How do I change the number of presented stimuli in the LabTutor VEP experiment?

The VEP experiment uses a HTML files with java scripting to display the flashes and the checkerboard to evoke VEPs. To modify the number of stimuli you need to make a little modification on the code. Please do only so if you feel comfortable to do such changes.

Use the 'Install Experiment' LabAuthor Utility to install the VEP experiment to your local PC. Navigate to the Experiment Files folder on your computer. By default they are located under

C:\Users\Public\Public Documents\ADInstruments\LabTutor\Experiment Files

Within the folder 'Visual Evoked Potential (VEP)' open the 'Support Files' folder and open flash.html and checker.html with a text editor, e.g. with Notepad++.

In flash.html locate in line 17 the code:

    if(c==101) { clearTimeout(t); window.close();}

Change the value for c to your needs, say to 121, save and close.

In checker.html locate in line 32 the code

    if(c==101) { clearTimeout(t); window.close();

Change the value for c to your needs, say to 121, save and close.

Now that you have changed the number of stimuli presentation you need to change the number of scope averaging within the LabTutor experiment.

Open the LabTutor experiment with LabAuthor and change to the LabTutor Kernel window.

Within the scope View window click 'Event Settings..' and change the Average value to 120 and click 'OK'. Then go to Setup > Sampling... and change the Scope Average to 120 and 'Close'.


Go back to the LabAuthor window and change the text fields in the Contend Pages accordingly (… 100 sweeps... should be replaced by … 120 sweeps...).

Edit the Experiment Properties, save the file and export a new experiment installer, which then can be uploaded to your LabTutor Server.