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  • Digital Output/event markers for Pictures in a list

    I need to present pictures as stimuli from a list. This is basically a Stroop task, with some variations. I also want to send event markers for Congruent and Incongruent stimuli - say 1 and 2 respectively for classical stroop stimuli and 11 and 12 for one variation, and also 21 and 22 for another kind of variation. These are sent to Cedrus Stimtracker.
    When I try to use Digital Output, I cannot add pictures to the list, only event marker numbers.
    With Picture files, I cannot see a way to add markers.
    I am a little confused, if I just choose digital output, then what stimuli will be shown or presented since its not associated with any pictures/sounds ?
    Please advise.
    Thanks

  • #2
    I'm not sure if this answers your questions, but for our stimuli that need to be marked with event markers the event marker is a separate event than the stimulus presentation. For example we have two events, one that marks CS+ presentations and one that marks CS- presentations for a conditioning program we use. We have an event called "Event marker CS+" that directly precedes the CS+ events (pictures lists). For the trial, both the event marker event and the CS+ event is chosen. The same for CS- events - there is both an event marker event and a CS- stimulus list (both different events).

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    • #3
      Thanks aisn557 for the suggestion. That could be one way to do it. But I still cannot understand how I will integrate the presentation of markers and pictures - both from separate lists.
      Say in the Stroop task, I have Congruent and Incongruent pictures (say 10 each), which are presented from a list where they are randomly arranged - C1, C2, I1, I2,...
      Now I need to send marker 1 for Congruent and 2 for Incongruent - say I put the corresponding markers in this Digital Output list - 1, 1, 2, 2....
      When I select both in the event marker list and the picture list for a block - will the markers be sent in a sequence first and followed by the pictures in a sequence - or there will be the first picture presented along with the first marker, then second picture with second marker and so forth ?
      Its a little hard for me to understand the integration between particular stimulus event and the marker event.

      Originally posted by aisn557 View Post
      I'm not sure if this answers your questions, but for our stimuli that need to be marked with event markers the event marker is a separate event than the stimulus presentation. For example we have two events, one that marks CS+ presentations and one that marks CS- presentations for a conditioning program we use. We have an event called "Event marker CS+" that directly precedes the CS+ events (pictures lists). For the trial, both the event marker event and the CS+ event is chosen. The same for CS- events - there is both an event marker event and a CS- stimulus list (both different events).

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      • #4
        aisn557 is correct: you will need to have two (or more) events per trial, one for the pictures and one for the event codes. When SuperLab presents them, the default is to pair items from different lists, meaning that the first picture from the pictures list will always be paired with the first event code, the second picture will always be paired with the second event code, etc. The order of pairs can be randomized, of course.

        I suggest that you have at least two trials, one for congruent and one for incongruent pictures, i.e. avoid have one list for all pictures.

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        • #5
          Originally posted by Hisham View Post
          aisn557 is correct: you will need to have two (or more) events per trial, one for the pictures and one for the event codes. When SuperLab presents them, the default is to pair items from different lists, meaning that the first picture from the pictures list will always be paired with the first event code, the second picture will always be paired with the second event code, etc. The order of pairs can be randomized, of course.

          I suggest that you have at least two trials, one for congruent and one for incongruent pictures, i.e. avoid have one list for all pictures.
          Thanks Hisham for the clarification and the suggestion about 2 separate trials for Congruent and Incongruent stimuli. Will try it.

          Another thing - is there a way to test whether markers are being sent without connecting to any hardware (Stimtracker or IO). Because if I make some changes in the experiment, I can only test it once I go back to the main stimulus presentation PC which is connected to Stimtracker.
          It would be great if there was some virtual Stimtracker option, which could show the markers being sent on the fly or at least let a data file be saved, so that I can check it and confirm things are working as expected.

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          • #6
            The idea of a “virtual” StimTracker is a good one, but does not exist yet. We’ll keep it in mind for future versions.

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            • #7
              Originally posted by Hisham View Post
              The idea of a “virtual” StimTracker is a good one, but does not exist yet. We’ll keep it in mind for future versions.
              Using a separate digital output list in addition to picture list, does make things work as intended - one picture - one digital output.

              We are using this setup, with Brain Products' actiCHamp and Pycorder for recording EEG. The problem is that any event sent from the event list just shows up in the EEG data as the same event.
              Say in the digital output list I have 8 different events - 1,2,11,12,21,22,31,32 but in the EEG data I can only see S1.
              How can I have my intended event markers in the EEG data ?

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              • #8
                We do not provide a signal adapter kit for Brain Products’ actiCHamp -- only for their USB2 interface. So I have no idea how many of the 8 available lines are dedicated to the event codes coming from the stimulus presentation computer’s USB port.

                On the signal adapters that we do provide, we typically dedicated 3 data lines for event codes on EEG recorders that have 8 bits of input, and 5 data lines on EEG recorders that have 16 bits of input. This gives you 7 and 31 different values, respectively.

                One way you can find out is to send event codes using 1 bit at a time and then see which ones are captured by Pycorder.

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                • #9
                  If we want to separate the congruent and incongruent pictures into separate lists, then maybe we can use one marker event for each separate list by ticking on the EC0 / EC1 or other lines.
                  How do I randomize the presentation of the events - so that congruent and incongruent trials are mixed ?
                  If I select randomization at block level, it randomizes the trials and if I select randomization at trial level, all events within that trial will be randomized.

                  Lets say for 1 block - which has 10 congruent and 10 incongruent pictures - should mix few stimuli from each of these lists to have a presentation of total 20 stimuli.
                  When any item from congruent list is called - then I can send an event marker by having a digital output event with EC0 ticked; while whenever an item from incongruent list is called, a digital output event of EC1 can be sent.

                  Similarly I can plan for the other 3 blocks.

                  Thanks

                  Originally posted by Hisham View Post
                  We do not provide a signal adapter kit for Brain Products’ actiCHamp -- only for their USB2 interface. So I have no idea how many of the 8 available lines are dedicated to the event codes coming from the stimulus presentation computer’s USB port.

                  On the signal adapters that we do provide, we typically dedicated 3 data lines for event codes on EEG recorders that have 8 bits of input, and 5 data lines on EEG recorders that have 16 bits of input. This gives you 7 and 31 different values, respectively.

                  One way you can find out is to send event codes using 1 bit at a time and then see which ones are captured by Pycorder.

                  Comment

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