Retrograde Procedural Memory in Parkinson's Disease: A Cross-Sectional, Case-Control Study

Background: The analysis of the procedural memory is particularly relevant in neurodegenerative disorders like Parkinson's disease, due to the central role of the basal ganglia in procedural memory. It has been shown that anterograde procedural memory, the ability to learn a new skill, is impaired in Parkinson's disease. However, retrograde procedural memory, the long-term retention and execution of skills learned in earlier life stages, has not yet been systematically investigated in Parkinson's disease. Objective: This study aims to investigate retrograde procedural memory in people with Parkinson's disease. We hypothesized that retrograde procedural memory is impaired in people with Parkinson's disease compared to an age- and gender-matched control group. Methods: First, we developed the CUPRO evaluation system, an extended evaluation system based on the Cube Copying Test, to distinguish the cube copying procedure, representing functioning of retrograde procedural memory, and the final result, representing the visuo-constructive abilities. Development of the evaluation system included tests of discriminant validity. Results: Comparing people with typical Parkinson's disease (n = 201) with age- and gender-matched control subjects (n = 201), we identified cube copying performance to be significantly impaired in people with Parkinson's disease (p = 0.008). No significant correlation was observed between retrograde procedural memory and disease duration. Conclusion: We demonstrated lower cube copying performance in people with Parkinson's disease compared to control subjects, which suggests an impaired functioning of retrograde procedural memory in Parkinson's disease.