scholarly journals Effects of theta transcranial alternating current stimulation (tACS) on exploration and exploitation during uncertain decision-making

2021 ◽  
Author(s):  
Miles Wischnewski ◽  
Boukje Compen
Keyword(s):  
Risk Taking ◽  
Current Flow ◽  
Flow Direction ◽  
Alternating Current ◽  
Double Blind ◽  
Theta Frequency ◽  
Transcranial Alternating Current Stimulation ◽  
Exploration Exploitation ◽  
The Relationship ◽  
Posterior Anterior

Exploring ones surroundings may yield unexpected rewards, but is associated with uncertainty and risk. Alternatively, exploitation of certain outcomes is related to low risk, yet potentially better outcomes remain unexamined. As such, risk-taking behavior depends on perceived uncertainty and a trade-off between exploration-exploitation. Previously, it has been suggested that risk-taking may relate to theta activity in the prefrontal cortex. Furthermore, previous studies hinted at a relationship between a right-hemispheric bias in frontal theta asymmetry and risky behavior. In the present double-blind sham-controlled within-subject study, we applied bifrontal transcranial alternating current stimulation (tACS) at the theta frequency (5 Hz) on eighteen healthy volunteers during a gambling task. Two tACS montages with either left-right or posterior-anterior current flow were employed at an intensity of 1 mA. Results showed that, compared to sham, theta tACS increased perceived uncertainty irrespective of current flow direction. Despite this observation, no direct effect of tACS on exploration behavior and general risk-taking was observed. Furthermore, frontal theta asymmetry was more right-hemispherically biased after posterior-anterior tACS, compared to sham. Finally, we used electric field simulation to identify which regions were targeted by the tACS montages as an overlap in regions may explain why the two montages resulted in comparable outcomes. Our findings provide a first step towards understanding the relationship between frontal theta oscillations and different features of risk-taking.

scholarly journals Conducting double-blind placebo-controlled clinical trials of transcranial alternating current stimulation (tACS)

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Flavio Frohlich ◽  
Justin Riddle
Keyword(s):  
Rational Design ◽  
Target Identification ◽  
Alternating Current ◽  
Sine Wave ◽  
Brain Network ◽  
Double Blind ◽  
Double Blind Placebo ◽  
Cortical Oscillations ◽  
Transcranial Alternating Current Stimulation ◽  
Therapeutic Platform

AbstractMany psychiatric and neurological illnesses can be conceptualized as oscillopathies defined as pathological changes in brain network oscillations. We previously proposed the application of rational design for the development of non-invasive brain stimulation for the modulation and restoration of cortical oscillations as a network therapeutic. Here, we show how transcranial alternating current stimulation (tACS), which applies a weak sine-wave electric current to the scalp, may serve as a therapeutic platform for the treatment of CNS illnesses. Recently, an initial series of double-blind, placebo-controlled treatment trials of tACS have been published. Here, we first map out the conceptual underpinnings of such trials with focus on target identification, engagement, and validation. Then, we discuss practical aspects that need to be considered for successful trial execution, with particular regards to ensuring successful study blind. Finally, we briefly review the few published double-blind tACS trials and conclude with a proposed roadmap to move the field forward with the goal of moving from pilot trials to convincing efficacy studies of tACS.

scholarly journals Theta-gamma cross-frequency transcranial alternating current stimulation over the trough impairs cognitive control

2020 ◽  
Author(s):  
Zsolt Turi ◽  
Matthias Mittner ◽  
Albert Lehr ◽  
Hannah Bürger ◽  
Andrea Antal ◽  
...  
Keyword(s):  
Cognitive Control ◽  
Repeated Measures ◽  
Instrumental Learning ◽  
Learning Task ◽  
Alternating Current ◽  
Double Blind ◽  
Bayesian Hierarchical ◽  
Theta Wave ◽  
Gamma Frequency ◽  
Transcranial Alternating Current Stimulation

Cognitive control is a hypothetical mental process, which underlies adaptive goal-directed decisions. Previous studies have linked cognitive control to electrophysiological fluctuations in the theta band and theta-gamma cross-frequency coupling (CFC) arising from the cingulate and frontal cortices. Yet, to date the behavioral consequences of different forms of theta-gamma CFC remain elusive. Here, we studied the behavioral effects of the theta-gamma CFC via transcranial alternating current stimulation (tACS) designed to stimulate the frontal and cingulate cortices. Using a double-blind, randomized, repeated measures study design, 24 healthy participants were subjected to three main, active CFC-tACS protocols: Short gamma frequency bursts (80 Hz) were coupled to an ongoing theta cycle (4 Hz) to coincide with either the peaks or the troughs of the theta wave. In a third condition, the amplitude of the gamma oscillation was modulated by the phase of a theta cycle. In the fourth, control protocol, gamma was continuously superimposed over the theta cycle, therefore lacking any phase-specificity in the CFC. During the 20-minute stimulations, the participants performed a Go/NoGo monetary reward- and punishment-based instrumental learning task. A Bayesian hierarchical logistic regression analysis revealed that CFC-tACS over peak had no effects on the behavioral performance, whereas CFC-tACS over trough and, to a lesser extent, amplitude-modulated tACS reduced performance in conflicting trials. Our results suggest that cognitive control depends on the phase-specificity of the theta-gamma CFC.

scholarly journals Motor Learning Based on Oscillatory Brain Activity Using Transcranial Alternating Current Stimulation: A Review

2021 ◽  
Vol 11 (8) ◽  
pp. 1095
Author(s):  
Naoyuki Takeuchi ◽  
Shin-Ichi Izumi
Keyword(s):  
Motor Learning ◽  
Brain Activity ◽  
Alternating Current ◽  
Social Effects ◽  
Motor Deficits ◽  
Noninvasive Brain Stimulation ◽  
Transcranial Alternating Current Stimulation ◽  
Oscillatory Brain Activity ◽  
Teaching Learning ◽  
The Relationship

Developing effective tools and strategies to promote motor learning is a high-priority scientific and clinical goal. In particular, motor-related areas have been investigated as potential targets to facilitate motor learning by noninvasive brain stimulation (NIBS). In addition to shedding light on the relationship between motor function and oscillatory brain activity, transcranial alternating current stimulation (tACS), which can noninvasively entrain oscillatory brain activity and modulate oscillatory brain communication, has attracted attention as a possible technique to promote motor learning. This review focuses on the use of tACS to enhance motor learning through the manipulation of oscillatory brain activity and its potential clinical applications. We discuss a potential tACS–based approach to ameliorate motor deficits by correcting abnormal oscillatory brain activity and promoting appropriate oscillatory communication in patients after stroke or with Parkinson’s disease. Interpersonal tACS approaches to manipulate intra- and inter-brain communication may result in pro-social effects and could promote the teaching–learning process during rehabilitation sessions with a therapist. The approach of re-establishing oscillatory brain communication through tACS could be effective for motor recovery and might eventually drive the design of new neurorehabilitation approaches based on motor learning.

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 Remotely Monitored Home-Based Neuromodulation With Transcranial Alternating Current Stimulation (tACS) for Mal de Débarquement Syndrome

2021 ◽  
Vol 12 ◽  
Author(s):  
Yoon-Hee Cha ◽  
Jeff Riley ◽  
Diamond Gleghorn ◽  
Benjamin Doudican
Keyword(s):  
Treatment Option ◽  
Treatment Options ◽  
Alternating Current ◽  
Open Label ◽  
Double Blind ◽  
Entire Study ◽  
Safe Treatment ◽  
Mal De Debarquement Syndrome ◽  
Transcranial Alternating Current Stimulation ◽  
Safe Treatment Option

Objective: To determine whether remotely-monitored transcranial alternating current stimulation (tACS) may be a viable and safe treatment option for Mal de Débarquement Syndrome (MdDS).Background: Mal de Débarquement Syndrome is a neurotological disorder characterized by persistent oscillating vertigo that is triggered by entrainment to passive oscillatory motion such as occurs during water-based travel. Treatment options for MdDS are limited, variably effective, and can be undone by further travel.Design and Methods: This was a remotely-monitored open-label optional extension phase of a double-blind randomized onsite study of tACS for medically refractory MdDS. The primary goal was to determine safety, feasibility, and blinded participant feedback. The secondary goal was to determine efficacy. Thirteen participants (all women), aged 22–67 years, experiencing a duration of illness of 11–72 months, were a subset of 24 individuals who participated in an on-site study of tACS. They had either not responded to the on-site protocol or had relapsed after travel home. Treatment accessories and a tablet controlled tACS stimulator (Pulvinar XCSITE-100) were mailed to participants. Three teaching sessions were performed via webcam followed by on-going remote monitoring of treatment logs and participants' reports through a daily on-line diary and weekly questionnaires. Treatment continued until an effective protocol was administered for 4 weeks and then tapered over 4 weeks. Participants completed a blinded feedback survey and a debriefing interview at the completion of the entire study.Results: Treatment duration ranged from 4 to 31 weeks followed by a 4-week taper accounting for 578 verified sessions. Of the 13 total participants, seven agreed or agreed strongly in the blinded survey that tACS treatment was beneficial; 2) Twelve were comfortable utilizing tACS on their own; 3) Eleven preferred stimulation above their individual alpha frequency; 4) Side effects were generally mild and typical of tACS. In the debriefing interview completed 2–9 months after the last stimulation, five participants reported doing “great,” with no to minimal symptoms, four reported doing “good,” with moderate symptoms, and four reported no change compared to pre-study baseline.Conclusion: Remotely-monitored tACS may be a safe treatment option for MdDS with the potential for lasting outcomes, increased accessibility, and reduction in travel-related treatment reversal.

scholarly journals Low Intensity, Transcranial, Alternating Current Stimulation Reduces Migraine Attack Burden in a Home Application Set-Up: A Double-Blinded, Randomized Feasibility Study

2020 ◽  
Vol 10 (11) ◽  
pp. 888
Author(s):  
Andrea Antal ◽  
Rebecca Bischoff ◽  
Caspar Stephani ◽  
Dirk Czesnik ◽  
Florian Klinker ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Sham Group ◽  
Motor Evoked Potentials ◽  
Alternating Current ◽  
Drop Out ◽  
Double Blind ◽  
Sham Stimulation ◽  
Low Intensity ◽  
Transcranial Alternating Current Stimulation ◽  
Set Up

Background: Low intensity, high-frequency transcranial alternating current stimulation (tACS) applied over the motor cortex decreases the amplitude of motor evoked potentials. This double-blind, placebo-controlled parallel group study aimed to test the efficacy of this method for acute management of migraines. Methods: The patients received either active (0.4 mA, 140 Hz) or sham stimulation for 15 min over the visual cortex with the number of terminated attacks two hours post-stimulation as the primary endpoint, as a home therapy option. They were advised to treat a maximum of five migraine attacks over the course of six weeks. Results: From forty patients, twenty-five completed the study, sixteen in the active and nine in the sham group with a total of 102 treated migraine attacks. The percentage of terminated migraine attacks not requiring acute rescue medication was significantly higher in the active (21.5%) than in the sham group (0%), and the perceived pain after active stimulation was significantly less for 2–4 h post-stimulation than after sham stimulation. Conclusion: tACS over the visual cortex has the potential to terminate migraine attacks. Nevertheless, the high drop-out rate due to compliance problems suggests that this method is impeded by its complexity and time-consuming setup.

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