No graded responses of finger muscles to TMS during motor imagery of isometric finger forces

► The MEP increased in the FDS during motor imagery of isometric flexion force. ► The MEP increased in the EDC during motor imagery of isometric extension force. ► The MEP size was similar across the force levels. ► Motor imagery enhances corticospinal excitability in subthreshold level. ► The subliminally facilitated MEP could not be further graded during motor imagery.