Deep Pain: Exploiting Long Short-Term Memory Networks for Facial Expression Classification

• Published in: IEEE transactions on cybernetics Vol. 52; no. 5; pp. 3314 - 3324
• Main Authors: Rodriguez, Pau, Cucurull, Guillem, Gonzalez, Jordi, Gonfaus, Josep M., Nasrollahi, Kamal, Moeslund, Thomas B., Roca, F. Xavier
• Format: Journal Article
• Language: English
• Published: United States IEEE 01.05.2022; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Affective computing; Artificial neural networks; computer applications; cybercare industry applications; Emotions; Estimation; Face; Face recognition; Facial Expression; Feature extraction; Frames (data processing); Hidden Markov models; human factors engineering in medicine and biology; Human resources; Humans; Machine learning; medical services; monitoring; Motion perception; Neural Networks, Computer; Pain; patient monitoring computers and information processing; pattern recognition
• ISSN: 2168-2267; 2168-2275; 2168-2275
• DOI: 10.1109/TCYB.2017.2662199

Pain is an unpleasant feeling that has been shown to be an important factor for the recovery of patients. Since this is costly in human resources and difficult to do objectively, there is the need for automatic systems to measure it. In this paper, contrary to current state-of-the-art techniques in pain assessment, which are based on facial features only, we suggest that the performance can be enhanced by feeding the raw frames to deep learning models, outperforming the latest state-of-the-art results while also directly facing the problem of imbalanced data. As a baseline, our approach first uses convolutional neural networks (CNNs) to learn facial features from VGG_Faces, which are then linked to a long short-term memory to exploit the temporal relation between video frames. We further compare the performances of using the so popular schema based on the canonically normalized appearance versus taking into account the whole image. As a result, we outperform current state-of-the-art area under the curve performance in the UNBC-McMaster Shoulder Pain Expression Archive Database. In addition, to evaluate the generalization properties of our proposed methodology on facial motion recognition, we also report competitive results in the Cohn Kanade+ facial expression database.