Extended enhancement of corticospinal connectivity with concurrent cortical and peripheral stimulation controlled by sensorimotor desynchronization

Background: Pairing cortical and peripheral input during motor imagery (MI)-related sensorimotor desynchronization (ERD) modulates corticospinal excitability at the cortical representation (hotspot) of the imagined movement. Objective: To determine the effects of this associative stimulation protocol on the cortical motor map beyond the hotspot. Methods: In healthy subjects, peripheral stimulation through passive hand opening by a robotic orthosis and single-pulse transcranial magnetic stimulation to the respective cortical motor representation were applied in a brain-machine interface environment. State-dependency was investigated by concurrent, delayed or non-specific stimulation with respect to ERD in the beta-band (16-22 Hz) during MI of finger extension. Results: Concurrent stimulation led to increased excitability of an extended motor map. Delayed and nonspecific stimulation led to heterogeneous changes, i.e., opposite patterns of increased excitability in either the center or the periphery of the motor map. Conclusion: These results could be instrumental in closed-loop, state-dependent stimulation in the context of neurorehabilitation. (C) 2018 Elsevier Inc. All rights reserved.