Real-time Phase Detection for EEG-based tACS Closed-loop System

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

doi:10.5220/0006927300130020

Cited by 7 publications

(11 citation statements)

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“…We used a closed-loop implementation based on a model described earlier (see Figure 1A and Zarubin et al, 2018 ) to apply tACS stimulation either in-phase or in anti-phase (phase-shifted by 180°) of ongoing visual alpha-band activity. In brief EEG signals were extracted online.…”

Section: Methodsmentioning

confidence: 99%

“…In this work, we present the results of a study using a previously used closed-loop EEG-tACS protocol (Zarubin et al, 2018 ) by which the stimulation signal was phase coupled with ongoing alpha oscillations. In particular, we investigated the effects of repeated short durations of tACS (1 s) applied over the visual cortex on alpha amplitude when tACS signals and ongoing alpha visual alpha oscillations were phase-synchronized (in-phase) or in opposite phase (anti-phase) and in different states, when alpha levels were high in amplitude (eyes closed, EC) or low (eyes opened, EO).…”

Section: Introductionmentioning

confidence: 99%

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

Zarubin

Gundlach

Nikulin

et al. 2020

Front. Hum. Neurosci.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Zarubin

Gundlach

Nikulin

et al. 2020

Front. Hum. Neurosci.

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“…For phase prediction we utilized the same Hilbert-based approach as tested and validated in our previous study (Zarubin et al, 2018). This method is based on the assumption that with short time intervals we can consider phase dynamics to be quasi stationary, which allows us to perform phase prediction by the extraction phase information from a current (pre-stimulation) interval in order to forecast phase dependent stimulation for the following interval.…”

Section: Phase Prediction Delay Estimation and Compensationmentioning

confidence: 99%

“…Euclidean difference (L 2 norm) for vectors of instantaneous phase between extraction interval and various generated sine waves was criteria for minimization -in case of "in-phase" relation, and maximization in case of "anti-phase" relation. Transduction and optimization delays were estimated and compensated with the same procedure as validated in (Zarubin et al, 2018). For the chosen phase prediction method (Hilbert-based), the average value of optimization delay across all subjects was 15±2.4 ms and average transduction delay was 72 ms.…”

Section: Phase Prediction Delay Estimation and Compensationmentioning

confidence: 99%

“…In this work, we present results of a study using a closed-loop EEG-tACS protocol by which the stimulation signal was phase coupled with ongoing alpha oscillations. Our research is based on a closed-loop model that we developed and presented previously (Zarubin et al, 2018), using an approach with intermittent stimulation. In particular, we investigated the effects of repeated short durations of tACS (1 s) applied over the visual cortex on alpha amplitude when tACS signals and ongoing alpha visual alpha oscillations were phase-synchronized (in-phase) or in opposite phase (antiphase) and in different states, when alpha levels were high in amplitude (eyes closed) or low (eyes opened).…”

Section: Introductionmentioning

confidence: 99%

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

Zarubin

Gundlach

Nikulin

et al. 2020

Preprint

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Non-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 interindividual 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 antiphase 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.

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The Portiloop: A deep learning-based open science tool for closed-loop brain stimulation

et al. 2022

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Closed-loop brain stimulation refers to capturing neurophysiological measures such as electroencephalography (EEG), quickly identifying neural events of interest, and producing auditory, magnetic or electrical stimulation so as to interact with brain processes precisely. It is a promising new method for fundamental neuroscience and perhaps for clinical applications such as restoring degraded memory function; however, existing tools are expensive, cumbersome, and offer limited experimental flexibility. In this article, we propose the Portiloop, a deep learning-based, portable and low-cost closed-loop stimulation system able to target specific brain oscillations. We first document open-hardware implementations that can be constructed from commercially available components. We also provide a fast, lightweight neural network model and an exploration algorithm that automatically optimizes the model hyperparameters to the desired brain oscillation. Finally, we validate the technology on a challenging test case of real-time sleep spindle detection, with results comparable to off-line expert performance on the Massive Online Data Annotation spindle dataset (MODA; group consensus). Software and plans are available to the community as an open science initiative to encourage further development and advance closed-loop neuroscience research [https://github.com/Portiloop].

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Real-time Phase Detection for EEG-based tACS Closed-loop System

Cited by 7 publications

References 2 publications

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

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

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

The Portiloop: A deep learning-based open science tool for closed-loop brain stimulation

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