Reduced emotional mirroring in Parkinson Disease

Besides motor symptoms, Parkinson Disease (PD) is characterized by cognitive and affective impairments. For example, a facial emotion recognition deficit has often been reported (Grey & Tickle-Degnen, 2010). Neuroimaging studies suggest that perception and execution of emotional facial expressions are closely linked by mirror neurons in the pars opercularis and that the activation of these neurons during perception triggers intention understanding (Hennenlotter et al., 2005). The goal of our study was to examine the neural correlates of emotion processing in PD. Nine patients with PD and nine matched controls underwent functional magnetic resonance imaging. The experiment was implemented as a two-by-three factorial design with the factors task (observation of facial gestures, expression of facial gestures) and type of facial gesture (happy, non-emotional, neutral). Video clips depicting actors and scrambled video clips were used as stimulus material. Participants were instructed to observe whenever they saw the actors and to execute whenever they saw the scrambled videos. We found conjoint activation for observation and expression of the emotional facial gesture in the right pars opercularis, the left amygdala, and right occipito-temporal areas extending to the inferior parietal lobule, when data were pooled across all participants. In the group comparison, region of interest analysis revealed weaker activation of the right pars opercularis during observation of the emotional facial gestures in patients with PD. The results provide evidence for altered neural processing of emotional facial expressions in patients with PD. Previous research has shown increased activation of the IFG in asymptomatic Parkin mutation carriers during processing of emotions. This was interpreted as compensatory mechanism (Anders et al., 2011). It is possible that decreased activation of the pars opercularis is a result of a break down of this compensatory mechanism.

Literatur: Anders et al. (2011). Compensatory premotor activity during affective face processing in subclinical carriers of a single mutant Parkin allele. Brain, accepted. Gray and Tickle-Degnen (2010). A Meta-Analysis of Performance on Emotion Recognition Tasks in Parkinson‘s Disease. Neuropsychology, vol.24, pp. 176-191. Hennenlotter et al. (2005), ‘A common neural basis for receptive and expressive communication of pleasant facial affect’ Neuroimage, vol.26, pp. 581-591