Andrea Guerra1, Antonio Suppa2, Francesco Asci3, Giovanna De Marco3, Valentina D'Onofrio3, Matteo Bologna2, Vincenzo Di Lazzaro4, Alfredo Berardelli5. 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.
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.
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.
Authors: Caroline A Lea-Carnall; Stephen R Williams; Faezeh Sanaei-Nezhad; Nelson J Trujillo-Barreto; Marcelo A Montemurro; Wael El-Deredy; Laura M Parkes Journal: iScience Date: 2020-10-08