Can feedback transparency improve Motor-Imagery BCI performance?

International audienceMotor Imagery-based BCI (MI-BCI) performances remain highly variable, with up to 30% of users unable to achieve control. Operating a BCI system requires users to learn to modulate their neural activity. This is a complex task, thus the training procedure is crucial. Our study draws on task-feedback transparency to improve the feedback given during training. MI-BCI protocols often feature abstract feedback (e.g., visual gauge) unrelated to the imagined movement. Transparent feedback, directly related to the task, may reinforce agency-the ability to self-attribute actions, such as feedback movements-and embodiment, facilitating kinesthetic MI. This could lessen complexity in BCI control and ultimately improve BCI performance.We tested this hypothesis in a beta-based MI neurofeedback task with electroencephalography (EEG). Twenty-three subjects participated in a single MIneurofeedback session that consisted in imagining clenching their right hand rhythmically. Feedback was based on online laplacian-filtered 8-30Hz power on C3 electrode computed with OpenViBE. There were 3 feedback conditions of expected increasing transparency: pendulum; virtual hand; virtual hand with additional motor illusion induced by vibrations to the participant's hand. The amplitude of the pendulum and virtual hand movements was proportional to beta desynchronisation. Each participant performed two runs of five 24s-trials per condition. Agency, embodiment, and user experience questionnaires were included. Repeated-measures ANOVA showed better BCI performance when using the virtual hand than the pendulum. However, participants had lower performance in the visuotactile condition compared to the virtual hand-only feedback. Agency showed a similar pattern.Feeling of success in the task did not vary with feedback conditions, but the virtual hand feedback felt easier to use. BCI performance correlated positively with agency for all conditions and with embodiment in conditions with a virtual hand.Thus, visual transparency—but not tactile feedback addition—increased BCI performance and this was associated with better agency and embodiment