scholarly journals Is Transcranial Alternating Current Stimulation Effective in Modulating Brain Oscillations?

PLoS ONE ◽  
2013 ◽  
Vol 8 (2) ◽  
pp. e56589 ◽  
Author(s):  
Debora Brignani ◽  
Manuela Ruzzoli ◽  
Piercarlo Mauri ◽  
Carlo Miniussi
Keyword(s):  
Alternating Current ◽  
Brain Oscillations ◽  
Transcranial Alternating Current Stimulation

scholarly journals Probing the Link Between Perception and Oscillations: Lessons from Transcranial Alternating Current Stimulation

2019 ◽  
Vol 26 (1) ◽  
pp. 57-73 ◽  
Author(s):  
Yuranny Cabral-Calderin ◽  
Melanie Wilke
Keyword(s):  
Time Windows ◽  
Gamma Oscillations ◽  
Alternating Current ◽  
Brain Regions ◽  
Causal Link ◽  
Brain Oscillations ◽  
Promising Tool ◽  
Transcranial Alternating Current Stimulation ◽  
Close Time ◽  
Auditory Cortices

Brain oscillations are regarded as important for perception as they open and close time windows for neural spiking to enable the effective communication within and across brain regions. In the past, studies on perception primarily relied on the use of electrophysiological techniques for probing a correlative link between brain oscillations and perception. The emergence of noninvasive brain stimulation techniques such as transcranial alternating current stimulation (tACS) provides the possibility to study the causal contribution of specific oscillatory frequencies to perception. Here, we review the studies on visual, auditory, and somatosensory perception that employed tACS to probe the causality of brain oscillations for perception. The current literature is consistent with a causal role of alpha and gamma oscillations in parieto-occipital regions for visual perception and theta and gamma oscillations in auditory cortices for auditory perception. In addition, the sensory gating by alpha oscillations applies not only to the visual but also to the somatosensory domain. We conclude that albeit more refined perceptual paradigms and individualized stimulation practices remain to be systematically adopted, tACS is a promising tool for establishing a causal link between neural oscillations and perception.

scholarly journals Effects of Transcranial Alternating Current Stimulation on Cognitive Functions in Healthy Young and Older Adults

2016 ◽  
Vol 2016 ◽  
pp. 1-13 ◽  
Author(s):  
Daria Antonenko ◽  
Miriam Faxel ◽  
Ulrike Grittner ◽  
Michal Lavidor ◽  
Agnes Flöel
Keyword(s):  
Older Adults ◽  
Language Learning ◽  
Cognitive Functions ◽  
Alternating Current ◽  
Future Research ◽  
Brain Oscillations ◽  
Specific Patient ◽  
Transcranial Alternating Current Stimulation ◽  
Young Subjects ◽  
Interaction With Age

Recently, transcranial alternating current stimulation (tACS) has emerged as a tool to enhance human cognitive processes. Here, we provide a brief summary of the rationale behind tACS-induced effects on task-relevant brain oscillations and associated cognitive functions and review previous studies in young subjects that have applied tACS in cognitive paradigms. Additionally, we present pilot data where we administered theta-tACS (6 Hz) over the temporoparietal cortex and a supraorbital reference for 20 min during implicit language learning in healthy young (mean/SD age: 22/2) and older (mean/SD age: 66/4) adults, in a sham-controlled crossover design. Linear mixed models revealed significantly increased retrieval accuracy following tACS-accompanied associative learning, after controlling for session order and learning success. These data provide the first implementation of tACS during cognitive performance in older adults and support recent studies suggesting that tACS in the theta frequency range may serve as a tool to enhance cognition, possibly through direct modulation of task-relevant brain oscillations. So far, studies have been heterogeneous in their designs, leaving a number of issues to be addressed in future research, including the setup of electrodes and optimal stimulation frequencies to be employed, as well as the interaction with age and underlying brain pathologies in specific patient populations.

scholarly journals Transcranial alternating current stimulation (tACS): from basic mechanisms towards first applications in psychiatry

2020 ◽  
Author(s):  
Osama Elyamany ◽  
Gregor Leicht ◽  
Christoph S. Herrmann ◽  
Christoph Mulert
Keyword(s):  
Psychiatric Disorders ◽  
Cortical Neurons ◽  
Alternating Current ◽  
Brain Network ◽  
Brain Oscillations ◽  
Serious Adverse Events ◽  
Double Blind ◽  
Response Predictors ◽  
Transcranial Alternating Current Stimulation ◽  
The Brain

AbstractTranscranial alternating current stimulation (tACS) is a unique form of non-invasive brain stimulation. Sinusoidal alternating electric currents are delivered to the scalp to affect mostly cortical neurons. tACS is supposed to modulate brain function and, in turn, cognitive processes by entraining brain oscillations and inducing long-term synaptic plasticity. Therefore, tACS has been investigated in cognitive neuroscience, but only recently, it has been also introduced in psychiatric clinical trials. This review describes current concepts and first findings of applying tACS as a potential therapeutic tool in the field of psychiatry. The current understanding of its mechanisms of action is explained, bridging cellular neuronal activity and the brain network mechanism. Revisiting the relevance of altered brain oscillations found in six major psychiatric disorders, putative targets for the management of mental disorders using tACS are discussed. A systematic literature search on PubMed was conducted to report findings of the clinical studies applying tACS in patients with psychiatric conditions. In conclusion, the initial results may support the feasibility of tACS in clinical psychiatric populations without serious adverse events. Moreover, these results showed the ability of tACS to reset disturbed brain oscillations, and thus to improve behavioural outcomes. In addition to its potential therapeutic role, the reactivity of the brain circuits to tACS could serve as a possible tool to determine the diagnosis, classification or prognosis of psychiatric disorders. Future double-blind randomised controlled trials are necessary to answer currently unresolved questions. They may aim to detect response predictors and control for various confounding factors.

scholarly journals A Comparison of Closed Loop vs. Fixed Frequency tACS on Modulating Brain Oscillations and Visual Detection

2021 ◽  
Vol 15 ◽  
Author(s):  
Heiko I. Stecher ◽  
Annika Notbohm ◽  
Florian H. Kasten ◽  
Christoph S. Herrmann
Keyword(s):  
Closed Loop ◽  
Alternating Current ◽  
Alpha Activity ◽  
Stimulation Frequency ◽  
Alpha Power ◽  
Brain Oscillations ◽  
Stimulation Protocol ◽  
Fixed Frequency ◽  
Transcranial Alternating Current Stimulation ◽  
Synaptic Changes

Transcranial alternating current stimulation has emerged as an effective tool for the exploration of brain oscillations. By applying a weak alternating current between electrodes placed on the scalp matched to the endogenous frequency, tACS enables the specific modulation of targeted brain oscillations This results in alterations in cognitive functions or persistent physiological changes. Most studies that utilize tACS determine a fixed stimulation frequency prior to the stimulation that is kept constant throughout the experiment. Yet it is known that brain rhythms can encounter shifts in their endogenous frequency. This could potentially move the ongoing brain oscillations into a frequency region where it is no longer affected by the stimulation, thereby decreasing or negating the effect of tACS. Such an effect of a mismatch between stimulation frequency and endogenous frequency on the outcome of stimulation has been shown before for the parietal alpha-activity. In this study, we employed an intermittent closed loop stimulation protocol, where the stimulation is divided into short epochs, between which an EEG is recorded and rapidly analyzed to determine a new stimulation frequency for the next stimulation epoch. This stimulation protocol was tested in a three-group study against a classical fixed stimulation protocol and a sham-treatment. We targeted the parietal alpha rhythm and hypothesized that this setup will ensure a constant close match between the frequencies of tACS and alpha activity. This closer match should lead to an increased modulation of detection of visual luminance changes depending on the phase of the tACS and an increased rise in alpha peak power post stimulation when compared to a protocol with fixed pre-determined stimulation frequency. Contrary to our hypothesis, our results show that only a fixed stimulation protocol leads to a persistent increase in post-stimulation alpha power as compared to sham. Furthermore, in none of the stimulated groups significant modulation of detection performance occurred. While the lack of behavioral effects is inconclusive due to the short selection of different phase bins and trials, the physiological results suggest that a constant stimulation with a fixed frequency is actually beneficial, when the goal is to produce persistent synaptic changes.

scholarly journals Transcranial alternating current stimulation (tACS) reveals causal role of brain oscillations in visual attention

2016 ◽  
Vol 16 (12) ◽  
pp. 937 ◽  
Author(s):  
Daniel Baldauf ◽  
Nir Grossman ◽  
An-Ming Hu ◽  
Ed Boyden ◽  
Robert Desimone
Keyword(s):  
Visual Attention ◽  
Alternating Current ◽  
Causal Role ◽  
Brain Oscillations ◽  
Transcranial Alternating Current Stimulation

scholarly journals Transcranial Alternating Current and Random Noise Stimulation: Possible Mechanisms

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
Andrea Antal ◽  
Christoph S. Herrmann
Keyword(s):  
Random Noise ◽  
Animal Experiments ◽  
Alternating Current ◽  
Brain Oscillations ◽  
Physiological Mechanisms ◽  
Fine Grained ◽  
Transcranial Random Noise Stimulation ◽  
Transcranial Alternating Current Stimulation ◽  
Network Simulations ◽  
And Behavior

Background. Transcranial alternating current stimulation (tACS) is a relatively recent method suited to noninvasively modulate brain oscillations. Technically the method is similar but not identical to transcranial direct current stimulation (tDCS). While decades of research in animals and humans has revealed the main physiological mechanisms of tDCS, less is known about the physiological mechanisms of tACS.Method. Here, we review recent interdisciplinary research that has furthered our understanding of how tACS affects brain oscillations and by what means transcranial random noise stimulation (tRNS) that is a special form of tACS can modulate cortical functions.Results. Animal experiments have demonstrated in what way neurons react to invasively and transcranially applied alternating currents. Such findings are further supported by neural network simulations and knowledge from physics on entraining physical oscillators in the human brain. As a result, fine-grained models of the human skull and brain allow the prediction of the exact pattern of current flow during tDCS and tACS. Finally, recent studies on human physiology and behavior complete the picture of noninvasive modulation of brain oscillations.Conclusion. In future, the methods may be applicable in therapy of neurological and psychiatric disorders that are due to malfunctioning brain oscillations.

Mapping entrained brain oscillations during transcranial alternating current stimulation (tACS)

NeuroImage ◽  
2016 ◽  
Vol 140 ◽  
pp. 89-98 ◽  
Author(s):  
Matthias Witkowski ◽  
Eliana Garcia-Cossio ◽  
Bankim S. Chander ◽  
Christoph Braun ◽  
Niels Birbaumer ◽  
...  
Keyword(s):  
Alternating Current ◽  
Brain Oscillations ◽  
Transcranial Alternating Current Stimulation
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