Triggering Task Start

The Prisma scanners send a = key push to the task computer every TR (see TTL hardware). To ensure your task and the MR image acquisition are in sync, a “Waiting For Scanner” screen in your task should pause until it receives this key.

The scanner will send the first = when all the “discarded volumes” ¹⁾. This should happen and trigger the task when the bottom left timer and volume count change. Time starts to decrease and count changes from 0 to 1.

For Psychopy, example code can be found in lncdtask.screen.wait_for_scanner.

textbox.setText('Waiting for scanner (pulse trigger)')
textbox.draw()
textbox.win.flip()
event.waitKeys(keyList=['equal'])
starttime = core.getTime() # save start time to file!