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

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

doi:10.1016/j.brs.2019.06.029

Cited by 40 publications

(44 citation statements)

References 70 publications

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“…that performed iTBS1200 (Gamboa et al, 2010) and cTBS (Guerra et al, 2019), which inhibits cortical excitability. Because we did not compare the iTBS1200 group and classical iTBS group, we could not compare the inhibitory effect of the three protocols.…”

Section: Discussionmentioning

confidence: 99%

The After-Effect of Accelerated Intermittent Theta Burst Stimulation at Different Session Intervals

Tang

et al. 2020

Front. Neurosci.

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The study aims to investigate the after-effect of three sessions of intermittent theta-burst stimulation (iTBS) on motor cortical excitability. The iTBS was induced over the primary motor cortex (M1) at different time intervals. Methods: The study has a crossover design. Sixteen participants were assigned to three groups and received different accelerated iTBS (aiTBS) protocols during each visit: (1) three continuous sessions with no interval (iTBS18000); (2) three iTBS sessions with 10-min intervals (iTBS600 × 3 * 10); and (3) three iTBS sessions with 30-min intervals (iTBS600 × 3 * 30). As washout period, each visit is separated by at least 7 days. We measured the motor cortical excitability changes and intracortical inhibition. Results: A dose of 1,800 pulses of aiTBS per day is tolerable. The iTBS1800 led to a reduced cortical excitability; whereas iTBS600 × 3 * 10 and iTBS600 × 3 * 30 enhanced cortical excitability to a differential extent. After a total dose of 1,800 pulses, iTBS600 × 3 * 30 exhibited the longer effect and highest percentage of individuals with enhanced cortical excitability. Conclusion: The results suggest that aiTBS protocols at different time intervals result in different motor cortical excitability after-effects.

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Section: Discussionmentioning

confidence: 99%

The After-Effect of Accelerated Intermittent Theta Burst Stimulation at Different Session Intervals

Tang

et al. 2020

Front. Neurosci.

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“…Similarly, STDT underlies interneuronal inhibitory circuits in L5 and L6 layers in S1 37,38 . To date, the specific features and location of neurons entrained by tACS are not fully understood, but recent data has suggested that candidate elements are interneurons in L2 or L3, or cells located in L1 such as single-bouquet and elongated neurogliaform cells, which are reciprocally connected with L2 and L3 interneurons 39,40 . Thus, we may speculate that tACS is not able to reach deeper layers within S1 (i.e.…”

Section: Discussionmentioning

confidence: 99%

“…One remaining question is why an ample body of studies using tACS applied over the primary motor cortex (M1) showed an effect of tACS on motor neurophysiological parameters encoded in M1 in healthy subjects [28][29][30][40][41][42][43][44][45] . It is important to consider that the effectiveness of an externally applied field may be influenced by a variety of factors, including neuronal density and architecture, alignment of dendrites and axons relative to the induced field, type and distribution of ion channels in the neurons, degree of myelination, and glia density.…”

Section: Discussionmentioning

confidence: 99%

Investigating the effects of transcranial alternating current stimulation on primary somatosensory cortex

Manzo

Guerra

Giangrosso

et al. 2020

Sci Rep

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Near-threshold tactile stimuli perception and somatosensory temporal discrimination threshold (STDT) are encoded in the primary somatosensory cortex (S1) and largely depend on alpha and beta S1 rhythm. Transcranial alternating current stimulation (tACS) is a non-invasive neurophysiological technique that allows cortical rhythm modulation. We investigated the effects of tACS delivered over S1 at alpha, beta, and gamma frequencies on near-threshold tactile stimuli perception and STDT, as well as phase-dependent tACS effects on near-threshold tactile stimuli perception in healthy subjects. In separate sessions, we tested the effects of different tACS montages, and tACS at the individualised S1 μ-alpha frequency peak, on STDT and near-threshold tactile stimuli perception. We found that tACS applied over S1 at alpha, beta, and gamma frequencies did not modify STDT or near-threshold tactile stimuli perception. Moreover, we did not detect effects of tACS phase or montage. Finally, tACS did not modify near-threshold tactile stimuli perception and STDT even when delivered at the individualised μ-alpha frequency peak. Our study showed that tACS does not alter near-threshold tactile stimuli or STDT, possibly due to the inability of tACS to activate deep S1 layers. Future investigations may clarify tACS effects over S1 in patients with focal dystonia, whose pathophysiology implicates increased STDT.

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“…Similarly, beta tACS entrainment (at-resonance) has been shown to induce NMDAR-mediated plasticity in the human motor cortex using pharmacological intervention ( Wischnewski et al, 2019 ). However, gamma tACS entrainment of the motor cortex (above-resonance) appears to have the unique effect of boosting plasticity via GABA A disinhibition as has been replicated in the literature ( Guerra et al., 2019 , 2018 ). It has been suggested that tACS targets interneurons and pyramidal cells differently, affecting the overall balance of activity and furthermore that inhibitory subnetworks which exhibit resonance frequencies in the gamma range may be more susceptible to activation by similar stimulus frequencies ( Nowak et al, 2017 ; Wischnewski et al, 2019 ).…”

Section: Discussionmentioning

confidence: 99%

GABA Modulates Frequency-Dependent Plasticity in Humans

et al. 2020

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Summary Frequency-dependent reorganization of the primary somatosensory cortex, together with perceptual changes, arises following repetitive sensory stimulation. Here, we investigate the role of GABA in this process. We co-stimulated two finger tips and measured GABA and Glx using magnetic resonance (MR) spectroscopy at the beginning and end of the stimulation. Participants performed a perceptual learning task before and after stimulation. There were 2 sessions with stimulation frequency either at or above the resonance frequency of the primary somatosensory cortex (23 and 39 Hz, respectively). Perceptual learning occurred following above resonance stimulation only, while GABA reduced during this condition. Lower levels of early GABA were associated with greater perceptual learning. One possible mechanism underlying this finding is that cortical disinhibition “unmasks” lateral connections within the cortex to permit adaptation to the sensory environment. These results provide evidence in humans for a frequency-dependent inhibitory mechanism underlying learning and suggest a mechanism-based approach for optimizing neurostimulation frequency.

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

Cited by 40 publications

References 70 publications

The After-Effect of Accelerated Intermittent Theta Burst Stimulation at Different Session Intervals

The After-Effect of Accelerated Intermittent Theta Burst Stimulation at Different Session Intervals

Investigating the effects of transcranial alternating current stimulation on primary somatosensory cortex

GABA Modulates Frequency-Dependent Plasticity in Humans

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