Cortical activation during gait adaptability in people with Parkinson's disease.

BACKGROUND: People with Parkinson's disease (PD) have difficulties adapting their gait. While underlying neural mechanisms involving the prefrontal cortex (PFC) have been studied across various complex walking tasks, less is known about the premotor cortex (PMC) and supplementary motor area (SMA), key cortical regions for motor planning. This study compared frontal cortical regions activation patterns using functional near-infrared spectroscopy (fNIRS), between people with PD and healthy controls (HC) during gait adaptability tasks. METHODS: Forty-nine people with PD (mean (SD) age: 69.5 (7.9) years) and 21 HC (69.0 (5.9) years) completed a simple walk and three randomly presented gait adaptability tasks: (i) stepping on targets, (ii) avoiding obstacles and (iii) negotiating both targets and obstacles. Cortical activity in the dorsolateral PFC (DLPFC), SMA and PMC were recorded using fNIRS. Step length, velocity and accuracy and cortical activity were contrasted between the groups and walking conditions. RESULTS: Compared with the HC, the PD group exhibited greater PMC activation and walked significantly slower and took shorter steps in all conditions. A statistically significant group by condition interaction indicated an increase in DLPFC cortical activation in the HC participants when undertaking the obstacle avoidance task compared with the simple walk but no increase in cortical activation in the PD group when undergoing this more challenging gait task. CONCLUSIONS: Our findings suggest people with PD have little or no DLPFC, SMA and PMC capacity beyond what they need for simple walking and in consequence need to slow their gait velocity to meet the demands of target stepping and obstacle avoidance tasks. Such behavioral and neural patterns appear consistent with concepts of compensatory over-activation and capacity limitation.