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

Orendáčová, Mária; Kvašňák, Eugen

doi:10.3389/fnhum.2021.628229

“…The spatial separation of different posterior alpha rhythms through ICA in single subjects could resolve some of the previous inconsistencies in the literature concerning the role of alpha phase, power and frequency in cognition (Michail et al, 2021; Pavlov & Kotchoubey, 2020; Samaha et al, 2020; Zazio et al, 2021). Similarly, separating different posterior alpha rhythms could allow us to understand why some neurofeedback and neurostimulation protocols do not have the expected effect in some subjects (Orendáčová & Kvašňák, 2021). If we tune the neurofeedback/stimulation parameters (and/or assess their effects) at sensor level, we cannot know whether we are modulating the power or frequency of one or several alpha rhythms.…”

Section: Discussionmentioning

confidence: 99%

Visual working memory recruits two functionally distinct alpha rhythms in posterior cortex

Larios

¹

,

ElShafei

²

,

Wiehe

³

et al. 2022

Preprint

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Oscillatory activity in the human brain is dominated by posterior alpha oscillations (8-14 Hz), which have been shown to be functionally relevant in a wide variety of cognitive tasks. Although posterior alpha oscillations are commonly considered a single oscillator anchored at an individual alpha frequency (IAF; ~10 Hz), previous work suggests that IAF reflects a spatial mixture of different brain rhythms. In this study, we assess whether Independent Component Analysis (ICA) can disentangle functionally distinct posterior alpha rhythms in the context of visual short-term memory retention. Magnetoencephalography (MEG) was recorded in 33 subjects while performing a visual working memory task. Group analysis at sensor level suggested the existence of a single posterior alpha oscillator that increases in power and decreases in frequency during memory retention. Conversely, single-subject analysis of independent components revealed the existence of two dissociable alpha rhythms: one that increases in power during memory retention (Alpha1) and another one that decreases in power (Alpha2). Alpha1 and Alpha2 rhythms were differentially modulated by the presence of visual distractors (Alpha1 increased in power while Alpha2 decreased) and had an opposite relationship with accuracy (positive for Alpha1 and negative for Alpha2). In addition, Alpha1 rhythms showed a lower peak frequency, a narrower peak width, a greater relative peak amplitude and a more central source than Alpha2 rhythms. Together, our results demonstrate that modulations in posterior alpha oscillations during short-term memory retention reflect the dynamics of at least two distinct brain rhythms with different functions and spatiospectral characteristics.

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“…Similarly, separating different alpha rhythms could allow us to understand why some neurofeedback and neurostimulation protocols do not have the expected effect in some subjects (Orendáčová & Kvašňák, 2021). If we tune the neurofeedback/stimulation parameters (and/or assess their effects) at sensor level, we cannot know whether we are modulating the power or frequency of one or several alpha rhythms.…”

Section: Discussionmentioning

confidence: 99%

“…The spatial separation of different alpha rhythms could resolve some of the previous inconsistencies in the literature concerning the role of alpha phase, power and frequency in cognition ( Samaha et al, 2020 ; Michail et al, 2022 ; Pavlov and Kotchoubey, 2022 ; Zazio et al, 2022 ). Similarly, separating different alpha rhythms could allow us to understand why some neurofeedback and neurostimulation protocols do not have the expected effect in some subjects ( Orendáčová and Kvašňák, 2021 ). If we tune the neurofeedback/stimulation parameters (and/or assess their effects) at sensor level, we cannot know whether we are modulating the power or frequency of one or several alpha rhythms.…”

Section: Discussionmentioning

confidence: 99%

Visual Working Memory Recruits Two Functionally Distinct Alpha Rhythms in Posterior Cortex

Rodriguez‐Larios

¹

,

ElShafei²,

Wiehe³

et al. 2022

eNeuro

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Oscillatory activity in the human brain is dominated by posterior alpha oscillations (8-14 Hz), which have been shown to be functionally relevant in a wide variety of cognitive tasks. Although posterior alpha oscillations are commonly considered a single oscillator anchored at an individual alpha frequency (IAF; ~10 Hz), previous work suggests that IAF reflects a spatial mixture of different brain rhythms. In this study, we assess whether Independent Component Analysis (ICA) can disentangle functionally distinct posterior alpha rhythms in the context of visual short-term memory retention. Magnetoencephalography (MEG) was recorded in 33 subjects while performing a visual working memory task. Group analysis at sensor level suggested the existence of a single posterior alpha oscillator that increases in power and decreases in frequency during memory retention. Conversely, single-subject analysis of independent components revealed the existence of two dissociable alpha rhythms: one that increases in power during memory retention (Alpha1) and another one that decreases in power (Alpha2). Alpha1 and Alpha2 rhythms were differentially modulated by the presence of visual distractors (Alpha1 increased in power while Alpha2 decreased) and had an opposite relationship with accuracy (positive for Alpha1 and negative for Alpha2). In addition, Alpha1 rhythms showed a lower peak frequency, a narrower peak width, a greater relative peak amplitude and a more central source than Alpha2 rhythms. Together, our results demonstrate that modulations in posterior alpha oscillations during short-term memory retention reflect the dynamics of at least two distinct brain rhythms with different functions and spatiospectral characteristics. 4 Significance statementAlpha oscillations are the most prominent feature of the human brain's electrical activity, and consist of rhythmic neuronal activity in posterior parts of the cortex.Alpha is usually considered a single brain rhythm that changes in power and frequency to support cognitive operations. We here show that posterior alpha entails at least two dissociable rhythms with distinct functions and characteristics. These findings could solve previous inconsistencies in the literature regarding the direction of task-related alpha power/frequency modulations and their relation to cognitive performance. In addition, the existence of two distinct posterior alpha rhythms could have important consequences for the design of neurostimulation protocols aimed at modulating alpha oscillations and subsequently cognition.

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“…Further work is required to establish the validity of resting state EEG as a decisive criterion for the inclusion of individuals in NFB training. In future investigations, it may be possible to better understand the relationship between resting state EEG and neuromodulation capacity by using a neurostimulation technique such as transcranial alternating current stimulation (tACS) on the trained frequency just before NFB training (Orendáčová & Kvašňák, 2021). The application of tACS allows the increase of endogenous neurophysiological activity by rhythmic stimulation (Liu et al, 2018;Zaghi et al, 2010).…”

Section: B Predictor Variables Of Neuromodulationmentioning

confidence: 99%

Mental strategies and resting state EEG: Effect on high alpha amplitude modulation by neurofeedback in healthy young adults

Chikhi

¹

,

Matton

²

,

Sanna

³

et al. 2023

Biological Psychology

6

1

0

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

Cited by 12 publications

References 209 publications

Visual working memory recruits two functionally distinct alpha rhythms in posterior cortex

Visual working memory recruits two functionally distinct alpha rhythms in posterior cortex

Visual Working Memory Recruits Two Functionally Distinct Alpha Rhythms in Posterior Cortex

Mental strategies and resting state EEG: Effect on high alpha amplitude modulation by neurofeedback in healthy young adults

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