# Cognitive Aspects of the Motor Planning Stage of Gait: Effects of Aging and Parkinson’s Disease

## TL;DR

This study explores how aging and Parkinson’s disease affect the cognitive processes involved in preparing to walk, finding that the initial planning phase is more complex than previously thought.

## Contribution

The study identifies the cognitive complexity of the anticipatory postural adjustment phase in gait initiation, particularly in older adults and those with Parkinson’s disease.

## Key findings

- Time-to-APA was significantly longer than simple reaction time in all groups, indicating a more complex cognitive process.
- In older adults and Parkinson’s disease patients, time-to-APA was not significantly different from complex reaction time.
- Time-to-APA was associated with cognitive performance on the Color-Trails Test, suggesting a link to executive function.

## Abstract

The response to a request to walk involves a motor planning phase followed by an execution phase. The initial phase of gait initiation, specifically the time to anticipatory postural adjustment (APA), can be viewed as a form of reaction time. However, it is not clear how to characterize the cognitive processes involved in this stage. To address this question, time-to-APA, simple and complex upper limb visuomotor reaction time (SRT, CRT), cognitive, and motor performance were evaluated in 27 people with Parkinson’s disease (PD), 31 older adults (OA), and 34 young adults (YA). Our results showed that time-to-APA was significantly longer than SRT in all three groups (p < 0.001), indicating a more complex cognitive process. In YA, time-to-APA was significantly shorter than CRT (p < 0.001). In the OA and PD, time-to-APA was not significantly different from CRT. Mixed-effects analysis showed significant time (p < 0.001), group (p = 0.037), and group × time interaction effects (p = 0.002). Among all subjects, time-to-APA, but not APA duration, was associated with the Color-Trails Test (part B: rs = 0.406, p < 0.001). In PD, APA duration was correlated with MDS-UPDRS-part 3 (motor) scores (rs = 0.535, p = 0.004), but time-to-APA was not (p = 0.892). These findings suggest that time-to-APA is a cognitive process that is more complex than a SRT task and shares properties of a CRT task, especially among older adults and people with PD. In PD, this initial movement planning stage is not related to motor impairment, in contrast to APA duration. Further research is necessary to identify the factors underlying this initial stage of gait initiation.