Facial feedback effect explains the autonomic impairment in PD for emotional recognition

Parkinson’s Disease (PD) is a degenerative neurological disorder of the central\r\nnervous system with a strong impact on both social and emotional level. Parkinson\r\npatients typically present with emotional processing impairment in emotional\r\nexperience and emotion recognition. However, it is not yet known whether these\r\npatients have lost the capability to feel the emotions intrinsically, to modulate to\r\nemotional experience associating subjective response with physiological modulations,\r\nor to decipher emotions in others. The present research aims at investigating\r\nthe contribution of central, peripheral and facial feedback measures in PD patients\r\nwhen they processed emotional cues using a multilevel approach, comparting selfreport\r\n(appraisal), autonomic (Skin Conductance Response, SCR) and motor electromyographic\r\n(EMG zygomaticus and corrugators facial muscles) measures. The\r\nintegration of these measures allowed firstly a direct comparison between the explicit\r\nappraisal of emotions (with specific reference to the two parameters of valence and\r\narousal) and the autonomic responsiveness to emotions. Secondly the role of EMG\r\n(zygomaticus and corrugators muscle) in determining the central and peripheral\r\nmodulation was explored. Indeed the facial feedback model supposed that the\r\nautonomic facial response by facial muscles may affect both the emotional appraisal\r\nand the physiological modulation. 20 patients have been selected and 34 healthy\r\nvolunteers (HC), matched for age and education. PD patients observed and evaluated\r\naffective pictures that were chosen from International Affective Picture System\r\n(IAPS). These pictures concerned four types of stimuli: 10 pleasant – low and high\r\narousal; 10 unpleasant – low and high arousal, 5 neutral. PD patients seemed to\r\nnot adequately answer to the emotional categories which were considered salient in\r\nstandard conditions (HC). Indeed, there was an autonomic impairment for a category-\r\nspecific emotion (negative and high arousal). Particularly, patients have revealed\r\nan inadequate sensibility (reduced SCR) only for negative emotional condition. In\r\nparallel EMG behavior was disrupted (reduced corrugators activity) in response to\r\nnegative high arousal emotional cues. However, PD patients were able to correctly\r\ncategorize the emotional cues based on their valence/arousal, probably due to a “gap”\r\nbetween this central process and the autonomic system activity. Then, the regression\r\nanalysis pointed out the predictive role of the corrugators activity to explain the\r\nimpaired autonomic response: a reduced corrugators mimic was linked to a reduced\r\nperipheral responsiveness toward the negative and high arousal emotional stimuli.