello Ali, some thoughts below, best wishes.
>>
>>
>> A simple method is to use an experimental software such as psychtoolbox,
>> and have it "synch up" with your eeg amplifier, and generate events with
>> each beep.
>> Another more principled/accurate way to do this is to have a audio sensor
>> that picks up the sound and records it's time. Of course the sensor also
>> needs to be fully aligned with eeg time.
>>
>> If you trust your beep event times, and they are aligned with the EEG,
>> then you might be good as you are, just import your event list into eeglab
>> (into the eeg file).
>>
>> One thing to be careful of here is that your eeg and time signal are
>> properly aligned (find a way to make sure that 0 time is 0 time in both the
>> eeg record and the beep events record).
>> Also watch out for jitter (e.g., inaccurate event timing info, unevenly
>> spaced beeps), and for "uncoupling or drift" of your eeg time and beep time
>> over the whole period of the recording.
>>
>>
>>
>>
>>
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