Parkinson’s disease and anticipatory postural adjustments: Decreased cortical activity during step initiation

Background Step initiation is a critical movement that combines motor and cognitive elements, notably in individuals with Parkinson's Disease (PD) who experience marked difficulties due to disrupted anticipatory postural adjustments (APA). This study investigated the involvement of the Supplementary Motor Area (SMA) and the Dorsolateral Prefrontal Cortex (DLPFC) associated with step initiation that requires high cognitive processing (e.g., cognitive-motor conflicts) in individuals with PD compared to healthy controls. Methods We used functional near-infrared spectroscopy (fNIRS) to assess the cortical hemodynamic responses of 33 individuals with PD and 17 healthy controls as they performed step initiation in both congruent (all cues aligned) and incongruent (conflicting cues) conditions. The study sought to analyze variations in the hemodynamic responses related to these conditions, hypothesizing that PD individuals would exhibit reduced cortical activation in the SMA and DLPFC due to motor cortex inefficiencies affecting APA. Results Individuals with PD exhibited significant deficits in biomechanical performance (e.g., increased APA delays and errors) and altered hemodynamic responses in the SMA and DLPFC compared to controls, particularly under incongruent conditions. These observations indicate diminished cortical efficiency in PD during motor execution coupled with cognitive demands. Conclusion The findings suggest that PD involves impairments in cortical areas linked to movement planning and cognitive control. These findings suggest potential avenues for targeted rehabilitation strategies that enhance cognitive-motor integration, possibly improving mobility and reducing fall risk in PD.