Emotion processing in Parkinson’s disease: Dissociation between early neuronal processing and explicit ratings Matthias J. Wieser * , Andreas Mu ¨hlberger, Georg W. Alpers, Michael Macht, Heiner Ellgring, Paul Pauli Department of Psychology, University of Wu ¨rzburg, Wu ¨rzburg, Germany Accepted 15 September 2005 Available online 5 December 2005 Abstract Objective: Patients suffering from Parkinson’s disease (PD) have a diminished ability to discriminate facial expressions of emotion. We investigated early emotion discrimination deficits in PD by means of event-related potentials (ERPs). Methods: Emotional pictures were presented to 14 PD patients and 14 healthy controls in a rapid serial visual presentation paradigm (three frames per second) while EEG was recorded. In addition, valence and arousal ratings were obtained for a representative subsample of 54 pictures. Results: PD patients rated pictures of highly arousing content as less exciting than did healthy controls. Pictures of high compared to low emotional arousal were associated with a pronounced relative negative shift in the ERP waveform over parietal and occipital sites developing about 220 ms after picture onset. This early posterior negativity (EPN) did not differ between PD and control group. Conclusions: This dissociation of affective ratings and early ERP components supports the view that PD is associated with blunted emotional responses, but there is no evidence for a deteriorated early visual processing of emotional stimuli. Significance: Frequently reported deficits in emotion discrimination are likely not due to deficits in early emotion processing. q 2005 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved. Keywords: Parkinson’s disease; Emotion processing; Early affective discrimination; ERPs 1. Introduction Parkinson’s disease (PD) is caused by an irreversible degeneration of dopaminergic neurons in the substantia nigra pars compacta, which leads to dysfunction of the striatal structures innervated by those neurons (e.g., Parent, 1990). Research on PD mostly focused on the characteristic motor symptoms (Hoehn and Yahr, 1967) and cognitive impairments such as disturbed executive functioning (e.g., Pillon et al., 1996). In recent years, the observation that emotional processing can be affected in PD has received growing attention. Both spontaneous and posed facial expressions have been shown to be disturbed and reduced in PD patients (Jacobs et al., 1995; Madeley et al., 1995; Smith et al., 1996; Simons et al., 2003). PD patients showed fewer and less expressive spontaneous facial expressions in response to emotional video clips (Smith et al., 1996) as well as in response to unpleasant odors (Simons et al., 2003). PD is also associated with a reduced ability to pose facial expressions voluntarily (Jacobs et al., 1995; Madeley et al., 1995). While these findings suggest an association of PD with reduced emotional behavioral outputs, few studies focused on emotion perception. Guided by clinical observations PD-related deficits were examined with respect to affective prosody (Pell, 1996; Benke et al., 1998; Breitenstein et al., 2001) and facial expression (Scott et al., 1984; Dewick et al., 1991; Jacobs et al., 1995) which are the most relevant cues on emotional communication. In Pell’s study (1996), PD patients completed a battery of emotional prosody tasks which included sentences with both Clinical Neurophysiology 117 (2006) 94–102 www.elsevier.com/locate/clinph 1388-2457/$30.00 q 2005 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.clinph.2005.09.009 * Corresponding author. Address: Department of Psychology, Biological Psychology, Clinical Psychology, and Psychotherapy, University of Wu ¨rzburg, Marcusstr. 9-11, 97070 Wu ¨rzburg, Germany. Tel.: C49 931 312426; fax: C49 931 312733. E-mail address: wieser@psychologie.uni-wuerzburg.de (M.J. Wieser).