Contrastive Decoupling and Enhancement of Multi-view EEG Features for Imagined Speech Decoding.

Imagined speech decoding remains challenging in brain-computer interfaces (BCIs) due to the low signal-to-noise ratio and complex spatio-temporal-spectral structure of Electroencephalogram (EEG) data. Existing studies mainly rely on single-view features or simple fusion strategies, limiting their ability to capture diverse neural characteristics during speech imagery. To address this limitation, we propose a Multi-view Feature Contrastive Decoupling and Enhancement (MFCDE) framework that integrates multi-view feature construction, feature decoupling, and adaptive masking. Four complementary views, including temporal, frequency-domain, phase-locking value (PLV), and graph-theoretic features, are extracted to characterize speech imagery-related neural dynamics. The decoupling mechanism reduces cross-view redundancy while preserving the discriminative information of each view. Experiments show that MFCDE consistently outperforms existing baselines in classification performance and stability. The learned view-shared and view-specific representations further provide neurophysiological insights by revealing the complementary contributions of temporal, spectral, and connectivity-based EEG patterns to imagined speech discrimination, indicating that reliable decoding depends on the joint utilization of neural dynamics, oscillatory activity, and inter-regional functional interactions.