Cortical Activation During Split-Belt Treadmill Walking in People With Parkinson’s Disease and Healthy Controls

BackgroundPeople with Parkinson's disease (PwPD) have difficulty adapting their gait to asymmetrical conditions. <i>Objective.</i> We investigated cortical activity between 42 PwPD (HY 2-3) and 42 healthy controls using functional near-infrared spectroscopy during tied-belt (TB) and split-belt (SB) treadmill walking.MethodsOxygenated hemoglobin (HbO2) was measured in the prefrontal cortex, supplementary motor area (SMA), premotor cortex (PMC), and posterior parietal cortex (PPC) during 3 blocks of treadmill walking: (1) with the belts moving at the same speed (TB) and (2) when the speed of 1 side was reduced by 50% (SB; 2 blocks). The ability to adjust gait to asymmetric conditions was quantified by step length asymmetry and its variability.ResultsAdaptive gait was worse during the last 5 steps of SB versus TB in PwPD compared to controls. PwPD showed higher HbO2 in the PMC (<i>P</i> = .005) and PPC (<i>P</i> = .004) relative to controls, regardless of condition. However, an increase in HbO2 in the SMA during SB was shown relative to TB in PwPD, a change not observed in controls (group × condition interaction <i>P</i> = .048; pairwise post hoc <i>P</i> = .032). Interestingly, increased PPC activity in PwPD was associated with poorer adapted gait.ConclusionsBoth regular and adaptive gait required enhanced cortical processing in PwPD, as evidenced by the increased activation in the PMC and PPC. However, this heightened cortical activity did not correlate with a reduction in gait asymmetry, suggesting that these changes might be maladaptive. Instead, the elevated cortical activity may reflect the challenges PwPD face in adapting to asymmetrical walking conditions. Careful interpretation is warranted given the relatively small sample of mildly affected PwPD, limiting generalizability to the broader population and the measurement errors inherent to functional near-infrared spectroscopy .