Primate Research Institute, Kyoto University, Inuyama, Japan.
Center for the Evolutionary Origins of Human Behavior, Kyoto University, 41-2 Kanrin, Inuyama, Aichi, 484-8506, Japan.
Sci Rep. 2022 Nov 16;12(1):19675. doi: 10.1038/s41598-022-23595-x.
Changes in facial expression provide cues for assessing emotional states in mammals and may provide non-verbal signals of pain. This study uses geometric morphometrics (GMM) to explore the facial shape variation in female Japanese macaques who underwent experimental laparotomy. Face image samples were collected from video footage of fourteen macaques before surgery and 1, 3, and 7 days after the procedure. Image samples in the pre-surgical condition were considered pain-free, and facial expressions emerging after surgery were investigated as potential indicators of pain. Landmarks for shape analysis were selected based on the underlying facial musculature and their corresponding facial action units and then annotated in 324 pre-surgical and 750 post-surgical images. The expression of pain is likely to vary between individuals. Tightly closed eyelids or squeezed eyes and lip tension were the most commonly observed facial changes on day 1 after surgery (p < 0.01974). A good overall inter-rater reliability [ICC = 0.99 (95% CI 0.75-1.0)] was observed with the method. The study emphasizes the importance of individualized assessment and provides a better understanding of facial cues to pain for captive macaque care.
面部表情的变化为评估哺乳动物的情绪状态提供了线索，并且可能提供疼痛的非言语信号。本研究使用几何形态测量学（GMM）来探索接受实验性剖腹手术的雌性日本猕猴的面部形状变化。从 14 只猕猴的手术前和手术后 1、3 和 7 天的视频片段中采集面部图像样本。手术前的图像样本被认为是无痛的，而手术后出现的面部表情被视为疼痛的潜在指标。基于面部肌肉及其对应的面部动作单元选择了形状分析的标记点，然后在 324 个术前和 750 个术后图像中进行了注释。疼痛的表达可能在个体之间有所不同。手术后第一天（p<0.01974）最常观察到的面部变化是紧闭的眼睑或挤眼和唇部紧张。该方法观察到很好的总体评分者间可靠性[ICC=0.99（95%CI 0.75-1.0）]。该研究强调了个体化评估的重要性，并为圈养猕猴护理中疼痛的面部线索提供了更好的理解。
