[Eeglablist] The parallel port - TRIGGERS

[Abigail Noyce]

Hi Davide,
We have a direct (but not perfectly synchronous) TCP/IP connection between
the display and the EEG recording computers that is used to send specific
flags that identify events. In combination with this,we use a photodiode
that's looking at a small patch of the screen to capture precise display
timing; the photodiode signal is input directly to the EEG recording
computer. (That is, a rectangle on one corner of the screen flips from
black to white when a stimulus is displayed. A mask around the photodiode
prevents subjects from being distracted by the luminance change.)

Then, we adjust the timing of the flag events to match the timing of the
adjacent photodiode input, so as to be sure we're getting the timepoint
when the display actually changed. Especially with LCD monitors, I'd be
concerned about the timing of the display, and this may help.

Hope that's helpful as a contrasting example,
Abby Noyce

On Thu, Jul 12, 2012 at 9:20 AM, Davide Baldo <davidebaldo84 at gmail.com>wrote:

> Hello all,
>
> When running EEG experiments, I use Psychtoolbox (in Matlab) to
> present subjects with different stimuli
> So far, I have been using a desktop, that has a parallel port that
> allows me to send out the triggers related to the stimuli.
> The triggers are accepted in input from the EEG recording system again
> via a parallel port.
>
> I would like to use a laptop rather than a desktop to present the
> subjects with the stimuli and to send out the related triggers.
> The problem is that is hard to find a laptop with a parallel port. I
> was wondering if any of you found a solution to this problem.
>
> That would be very helpful!
>
> Thanks in advance,
>
>
> Davide.
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-- 

Abigail Noyce
Ph.D. student, Cognitive Neuroscience

Department of Psychology, MS 062
Brandeis University
415 South St
Waltham, MA 02453

781-736-3266
anoyce at brandeis.edu
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