Abstract
Affective dysfunctions are common in patients with Parkinson's disease, but the underlying neurobiological deviations have rarely been examined. Parkinson's disease is characterized by a loss of dopamine neurons in the substantia nigra resulting in impairment of motor and non-motor basal ganglia-cortical loops. Concerning emotional deficits, some studies provide evidence for altered brain processing in limbic- and lateral-orbitofrontal gating loops. In a second line of evidence, human premotor and inferior parietal homologs of mirror neuron areas were involved in processing and understanding of emotional facial expressions. We examined deviations in brain activation during processing of facial expressions in patients and related these to emotion recognition accuracy. 13 patients and 13 healthy controls underwent an emotion recognition task and a functional magnetic resonance imaging (fMRI) measurement. In the Emotion Hexagon test, participants were presented with blends of two emotions and had to indicate which emotion best described the presented picture. Blended pictures with three levels of difficulty were included. During fMRI scanning, participants observed video clips depicting emotional, non-emotional, and neutral facial expressions or were asked to produce these facial expressions themselves. Patients performed slightly worse in the emotion recognition task, but only when judging the most ambiguous facial expressions. Both groups activated inferior frontal and anterior inferior parietal homologs of mirror neuron areas during observation and execution of the emotional facial expressions. During observation, responses in the pars opercularis of the right inferior frontal gyrus, in the bilateral inferior parietal lobule and in the bilateral supplementary motor cortex were decreased in patients. Furthermore, in patients, activation of the right anterior inferior parietal lobule was positively related to accuracy in the emotion recognition task. Our data provide evidence for a contribution of human homologs of monkey mirror areas to the emotion recognition deficit in Parkinson's disease.
Highlights
Patients with idiopathic Parkinson’s disease (PD) suffer from a wide range of emotional disturbances including subjective feeling of emotions and the related physiological arousal states, and recognizing and expressing them [1]
A meta-analysis of structural imaging data revealed a reduction of left lateral orbitofrontal cortex (OFC) (BA47) gray matter volume in PD [6], which in turn was associated with disturbed facial emotion recognition [7]
We examined whether patients with manifest idiopathic Parkinson’s disease show altered emotion recognition abilities and altered involvement of human homologs of mirror neuron areas and/or structures embedded in limbic- or lateral-orbitofrontal-basal ganglia circuits during execution and observation of emotional facial expressions
Summary
Patients with idiopathic Parkinson’s disease (PD) suffer from a wide range of emotional disturbances including subjective feeling of emotions and the related physiological arousal states, and recognizing and expressing them [1]. These deficits are important as life quality is reduced and social interactions are hampered. Dopamine deficiency due to loss of nerve cells in the substantia nigra results in an imbalance of dopaminergic innervation in subcortico-cortical circuits, which causes typical motor and non-motor symptoms in PD [4]. We examined deviations in brain activation during processing of facial expressions in patients and related these to emotion recognition accuracy
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