Freezing of gait and affective theory of mind in Parkinson disease.

Abstract

Affective "Theory of Mind" (ToM) is the specific ability to represent own and others' emotional states and feelings. Several studies examined affective ToM ability in patients with Parkinson's disease (PD), using the "Reading the Mind in the Eyes test" (RMET). However, there has been no agreement as to whether or not affective ToM ability is impaired in PD and such discrepancy may be due to the heterogeneous clinical presentation of PD. Affective disturbance has been linked to the akinetic-rigid form of PD and to gait disturbances, like freezing of gait (FOG). Particularly, FOG has been associated with dysfunction in striatum ability of processing affective inputs. Here we hypothesized that the presence of FOG can be associated with impaired affective ToM ability in PD patients. We evaluated ToM by means of RMET and executive functions using the Tower Of London (ToL) test in 29 PD patients (15 with FOG and 14 without FOG) and 19 healthy age-matched subjects. Our results showed that affective ToM is abnormal in PD patients, compared to healthy subjects and that it is more impaired in patients with FOG than in patients without FOG. Further, PD patients with FOG performed worse than PD patients without FOG on the ToL test. The affective aspects of ToM can be associated to FOG in patients with PD, thus supporting the idea that FOG is caused by a complex interplay between motor, cognitive and affective factors, rather than being a pure motor problem.