A systematic review of the proposed mechanisms underpinning pain relief by primary motor cortex stimulation in animals

•Mechanisms involved in alleviating pain by use of TMS and iMCS have considerable amount of overlap.•Key regions which were impacted by TMS and/or iMCS consisted of the thalamus, striatum, PAG, RVM and dorsal horn.•Both functional and structural changes were observed to occur within these key regions after TMS and iMCS.•All key regions are known to be interconnected anatomically, providing a rational for further investigation.