“…To solve this problem, transfer learning (TL), which applies the dataset in source domains for compensating insufficient labeled data in a target domain, has been proposed for MI-BCIs (Samek et al, 2013b ; Azab et al, 2018 ). This technology is developed in several ways, such as instance selection (Wu, 2016 ; Hossain et al, 2018 ), feature calibration (Samek et al, 2013a ; Zhao et al, 2019 ) and classification domains (Vidaurre et al, 2010 ; He and Wu, 2019 ). For instance, for selection, active learning is typically presented for selecting training data from intra- or inter-subject labeled trials (Hossain et al, 2018 ).…”