Single and paired TMS pulses engage spatially distinct corticomotor representations in human pericentral cortex

Single- and paired-pulse transcranial magnetic stimulation (TMS) is widely used to study corticomotor physiology in humans, but do they engage the same intracortical circuits? We compared the spatial properties of corticomotor maps elicited by single-pulse TMS to those elicited by paired-pulse short-latency intracortical facilitation (SICF). SICF maps consistently showed a posterior shift in center of gravity compared with single-pulse maps, suggesting that paired-pulse TMS engages cortical circuits that are spatially distinct from single-pulse TMS.