SPDAlign: Interpretable Riemannian Alignment for EEG Forward Modeling Shifts
This study addresses the cross-domain distribution shift caused by the non-stationarity of EEG signals by proposing an unsupervised domain adaptation framework grounded in Riemannian geometry. We theoretically prove that forward modeling shifts can be fully recovered via linear transformations on the symmetric positive definite (SPD) manifold, thereby establishing a globally linear and intrinsically interpretable alignment mechanism. Furthermore, Wasserstein Procrustes optimal transport is introduced to jointly align means and correct rotational discrepancies. Experimental evaluations on both simulated and public EEG datasets demonstrate that the proposed method achieves superior performance, accurately identifies critical frequency bands and spatial patterns, and effectively overcomes inter-subject variability.