Objective: We wanted to determine how the multiple step saccade pattern responds to antiparkinson medication, as it has been proposed to use this pattern as a potential biomarker for Parkinson’s disease (PD).

Background: Previous studies have consistently found that people with PD have a higher incidence of multiple step saccades than healthy controls during the memory-guided saccade task. This multiple step saccade pattern is an uncommon series of smaller amplitude or hypometric saccades to reach the remembered target location. This is in contrast to typical task performance, which involves making a larger amplitude primary saccade to the remembered location with the occasional small amplitude corrective saccade if needed.

Method: Thirty-three people with PD and 14 older adult healthy controls completed a memory-guided saccade task. Participants maintained fixation on a central point when a peripheral target briefly appeared for 50 ms. Participants were instructed to memorize the target location using peripheral vision. Following a variable delay (0.5 or 5 seconds), the disappearance of the central fixation point served as a cue to make a saccade to the remembered target location. People with PD performed this task over 2 days: 1 after overnight withdrawal from medication (off-meds) and 1 while on their usual medication (on-meds). The order of these conditions was randomized. Healthy controls performed the task once. Multiple step pattern was defined as the occurrence of 3 or more saccades in the direction of the target. This was a binary outcome for each trial. We used generalized mixed model logistic regression to calculate the probability of the multiple step pattern.

Results: Our findings confirm that people with PD have an increased probability of the multiple step pattern to the remembered target compared to healthy controls. In addition, we found that antiparkinson medication significantly reduced the probability of the multiple step pattern compared to off medication. Further analyses will be performed to test our hypothesis that this probability reduction is accompanied by an increase in primary saccade amplitude, which would suggest a beneficial modulation of saccade amplitude by dopaminergic circuits.

Conclusion: Medication benefits memory-guided saccades by reducing the probability of the multiple step pattern.

References: This abstract has been previously presented at the Neural Control of Movement Meeting (April 28-May 2, 2025).

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MDS Abstracts - https://www.mdsabstracts.org/abstract/antiparkinson-medication-reduces-the-probability-of-the-multiple-step-saccade-pattern-during-a-memory-guided-saccade-task/