Freezing of gait in Parkinson's disease is related to impaired motor switching during stepping

BackgroundParkinson's disease (PD) has been associated with set switching difficulty in both the motor and the cognitive domain. However, the contribution of these set switching deficits to the primary motor symptoms of the disease is unclear. We investigated whether set switching deficits contribute to gait and stepping problems in PD. By contrasting motor and cognitive set switching within the same paradigm, we investigated the nature of set switching deficits associated with freezing of gait (FOG). MethodsWe integrated step initiation with set switching within one task and compared patients with and without FOG with healthy subjects. Motor set switching was defined as a change in stepping direction from one trial to the next. Cognitive set switching was defined as a change in task rule (ie, respond according to the shape or color of the presented stimulus). ResultsWe found delayed motor switching in PD patients with FOG. We did not observe impaired cognitive switching. ConclusionsThese findings suggest that motor set switching deficits, commonly reported in tasks using verbal or tapping responses, extend to stepping and can contribute to the occurrence of freezing episodes during gait initiation. (c) 2015 International Parkinson and Movement Disorder Society