[Eeglablist] About stimulus presentation delay

[Makoto Miyakoshi]

Dear Chao,

> We measured this delay and found that the delay was not constant across
trials but instead jitters within certain range around the average.

If you are using E-Prime properly, this jitter must be controlled to cancel
across trials so that the lag never accumulate along with time. If this is
not the case, your set up with E-Prime is wrong. If you are using two
monitors (like one is normal display and the other one is the projector), I
guess E-prime can only control whichever one of them, and the other one is
NOT controlled. I strongly recommend it first.

Makoto




On Tue, Sep 20, 2016 at 6:39 PM, chao wang <hnchaowang at gmail.com> wrote:

> Hi, everyone,
>
> We're recording EEG data and we use E-Prime to present stimuli. During
> recording, stimuli are presented to subjects via a projector. The projector
> induces a delay between stimulus presentation on E-Prime computer and in
> front of subjects. We measured this delay and found that the delay was not
> constant across trials but instead jitters within certain range around the
> average. I would like to know is there a typical range of the jitter that
> can be accepted in ERP experiments? And in this situation, what should I do
> to segment EEG data with respect to stimulus onset? I mean, use the average
> delay to determine the real instant of stimulus presentation, or any other
> ways exist? Forgive me if my words is not clear :)
>
> Thank you in advance!
>
> Chao
>
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-- 
Makoto Miyakoshi
Swartz Center for Computational Neuroscience
Institute for Neural Computation, University of California San Diego
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