Delayed ERP components

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irsikv
Posts: 5
Joined: Tue Mar 25, 2014 9:00 pm

Delayed ERP components

Post by irsikv » Tue May 06, 2014 10:04 pm

Hello,

I am not quite sure if this is necessarily an issue with ActiView but I am currently running an EEG experiment and am using Presentation software to present stimuli. When I am analyzing the data in BESA all the ERP components are delayed by exactly 100ms. What seems to be the problem is that my port code and sound are not being presented simultaneously. There are no issues with the scenario file in Presentation. Could this be an issue with ActiView not receiving the codes? I am a novice with this equipment so any pointers will be greatly appreciated.

Coen
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Re: Delayed ERP components

Post by Coen » Wed May 07, 2014 10:53 am

ActiveTwo + ActiView offers a timing accuracy between EEG data and triggers of +/- 1 sample.

During the past 10 years, we have sold hundreds of microphones and hundreds of photocells to customers who wanted to check the above by themselves. No deviations from the above statement were ever reported.

So, you can be pretty sure that the unexpected 100 ms delay between response and triggers is caused by your stimulus setup.

Best regards, Coen (BioSemi)

irsikv
Posts: 5
Joined: Tue Mar 25, 2014 9:00 pm

Re: Delayed ERP components

Post by irsikv » Mon May 12, 2014 1:58 am

I understand that ActiveTwo + ActiView has great timing accuracy. What I am wondering is what elements can affect the timing of port codes sent from Presentation?

I recently updated my computers from 32- to 64-bit (running Windows 7) and installed the most updated version of ActiView. When I was running studies using the 32 bit set up I had no issues with timing, now I seem to have a 100 ms delay and I am hoping that there is simply a setting that I need to change in my cfg file to solve this issue. I have looked at the RespSwitch settings and those settings do not affect the timing issue. Should I look into changing TCP/IP information? Could my parallel port be set up incorrectly from the Presentation computer to the ActiView Computer? Are there other issues that I am overlooking? Any insight into how this issue may have popped up would be very helpful! We also recently updated the Response Box and, while I don't think there are any issues with its set up, could this be related to our odd timing delays?

Thank you.

Coen
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Joined: Fri Mar 26, 2004 7:00 pm
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Re: Delayed ERP components

Post by Coen » Mon May 12, 2014 9:18 am

As I said: you can be pretty sure that the unexpected 100 ms delay between response and triggers is caused by your stimulus setup. Measure the delay/jitter between stimuli and triggers (with an oscilloscope).

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