The specific contributions of set-shifting to freezing of gait in Parkinson's disease.

Freezing of gait (FOG) in Parkinson's disease (PD) is common and the pathophysiology of FOG is poorly understood. It has been hypothesized to reflect complementary yet competing frontostriatal pathways that reduce the ability to keep different tasks (motor or cognitive) on-line. This inability to "set-shift" has been proposed to trigger a freezing episode. If correct, this hypothesis would predict a differential pattern of executive dysfunction with FOG being most specifically related to attentional set-shifting. In this study, 31 patients with a range of self-reported FOG symptom severities were administered tests of executive functioning. The results demonstrate that FOG symptoms were selectively correlated with poorer performance on tasks of set-shifting, but not with a range of other executive tasks. This was apparent even after controlling for slowed processing speed, disease stage and depressive symptoms. The results support the recently proposed hypothesis for the pathophysiology underlying FOG in PD.