Attentional set-shifting in Parkinson's disease patients with freezing of gait-acquisition and discrimination set learning deficits at the background?

Cognitive loading aggravates the freezing of gait (FoG), which is observed in approximately 50% of patients with Parkinson's disease (PD) in the advanced stages. To investigate whether a specific pattern of executive deficits, that is, attentional set-shifting and/or inhibitory control, are associated with FoG in PD, 30 PD patients with FoG (PD-FoG+) and 36 PD patients without FoG (PD-FoG-) and 22 control healthy subjects were examined with a comprehensive neuropsychological battery. Intra-Extra Dimensional Set shifting Test (IED) and Stop Signal Task (SST), selected from the Cambridge Automated Neuropsychological Battery (CANTAB battery), were administered to analyze set-shifting and motor inhibition, respectively. The IED task was significantly sensitive for differentiating between PD-FoG+ and PD-FoG- groups (p<.01), as well Adenbrook's clock drawing task (p=.033). By contrast, no differences emerged on any aspect of the SST task and other cognitive tasks. The attrition rate during the IED task showed that the problem in the PD-FoG+ group appeared at the pre-ID level, on the discrimination-learning set; the 32% PD-FoG+ subjects did not achieve the ID level of the task in comparison to negligible 4% of the PD-FoG- patients (p=.011). The logistic regression analysis, indicated the higher the IED stage successfully completed, the less likely presence of FoG in PD subjects. These results demonstrate that the complex cognitive-motor interplay might be responsible for FoG in PD and have had real life implication for the patients.