Figure 3.

Example of a single trial in Sessions 1, 2, and 3. (A) Participants with PD and age- and education-matched controls learned to associate six abstract images with either a “left” or “right” verbal response in Session 1. The following is an example of a trial: (1) a fixation cross appeared in the center of the computer screen for 700 msec; (2) a blank screen was presented for 300 msec; (3) an image was presented in the center of the computer screen until the participant vocalized a response that was recorded by the microphone; (4) the image disappeared and the experimenter coded the response using a keyboard; (5) feedback, either the word “correct” or “incorrect” was presented for 750 msec before the next trial began. (B) Participants recalled the responses to the learned images in the absence of feedback in Session 2. (C) Images appeared on the left or right side of the screen and participants indicated the location of the images (either left or right of center) with a vocal response. Stimuli included the six learned images presented in Sessions 1 and 2 as well as six new images. Trials in Sessions 2 and 3 were identical to Session 1 except that feedback was omitted in both and the images appeared on the left and right side of the screen in Session 3.