Bi-hemisphere Interaction Convolutional Neural Network for Motor Imagery Classification

Decoding EEG-based, Motor Imagery Brain-Computer Interfaces (MI-BCI) in a subject-independent manner is very challenging due to high dimensionality of the EEG signal, and high inter-subject variability. In recent years, Convolutional neural networks (CNNs) have significantly enhanced decoding accuracy. Nevertheless, the majority of these CNN designs did not explicitly incorporate the inter-hemisphere functional connections, omitting crucial spatial information. Notably, in binary MI decoding of the left-hand versus right-hand, the Event-Related Desynchronization is observed in the contralateral hemisphere. Building upon this concept and various Neuroscience research, we have designed a CNN architecture that forges a functional connection between the two hemispheres. Specifically, we applied the Channel Average Referencing to one hemisphere and compared the output with all channels of the opposite hemisphere. Then, we utilized the cosine similarity to identify the most correlated channels and combined with them the original hemisphere for spatial filtering to learn the inter-hemispheric connections. This innovative technique aligns more closely with the actual brain functionality. Our method has demonstrated superior results on the Cho2017 and OpenBMI datasets, underscoring its effectiveness.