Millisecond Forums

How to program port communication to EEG machine for multiple stimulus onsets during a video

By Laura.Mc - 8/26/2016

Hi there, 

For my study, I am going to have participants watching a video while they are hooked up to EEG. During this video, there are a number of events of interest occurring and I would like to program for a signal to be transmitted to the EEG machine to mark their occurrence to allow for ERP analysis. I have the timing of the event occurrences recorded in milliseconds for the duration of the video from the initial video stimulus onset. Is it possible to instruct inquisit to simply send a signal by somehow defining each of these time points in the coding? 

Any help you can provide would be greatly appreciated!



By Dave - 8/26/2016

Yes, of course. <port> elements work just like other stimulus types (<text>, <picture>, etc.). You simply display them via a <trial>'s /stimulustimes at the desired point(s) in time. Suppose you have a video and want to sent different markers a, b, c at 5000ms, 10000ms and 15000ms respectively (and lower any bits in-between to avoid any crosstalk).

<trial sometrial>
/ stimulustimes = [0=myvideo; 5000=signal_a; 5100=allbitstolow; 10000=signal_b; 10100=allbitstolow; 15000=signal_c; 15100=allbitstolow]


<video myvideo>
/ items = ("thevideo.mpg")


<port signal_a>
/ items = ("00000001")

<port signal_b>
/ items = ("00000010")

<port signal_c>
/ items = ("00000011")

<port allbitstolow>
/ items = ("00000000")