Closed-Loop Transcranial Alternating Current Stimulation: Towards Personalized Non-invasive Brain Stimulation for the Treatment of Psychiatric Illnesses

2021 ◽  
Author(s):  
Flavio Frohlich ◽  
Leah Townsend
Keyword(s):  
Brain Stimulation ◽  
Closed Loop ◽  
Alternating Current ◽  
Psychiatric Illnesses ◽  
Non Invasive ◽  
Transcranial Alternating Current Stimulation

scholarly journals Closed-loop transcranial alternating current stimulation of slow oscillations

2015 ◽  
Vol 1 (1) ◽  
pp. 85-88 ◽  
Author(s):  
Christian Wilde ◽  
Ralf Bruder ◽  
Sonja Binder ◽  
Lisa Marshall ◽  
Achim Schweikard
Keyword(s):  
Closed Loop ◽  
Alternating Current ◽  
Electrical Measurements ◽  
Slow Oscillations ◽  
Non Invasive ◽  
Transcranial Alternating Current Stimulation ◽  
Novel Method ◽  
Endogenous Activity ◽  
Stimulation Of

AbstractTranscranial alternating current stimulation (tACS) is an emerging non-invasive tool for modulating brain oscillations. There is evidence that weak oscillatory electrical stimulation during sleep can entrain cortical slow oscillations to improve the memory consolidation in rodents and humans. Using a novel method and a custom built stimulation device, automatic stimulation of slow oscillations in-phase with the endogenous activity in a real-time closed-loop setup is possible. Preliminary data from neuroplasticity experiments show a high detection performance of the proposed method, electrical measurements demonstrate the outstanding quality of the presented stimulation device.

scholarly journals Working Memory and Cross-Frequency Coupling of Neuronal Oscillations

2021 ◽  
Vol 12 ◽  
Author(s):  
Mohammed Abubaker ◽  
Wiam Al Qasem ◽  
Eugen Kvašňák
Keyword(s):  
Working Memory ◽  
Cognitive Impairment ◽  
Brain Stimulation ◽  
Large Body ◽  
Cognitive Outcomes ◽  
Essential Component ◽  
Non Invasive ◽  
Transcranial Alternating Current Stimulation ◽  
Frequency Coupling ◽  
Cross Frequency Coupling

Working memory (WM) is the active retention and processing of information over a few seconds and is considered an essential component of cognitive function. The reduced WM capacity is a common feature in many diseases, such as schizophrenia, attention deficit hyperactivity disorder (ADHD), mild cognitive impairment (MCI), and Alzheimer's disease (AD). The theta-gamma neural code is an essential component of memory representations in the multi-item WM. A large body of studies have examined the association between cross-frequency coupling (CFC) across the cerebral cortices and WM performance; electrophysiological data together with the behavioral results showed the associations between CFC and WM performance. The oscillatory entrainment (sensory, non-invasive electrical/magnetic, and invasive electrical) remains the key method to investigate the causal relationship between CFC and WM. The frequency-tuned non-invasive brain stimulation is a promising way to improve WM performance in healthy and non-healthy patients with cognitive impairment. The WM performance is sensitive to the phase and rhythm of externally applied stimulations. CFC-transcranial-alternating current stimulation (CFC-tACS) is a recent approach in neuroscience that could alter cognitive outcomes. The studies that investigated (1) the association between CFC and WM and (2) the brain stimulation protocols that enhanced WM through modulating CFC by the means of the non-invasive brain stimulation techniques have been included in this review. In principle, this review can guide the researchers to identify the most prominent form of CFC associated with WM processing (e.g., theta/gamma phase-amplitude coupling), and to define the previously published studies that manipulate endogenous CFC externally to improve WM. This in turn will pave the path for future studies aimed at investigating the CFC-tACS effect on WM. The CFC-tACS protocols need to be thoroughly studied before they can be considered as therapeutic tools in patients with WM deficits.

scholarly journals Transient amplitude modulation of alpha-band oscillations by short-time intermittent closed-loop tACS

2020 ◽  
Author(s):  
G. Zarubin ◽  
C. Gundlach ◽  
V. Nikulin ◽  
A. Villringer ◽  
M. Bogdan
Keyword(s):  
Individual Differences ◽  
Visual System ◽  
Amplitude Modulation ◽  
Closed Loop ◽  
Alternating Current ◽  
Stimulation Protocol ◽  
Spatial Filters ◽  
Alpha Oscillations ◽  
Transcranial Alternating Current Stimulation ◽  
Short Time

AbstractNon-invasive brain stimulation techniques such as transcranial alternating current stimulation (tACS) have recently become extensively utilized due to their potential to modulate ongoing neuronal oscillatory activity and consequently to induce cortical plasticity relevant for various cognitive functions. However, the neurophysiological basis for stimulation effects as well as their inter-individual differences are not yet understood. In the present study we used a closed-loop EEG transcranial alternating current stimulation protocol (EEG-tACS) to examine the modulation of alpha oscillations generated in occipito-parietal areas. In particular, we investigated the effects of a repeated short-time intermittent stimulation protocol (1 s in every trial) applied over the visual cortex (Cz and Oz) and adjusted according to the phase and frequency of visual alpha oscillations on the amplitude of these oscillations. Based on previous findings, we expected higher increases in alpha amplitudes for tACS applied in-phase with ongoing oscillations as compared to an application in anti-phase and this modulation to be present in low-alpha amplitude states of the visual system (eyes opened) but not high (eyes closed).Contrary to our expectations, we found a transient suppression of alpha power in inter-individually derived spatially specific parieto-occipital components obtained via the estimation of spatial filters by using the common spatial patterns approach. The amplitude modulation was independent of the phase relationship between tACS signal and alpha oscillations, and the state of the visual system manipulated via closed- and open-eye conditions. It was also absent in conventionally analyzed single-channel and multi-channel data from an average parieto-occipital region.The fact that the tACS modulation of oscillations was phase-independent suggests that mechanisms driving the effects of tACS may not be explained by entrainment alone, but rather require neuroplastic changes or transient disruption of neural oscillations. Our study also supports the notion that the response to tACS is subject specific, where the modulatory effects are shaped by the interplay between the stimulation and different alpha generators. This favors stimulation protocols as well as analysis regimes exploiting inter-individual differences, such as spatial filters to reveal otherwise hidden stimulation effects and, thereby, comprehensively induce and study the effects and underlying mechanisms of tACS.

scholarly journals Endogenous and exogenous electric fields as modifiers of brain activity: rational design of noninvasive brain stimulation with transcranial alternating current stimulation

2014 ◽  
Vol 16 (1) ◽  
pp. 93-102 ◽  
Keyword(s):  
Electric Fields ◽  
Brain Stimulation ◽  
Rational Design ◽  
Brain Activity ◽  
Field Potential ◽  
Alternating Current ◽  
Noninvasive Brain Stimulation ◽  
Starting Point ◽  
Recent Developments ◽  
Transcranial Alternating Current Stimulation

Synchronized neuronal activity in the cortex generates weak electric fields that are routinely measured in humans and animal models by electroencephalography and local field potential recordings. Traditionally, these endogenous electric fields have been considered to be an epiphenomenon of brain activity. Recent work has demonstrated that active cortical networks are surprisingly susceptible to weak perturbations of the membrane voltage of a large number of neurons by electric fields. Simultaneously, noninvasive brain stimulation with weak, exogenous electric fields (transcranial current stimulation, TCS) has undergone a renaissance due to the broad scope of its possible applications in modulating brain activity for cognitive enhancement and treatment of brain disorders. This review aims to interface the recent developments in the study of both endogenous and exogenous electric fields, with a particular focus on rhythmic stimulation for the modulation of cortical oscillations. The main goal is to provide a starting point for the use of rational design for the development of novel mechanism-based TCS therapeutics based on transcranial alternating current stimulation, for the treatment of psychiatric illnesses.

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.

scholarly journals The hidden state-dependency of transcranial alternating current stimulation (tACS)

2020 ◽  
Author(s):  
Florian H. Kasten ◽  
Christoph S. Herrmann
Keyword(s):  
Markov Models ◽  
Alternating Current ◽  
Oscillatory Activity ◽  
Brain Disorders ◽  
State Dependency ◽  
Non Invasive ◽  
Transcranial Alternating Current Stimulation ◽  
Brain States ◽  
Invasive Techniques ◽  
The Brain

AbstractNon-invasive techniques to electrically stimulate the brain such as transcranial direct and alternating current stimulation (tDCS/tACS) are increasingly used in human neuroscience and offer potential new avenues to treat brain disorders. However, their often weak and variable effects have also raised concerns in the scientific community. A possible factor influencing the efficacy of these methods is the dependence on brain-states. Here, we utilized Hidden Markov Models (HMM) to decompose concurrent tACS-magnetoencephalography data into transient brain-states with distinct spatial, spectral and connectivity profiles. We found that out of four spontaneous brain-states only one was susceptible to tACS. No or only marginal effects were found in the remaining states. TACS did not influence the time spent in each state. Our results suggest, that tACS effects may be mediated by a hidden, spontaneous state-dependency and provide novel insights to the changes in oscillatory activity underlying aftereffects of tACS.

scholarly journals The Benefits of Closed-Loop Transcranial Alternating Current Stimulation on Subjective Sleep Quality

2018 ◽  
Vol 8 (12) ◽  
pp. 204 ◽  
Author(s):  
Charles Robinson ◽  
Natalie Bryant ◽  
Joshua Maxwell ◽  
Aaron Jones ◽  
Bradley Robert ◽  
...  
Keyword(s):  
Sleep Quality ◽  
Slow Wave ◽  
Closed Loop ◽  
Slow Wave Sleep ◽  
The United States ◽  
Alternating Current ◽  
Poor Sleep ◽  
Subjective Sleep Quality ◽  
Subjective Sleep ◽  
Transcranial Alternating Current Stimulation

Background: Poor sleep quality is a common complaint, affecting over one third of people in the United States. While sleep quality is thought to be related to slow-wave sleep (SWS), there has been little investigation to address whether modulating slow-wave oscillations (SWOs) that characterize SWS could impact sleep quality. Here we examined whether closed-loop transcranial alternating current stimulation (CL-tACS) applied during sleep impacts sleep quality and efficiency. Methods: CL-tACS was used in 21 participants delivered at the same frequency and in phase with endogenous SWOs during sleep. Sleep quality was assessed in the morning following either verum or sham control stimulation during sleep, with order counterbalanced within participants. Results: Higher sleep quality and efficiency were found after verum stimulation nights compared to control. The largest effects on sleep quality were found immediately following an adaptation night in the laboratory for which sleep quality was reduced. Conclusions: Applying CL-tACS at the same frequency and phase as endogenous SWOs may offer a novel method to improve subjective sleep quality after a night with poor quality sleep. CL-tACS might be helpful for increasing sleep quality and efficiency in otherwise healthy people, and in patients with clinical disorders that involve sleep deficits.

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.

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