Objective: We aimed to investigate the relationship between exposure trials and the acquisition of prism adaptation or the after-effect (AE) in patients with Parkinson’s disease (PD) and age-matched healthy volunteers (HVs).

Background: Prism adaptation is used to study the cerebellar adaptive functions in neurological disorders. It is well-known that some cerebellar functional changes should occur in Parkinson’s disease (PD). Because the previous results of prism adaptation were inconsistent in PD, we aimed to investigate the acquisition of prism adaptation and the after-effect (AE) in PD patients and age-matched healthy volunteers (HVs). Another aim was to see the effects of trial numbers on adaptation parameters.

Method: Patients performed a finger-reaching task while wearing 20-D wedge-prism lenses, for 50 and 200 trials. The average of the errors in the last 10 prism exposure trials was considered an adaptation acquisition parameter. We also measured the first AE at the beginning of the post-exposure period and the recovered AE by blocking visual feedback during the post-exposure period. Forty-one patients with PD (21 men, 20 women; 68.1 ± 1.4 years; range 57−81 years) and 35 HVs (17 men, 18 women; age 66.4 ± 1.5 years; range 52–81 years) were enrolled in the study.

Results: In the HVs, 200 trials enlarged the recovered AE compared to 50 trials, without any effects of trail number on adaptation acquisition or the first AE. In the PD group, neither the adaptation acquisition nor first AE was affected by the trial number, but the recovered AE was larger than that of the HVs in 50 trials. No prism adaptation parameters correlated with any clinical severity scores.

Conclusion: In PD, 50 trials induced an increase of the recovered AE, which may reflect the cerebellar hyperfunction to compensate for the basal-ganglia dysfunction.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/the-effect-of-trial-numbers-on-prism-adaptation-in-parkinsons-disease/