scholarly journals Commentary: On the possible role of stimulation duration for after-effects of transcranial alternating current stimulation

2015 ◽  
Vol 9 ◽  
Author(s):  
Kohitij Kar
Keyword(s):  
Alternating Current ◽  
After Effects ◽  
Transcranial Alternating Current Stimulation

Comparatively weak after-effects of transcranial alternating current stimulation (tACS) on cortical excitability in humans

2008 ◽  
Vol 1 (2) ◽  
pp. 97-105 ◽  
Author(s):  
Andrea Antal ◽  
Klára Boros ◽  
Csaba Poreisz ◽  
Leila Chaieb ◽  
Daniella Terney ◽  
...  
Keyword(s):  
Cortical Excitability ◽  
Alternating Current ◽  
After Effects ◽  
Transcranial Alternating Current Stimulation

Changes in TMS measures of cortical excitability induced by transcranial direct and alternating current stimulation

2021 ◽  
Author(s):  
Michael A. Nitsche ◽  
Walter Paulus ◽  
Gregor Thut
Keyword(s):  
Brain Stimulation ◽  
Cortical Excitability ◽  
Brain Activity ◽  
Alternating Current ◽  
Transcranial Electrical Stimulation ◽  
Electrical Currents ◽  
After Effects ◽  
Brain Physiology ◽  
Transcranial Alternating Current Stimulation ◽  
Oscillatory Brain Activity

Brain stimulation with weak electrical currents (transcranial electrical stimulation, tES) is known already for about 60 years as a technique to generate modifications of cortical excitability and activity. Originally established in animal models, it was developed as a noninvasive brain stimulation tool about 20 years ago for application in humans. Stimulation with direct currents (transcranial direct current stimulation, tDCS) induces acute cortical excitability alterations, as well as neuroplastic after-effects, whereas stimulation with alternating currents (transcranial alternating current stimulation, tACS) affects primarily oscillatory brain activity but has also been shown to induce neuroplasticity effects. Beyond their respective regional effects, both stimulation techniques have also an impact on cerebral networks. Transcranial magnetic stimulation (TMS) has been pivotal to helping reveal the physiological effects and mechanisms of action of both stimulation techniques for motor cortex application, but also for stimulation of other areas. This chapter will supply the reader with an overview about the effects of tES on human brain physiology, as revealed by TMS.

Gamma-transcranial alternating current stimulation and theta-burst stimulation: inter-subject variability and the role of BDNF

2020 ◽  
Vol 131 (11) ◽  
pp. 2691-2699
Author(s):  
Andrea Guerra ◽  
Francesco Asci ◽  
Alessandro Zampogna ◽  
Valentina D'Onofrio ◽  
Simona Petrucci ◽  
...  
Keyword(s):  
Alternating Current ◽  
Theta Burst Stimulation ◽  
Burst Stimulation ◽  
Subject Variability ◽  
Transcranial Alternating Current Stimulation ◽  
Theta Burst

scholarly journals Perception of Rhythmic Speech Is Modulated by Focal Bilateral Transcranial Alternating Current Stimulation

2020 ◽  
Vol 32 (2) ◽  
pp. 226-240 ◽  
Author(s):  
Benedikt Zoefel ◽  
Isobella Allard ◽  
Megha Anil ◽  
Matthew H. Davis
Keyword(s):  
Speech Perception ◽  
Speech Processing ◽  
Alternating Current ◽  
Stream Segregation ◽  
Causal Role ◽  
Oscillatory Activity ◽  
Transcranial Alternating Current Stimulation ◽  
Neural Entrainment ◽  
Actual Speech

Several recent studies have used transcranial alternating current stimulation (tACS) to demonstrate a causal role of neural oscillatory activity in speech processing. In particular, it has been shown that the ability to understand speech in a multi-speaker scenario or background noise depends on the timing of speech presentation relative to simultaneously applied tACS. However, it is possible that tACS did not change actual speech perception but rather auditory stream segregation. In this study, we tested whether the phase relation between tACS and the rhythm of degraded words, presented in silence, modulates word report accuracy. We found strong evidence for a tACS-induced modulation of speech perception, but only if the stimulation was applied bilaterally using ring electrodes (not for unilateral left hemisphere stimulation with square electrodes). These results were only obtained when data were analyzed using a statistical approach that was identified as optimal in a previous simulation study. The effect was driven by a phasic disruption of word report scores. Our results suggest a causal role of neural entrainment for speech perception and emphasize the importance of optimizing stimulation protocols and statistical approaches for brain stimulation research.

NMDA Receptor-Mediated Motor Cortex Plasticity After 20 Hz Transcranial Alternating Current Stimulation

2018 ◽  
Vol 29 (7) ◽  
pp. 2924-2931 ◽  
Author(s):  
M Wischnewski ◽  
M Engelhardt ◽  
M A Salehinejad ◽  
D J L G Schutter ◽  
M -F Kuo ◽  
...  
Keyword(s):  
Motor Cortex ◽  
Primary Motor Cortex ◽  
Cortical Excitability ◽  
Alternating Current ◽  
Beta Oscillations ◽  
Human Motor Cortex ◽  
After Effects ◽  
Transcranial Alternating Current Stimulation ◽  
Human Motor ◽  
Motor Cortex Plasticity

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.

scholarly journals Probing the causal role of prestimulus interregional synchrony for perceptual integration via tACS

2016 ◽  
Author(s):  
Rolandas Stonkus ◽  
Verena Braun ◽  
Jess Kerlin ◽  
Gregor Volberg ◽  
Simon Hanslmayr
Keyword(s):  
Specific Activity ◽  
Brain Regions ◽  
Causal Role ◽  
Oscillatory Activity ◽  
Perceptual Integration ◽  
After Effects ◽  
Activity Phase ◽  
Fmri Study ◽  
Transcranial Alternating Current Stimulation

The phase of prestimulus oscillations at 7-10 Hz has been shown to modulate perception of briefly presented visual stimuli. Specifically, a recent combined EEG-fMRI study suggested that a prestimulus oscillation at around 7 Hz represents open and closed windows for perceptual integration by modulating connectivity between lower order occipital and higher order parietal brain regions. We here utilized brief event-related transcranial alternating current stimulation (tACS) to specifically modulate this prestimulus 7 Hz oscillation, and the synchrony between parietal and occipital brain regions. To this end we tested for a causal role of this particular prestimulus oscillation for perceptual integration. The EEG was acquired at the same time allowing us to investigate frequency specific after effects phase-locked to stimulation offset. On a behavioural level our results suggest that the tACS did modulate perceptual integration, however, in an unexpected manner. On an electrophysiological level our results suggest that brief tACS does induce oscillatory entrainment, as visible in frequency specific activity phase-locked to stimulation offset. Together, our results do not strongly support a causal role of prestimulus 7 Hz oscillations for perceptual integration. However, our results suggest that brief tACS is capable of modulating oscillatory activity in a temporally sensitive manner.

scholarly journals Synchronization of sensory gamma oscillations promotes multisensory communication

2019 ◽  
Author(s):  
Jonas Misselhorn ◽  
Bettina C. Schwab ◽  
Till R. Schneider ◽  
Andreas K. Engel
Keyword(s):  
Gamma Oscillations ◽  
Alternating Current ◽  
High Density ◽  
Network Communication ◽  
High Definition ◽  
Sensory Modalities ◽  
Transcranial Alternating Current Stimulation ◽  
Sensory Cortices ◽  
Fundamental Mechanism

AbstractRhythmic neuronal activity in the gamma range is a signature of active cortical processing and its synchronization across distant sites has been proposed as a fundamental mechanism of network communication. While this has been shown within sensory modalities, we tested whether crosstalk between the senses relies on similar mechanisms. In two consecutive experiments, we used a task in which human participants (male and female) matched amplitude changes of concurrent visual, auditory and tactile stimuli. In this task, matching of congruent stimuli was associated with a behavioral benefit compared to matching of incongruent stimuli. In the first experiment, we used source-level analysis of high-density electroencephalography (EEG) and observed that cross-modal matching of congruent inputs was associated with relatively weaker coherence between gamma oscillations in early sensory regions. Next, we used bifocal high-definition transcranial alternating current stimulation (hd-tACS) to manipulate the strength of coupling between sensory cortices. Here, we used a lateralized version of the task in which hd-tACS was applied either ipsilateral or contralateral to the hemisphere receiving sensory stimuli. Ipsilateral gamma, but not alpha stimulation slowed responses to congruent trials whereas responding to incongruent trials was not changed by tACS. We speculate that fast responding to congruent stimuli involves decoupling of sensory gamma oscillations, which was prevented by tACS. These results indicate that synchronization of gamma oscillations promotes direct communication between sensory modalities. The framework of coupled gamma oscillations underlying cortical communication might thus be generalizable from processing within sensory streams to interactions between sensory networks.Significance statementCortical gamma oscillations structure segregated neural activity and were suggested to represent a fundamental mechanism of network communication. While there is ample evidence for the role of long-range gamma synchronization in unisensory processing, its significance in multisensory networks is still unclear. We show that direct interactions between sensory cortices rely on synchronization of gamma band activity. To that end, we carried out two consecutive experiments using state-of-the-art high-density electroencephalography (EEG) and high-definition transcranial alternating current stimulation (hd-tACS). By complementing an observational with an interventional method, we provide novel evidence for the role of synchronized gamma oscillations in multisensory communication.

Sign in / Sign up

Export Citation Format

Share Document