Modeling motor-evoked potentials from neural field simulations of transcranial magnetic stimulation.

Marcus T Wilson, Bahar Moezzi, Nigel C Rogasch

Journal: Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology 2021;132(2):412-428

PMID: 33450564

Full Text on Elsevier Science View on PubMed

Abstract

OBJECTIVE

To develop a population-based biophysical model of motor-evoked potentials (MEPs) following transcranial magnetic stimulation (TMS).

METHODS

We combined an existing MEP model with population-based cortical modeling. Layer 2/3 excitatory and inhibitory neural populations, modeled with neural-field theory, are stimulated with TMS and feed layer 5 corticospinal neurons, which also couple directly but weakly to the TMS pulse. The layer 5 output controls mean motoneuron responses, which generate a series of single motor-unit action potentials that are summed to estimate a MEP.

RESULTS

A MEP waveform was generated comparable to those observed experimentally. The model captured TMS phenomena including a sigmoidal input-output curve, common paired pulse effects (short interval intracortical inhibition, intracortical facilitation, long interval intracortical inhibition) including responses to pharmacological interventions, and a cortical silent period. Changes in MEP amplitude following theta burst paradigms were observed including variability in outcome direction.

CONCLUSIONS

The model reproduces effects seen in common TMS paradigms.

SIGNIFICANCE

The model allows population-based modeling of changes in cortical dynamics due to TMS protocols to be assessed in terms of changes in MEPs, thus allowing a clear comparison between population-based modeling predictions and typical experimental outcome measures.

Address: Te Aka Mātuatua-School of Science, University of Waikato, Hamilton, New Zealand. Electronic address: [email protected].; Cognitive Ageing and Impairment Neurosciences Laboratory, School of Psychology, Social Work and Social Policy, The University of South Australia, Australia.; Discipline of Psychiatry, Adelaide Medical School, University of Adelaide, Australia; South Australian Health and Medical Research Institute, Australia; Brain, Mind and Society Research Hub, The School of Psychologcial Sciences, The Turner Institute for Brain and Mental Health and Monash Biomedical Imaging, Monash University, Australia.

DOI: 10.1016/j.clinph.2020.10.032

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MeSH Terms: Brain, Evoked Potentials, Motor, Humans, Models, Neurological, Motor Neurons, Muscle, Skeletal, Theta Rhythm, Transcranial Magnetic Stimulation