Fig. 4From: A brain-computer interface driven by imagining different force loads on a single hand: an online feasibility studyTime-frequency analysis of EEG for different mental tasks. a The averaged time-frequency maps on C3 under multiple force load motor imagery tasks. The vertical line was marked at the onset of task, the blue color indicates the ERD phenomenon. b The mean ERSP on C3 at mu and beta rhythms during two stages of the experiment. c The averaged ERSP topography under multiple force load motor imagery tasks. d The significant difference topography between the high force load MI and low force load MIBack to article page