scholarly journals Alpha Power Increase After Transcranial Alternating Current Stimulation at Alpha Frequency (α-tACS) Reflects Plastic Changes Rather Than Entrainment

2015 ◽  
Vol 8 (3) ◽  
pp. 499-508 ◽  
Author(s):  
Alexandra Vossen ◽  
Joachim Gross ◽  
Gregor Thut
Keyword(s):  
Alternating Current ◽  
Alpha Power ◽  
Alpha Frequency ◽  
Power Increase ◽  
Transcranial Alternating Current Stimulation ◽  
Plastic Changes

scholarly journals Local network-level integration mediates effects of transcranial Alternating Current Stimulation

2017 ◽  
Author(s):  
Marco Fuscà ◽  
Philipp Ruhnau ◽  
Toralf Neuling ◽  
Nathan Weisz
Keyword(s):  
Occipital Cortex ◽  
Alternating Current ◽  
Functional Network ◽  
Local Network ◽  
Oscillatory Activity ◽  
Alpha Power ◽  
State Dependency ◽  
External Stimulation ◽  
Posterior Cingulate ◽  
Transcranial Alternating Current Stimulation

AbstractTranscranial alternating current stimulation (tACS) has been proposed as a tool to draw causal inferences on the role of oscillatory activity in cognitive functioning and has the potential to induce long-term changes in cerebral networks. However, the mechanisms of action of tACS are not yet clear, though previous modeling works have suggested that variability may be mediated by local and network-level brain states. We used magnetoencephalography (MEG) to record brain activity from 17 healthy participants as they kept their eyes open (EO) or closed (EC) while being stimulated either with sham, weak, or strong alpha-tACS using a montage commonly assumed to target occipital areas. We reconstructed the activity of sources in all stimulation conditions by means of beamforming. The analysis of resting-state data revealed an interaction of the external stimulation with the endogenous alpha power difference between EO and EC in the posterior cingulate. This region is remote from occipital cortex, which showed strongest EC vs. EO alpha modulation, thus suggesting state-dependency long-range effects of tACS. In a follow-up analysis of this online-tACS effect, we find evidence that this dependency effect could be mediated by functional network changes: connection strength from the precuneus, a region adjusting for a measure of network integration in the two states (EC vs. EO during no-tACS), was significantly correlated with the state-dependency effect in the posterior cingulate (during tACS). No analogous correlation could be found for alpha power modulations in occipital cortex. Altogether, this is the first strong evidence to illustrate how functional network architectures can shape tACS effects.

scholarly journals Investigating the effects of transcranial alternating current stimulation on primary somatosensory cortex

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Nicoletta Manzo ◽  
Andrea Guerra ◽  
Margherita Giangrosso ◽  
Daniele Belvisi ◽  
Giorgio Leodori ◽  
...  
Keyword(s):  
Somatosensory Cortex ◽  
Alternating Current ◽  
Primary Somatosensory Cortex ◽  
Alpha Frequency ◽  
Tactile Stimuli ◽  
Frequency Peak ◽  
Transcranial Alternating Current Stimulation ◽  
Gamma Frequencies ◽  
Alpha Beta ◽  
Near Threshold

Abstract Near-threshold tactile stimuli perception and somatosensory temporal discrimination threshold (STDT) are encoded in the primary somatosensory cortex (S1) and largely depend on alpha and beta S1 rhythm. Transcranial alternating current stimulation (tACS) is a non-invasive neurophysiological technique that allows cortical rhythm modulation. We investigated the effects of tACS delivered over S1 at alpha, beta, and gamma frequencies on near-threshold tactile stimuli perception and STDT, as well as phase-dependent tACS effects on near-threshold tactile stimuli perception in healthy subjects. In separate sessions, we tested the effects of different tACS montages, and tACS at the individualised S1 μ-alpha frequency peak, on STDT and near-threshold tactile stimuli perception. We found that tACS applied over S1 at alpha, beta, and gamma frequencies did not modify STDT or near-threshold tactile stimuli perception. Moreover, we did not detect effects of tACS phase or montage. Finally, tACS did not modify near-threshold tactile stimuli perception and STDT even when delivered at the individualised μ-alpha frequency peak. Our study showed that tACS does not alter near-threshold tactile stimuli or STDT, possibly due to the inability of tACS to activate deep S1 layers. Future investigations may clarify tACS effects over S1 in patients with focal dystonia, whose pathophysiology implicates increased STDT.

scholarly journals Ameliorating Emotional Attention through Modulation of Neural Oscillations with Transcranial Alternating Current Stimulation

2021 ◽  
Author(s):  
Shuang Liu ◽  
Yuchen He ◽  
Dongyue Guo ◽  
Xiaoya Liu ◽  
Xinyu Hao ◽  
...  
Keyword(s):  
Emotional Processing ◽  
Emotion Processing ◽  
Alternating Current ◽  
Event Related Potential ◽  
Facial Emotion ◽  
Alpha Power ◽  
Emotion Identification ◽  
Transcranial Alternating Current Stimulation ◽  
Emotional Attention ◽  
P200 Amplitude

AbstractBackgroundNumerous clinical reports suggest that psychopathy like schizophrenia, anxiety and depressive disorder is accompanied by early attentional abnormalities in emotional information processing. In the past decade, the efficacy of transcranial alternating current stimulation (tACS) in changing emotional functioning has been repeatedly observed and has demonstrated a causal relationship between endogenous oscillations and emotional processing. However, tACS effects on emotional attention have not yet been tested.MethodsA total of 53 healthy participants were randomized to 2 groups, and they were subjected to active or sham tACS at individual alpha frequency (IAF) in the bilaterally dorsolateral prefrontal cortex (dlPFC). Participants and received this treatment for 20 min durations daily for 7 consecutive days. On days 1 and 7, electroencephalogram (EEG) recording of 8 minute resting with eyes open and closed. Responses to a facial emotion identification task were also recorded to measure alpha changes and event-related potential (ERP) alterations.ResultsOn day 7 after tACS, the active group showed a more clear elevation in alpha power at rest, especially in open state around stimulation area, compared to the sham group. ERPs revealed a significant larger P200 amplitude after active stimulation (p < 0.05), indicating attentional improvement in facial emotion processing. Additionally, a notable positive correlation (p < 0.05) between alpha power and P200 amplitude was found, providing an electrophysiological interpretation regarding the role of tACS in emotional attention modulation. In addition, the IAF-tACS showed an obvious advantage in alpha entrainment compared to an additional 10 Hz-tACS.ConclusionsThese results support a seminal outcome for the effect of IAF-tACS on emotional attention modulation, demonstrating a feasible and individual-specific therapy for neuropsychiatric disorders related to emotion processing, especially regarding oscillatory disturbances.

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.

scholarly journals Reduction in left frontal alpha oscillations by transcranial alternating current stimulation in major depressive disorder is context-dependent in a randomized-clinical trial

2021 ◽  
Author(s):  
Justin Riddle ◽  
Morgan L. Alexander ◽  
Crystal Edler Schiller ◽  
David R. Rubinow ◽  
Flavio Frohlich
Keyword(s):  
Clinical Trial ◽  
Major Depressive Disorder ◽  
Depressive Disorder ◽  
Alpha Power ◽  
Single Session ◽  
Major Depressive ◽  
Alpha Oscillations ◽  
Alpha Frequency ◽  
Alpha Oscillation ◽  
Transcranial Alternating Current Stimulation

Background: Left frontal alpha oscillations are associated with decreased approach motivation and have been proposed as a target for non-invasive brain stimulation for the treatment of depression and anhedonia. Indeed, transcranial alternating current stimulation (tACS) at the alpha frequency reduced left frontal alpha power and was associated with a higher response rate than placebo stimulation in patients with major depressive disorder (MDD) in a recent double-blind placebo controlled clinical trial. Methods: In this current study, we aimed to replicate such successful target engagement by delineating the effects of a single session of bifrontal tACS at the individualized alpha frequency (IAF-tACS) on alpha oscillations in patients with MDD. Electrical brain activity was recorded during rest and while viewing emotionally-salient images before and after stimulation to investigate if the modulation of alpha oscillation by tACS exhibited specificity with regards to valence. Results: In agreement with the previous study of tACS in MDD, we found that a single session of bifrontal IAF-tACS reduced left frontal alpha power during the resting state when compared to placebo. Furthermore, the reduction of left frontal alpha oscillation by tACS was specific for stimuli with positive valence. In contrast, these effects on left frontal alpha power were not found in healthy control participants. Conclusion: Together these results support an important role of tACS in reducing left frontal alpha oscillations as a future treatment for MDD. National Clinical Trial: NCT03449979, Single Session of tACS in a Depressive Episode (SSDE) https://www.clinicaltrials.gov/ct2/show/NCT03449979 .

scholarly journals Off‐line effects of alpha‐frequency transcranial alternating current stimulation on a visuomotor learning task

2020 ◽  
Vol 10 (9) ◽  
Author(s):  
Taiki Harada ◽  
Masayuki Hara ◽  
Kojiro Matsushita ◽  
Kenji Kawakami ◽  
Keisuke Kawakami ◽  
...  
Keyword(s):  
Learning Task ◽  
Alternating Current ◽  
Visuomotor Learning ◽  
Alpha Frequency ◽  
Transcranial Alternating Current Stimulation

scholarly journals Transcranial alternating current stimulation induces long-term augmentation of neural connectivity and sustained anxiety reduction

2017 ◽  
Author(s):  
Kevin J. Clancy ◽  
Sarah K. Baisley ◽  
Alejandro Albizu ◽  
Nicholas Kartvelishvili ◽  
Mingzhou Ding ◽  
...  
Keyword(s):  
Long Range ◽  
Large Scale ◽  
Neural Oscillations ◽  
Alpha Power ◽  
Anxious Arousal ◽  
Alpha Frequency ◽  
Large Scale Network ◽  
Transcranial Alternating Current Stimulation ◽  
Scale Network

ABSTRACTAlthough transcranial alternating current stimulation (tACS) has demonstrated short-term effects in modulating neural oscillations, potential clinical efficacy of tACS for treating “oscillopathies” (disorders associated with aberrant neural oscillations) hinges on its ability to generate long-term neural plasticity, which can translate into lasting behavioral changes. Administering alpha-frequency tACS over 4 consecutive days, we evaluated short- and long-term (> 24 hours) effects of α-tACS on local alpha power and oscillatory connectivity, along with behavioral outcomes in anxious arousal and affective sensory perception. The α-tACS (vs. sham stimulation) group exhibited increases in posterior alpha power immediately and 30 minutes post-stimulation but not 24 hours post-stimulation, suggesting transient effects on local neuronal synchrony. Strikingly, long-range alpha-frequency Granger causal connectivity (posterior→frontal) increased not only immediately and 30 minutes but also 24 hours post-stimulation, paralleled by sustained reductions in anxious arousal and aversion to auditory stimuli. Therefore, tACS is capable of eliciting long-term plasticity in long-range oscillatory connectivity with direct, lasting behavioral consequences, while leaving endogenous local oscillations unaltered. This temporal disparity in local and network effects favors the view of large-scale network strengthening by tACS, calling for research attention to the circuit and network impacts of tACS. Critically, with the growing recognition of large-scale network dysfunctions as a transdiagnostic pathophysiology of psychiatric disorders, this connectivity plasticity advocates for the clinical application of tACS with its unique advantage in tackling network pathologies.

scholarly journals Frequency-specific transcranial neuromodulation of oscillatory alpha power alters and predicts human visuospatial attention performance

2020 ◽  
Author(s):  
S. K. Kemmerer ◽  
A.T. Sack ◽  
T.A. de Graaf ◽  
S. ten Oever ◽  
P. De Weerd ◽  
...  
Keyword(s):  
Spatial Attention ◽  
Posterior Parietal Cortex ◽  
Attention Bias ◽  
Visuospatial Attention ◽  
Alpha Power ◽  
High Definition ◽  
Alpha Frequency ◽  
Transcranial Alternating Current Stimulation ◽  
Attention Performance ◽  
The Individual

AbstractUnilateral transcranial alternating current stimulation (tACS) at alpha frequency modulates the locus of spatial attention. However, the neural mechanisms by which tACS influences spatial attention remain poorly understood. Here, we applied high-definition tACS at the individual alpha frequency (IAF), two control frequencies (IAF+/-2Hz) and sham to the left posterior parietal cortex and measured its effects on visuospatial attention performance as well as alpha power (using electroencephalography, EEG). Our results revealed a leftward lateralization of alpha power relative to sham. At a high value of leftward alpha lateralization, we also observed a leftward attention bias, which differed from sham. Moreover, the magnitude of the alpha lateralization effect predicted the attention bias. These effects occurred for tACS at IAF but not for the control frequencies. This suggests that tACS operates through oscillatory interactions with ongoing brain rhythms in line with the synchronization theory. Our results also highlight the importance of personalized stimulation protocols, especially in potential clinical settings.

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