Gait initiation is influenced by emotion processing in Parkinson's disease patients with freezing

Background: Freezing of gait is a symptom that affects more than 50% of Parkinson's disease (PD) patients and increasing evidence suggests that nonmotor systems (i.e., limbic system) are involved in its underlying mechanisms. Objective: The objective of this study was to investigate whether gait initiation characteristics are influenced by emotional stimuli in patients with PD, with or without freezing of gait. Methods: A total of 44 participants, divided into 3 groups (15 PD patients with and 15 PD patients without freezing of gait and 14 controls), stood on a sensorized mat and were asked to take a step forward in response to a pleasant image and a step backward in response to an unpleasant one (congruent task, low cognitive load) or to take a step backward in response to a pleasant image and a step forward in response to an unpleasant one (incongruent task, high cognitive load). Reaction time, step size, anticipatory postural adjustments, and sway path were measured. Results: In PD with freezing of gait, the reaction time was longer and the step size was shorter than in the other groups when they took a step forward in response to an unpleasant image (incongruent task). Changes in reaction time performance in response to unpleasant images remained significant after having adjusted for executive dysfunction and positively correlated with the "frequency" of freezing episodes. Conclusions: This study demonstrates that gait initiation was influenced by the emotional valence of visual stimuli in addition to the cognitive load of the task suggesting that the limbic system may be involved in freezing of gait.