Motor cortical excitability and inhibition in acquired mirror pain

'Mirror pain' describes when the observation of another's pain experience induces a personal experience of pain. It has been suggested that mirror pain could result from changes in neural excitability or inhibition. In this study we used transcranial magnetic stimulation (TMS) to investigate motor cortical excitability in lower-limb amputees who experience mirror pain. Using paired-pulse TMS to assess motor cortical inhibition (CI) and cortical facilitation (CF), recordings were taken from the right first dorsal interosseus in lower-limb amputees who experience mirror pain (MP+), lower-limb amputees who do not experience mirror pain (MP-), and non-amputee controls. No differences in CI or CF were observed between the MP+ and both control groups. Thus, when not paired with a pain-related stimulus, changes in motor cortical excitability do not appear to contribute to the experience of mirror pain in lower-limb amputees.