Motor imagery perspective shapes corticospinal excitability with effector-specific effects

Motor imagery (MI) allows individuals to mentally simulate movements without execution, engaging neural pathways that overlap with those used during real actions. However, how imagery perspective influences corticospinal excitability across different effectors remains unclear. Using neuronavigated transcranial magnetic stimulation (TMS), we compared kinesthetic (KMI), first-person visual (VMI-1PP), and third-person visual (VMI-3PP) imagery of elbow flexion-extension in nineteen healthy adults. Single-pulse TMS was synchronized with a metronome marking the imagined peak contraction, and motor-evoked potentials were recorded from upper-arm and intrinsic hand muscles. All imagery types enhanced corticospinal excitability relative to a pacing-only baseline. For upper-arm muscles, VMI-3PP and KMI produced stronger facilitation than VMI-1PP, with no difference between KMI and VMI-3PP. In contrast, intrinsic hand muscles showed similar facilitation across all imagery types. These findings reveal that imagery perspective and effector interact to shape corticospinal output: proximal muscles are more sensitive to perspective, whereas distal muscles respond uniformly. The observation that third-person visual imagery can match kinesthetic imagery in enhancing corticospinal excitability highlights its potential as a practical and effective strategy for training and neurorehabilitation.