Abstract
Introduction: Parkinson’s disease (PD) is a degenerative brain disease. As it progresses, the patients often develop dementia (PD-D) which affect their mental functions. Previous studies revealed PD patients with impaired facial identity recognition and emotion perception; however, few studies explored face discrimination and dynamic facial emotion perception in PD-D patients. Therefore, with three tasks, we examined the PD-D patients’ face discrimination threshold, their capability to recognize the six-basic emotions in dynamic display, and their ability to imitate facial expressions. Method: We tested 25 PD-D patients (mean age: 74.72±6.05) and 21 healthy controls (mean age: 68.76±6.54) with three tasks: (1) Same/different morphing-face discrimination, where it involves comparing a target face and a comparison morphing face at 0% (same) or 20%, 40%, 60%, and 80% (different) sequentially; (2) Dynamic facial emotion task, in which participants were to identify the six basic emotions (anger, disgust, fear, happy, sad, and surprise); and (3) Expression imitation task, where they were asked to imitate the six basic expressions and coded by i-motion software. Results: (1) PD-D patients exhibited a similar discrimination threshold but have a shallower response function, indicating a high uncertainty in discriminating faces than healthy controls. (2) The patients performed worse in recognizing anger, disgust, sad, and surprise, and had a longer response time as compared to the controls. (3) The patients had a significantly lower probability when imitating “Happiness” and “Surprise”; additionally, their “Engagement” in facial muscle activation was also lower. Conclusion: Our findings suggested that PD-D patients suffer greater internal noises when discriminating faces. They are impaired in recognizing negative emotions but can imitate some emotions with less intensity. Although PD-D patients performed significantly worse in all three tasks, they retain face processing capacity at some level. Thus, the face perception neural network in PD-D patients seems partially intact.
Acknowledgement: MOST 105-2420-H-039-001-MY3, to Dr. Chien and MOST 107-2632-B-039-001-to Dr. Chien, Dr. Lane, and Dr. Tsai