Background: The basal ganglia are thought to be critical for the expression and possibly the perception of emotions. Processing of emotional faces was found to be impaired in Parkinson's disease (PD) in some but not all studies. The aim of this study was to test whether performance in emotion discrimination would differ as a function of stage of the disease.
Method: Early (N=21) and late stage (N=18) nondemented PD patients, and healthy controls (N=21), matched for age, sex and education level were studied. Early PD patients (mean±S.D. age: 61.7± 8.6; Hoehn and Yahr rating score: 2±0.5; PD duration (year): 3.9±1.9), had no signs of dementia as per the Mattis Dementia Rating Scale. Late stage PD patients (mean±S.D. age: 61.2± 9.5; H&Y: 3.9±0.5; disease duration (year): 11.9±5.4), were candidates for STNDBS neurosurgery, and not demented as per a comprehensive neuropsychological assessment (CAPSIT); a sub-sample was reassessed under STN-DBS. Emotion discrimination was assessed with a computeradministered task presenting facial exemplars of basic emotions paired to convey the same or different emotions.
Results: Late but not early stage PD patients showed significantly lower performance than healthy controls in emotion discrimination (p<0.0001). Performance did not differ on a control task for face recognition (Benton); lower performance in advanced PD was not explained by other variables such as depression, or impairments in executive functions.
Conclusion: Emotional processing is impaired in non-demented late stage PD patients and appears to be stage dependent.