The effect of motor imagery on corticospinal excitability and inhibition in healthy adults: a systematic review

Motor imagery (MI) activates motor networks without overt movement and is widely used in motor learning and rehabilitation. However, its effect on corticospinal excitability (CSE) and short-interval intracortical inhibition (SICI) have yet to be systematically evaluated. Following PRISMA guidelines, we searched PubMed, PsycINFO, MEDLINE, and SportDiscus in January 2021 and in June 2025. Studies were included if they used transcranial magnetic stimulation (TMS) to measure motor evoked potential amplitude or SICI during or after MI in healthy adults. We included 105 studies. Of 70 comparing MI with rest, 63 reported increased CSE. Post-MI facilitation was observed in 9 of 16 studies. Five of six showed greater CSE during motor execution than MI. SICI was examined in 16 studies; nine comparing MI to rest, five reported reduced inhibition, particularly with higher conditioning stimulus intensities (∼80% resting motor threshold). Type of task, imagined force, expertise and combined interventions (e.g., concurrent action observation) modulated CSE during MI. Overall, MI reliably increases CSE relative to rest and can reduce SICI under specific conditions. These results support MI as a tool for engaging motor circuits and highlight the need for standardised protocols.