Reduced Ventrolateral fMRI Response during Observation of Emotional Gestures Related to the Degree of Dopaminergic Impairment in Parkinson Disease
Recent findings point to a perceptive impairment of emotional facial expressions in patients diagnosed with Parkinson disease (PD). In these patients, administration of dopamine can modulate emotional facial recognition. We used fMRI to investigate differences in the functional activation in response to emotional and nonemotional gestures between PD patients and age-matched healthy controls (HC). In addition, we used PET to evaluate the striatal dopamine transporter availability (DAT) with [11C]d-threo-methylphenidate in the patient group. Patients showed an average decrease to 26% in DAT when compared to age-corrected healthy references. Reduction in the DAT of the left putamen correlated not only with motor impairment but also with errors in emotional gesture recognition. In comparison to HC, PD patients showed a specific decrease in activation related to emotional gesture observation in the left ventrolateral prefrontal cortex (VLPFC) and the right superior temporal sulcus. Moreover, the less DAT present in the left putamen, the lower the activation in the left VLPFC. We conclude that a loss of dopaminergic neurotransmission in the putamen results in a reduction of ventrolateral prefrontal access involved in the recognition of emotional gestures.