A general framework to estimate spatial and spatio-spectral filters for EEG signal classification

• The CSP algorithm is described as a sequential procedure of spatial filter estimation.
• Generalized version of the CSP is introduced.
• The general framework is used for simultaneously spatio-spectral filters estimation.
• From the proposed generalization, two new spatial and spatio-spectral filter estimation schemes are introduced.
• The proposed methods and similar algorithms are compared and implemented.
• Improving in classification accuracy and stability is shown.

In this paper, a general framework is proposed for simultaneous design of spatial and spectral filters, which are used to extract discriminant features from EEG signals in Brain Computer Interfacing (BCI) systems. This paper introduces Common Spatial Patterns (CSP) as a step-by-step filter optimization algorithm, and then proposes a generalized type of the CSP which is not limited in a specific optimization constraint. Moreover, it is shown that how this generalization can be extended to a spatio-spectral filter estimation scheme. Then, two specific versions of the generalized CSP are proposed, where a specific target function and optimization constraint are used for estimating the spatial and spectral filters. Unlike the traditional CSP which is not very closely linked to the classification accuracy, the proposed algorithms are able to be more directly aimed at achieving better accuracy and stability. Experimental results obtained from applying the introduced methods on the recorded imagery signals from two datasets, demonstrate considerable improvement in the classification accuracy and stability compared to the standard CSP and other similar methods.