LTD-like plasticity of the human primary motor cortex can be reversed by γ-tACS

Andrea Guerra; Antonio Suppa; Francesco Asci; Giovanna De Marco; Valentina D'Onofrio; Matteo Bologna; Vincenzo Di Lazzaro; Alfredo Berardelli

doi:10.1016/j.brs.2019.06.029

LTD-like plasticity of the human primary motor cortex can be reversed by γ-tACS

Brain Stimul. 2019 Nov-Dec;12(6):1490-1499. doi: 10.1016/j.brs.2019.06.029. Epub 2019 Jul 3.

Authors

Andrea Guerra¹, Antonio Suppa², Francesco Asci³, Giovanna De Marco³, Valentina D'Onofrio³, Matteo Bologna², Vincenzo Di Lazzaro⁴, Alfredo Berardelli⁵

Affiliations

¹ IRCCS Neuromed, Via Atinense 18, 86077, Pozzilli (IS), Italy.
² IRCCS Neuromed, Via Atinense 18, 86077, Pozzilli (IS), Italy; Department of Human Neurosciences, Sapienza University of Rome, Viale dell'Università 30, 00185, Rome, Italy.
³ Department of Human Neurosciences, Sapienza University of Rome, Viale dell'Università 30, 00185, Rome, Italy.
⁴ Unit of Neurology, Neurophysiology, Neurobiology, Department of Medicine, University Campus Bio-Medico, Via Álvaro Del Portillo 21, 00128, Rome, Italy.
⁵ IRCCS Neuromed, Via Atinense 18, 86077, Pozzilli (IS), Italy; Department of Human Neurosciences, Sapienza University of Rome, Viale dell'Università 30, 00185, Rome, Italy. Electronic address: alfredo.berardelli@uniroma1.it.

PMID: 31289014
DOI: 10.1016/j.brs.2019.06.029

Abstract

Background: Cortical oscillatory activities play a role in regulating several brain functions in humans. However, whether motor resonant oscillations (i.e. β and γ) modulate long-term depression (LTD)-like plasticity of the primary motor cortex (M1) is still unclear.

Objective: To address this issue, we combined transcranial alternating current stimulation (tACS), a technique able to entrain cortical oscillations, with continuous theta burst stimulation (cTBS), a transcranial magnetic stimulation (TMS) protocol commonly used to induce LTD-like plasticity in M1.

Methods: Motor evoked potentials (MEPs) elicited by single-pulse TMS, short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF) were evaluated before and 5, 15 and 30 min after cTBS alone or cTBS delivered during β-tACS (cTBS-β) or γ-tACS (cTBS-γ). Moreover, we tested the effects of β-tACS (alone) on short-latency afferent inhibition (SAI) and γ-tACS on SICI in order to verify whether tACS-related interneuronal modulation contributes to the effects of tACS-cTBS co-stimulation.

Results: cTBS-γ turned the expected after-effects of cTBS from inhibition to facilitation. By contrast, responses to cTBS-β were similar to those induced by cTBS alone. β- and γ-tACS did not change MEPs evoked by single-pulse TMS. β-tACS reduced SAI and γ-tACS reduced SICI. However, the degree of γ-tACS-induced modulation of SICI did not correlate with the effects of cTBS-γ.

Conclusion: γ-tACS reverses cTBS-induced plasticity of the human M1. γ-oscillations may therefore regulate LTD-like plasticity mechanisms.

Keywords: Beta; Gamma; Plasticity; TMS; cTBS; tACS.

MeSH terms

Adult
Evoked Potentials, Motor / physiology*
Female
Humans
Inhibition, Psychological
Interneurons / physiology
Long-Term Synaptic Depression / physiology*
Male
Motor Cortex / physiology*
Neuronal Plasticity / physiology*
Transcranial Direct Current Stimulation / methods*
Transcranial Magnetic Stimulation / methods