The Emotional Expression Response of a Patient Based on their Facial Expression
—Focus on Music Stimuli

Objective: To determine whether patients with unresponsive wakefulness syndrome respond to auditory stimuli based on changes in facial expressions. Participants: Six patients diagnosed with disorders of consciousness due to brain injury with permission for participation from their doctor. Design: In this hypothesis-driven observational study, the facial expressions of patients with unresponsive wakefulness syndrome were video-recorded for 5 min before and during auditory stimulation in three consecutive weekly sessions. Main Measures: Facial muscle movement was quantified using FaceReader^®？software (Noldus, Wageningen, Netherlands). Valence/action unit values were plotted to detail facial expression changes. Heart rate values were also plotted. These parameters were compared before and after stimulation. Results: No significant differences in valence integral values or average heart rate were observed between the pre- and intra-stimulus conditions. However, valence signals increased in approximately half of the sessions, indicating that some patients with unresponsive wakefulness syndrome may exhibit emotional responses to auditory stimuli. Analysis of action unit integral values indicated that movement of the eyebrows and eyelids on the upper part of the face occurred during auditory stimulation. Furthermore, the types of auditory stimuli differed depending on the session for the 12 sessions of voice stimuli, whereas the changes in average heart rate differed in each of nine sessions of music stimuli. Because the changes in average heart rate were similar, it is possible that musical stimuli are more suitable than voice stimuli. Conclusion: Some patients with unresponsive wakefulness syndrome may have an emotional response to auditory stimuli. Our findings indicate that it may be possible to distinguish the emotional expression response of a patient based on their facial expression.