The presentation of our stimuli is divided into 3 parts:
Pretime, when a background image is presented for a specified period of time. At the onset of pretime, the program generates a trigger message "Stim_BGpre_trigger" that is handled by any StimTrigger devices that have been setup.
The stimulus presentation itself. At the onset of the stimulus presentation, the program generates a trigger message "Stim_ONSET_trigger". Immediate at the conclusion of each data frame (when the image on the video display is updated by the program; note that this is different from the video frame rate), the program generates a "Stim_afterframe_trigger" trigger message, followed shortly by a "Stim_beforeframe_trigger" message that sets the voltage back to its original value before the "Stim_afterframe_trigger". At the conclusion of the stimulus presentation, the trigger message "Stim_ONSET_trigger" is generated.
Posttime when a background image is presented for a specified period of time.