Illustration of event-related desynchronization (ERD) of electroencephalographic (EEG) sensorimotor rhythm activity (SMR, 8-15Hz) related to motor imagery of hand closing motions in a representative participant during calibration. The red line indicates ERD during the instruction to rest (red square presentations), while the black line indicates ERD during the instruction to imagine hand-closing motions (green square presentations). ERD was calculated relative to a reference period at -1.5 to -0.5 s before the visual cue. The 95% confidence levels are shown as red and green areas, respectively. The discrimination threshold for detection of motor imagery-related ERD for BNCI control is indicated as red dotted line.