Impaired recognition of facial expressions of anger in Parkinson's disease patients acutely withdrawn from dopamine replacement therapy

We have previously reported that acute dopaminergic blockade in healthy volunteers results in a transient disruption of the recognition of facial expressions of anger, whilst leaving intact the recognition of other facial expressions (including fear and disgust) and facial identity processing. Parkinson's disease (PD) is characterised by cell loss in dopaminergic neuronal populations, and hence we predicted that PD would be associated with impaired anger recognition. We reasoned that treatment with dopamine replacement therapy (DRT) could mask any deficit present in PD, and therefore studied facial expression recognition in a group of PD patients transiently withdrawn from DRT. Seventeen PD patients were compared to 21 age- and IQ-matched controls on the Ekman 60 task, which required the forced-choice labelling of 10 exemplars of each of six facial expressions (anger, disgust, fear, sadness, happiness, surprise). In line with our predictions, PD patients showed a selective impairment in the recognition of facial expressions of anger. This deficit was not related to the PD patients' performance on the Benton unfamiliar-face matching task, which was normal, nor was the deficit related to overall disease severity, or to depression symptoms. However, as predicted by simulation theories, impaired anger recognition in PD was related to reduced levels of the anger-linked temperament trait, exploratory excitability. The results extend our previous findings of a role for dopamine in the processing of facial expressions of anger, and demonstrate the power of adopting a phylogenetic, comparative perspective on emotions.