Keywords: common spatial patterns, brain-computer interfaces (BCI), motor imagery, electroencephalography (EEG)
TL;DR: We develop the Spectrally Adaptive Common Spatial Patterns (SACSP) method that learns temporal/spectral filters with spatial filters and gives better transfer performance from calibration to online data in motor imagery brain-computer interfaces.
Abstract: The method of Common Spatial Patterns (CSP) is widely used for feature extraction of electroencephalography (EEG) data such as in motor imagery brain-computer interface (BCI) systems. It is a data-driven method estimating a set of spatial filters so that the power of the filtered EEG data is maximally separated between imagery classes. This method, however, is prone to overfitting and is known to suffer from poor generalization especially with limited calibration data. In this work, we propose a novel algorithm called Spectrally Adaptive Common Spatial Patterns (SACSP) that improves CSP by learning a temporal/spectral filter for each spatial filter so that the spatial filters are concentrated on the most relevant temporal frequencies for each user. We show the efficacy of SACSP in motor imagery BCI in providing better generalizability and higher classification accuracy from calibration to online control compared to existing methods while providing neurophysiologically relevant information about the temporal frequencies of the filtered signals.