[Social cognitive impairment is an integral part of Parkinson disease]

Parkinson disease (PD) is thought to be primarily a disorder of the motor system due to dysfunction of the nigrostriatal dopaminergic system. However, recent studies have revealed that social cognition tasks, such as facial expression recognition, decision-making, and mind-reading, are also impaired in PD. The studies also demonstrated that these impairments can occur due to dysfunctions of mesocorticolimbic dopaminergic system, particularly in the amygdala. Furthermore social cognitive impairments may develop in the early stage of PD. Therefore we have to understand PD as a not only movement but also cognitive disorder.