PARSE: Pairwise Alignment of Representations in Semi-Supervised EEG Learning for Emotion Recognition

We propose pairwise alignment of representations for semi-supervised Electroencephalogram (EEG) learning (PARSE), a novel semi-supervised architecture for learning reliable EEG representations for emotion recognition. To reduce the potential distribution mismatch between large amounts of unlabeled data and a limited number of labeled data, PARSE uses pairwise representation alignment. First, our model performs data augmentation followed by label guessing for large amounts of original and augmented unlabeled data. The model is then followed by sharpening the guessed labels and convex combinations of the unlabeled and labeled data. Finally, it performs representation alignment and emotion classification. To rigorously test our model, we compare PARSE to several state-of-the-art semi-supervised approaches, which we implement and adapt for EEG learning. We perform these experiments on four public EEG-based emotion recognition datasets, SEED, SEED-IV, SEED-V and AMIGOS (valence and arousal). The experiments show that our proposed framework achieves the overall best results with varying amounts of limited labeled samples in SEED, SEED-IV and AMIGOS (valence), while approaching the overall best result (reaching the second-best) in SEED-V and AMIGOS (arousal). The analysis shows that our pairwise representation alignment considerably improves the performance by performing the distribution alignment between unlabeled and labeled data, especially when only 1 sample per class is labeled. The source code of our article is publicly available at
https://github.com/guangyizhangbci/PARSE
.