Trigger Extension for Psyscope
Functional MRI studies of speech are problematic for several reasons. In speech production experiments, movement of the mouth and jaw causes susceptibility artifacts in images obtained during movement. In both perception and production studies, the subject must deal with the very loud noises that accompany echo planar imaging. This noise may affect the perceptual system’s response and may alter the strategies used for speech production.
In order to overcome these problems, we have used an event-related technique in which we trigger the scanner to begin image acquisition just following jaw movement in production studies or auditory stimulus presentation in speech perception studies. Because of the delay in the hemodynamic response, we can actually collect data about the areas that were active during production or during the presentation of the auditory stimulus.
In order to trigger the scanner at appropriate times, we developed an extension to the Psyscope program for stimulus presentation. This extension allows the experimenter to specify ‘trigger events’ within the experiment scripts that send a TTL pulse from the serial port of a Macintosh computer. This TTL pulse can be used to signal the start of image acquisition.