Facial EMG and the subjective experience of emotion in idiopathic Parkinson's disease in response to affectively laden visual stimuli.

Abstract

The purpose of the study was to investigate the possible role of facial musculature movement in the subjective experience of emotion. Nineteen nondemented, nondepressed patients with idiopathic Parkinson's disease and 19 demographically matched control subjects were asked to rate valence and arousal dimensions after viewing emotionally laden slides. The patients with Parkinson's disease viewed one set of slides at their peak levodopa dose and one set of slides after at least a 12 hour abstention from their levodopa medication. Normal control subjects underwent two similar testing sessions, although no drug was administered. Mean valence and mean arousal ratings of slides within groups were determined. During the viewing of the slides, bilateral facial electromyographic activity in the zygomatic and corrugator muscle regions was recorded. EMG change scores relative to individual slide presentation were determined. Comparisons were made between and within groups of the mean valence, arousal, and EMG change scores relative to the slide valence type (i.e., positive, neutral, or negative slide content) and on/off drug condition. Results suggest that a subgroup of Parkinson's Disease patients experience similar emotional valence and arousal, to that of normal controls, when confronted with emotional visual stimuli. However, they display significantly less facial muscular movement in the zygomatic muscle region and somewhat less facial muscular movement in the corrugator region than the normal controls. Implications of these results are discussed relative to the James-Lange theory that posits emotional experience to be dependent upon a peripheral "feedback" system versus the Cannon-Bard theory that posits emotion to be mediated centrally. Although the present results lend support to the Cannon-Bard theory of emotion, future research is necessary to determine the role of the skin of the face (with blood and temperature components), rather than the facial musculature per se, in the subjective experience of emotion. It may be that the skin of the face and the sound of one's own voice (among other factors) play important roles in the subjective experience of emotion as posited by S. S. Tomkins. If so, a modified peripheral mediation theory of emotion would be supported.