stop task questions.

[eliana quintero]

 Hi everybody:
I am trying to design a stop task.
I have a visual stimuli (duration: 750ms) which the person have to respond
(the go stimuli).
And I have a tone (sound) which is the stop stimuli and indicates that the
response have to be stopped.
The think is that I dont know how to present the auditory stimuly at 100ms
or 200 after the visual stimuli onset and with a 300ms duration.
Besides, I need to collect the RT to the go stimuli I(visual stimuli) and to
the stop stimuli (tone). Thanks a lot
In short I need:
-   A visual stimuli (duration 750 ms) alone (70% of the trials).
-   A auditory stimuli. A tone (duration 300 ms) will appear a little bit
after the visual stimuli (100 ms after in 15% of the trials and 200 ms after
in 15% of the trials).
-   I need the RT for the Visual stimuli alone and for the visual+auditory
stimuli. I need to refer the RT to the onset of the first signal (visual
stimuli).

I have edited in this way (but I am not sure if this is the correct way):
-   In the visual properties I set the timing mode: Cumulative, the duration
100ms and the pre-release 650ms for 15% of the trials and for the other 15%:
duration 200 ms and the pre-release 750 ms. Is that OK?.

I really thanks for your help. My experience is principally in the clinical
setting and try to designs task to assess process in clinical population is
quit hard to me.
Thanks again.
Regards, eliana.