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.

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

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.

scholarly journals Transkranielle elektrische Hirnstimulationsverfahren zur Behandlung der Negativsymptomatik bei Schizophrenie

2021 ◽  
Author(s):  
Nikolas Haller ◽  
Alkomiet Hasan ◽  
Frank Padberg ◽  
Wolfgang Strube ◽  
Leandro da Costa Lane Valiengo ◽  
...  
Keyword(s):  
Direct Current ◽  
Transcranial Direct Current Stimulation ◽  
Random Noise ◽  
Alternating Current ◽  
Direct Current Stimulation ◽  
Transkranielle Gleichstromstimulation ◽  
Transcranial Random Noise Stimulation ◽  
Transcranial Alternating Current Stimulation

ZusammenfassungÜber die letzten Jahre entwickelten sich Neuromodulationsverfahren zu einer dritten Säule neben Pharmakotherapie und Psychotherapie in der Behandlung psychischer Erkrankungen. Besonders in der Behandlung von Menschen mit einer Schizophrenie könnten Hirnstimulationsverfahren eine Alternative oder Ergänzung zu den etablierten Therapiestrategien darstellen. Die meist vorhandenen Positivsymptome können zumeist mit Antipsychotika adäquat behandelt werden. Gerade bei Patienten mit Schizophrenie besitzen jedoch Negativsymptome einen überdauernden Krankheitswert und beeinflussen den Verlauf durch globale Antriebsverarmung und beeinträchtigte Kognition im alltäglichen Leben negativ. Dieser Übersichtsartikel stellt eine Zusammenfassung über die verschiedenen nichtinvasiven Hirnstimulationsverfahren transkranielle Gleichstromstimulation (transcranial direct current stimulation, tDCS), Wechselstromstimulation (transcranial alternating current stimulation, tACS) sowie Rauschstromstimulation (transcranial random noise stimulation, tRNS) zur Behandlung der Negativsymptomatik bei Schizophrenie dar. Die neuen transkraniellen Hirnstimulationsverfahren könnten dabei helfen, gestörte neuronale Vernetzungen wieder herzustellen und die Konnektivität vor allem der dorsolateralen präfrontalen Anteile des Kortex zu verbessern. Einige Studien weisen auf eine Verbesserung der Negativsymptome durch Behandlung mit tDCS, tACS bzw. tRNS hin und könnten so neue Therapiemöglichkeiten in der Behandlung der Schizophrenie darstellen.

Sham transcranial electrical stimulation and its effects on corticospinal excitability: a systematic review and meta-analysis

2018 ◽  
Vol 29 (2) ◽  
pp. 223-232 ◽  
Author(s):  
Thusharika D. Dissanayaka ◽  
Maryam Zoghi ◽  
Michael Farrell ◽  
Gary F. Egan ◽  
Shapour Jaberzadeh
Keyword(s):  
Systematic Review ◽  
Electrical Stimulation ◽  
Meta Analysis ◽  
Random Noise ◽  
Corticospinal Excitability ◽  
Transcranial Electrical Stimulation ◽  
Placebo Effects ◽  
Randomized Controlled ◽  
Transcranial Random Noise Stimulation ◽  
Transcranial Alternating Current Stimulation

AbstractSham stimulation is used in randomized controlled trials (RCTs) to assess the efficacy of active stimulation and placebo effects. It should mimic the characteristics of active stimulation to achieve blinding integrity. The present study was a systematic review and meta-analysis of the published literature to identify the effects of sham transcranial electrical stimulation (tES) – including anodal and cathodal transcranial direct current stimulation (a-tDCS, c-tDCS), transcranial alternating current stimulation (tACS), transcranial random noise stimulation (tRNS) and transcranial pulsed current stimulation (tPCS) – on corticospinal excitability (CSE), compared to baseline in healthy individuals. Electronic databases – PubMed, CINAHL, Scopus, Science Direct and MEDLINE (Ovid) – were searched for RCTs of tES from 1990 to March 2017. Thirty RCTs were identified. Using a random-effects model, meta-analysis of a-tDCS, c-tDCS, tACS, tRNS and tPCS studies showed statistically non-significant pre-post effects of sham interventions on CSE. This review found evidence for statically non-significant effects of sham tES on CSE.

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 Investigating cognitive and therapeutic effects of transcranial electric stimulation (TES): a short guide for reproducible and transparent research

2020 ◽  
Author(s):  
Samuel James Westwood
Keyword(s):  
Random Noise ◽  
Evidence Base ◽  
Open Science ◽  
Transcranial Electrical Stimulation ◽  
Therapeutic Effects ◽  
Direct Stimulation ◽  
Causal Inferences ◽  
Science Practices ◽  
Transcranial Random Noise Stimulation ◽  
Transcranial Alternating Current Stimulation

Non-invasive brain stimulation (NIBS) is a useful tool for assisting causal inferences in cortical structure–function relationships and for developing treatment alternatives in neuropsychiatric disorders. Transcranial electrical stimulation (TES) techniques, namely transcranial direct stimulation (tDCS), transcranial alternating current stimulation (tACS), and transcranial random noise stimulation (tRNS), have grown in popularity in recent years because they are well tolerated, safe, and less costly compared to other forms of NIBS such as transcranial magnetic stimulation (TMS). The rigour and reproducibility of TES studies and their findings is therefore of key importance. However, in recent years, uncertainty has grown regarding the effectiveness of TES and the quality of its evidence base. Current recommended steps to improve the rigour and reproducibility of TES research have mainly focused on reducing variation and ambiguity in reported findings. To effectively deal with reported issues, Open Science practices provide a possible answer. The goal of this article is to give an overview of Open Science practices relevant to TES research (i.e., open materials/data, preregistration, registered reports, collaboration) and guidance in how to overcome challenges one may face in their implementation (e.g., data anonymity, costs of sharing materials/data, inappropriate incentives). The ultimate goal of this article is to instigate more engagement from TES researchers in how Open Science practices can be incorporated into standard research practice.

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.

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