Mouad Riyad1, Mohammed Khalil2, Abdellah Adib2. 1. Laboratory of Computer Science, Faculty of Sciences and Technology, Hassan II University Of Casablanca, LIM@II-FSTM, B.P. 146, Mohammedia 20650, Morocco. Electronic address: riyadmouad1@gmail.com. 2. Laboratory of Computer Science, Faculty of Sciences and Technology, Hassan II University Of Casablanca, LIM@II-FSTM, B.P. 146, Mohammedia 20650, Morocco.
Abstract
BACKGROUND: Brain-computer interfaces (BCI) permits humans to interact with machines by decoding brainwaves to command for a variety of purposes. Convolutional neural networks (ConvNet) have improved the state-of-the-art of motor imagery decoding in an end-to-end approach. However, shallow ConvNets usually perform better than their deep counterparts. Thus, we aim to design a novel ConvNet that is deeper than the existing models, with an increase in terms of performances, and with optimal complexity. NEW METHOD: We develop a ConvNet based on Inception and Xception architectures that uses convolutional layers to extract temporal and spatial features. We adopt separable convolutions and depthwise convolutions to enable faster and efficient ConvNet. Then, we introduce a new block that is inspired by Inception to learn more rich features to improve the classification performances. RESULTS: The obtained results are comparable with other state-of-the-art techniques. Also, the weights of the convolutional layers give us some insights onto the learned features and reveal the most relevant ones. COMPARISON WITH EXISTING METHOD(S): We show that our model significantly outperforms Filter Bank Common Spatial Pattern (FBCSP), Riemannian Geometry (RG) approaches, and ShallowConvNet (p < 0.05). CONCLUSIONS: The obtained results prove that motor imagery decoding is possible without handcrafted features.
BACKGROUND: Brain-computer interfaces (BCI) permits humans to interact with machines by decoding brainwaves to command for a variety of purposes. Convolutional neural networks (ConvNet) have improved the state-of-the-art of motor imagery decoding in an end-to-end approach. However, shallow ConvNets usually perform better than their deep counterparts. Thus, we aim to design a novel ConvNet that is deeper than the existing models, with an increase in terms of performances, and with optimal complexity. NEW METHOD: We develop a ConvNet based on Inception and Xception architectures that uses convolutional layers to extract temporal and spatial features. We adopt separable convolutions and depthwise convolutions to enable faster and efficient ConvNet. Then, we introduce a new block that is inspired by Inception to learn more rich features to improve the classification performances. RESULTS: The obtained results are comparable with other state-of-the-art techniques. Also, the weights of the convolutional layers give us some insights onto the learned features and reveal the most relevant ones. COMPARISON WITH EXISTING METHOD(S): We show that our model significantly outperforms Filter Bank Common Spatial Pattern (FBCSP), Riemannian Geometry (RG) approaches, and ShallowConvNet (p < 0.05). CONCLUSIONS: The obtained results prove that motor imagery decoding is possible without handcrafted features.