First steps matter: gait initiation reveals emotion-driven motor compensation in Parkinson's disease.

Parkinson's disease (PD) disrupts the intricate cognitive, emotional and sensorimotor circuits required for movement. In a recent study, we observed that fear-related embodied stimuli could enhance motor responses in early stage persons with PD (PwPD), potentially by activating neural compensatory mechanisms. In this observational study, we implemented a sensor-based 'Go/No-go' gait initiation task involving a response to emotional facial expressions-fear, happiness and neutral facial expressions-to elucidate whether and how emotional cues may drive compensatory mechanisms for motor performance in middle-stage PD. Furthermore, we investigated whether these mechanisms differ between PwPD exhibiting tremor-dominant (TD) or postural instability and gait disorders (PIGD) motor subtypes. By comparing gait initiation parameters between PD participants and age-matched healthy controls, we found that emotional stimuli reduced the duration of anticipatory postural adjustments and the step execution time across both groups, indicating a robust motor advantage. Specifically, happiness elicited a more pronounced advantage than fear, though PwPD displayed a diminished benefit relative to controls. Intriguingly, individuals with the PIGD subtype showed a weaker motor advantage for 'happiness' than those with the TD subtype, suggesting subtype-specific differences, possibly reflecting different underlying neural circuitry. Collectively, our findings reveal that while emotional cues generally facilitate gait initiation, fear and happiness exhibit distinct modulatory effects in PD. Compared to our earlier findings, the fear-related motor benefit appears to decline with disease progression, while the happiness-related advantage varies considerably across PD subtypes. These insights highlight the nuanced interplay between emotion and motor control in PD and suggest the use of a cognitive-emotional-sensorimotor integration task as a sensitive predictor for differentiating PD motor subtypes.