Differentiation of the motor cost associated with cognitive tasks in Parkinson's disease: A dual-task study.

Parkinson's disease is a neurodegenerative condition associated with motor and cognitive impairments. While the execution of dual cognitive-motor tasks imposes a cost on gait velocity, it has been barely determined if the gait deterioration depends on the specific cognitive domain involved in the dual-task. Twenty-four subjects (12 patients with Parkinson's disease and 12 healthy subjects) carried out a single task (gait alone) and several dual tasks where the concurrent second task was the Trail Making Test (Part A) and the six tasks of the Frontal Assessment Battery. Gait variables were measured by accelerometry via smartphone. Data analysis included analysis of variance (ANOVA) and exploratory factorial analysis. Both groups showed a similar gait performance, except for velocity, where patients exhibited a bradykinetic profile. The dual-task during the Trail Making Test showed the highest motor cost. Frontal Assessment Battery's tasks as conceptualization, mental flexibility and motor programming showed a higher motor cost than the other tasks (sensibility to interference, inhibitory control and environmental autonomy). The factorial analysis applied to the motor costs confirmed two profiles, grouping those related to the dorsolateral prefrontal cortex (mental flexibility and motor programming tasks) in an independent factor. Among cognitive functions, attention is critical for gait control in Parkinson's disease and healthy elderly people. The interference posed by several executive operations suggests a specific competition in prefrontal regions that support dual tasks. Moreover, the higher cost for patients with Parkinson's disease patients emphasizes the cognitive decline and compensatory cognitive strategy for gait control related to attention and executive functions.