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Disentangle scanner triggers from participant's responses

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  • Disentangle scanner triggers from participant's responses

    Hi,

    I have a question about triggering experiments from a fMRI scanner: I have a simple block design for a fMRI experiment (4 blocks, each of them with a resting period of 15sec + a Go/No-Go task of 60sec). I've included one event that waits for the trigger from the scanner at the beginning of each block, in order to synchronize them with the fMRI sequence. However every time the scanner sends a trigger (i.e. every 2.5sec) it is considered and logged as a participant's response. This conflicts with the actual responses from the participant. Is there any way to stop the triggers during the Go/No-Go task, or to disentangle them from the actual (behavioral) responses?
    Thanks in advance.

    Regards,

    Fernando

  • #2
    In the Event Editor, click on the Input tab and turn off the Record and save response option for the event that waits for scanner trigger.

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    • #3
      Originally posted by Hisham View Post
      In the Event Editor, click on the Input tab and turn off the Record and save response option for the event that waits for scanner trigger.
      Hi,

      Thanks for the suggestion. However, I turned off the "record and save response" option in both the event itself and by editing the Scanner Trigger on the participant's input, and none of the solutions worked. The scanner trigger is still being saved in the log file as if a participant's response.
      I would appreciate any other advice on how to solve this problem.

      Regards,

      Fernando
      Attached Files

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      • #4
        Your Event Editor's screen snapshot shows an event named "Trigger". In the data file, is the scanner's trigger being recorded during event "Trigger"? I'm wondering if the scanner's trigger is arriving during another event.

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        • #5
          No, the scanner's trigger is not being recorded during the event "Trigger". However, it is often recorded during the experimental events that follow (please refer to the attached log file), conflicting with the actual responses from the participant.

          Regards

          Fernando
          Attached Files

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          • #6
            If the scanner's trigger is being recorded during events other than "Trigger", this implies that the scanner triggers are arriving when you are not expecting them, probably before the trial is complete.

            Double-check your design. If you are still having a problem, send me a private message with your phone number or call me; it would be much faster on the phone.

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