Different presentation durations for simultaneous onset visual and auditory events

I am trying to make an auditory oddball task.
So I have one list of tones in random order (Tone1 - being less frequent and Tone2 being more frequent).
I cannot send digital markers yet, due to some hardware restrictions, so instead I would like to show images with sensor patches for this kind of stimuli.
I have a picture list, where sensor patch is shown on the left (needs to be shown when Tone1 is presented) and another image where patch is shown on right (needs to be shown with Tone2).
After this, when I put in photosensors at the correct positions - I can have 2 triggers for the frequent and less-frequent tones.

The tone and image presentation timing is about 983 ms for tones and 83 ms for images.
Now I would expect that the image is only presented for about 100 ms and the tone is played for its full time (about 250 ms) and then the next tone/image combination comes after about 1s.
But when 2 or more frequent tones are presented sequentially, it seems the sensor patch is presented almost continuously (not for about 100ms but for 1s), so there would be only one marker from the photosensor.
Similarly, if 2 infrequent tones are presented sequentially - only 1 marker will be sent.

How can I make the patch (image) presentation shorter (say 100 ms), but still have a interstimulus interval between 2 tones at around 1s ? And also keep the sync the tone and corresponding image ?

Can you post the experiment for me to look at?

I have attached the experiment.

Auditory Tones separate with sensor patch.zip (13.7 KB)

The problem is that your fixation cross is part of your stimulus images. If it was a separate event, then you could use the At event end: Erase Stimulus for finer control.

However, if you do not want to change all of your images, there is another work around:
- disable the Erase screen before presenting stimulus option in your stimulus events

  • create an image event that presents a screen-wide black rectangle (this will be used to “erase” your sensor patches)
  • place this image event in between your image and audio events

I have tweaked your experiment to demonstrate these steps. Please take a look and let me know if you have any questions.

manualEraser.zip (15.8 KB)