Boosting the LTP-like plasticity effect of intermittent theta-burst stimulation using gamma transcranial alternating current stimulation

Andrea Guerra; Antonio Suppa; Matteo Bologna; Valentina D'Onofrio; Edoardo Bianchini; Peter Brown; Vincenzo Di Lazzaro; Alfredo Berardelli

doi:10.1016/j.brs.2018.03.015

Boosting the LTP-like plasticity effect of intermittent theta-burst stimulation using gamma transcranial alternating current stimulation

Brain Stimul. 2018 Jul-Aug;11(4):734-742. doi: 10.1016/j.brs.2018.03.015. Epub 2018 Mar 24.

Authors

Andrea Guerra¹, Antonio Suppa², Matteo Bologna², Valentina D'Onofrio¹, Edoardo Bianchini¹, Peter Brown³, Vincenzo Di Lazzaro⁴, Alfredo Berardelli⁵

Affiliations

¹ Department of Human Neuroscience, Sapienza University of Rome, Viale dell'Università 30, 00185, Rome, Italy.
² Department of Human Neuroscience, Sapienza University of Rome, Viale dell'Università 30, 00185, Rome, Italy; IRCCS Neuromed Institute, Via Atinense 18, 86077, Pozzilli, IS, Italy.
³ Medical Research Council Brain Network Dynamics Unit and Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, OX3 9DU, United Kingdom.
⁴ Unit of Neurology, Neurophysiology, Neurobiology, Department of Medicine, University Campus Bio-Medico, via Álvaro del Portillo 21, 00128, Rome, Italy.
⁵ Department of Human Neuroscience, Sapienza University of Rome, Viale dell'Università 30, 00185, Rome, Italy; IRCCS Neuromed Institute, Via Atinense 18, 86077, Pozzilli, IS, Italy. Electronic address: alfredo.berardelli@uniroma1.it.

Abstract

Background: Transcranial Alternating Current Stimulation (tACS) consists in delivering electric current to the brain using an oscillatory pattern that may entrain the rhythmic activity of cortical neurons. When delivered at gamma frequency, tACS modulates motor performance and GABA-A-ergic interneuron activity.

Objective: Since interneuronal discharges play a crucial role in brain plasticity phenomena, here we co-stimulated the primary motor cortex (M1) in healthy subjects by means of tACS during intermittent theta-burst stimulation (iTBS), a transcranial magnetic stimulation paradigm known to induce long-term potentiation (LTP)-like plasticity.

Methods: We measured and compared motor evoked potentials before and after gamma, beta and sham tACS-iTBS. While we delivered gamma-tACS, we also measured short-interval intracortical inhibition (SICI) to detect any changes in GABA-A-ergic neurotransmission.

Results: Gamma, but not beta and sham tACS, significantly boosted and prolonged the iTBS-induced after-effects. Interestingly, the extent of the gamma tACS-iTBS after-effects correlated directly with SICI changes.

Conclusions: Overall, our findings point to a link between gamma oscillations, interneuronal GABA-A-ergic activity and LTP-like plasticity in the human M1. Gamma tACS-iTBS co-stimulation might represent a new strategy to enhance and prolong responses to plasticity-inducing protocols, thereby lending itself to future applications in the neurorehabilitation setting.

Keywords: GABA-A; Gamma; Interneurons; Plasticity; TMS; tACS.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Adult
Evoked Potentials, Motor
Female
Gamma Rhythm
Humans
Long-Term Potentiation*
Male
Motor Cortex / physiology*
Theta Rhythm*
Transcranial Direct Current Stimulation / methods*

Grants and funding

MC_UU_12024/1/MRC_/Medical Research Council/United Kingdom