P168 Modulating cortical excitability of human motor cortex byβ- andγ-band transcranial alternating current stimulation (tACS)

Abstract Transcranial alternating current stimulation (tACS) has been shown to modulate neural oscillations and excitability levels in the primary motor cortex (M1). These effects can last for more than an hour and an involvement of N-methyl-d-aspartate receptor (NMDAR) mediated synaptic plasticity has been suggested. However, to date the cortical mechanisms underlying tACS after-effects have not been explored. Here, we applied 20 Hz beta tACS to M1 while participants received either the NMDAR antagonist dextromethorphan or a placebo and the effects on cortical beta oscillations and excitability were explored. When a placebo medication was administered, beta tACS was found to increase cortical excitability and beta oscillations for at least 60 min, whereas when dextromethorphan was administered, these effects were completely abolished. These results provide the first direct evidence that tACS can induce NMDAR-mediated plasticity in the motor cortex, which contributes to our understanding of tACS-induced influences on human motor cortex physiology.

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Transcranial Alternating Current Stimulation at Beta Frequency: Lack of Immediate Effects on Excitation and Interhemispheric Inhibition of the Human Motor Cortex

Frontiers in Human Neuroscience ◽

10.3389/fnhum.2016.00560 ◽

2016 ◽

Vol 10 ◽

Cited By ~ 9

Author(s):

Viola Rjosk ◽

Elisabeth Kaminski ◽

Maike Hoff ◽

Christopher Gundlach ◽

Arno Villringer ◽

...

Keyword(s):

Motor Cortex ◽

Alternating Current ◽

Interhemispheric Inhibition ◽

Human Motor Cortex ◽

Transcranial Alternating Current Stimulation ◽

Human Motor ◽

Beta Frequency

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Online and offline effects of transcranial alternating current stimulation of the primary motor cortex

Scientific Reports ◽

10.1038/s41598-021-83449-w ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Ivan Pozdniakov ◽

Alicia Nunez Vorobiova ◽

Giulia Galli ◽

Simone Rossi ◽

Matteo Feurra

Keyword(s):

Motor Cortex ◽

Primary Motor Cortex ◽

Cortical Excitability ◽

Motor Evoked Potentials ◽

Random Noise ◽

Single Pulse ◽

Alternating Current ◽

Online Application ◽

Transcranial Random Noise Stimulation ◽

Transcranial Alternating Current Stimulation

AbstractTranscranial alternating current stimulation (tACS) is a non-invasive brain stimulation technique that allows interaction with endogenous cortical oscillatory rhythms by means of external sinusoidal potentials. The physiological mechanisms underlying tACS effects are still under debate. Whereas online (e.g., ongoing) tACS over the motor cortex induces robust state-, phase- and frequency-dependent effects on cortical excitability, the offline effects (i.e. after-effects) of tACS are less clear. Here, we explored online and offline effects of tACS in two single-blind, sham-controlled experiments. In both experiments we used neuronavigated transcranial magnetic stimulation (TMS) of the primary motor cortex (M1) as a probe to index changes of cortical excitability and delivered M1 tACS at 10 Hz (alpha), 20 Hz (beta) and sham (30 s of low-frequency transcranial random noise stimulation; tRNS). Corticospinal excitability was measured by single pulse TMS-induced motor evoked potentials (MEPs). tACS was delivered online in Experiment 1 and offline in Experiment 2. In Experiment 1, the increase of MEPs size was maximal with the 20 Hz stimulation, however in Experiment 2 neither the 10 Hz nor the 20 Hz stimulation induced tACS offline effects. These findings support the idea that tACS affects cortical excitability only during online application, at least when delivered on the scalp overlying M1, thereby contributing to the development of effective protocols that can be applied to clinical populations.

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Dopaminergic modulation of long-lasting direct current-induced cortical excitability changes in the human motor cortex

European Journal of Neuroscience ◽

10.1111/j.1460-9568.2006.04676.x ◽

2006 ◽

Vol 23 (6) ◽

pp. 1651-1657 ◽

Cited By ~ 189

Author(s):

Michael A. Nitsche ◽

Christian Lampe ◽

Andrea Antal ◽

David Liebetanz ◽

Nicolas Lang ◽

...

Keyword(s):

Motor Cortex ◽

Direct Current ◽

Cortical Excitability ◽

Human Motor Cortex ◽

Dopaminergic Modulation ◽

Human Motor

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Dopaminergic modulation of long-lasting direct current-induced cortical excitability changes in the human motor cortex

Aktuelle Neurologie ◽

10.1055/s-2006-952984 ◽

2006 ◽

Vol 33 (S 1) ◽

Cited By ~ 1

Author(s):

M.A. Nitsche ◽

C. Lampe ◽

A. Antal ◽

D. Liebetanz ◽

N. Lang ◽

...

Keyword(s):

Motor Cortex ◽

Direct Current ◽

Cortical Excitability ◽

Human Motor Cortex ◽

Dopaminergic Modulation ◽

Human Motor

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Can transcranial alternating current stimulation simultaneously increases and decreases cortical excitability? Supporting evidence from the rat motor cortex

Brain Stimulation ◽

10.1016/j.brs.2017.01.198 ◽

2017 ◽

Vol 10 (2) ◽

pp. 404

Author(s):

M. Mc Laughlin ◽

A. Khatoun

Keyword(s):

Motor Cortex ◽

Cortical Excitability ◽

Alternating Current ◽

Supporting Evidence ◽

Transcranial Alternating Current Stimulation

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Efficacy and Interindividual Variability in Motor-Cortex Plasticity following Anodal tDCS and Paired-Associative Stimulation

Neural Plasticity ◽

10.1155/2015/530423 ◽

2015 ◽

Vol 2015 ◽

pp. 1-10 ◽

Cited By ~ 9

Author(s):

Wolfgang Strube ◽

Tilmann Bunse ◽

Berend Malchow ◽

Alkomiet Hasan

Keyword(s):

Motor Cortex ◽

Cortical Excitability ◽

Response Variability ◽

Significant Group ◽

Paired Associative Stimulation ◽

Human Motor Cortex ◽

Motor Cortex Excitability ◽

Excitability Change ◽

Human Motor ◽

Baseline Values

Interindividual response variability to various motor-cortex stimulation protocols has been recently reported. Comparative data of stimulation protocols with different modes of action is lacking. We aimed to compare the efficacy and response variability of two LTP-inducing stimulation protocols in the human motor cortex: anodal transcranial direct current stimulation (a-tDCS) and paired-associative stimulation (PAS25). In two experiments 30 subjects received 1mA a-tDCS and PAS25. Data analysis focused on motor-cortex excitability change and response defined as increase in MEP applying different cut-offs. Furthermore, the predictive pattern of baseline characteristics was explored. Both protocols induced a significant increase in motor-cortical excitability. In the PAS25 experiments the likelihood to develop a MEP response was higher compared to a-tDCS, whereas for intracortical facilitation (ICF) the likelihood for a response was higher in the a-tDCS experiments. Baseline ICF (12 ms) correlated positively with an increase in MEPs only following a-tDCS and responders had significantly higher ICF baseline values. Contrary to recent studies, we showed significant group-level efficacy following both stimulation protocols confirming older studies. However, we also observed a remarkable amount of nonresponders. Our findings highlight the need to define sufficient physiological read-outs for a given plasticity protocol and to develop predictive markers for targeted stimulation.

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A Temporally Asymmetric Hebbian Rule Governing Plasticity in the Human Motor Cortex

Journal of Neurophysiology ◽

10.1152/jn.00900.2002 ◽

2003 ◽

Vol 89 (5) ◽

pp. 2339-2345 ◽

Cited By ~ 365

Author(s):

Alexander Wolters ◽

Friedhelm Sandbrink ◽

Antje Schlottmann ◽

Erwin Kunesch ◽

Katja Stefan ◽

...

Keyword(s):

Motor Cortex ◽

Median Nerve ◽

Cortical Excitability ◽

Long Term Potentiation ◽

Long Term Depression ◽

Human Motor Cortex ◽

Motor Cortical Excitability ◽

Human Motor ◽

Motor Cortical

Synaptic plasticity is conspicuously dependent on the temporal order of the pre- and postsynaptic activity. Human motor cortical excitability can be increased by a paired associative stimulation (PAS) protocol. Here we show that it can also be decreased by minimally changing the interval between the two associative stimuli. Corticomotor excitability of the abductor pollicis brevis (APB) representation was tested before and after repetitively pairing of single right median nerve simulation with single pulse transcranial magnetic stimulation (TMS) delivered over the optimal site for activation of the contralateral APB. Following PAS, depression of TMS-evoked motor-evoked potentials (MEPs) was induced only when the median nerve stimulation preceded the TMS pulse by 10 ms, while enhancement of cortical excitability was induced using an interstimulus interval of 25 ms, suggesting an important role of the sequence of cortical events triggered by the two stimulation modalities. Experiments using F-wave studies and electrical brain stem stimulation indicated that the site of the plastic changes underlying the decrease of MEP amplitudes following PAS (10 ms) was within the motor cortex. MEP amplitudes remained depressed for approximately 90 min. The decrease of MEP amplitudes was blocked when PAS(10 ms) was performed under the influence of dextromethorphan, an N-methyl-d-aspartate-receptor antagonist, or nimodipine, an L-type voltage-gated calcium-channel antagonist. The physiological profile of the depression of human motor cortical excitability following PAS(10 ms) suggests long-term depression of synaptic efficacy to be involved. Together with earlier findings, this study suggests that strict temporal Hebbian rules govern the induction of long-term potentiation/long-term depression-like phenomena in vivo in the human primary motor cortex.

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