A Fine-Grained Domain Adaptation Method for Cross-Session Vigilance Estimation in SSVEP-Based BCI

Brain-computer interface (BCI), a direct communication system between the human brain and external environment, can provide assistance for people with disabilities. Vigilance is an important cognitive state and has a close influence on the performance of users in BCI systems. In this study, a four-target BCI system for cursor control was built based on steady-state visual evoked potential (SSVEP) and twelve subjects were recruited and carried out two long-term BCI experimental sessions, which consisted of two SSVEP-based cursor-control tasks. During each session, electroencephalogram (EEG) signals were recorded. Based on the labeled EEG data of the source domain (previous session) and a small amount of unlabeled EEG data of the target domain (new session), we developed a fine-grained domain adaptation network (FGDAN) for cross-session vigilance estimation in BCI tasks. In the FGDAN model, the graph convolution network (GCN) was built to extract deep features of EEG. The fined-grained feature alignment was proposed to highlight the importance of the different channels figured out by the attention weightsmechanism and aligns the feature distributions between source and target domains at the channel level. The experimental results demonstrate that the proposed FGDAN achieved a better performance than the compared methods and indicate the feasibility and effectiveness of our methods for cross-session vigilance estimation of BCI users.