Transfer learning and active transfer learning for reducing calibration data in single-trial classification of visually-evoked potentials

Single-trial Event-Related Potential (ERP) classification is a key requirement for several types of Brain-Computer Interaction (BCI) technologies. However, strong individual differences make it challenging to develop a generic single-trial ERP classifier that performs well for all subjects. Usually some subject-specific training samples need to be collected in an initial calibration session to customize the classifier. However, if implemented into an actual BCI system, then this calibration process would decrease the utility of the system, potentially decreasing its usability. In this paper we propose a Transfer Learning approach for reducing the amount of subject-specific data in online single-trial ERP classifier calibration, and an Active Transfer Learning approach for offline calibration. By applying these approaches to data from a Visually-Evoked Potential EEG experiment, we demonstrate that they improve the classification performance, given the same number of labeled subject-specific training samples. In other words, these approaches can also attain a desired level of classification accuracy with less labeling effort when compared to a randomly selected training set.