Is "reading mind in the eyes" impaired in Parkinson's disease?

Theory of mind (ToM) is the specific cognitive ability to understand other people's mental states. Several studies have examined ToM ability in patients with Parkinson's disease (PD), using the "reading mind in the eyes" test (RMET). However, there has been no agreement as to whether or not ToM ability in this task is affected by PD. In order to obtain conclusive evidence regarding ToM ability in PD, we examined RMET-related performance in nondemented PD patients; we also used the semantic discrimination task to exclude the possibility that PD patients had difficulty in distinguishing emotional adjectives. Results indicated that ToM ability in the RMET is impaired in PD patients, and that this finding was not attributable to the visual processing of faces or the verbal comprehension of emotional adjectives. Thus, the affective aspects of ToM can be impaired in PD patients.