So, now I have figured out a way to display only the stimuli and keep the fixation point in view.

Now my problem is how to keep the fixation point there after removing the stimuli from the screen. I have a fixation point on the screen, and then a diamond comes on the screen, and the subjects are required to make a response even though the diamond disappears after 100ms (rt:9,1,clear100) However, I don't want the fixation point to disappear with the diamond...I want the fixation to remain on the screen while the subject makes his/her response. How do I do this?
STIM LOC TIME STIM LOC TIME
~+<3> 0,0,1 150 D 0,.43,0 rt:9,1,clear100