Transient Amplitude Modulation of Alpha-Band Oscillations by Short-Time Intermittent Closed-Loop tACS

Zarubin, Georgy; Gundlach, Christopher; Nikulin, Vadim V.; Villringer, Arno; Bogdan, Martin

doi:10.3389/fnhum.2020.00366

Cited by 30 publications

(26 citation statements)

References 96 publications

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“…Instead of pre-determining stimulation parameters, from experience and models alone, the parameters are dynamically tuned to the current brain activity in near real time ( Boyle and Frohlich, 2013 ; Wilde et al, 2015 ; Bergmann et al, 2016 ; Karabanov et al, 2016 ; Thut et al, 2017 ). Respective novel approaches of applying frequency and phase specific tACS corresponding to current brain activity have shown promising results in memory consolidation during sleep ( Jones et al, 2018 ; Ketz et al, 2018 ) and phase-dependent modulation of the α-rhythm via closed-loop tACS are currently studied ( Zarubin et al, 2020 ).…”

Section: Introductionmentioning

confidence: 99%

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

Stecher

Notbohm²,

Kasten

et al. 2021

Front. Hum. Neurosci.

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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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Section: Introductionmentioning

confidence: 99%

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

Stecher

Notbohm²,

Kasten

et al. 2021

Front. Hum. Neurosci.

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“…The capacity to induce or suppress target oscillatory activities within a relatively short period of time (within several seconds) is a unique and highly valuable feature of our online phase-locking closed-loop tACS system as compared to other currently available tACS techniques. Conventional long-term continuous tACS and recently published brain signal based closed-loop tACS set-ups have to date only reported unidirectional modulation of brain oscillations at the stimulation frequency (24,(44)(45)(46). This inflexibility regarding directionality is problematic for many functions and applications.…”

Section: Discussionmentioning

confidence: 99%

Alpha Oscillatory Activity Causally Linked to Working Memory Retention: Insights from Online Phase-corrected Closed-loop Transcranial Alternating Current Stimulation (tACS)

Chen

Zhang

et al. 2021

Preprint

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Although previous studies have reported correlations between alpha oscillations and the "retention" sub-process of working memory (WM), no direct causal evidence has been established in human neuroscience. Here, we developed an online phase-locking closed-loop transcranial alternating current stimulation (tACS) system capable of precisely controlling the phase difference between tACS and concurrent endogenous oscillations. This system permits both up- and down-regulation of brain oscillations at the target stimulation frequency, and is here applied to empirically demonstrate that parietal alpha oscillations causally relate to WM retention. Our experimental design included both in-phase and anti-phase alpha-tACS applied to 39 participants during the retention intervals of a modified Sternberg paradigm. Compared to in-phase alpha-tACS, anti-phase alpha-tACS decreased both WM performance and alpha activity. Moreover, the in-phase tACS-induced changes in WM performance were positively correlated with alpha oscillatory activity. These findings strongly support a causal link between alpha oscillations and WM retention, and illustrate the broad application prospects of phase-locking tACS.

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“…Within the alpha-band research, OTA has been reported by several NFB studies (Kluetsch et al, 2014 ; Peeters et al, 2014 ; Nicholson et al, 2016 ; Ros et al, 2017a , b ; Deiber et al, 2020 ) whereas the occurrence of OTA in tACS research is rather ambiguous (Gundlach et al, 2017 ; Haberbosch et al, 2019 ; Krawinkel et al, 2019 ; Zarubin et al, 2020 ). OTA has been attributed to the influence of homeostatic plasticity in both NFB (Kluetsch et al, 2014 ; Peeters et al, 2014 ; Nicholson et al, 2016 ; Ros et al, 2017a , b ; Deiber et al, 2020 ) and tACS research (Garside et al, 2015 ; Gundlach et al, 2017 ; Ketz et al, 2018 ; Haberbosch et al, 2019 ; Zarubin et al, 2020 ). However, to the best to our knowledge, so far, neither tACS nor NFB studies have investigated a direct link between OTA and the neural markers specific for homeostatic plasticity.…”

Section: Aftereffectsmentioning

confidence: 99%

“…This kind of aftereffect has been shown to occur immediately after the termination of intervention by NFB or tACS (Garside et al, 2015;Nicholson et al, 2016;Deiber et al, 2020). Within the alpha-band research, OTA has been reported by several NFB studies (Kluetsch et al, 2014;Peeters et al, 2014;Nicholson et al, 2016;Ros et al, 2017a,b;Deiber et al, 2020) whereas the occurrence of OTA in tACS research is rather ambiguous (Gundlach et al, 2017;Haberbosch et al, 2019;Krawinkel et al, 2019;Zarubin et al, 2020). OTA has been attributed to the influence of homeostatic plasticity in both NFB (Kluetsch et al, 2014;Peeters et al, 2014;Nicholson et al, 2016;Ros et al, 2017a,b;Deiber et al, 2020) and tACS research (Garside et al, 2015;Gundlach et al, 2017;Ketz et al, 2018;Haberbosch et al, 2019;Zarubin et al, 2020).…”

Section: Aftereffects and Their Potential Link With Brain Plasticitymentioning

confidence: 99%

Effects of Transcranial Alternating Current Stimulation and Neurofeedback on Alpha (EEG) Dynamics: A Review

Orendáčová

Kvašňák

2021

Front. Hum. Neurosci.

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Transcranial alternating current stimulation (tACS) and neurofeedback (NFB) are two different types of non-invasive neuromodulation techniques, which can modulate brain activity and improve brain functioning. In this review, we compared the current state of knowledge related to the mechanisms of tACS and NFB and their effects on electroencephalogram (EEG) activity (online period/stimulation period) and on aftereffects (offline period/post/stimulation period), including the duration of their persistence and potential behavioral benefits. Since alpha bandwidth has been broadly studied in NFB and in tACS research, the studies of NFB and tACS in modulating alpha bandwidth were selected for comparing the online and offline effects of these two neuromodulation techniques. The factors responsible for variability in the responsiveness of the modulated EEG activity by tACS and NFB were analyzed and compared too. Based on the current literature related to tACS and NFB, it can be concluded that tACS and NFB differ a lot in the mechanisms responsible for their effects on an online EEG activity but they possibly share the common universal mechanisms responsible for the induction of aftereffects in the targeted stimulated EEG band, namely Hebbian and homeostatic plasticity. Many studies of both neuromodulation techniques report the aftereffects connected to the behavioral benefits. The duration of persistence of aftereffects for NFB and tACS is comparable. In relation to the factors influencing responsiveness to tACS and NFB, significantly more types of factors were analyzed in the NFB studies compared to the tACS studies. Several common factors for both tACS and NFB have been already investigated. Based on these outcomes, we propose several new research directions regarding tACS and NFB.

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Transient Amplitude Modulation of Alpha-Band Oscillations by Short-Time Intermittent Closed-Loop tACS

Cited by 30 publications

References 96 publications

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

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

Alpha Oscillatory Activity Causally Linked to Working Memory Retention: Insights from Online Phase-corrected Closed-loop Transcranial Alternating Current Stimulation (tACS)

Effects of Transcranial Alternating Current Stimulation and Neurofeedback on Alpha (EEG) Dynamics: A Review

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