The retrograde procedural memory in people with Parkinson’s disease with or without freezing of gait – a cross-sectional study

Objective: To investigate the retrograde procedural memory in people with typical Parkinson’s disease (PwP) with or without freezing of gait (FOG). We hypothesized that the retrograde procedural memory is more strongly impaired in patients with FOG (FOG+) than in patients without FOG (FOG-).

Background: Given that cognitive functions, like executive control and automaticity, are crucial for mobility, it is of great importance to get a deeper knowledge of the cognitive impairment that may interfere with walking and causing gait disturbances in PwP, i.e. FOG.
The integrity of retrograde procedural memory, the ability to execute skills that have been learned in earlier life stages, is essential for a person’s ability to complete routine, procedural activities like walking. As FOG is characterized as a de-automatization disorder, we hypothesized an impairment of the retrograde procedural memory in patients with FOG.

Methods: A total of 194 patients from the Luxembourg Parkinson’s study were included into the cross-sectional study. All patients were assigned to the FOG+ / FOG- groups based on a semi-structured interview conducted by a study physician. The extended evaluation system of the cube copying test was applied to evaluate both the cube-drawing procedure, representing the retrograde procedural memory, and the final result, representing the visuo-constructive abilities (Pauly et al., 2020, MDS abstract). We compared the cube copying performance of n=97 FOG+ with n=97 age-, gender- and education-matched FOG-.

Results: FOG+ scored lower on the cube copying procedure compared to the FOG- (p=0.027), which is suggestive of an impaired retrograde procedural memory in FOG+. No significant differences in the visuo-constructional abilities were detected (p=0.945).

Conclusion: In line with FOG being considered a de-automatization of walking, a skill acquired in earlier life stages, the present results suggest that PwP with FOG have an impaired retrograde procedural memory in comparison to PwP without FOG. The results lend support to the ability of the extended evaluation system of the cube copying test to assess impaired retrograde procedural memory and help improve our understanding of behavioral symptoms in PwP.