We trigger our device (not anything standard like psyscope) using a pulse
from our GE 1.5 scanner. It comes off the osciliscope output. It can be a
noisy signal and we needed a capacitor to make it a little more stable. Our
software is DasyLab. So, when the scanner pulse sequence starts, the signal
from the scanner usually drops negative first and we just have a threshold
set. I'd hardly describe it as a TTL on/off pulse. Its noisier than that,
but workable.
Best,
David Kareken
-----Original Message-----
From: Russ Poldrack [mailto:[log in to unmask]]
Sent: Thursday, June 13, 2002 11:20 AM
To: [log in to unmask]
Subject: Re: synchronization betwwen scanner and visual stimuli
presentation
there are two ways to do this. one is to program the pulse sequence to
wait for a triggering pulse from your stimulus computer. this is how it
was done at Stanford on the old GE system (I'm not sure if they are
still doing it this way), using a psyscope button box and some custom
electronics to create a TTL pulse to trigger the scanner.
The second way is to have your stimulus computer wait for a trigger
pulse from the scanner. This is easy on a Siemens system, perhaps one
of the GE users on the list can speak to whether this is possible on
those systems. At MGH we used a Rowland button box
(http://pywacket.rowland.org/rurb/index.html) which takes in a TTL pulse
and turns it into a keypress on USB, then you just need to tell you
software to wait for that key.
cheers
russ
Harold Mouras wrote:
>Dear SPMers,
>
>we would like to synchronize the beginning of fMRI acquisitions performed
on
>a 1,5 GE and the beginning of functional runs where we show visual stimuli
>(bmp pictures).
>Please could you let me know if someone found a solution for such a
>synchronization between GE scanners and presentation softwares. Are
specific
>softwares more specific for such a synchronization?
>
>Thank your very much in advance for your help,
>H. Mouras
>----------------------------------------
>Harold Mouras
>Inserm U483 - Université Pierre et Marie Curie
>9, quai Saint Bernard
>75005 Paris
>Téléphone : 33 1 44272624
>Fax : 33 1 44273438
>[log in to unmask]
>------------------------------------------
>
>
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