An Efficient Multiobjective Feature Optimization Approach for Improving Motor Imagery-based Brain-computer Interface Performance

Background: Applying efficient feature extraction and selection methods is essential in improving the performance of machine learning algorithms employed in brain-computer interface (BCI) systems. Objectives: The current study aims to enhance the performance of a motor imagery-based BCI by improving the feature extraction and selection stages of the machine-learning algorithm applied to classify the different imagined movements. Materials & Methods: In this study, a multi-rate system for spectral decomposition of the signal is designed, and then the spatial and temporal features are extracted from each sub-band. To maximize the classification accuracy while simplifying the model and using the smallest set of features, the feature selection stage is treated as a multiobjective optimization problem, and the Pareto optimal solutions of these two conflicting objectives are obtained. For the feature selection stage, non-dominated sorting genetic algorithm II (NSGA-II), an evolutionary-based algorithm, is used wrapper-based, and its effect on the BCI performance is explored. The proposed method is implemented on a public dataset known as BCI competition III dataset IVa. Results: Extracting the spatial and temporal features from different sub-bands and selecting the features with an evolutionary optimization approach in this study led to an improved classification accuracy of ۹۲.۱۹% which has a higher value compared to the state of the art. Conclusion: The results show that the proposed improved classification accuracy could achieve a high-performance subject-specific BCI system.