Objective: To study the effects of Parkinson’s Disease (PD) on cortical activity during split-belt (SB) walking compared to tied-belt (TB) walking, and the impact of a second SB-exposure.

Background: People with PD (PwPD) have difficulty adapting gait. It remains unclear how PD affects cortical activity during gait adaptation. Previous fNIRS studies focused mainly on the prefrontal cortex (PFC) and did not include adaptive gait. A SB-treadmill induces gait asymmetry by reducing the speed of each leg separately. In this study, cortical activity was compared between TB- and SB-walking using functional near-infrared spectroscopy (fNIRS). The effects of a second SB-exposure and influence of leg and disease dominance were explored.

Method: 42 PwPD and 42 healthy controls (HC) performed TB- and SB-walking (50% reduction on each side, randomized), followed by another bout of SB-walking. fNIRS captured cortical activity (oxygenated hemoglobin, HbO) in the PFC, supplementary motor area (SMA), premotor cortex (PMC) and posterior parietal cortex (PPC). Adaptation was measured as step length asymmetry and variability. Clinical scales on balance, cognition and disease severity were also administered.

Results: Regardless of first or second SB-exposure, step length asymmetry during the last 5 steps was higher in PwPD than HC (p=0.036). Variability during the first 5 steps was higher in both groups during the first SB-exposure (p=0.010). PwPD showed higher PMC (p=0.007) and PPC (p=0.002) activity in both hemispheres compared to HC, regardless of condition (TB vs SB), first vs second SB-exposure (PMC p=0.005, PPC p=0.007), or leg/disease dominance (p>0.377). Higher PPC activity correlated with poor set-shifting (Trail-Making-Test B, r=0.317,p=0.041) and balance (MiniBEST, r=-0.333,p=0.031) in HC only. No other group differences or correlations with adaptation or disease characteristics were found.

Conclusion: PwPD were less able to reach symmetrical gait during SB-walking than HC, showing reduced ability for gait adaptation. Also, PwPD recruited more PMC and PPC activity than HC regardless of condition, leg or disease dominance. Higher HbO in PMC and PPC was associated with worse cognition and balance in HC, but not in PD.  Possibly, and unlike in HC, compensatory recruitment was saturated in PD during the SB-walking conditions, explaining the adaptation problems.

References: Previous results of this study have been submitted and accepted for poster presentation at the World Parkinson’s Congress (WPC), 4-7 July 2023 in Barcelona. The results in this abstract are a continuation of the ongoing data analysis and include new (sub)analyses and outcome measures.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/people-with-parkinsons-disease-present-compensatory-cortical-activity-patterns-during-split-belt-treadmill-walking-regardless-of-leg-or-disease-side-dominance/