Perturbational signature of the somato-cognitive action network in human primary motor cortex.

INTRODUCTION: Functional-MRI evidence recently identified inter-effector regions in the primary motor cortex that show preferential connectivity with the action mode network (AMN), constituting the somato-cognitive action network (SCAN). Direct causal evidence for the functional engagement of these regions remains limited. AIM: Here, we investigated the perturbational neural response of one inter-effector region using transcranial magnetic stimulation combined with electroencephalography (TMS-EEG). METHODS: Sixteen healthy participants underwent recording of transcranial evoked potentials from the first dorsal interosseus, tibialis anterior, and the inter-effector region between them, which was identified with TMS motor mapping. RESULTS: Differences between conditions were assessed using cluster-based permutation testing and generalized linear modeling. Inter-effector-specific TMS-EEG activity was observed at approximately 42 ms post-stimulation, partially involving regions of the AMN. DISCUSSION AND CONCLUSION: Our findings provide the first perturbational characterization of inter-effector regions in human M1 and identify TMS-EEG markers that enable probing of SCAN functional organization.