scholarly journals Disruption and rescue of interareal theta phase coupling and adaptive behavior

2017 ◽  
Vol 114 (43) ◽  
pp. 11542-11547 ◽  
Author(s):  
Robert M. G. Reinhart
Keyword(s):  
Executive Functions ◽  
Adaptive Behavior ◽  
Computer Training ◽  
Executive Dysfunction ◽  
Alternating Current ◽  
High Definition ◽  
Phase Coupling ◽  
Positive Effects ◽  
Transcranial Alternating Current Stimulation ◽  
Theta Phase

Rescuing executive functions in people with neurological and neuropsychiatric disorders has been a major goal of psychology and neuroscience for decades. Innovative computer-training regimes for executive functions have made tremendous inroads, yet the positive effects of training have not always translated into improved cognitive functioning and often take many days to emerge. In the present study, we asked whether it was possible to immediately change components of executive function by directly manipulating neural activity using a stimulation technology called high-definition transcranial alternating current stimulation (HD-tACS). Twenty minutes of inphase stimulation over medial frontal cortex (MFC) and right lateral prefrontal cortex (lPFC) synchronized theta (∼6 Hz) rhythms between these regions in a frequency and spatially specific manner and rapidly improved adaptive behavior with effects lasting longer than 40 min. In contrast, antiphase stimulation in the same individuals desynchronized MFC-lPFC theta phase coupling and impaired adaptive behavior. Surprisingly, the exogenously driven impairments in performance could be instantly rescued by reversing the phase angle of alternating current. The results suggest executive functions can be rapidly up- or down-regulated by modulating theta phase coupling of distant frontal cortical areas and can contribute to the development of tools for potentially normalizing executive dysfunction in patient populations.

scholarly journals Dual-site high-density 4Hz transcranial alternating current stimulation applied over auditory and motor cortical speech areas does not influence auditory-motor mapping

2019 ◽  
Author(s):  
Basil Preisig ◽  
Matthias J. Sjerps ◽  
Anne Kösem ◽  
Lars Riecke
Keyword(s):  
Low Frequency ◽  
Alternating Current ◽  
High Density ◽  
Phase Coupling ◽  
Motor Mapping ◽  
Oscillatory Phase ◽  
Transcranial Alternating Current Stimulation ◽  
Theta Phase ◽  
Verbal Repetition ◽  
Dual Site

AbstractBackgroundVerbal repetition of auditory speech requires the mapping of a sensory acoustic input onto articulatory motor plans (auditory-motor mapping). Recent evidence indicates that auditory-motor mapping could rely on low frequency neural synchronization (i.e., theta oscillatory phase coupling) between sensory and motor speech areas.ObjectiveIn the present study, we apply dual-site high-density (HD) Transcranial Alternating Current Stimulation (TACS) above the auditory and motor cortex to induce, or disrupt, theta phase coupling between the two areas. We predicted that functionally coupling the two areas would strengthen auditory-motor mapping, compared with functionally decoupling them. We assessed the strength of auditory-motor mapping using a verbal repetition task.ResultsWe found no significant effect of TACS-induced theta phase coupling on auditory-motor mapping as indexed by verbal repetition performance.ConclusionAuditory-motor mapping may rely on a different mechanism than we hypothesized, for example, oscillatory phase-coupling outside the theta range. Alternatively, modulation of interregional theta-phase coupling may require more effective stimulation protocols, for example, TACS at higher intensities.

scholarly journals Evaluation of a Modified High-Definition Electrode Montage for Transcranial Alternating Current Stimulation (tACS) of Pre-Central Areas

2016 ◽  
Vol 9 (5) ◽  
pp. 700-704 ◽  
Author(s):  
Kirstin-Friederike Heise ◽  
Nick Kortzorg ◽  
Guilherme Bicalho Saturnino ◽  
Hakuei Fujiyama ◽  
Koen Cuypers ◽  
...  
Keyword(s):  
Alternating Current ◽  
High Definition ◽  
Transcranial Alternating Current Stimulation

scholarly journals A Novel Program to Improve Cognitive Function in Individuals With Dementia Using Transcranial Alternating Current Stimulation (tACS) and Tutored Cognitive Exercises

2021 ◽  
Vol 2 ◽  
Author(s):  
Zahra Moussavi ◽  
Kazushige Kimura ◽  
Lonnie Kehler ◽  
Cristina de Oliveira Francisco ◽  
Brian Lithgow
Keyword(s):  
Older Adults ◽  
Healthy Aging ◽  
Study Groups ◽  
Long Term Potentiation ◽  
Alternating Current ◽  
Post Intervention ◽  
Positive Effects ◽  
Cognitive Improvement ◽  
Transcranial Alternating Current Stimulation

The effects of cognitive exercises on the healthy aging population is controversial. Transcranial alternating current stimulation (tACS) is considered a promising tool for modulating brain oscillation. Research is lacking on its long-lasting cognitive/therapeutic effect. This is the first pilot study to explore the effect of a regimen of cognitive exercises with and without tACS on older adults with dementia. The study groups were 28 individuals (age 56–83 years) enrolled into two groups: Exr Group, who received cognitive exercises only and the Exr + tACS Group who received tACS at 40 Hz simultaneously with cognitive exercises for a period of 4 consecutive weeks, 5 days/week, two 30 min-sessions/day; all the training sessions were tutored. The cognitive exercises were applied using the MindTriggers app. They were assessed at pre and post intervention and also one month after the end of trial (follow-up) with an independent assessment (WMS-IV) as the primary outcome measure. The results show significant cognitive improvement at post-intervention in both groups, while the Exr + tACS protocol lead to superior cognitive improvement at follow-up session. The most important outcomes of this study are: 1) The tutored repeated practice of the MindTriggers app exercises does significantly improve the cognitive functions of older adults with dementia and that that improvement lasts for at least one month after the end of the intervention, and 2) The application of tACS increases the positive effects of cognitive exercises with the positive effect lasting an even longer period of time than exercises alone; in other words we speculate that it may lead to long-term potentiation.

scholarly journals Bilateral Gamma/Delta Transcranial Alternating Current Stimulation Affects Interhemispheric Speech Sound Integration

2020 ◽  
Vol 32 (7) ◽  
pp. 1242-1250 ◽  
Author(s):  
Basil C. Preisig ◽  
Matthias J. Sjerps ◽  
Alexis Hervais-Adelman ◽  
Anne Kösem ◽  
Peter Hagoort ◽  
...  
Keyword(s):  
Auditory Cortex ◽  
Phase Synchronization ◽  
Speech Sound ◽  
Alternating Current ◽  
Phase Lag ◽  
Disruptive Effect ◽  
Phase Coupling ◽  
Gamma Frequency ◽  
Transcranial Alternating Current Stimulation ◽  
Speech Cues

Perceiving speech requires the integration of different speech cues, that is, formants. When the speech signal is split so that different cues are presented to the right and left ear (dichotic listening), comprehension requires the integration of binaural information. Based on prior electrophysiological evidence, we hypothesized that the integration of dichotically presented speech cues is enabled by interhemispheric phase synchronization between primary and secondary auditory cortex in the gamma frequency band. We tested this hypothesis by applying transcranial alternating current stimulation (TACS) bilaterally above the superior temporal lobe to induce or disrupt interhemispheric gamma-phase coupling. In contrast to initial predictions, we found that gamma TACS applied in-phase above the two hemispheres (interhemispheric lag 0°) perturbs interhemispheric integration of speech cues, possibly because the applied stimulation perturbs an inherent phase lag between the left and right auditory cortex. We also observed this disruptive effect when applying antiphasic delta TACS (interhemispheric lag 180°). We conclude that interhemispheric phase coupling plays a functional role in interhemispheric speech integration. The direction of this effect may depend on the stimulation frequency.

scholarly journals The Modulation of Cognitive Performance with Transcranial Alternating Current Stimulation: A Systematic Review of Frequency-Specific Effects

2020 ◽  
Vol 10 (12) ◽  
pp. 932
Author(s):  
Katharina Klink ◽  
Sven Paßmann ◽  
Florian H. Kasten ◽  
Jessica Peter
Keyword(s):  
Systematic Review ◽  
Executive Functions ◽  
Cognitive Performance ◽  
Real World ◽  
Cognitive Functions ◽  
Declarative Memory ◽  
Alternating Current ◽  
Healthy Adults ◽  
Real World Applications ◽  
Transcranial Alternating Current Stimulation

Transcranial alternating current stimulation (tACS) is a non-invasive brain stimulation technique that allows the manipulation of intrinsic brain oscillations. Numerous studies have applied tACS in the laboratory to enhance cognitive performance. With this systematic review, we aim to provide an overview of frequency-specific tACS effects on a range of cognitive functions in healthy adults. This may help to transfer stimulation protocols to real-world applications. We conducted a systematic literature search on PubMed and Cochrane databases and considered tACS studies in healthy adults (age > 18 years) that focused on cognitive performance. The search yielded n = 109 studies, of which n = 57 met the inclusion criteria. The results indicate that theta-tACS was beneficial for several cognitive functions, including working memory, executive functions, and declarative memory. Gamma-tACS enhanced performance in both auditory and visual perception but it did not change performance in tasks of executive functions. For attention, the results were less consistent but point to an improvement in performance with alpha- or gamma-tACS. We discuss these findings and point to important considerations that would precede a transfer to real-world applications.

scholarly journals Synchronization of sensory gamma oscillations promotes multisensory communication

2019 ◽  
Author(s):  
Jonas Misselhorn ◽  
Bettina C. Schwab ◽  
Till R. Schneider ◽  
Andreas K. Engel
Keyword(s):  
Gamma Oscillations ◽  
Alternating Current ◽  
High Density ◽  
Network Communication ◽  
High Definition ◽  
Sensory Modalities ◽  
Transcranial Alternating Current Stimulation ◽  
Sensory Cortices ◽  
Fundamental Mechanism

AbstractRhythmic neuronal activity in the gamma range is a signature of active cortical processing and its synchronization across distant sites has been proposed as a fundamental mechanism of network communication. While this has been shown within sensory modalities, we tested whether crosstalk between the senses relies on similar mechanisms. In two consecutive experiments, we used a task in which human participants (male and female) matched amplitude changes of concurrent visual, auditory and tactile stimuli. In this task, matching of congruent stimuli was associated with a behavioral benefit compared to matching of incongruent stimuli. In the first experiment, we used source-level analysis of high-density electroencephalography (EEG) and observed that cross-modal matching of congruent inputs was associated with relatively weaker coherence between gamma oscillations in early sensory regions. Next, we used bifocal high-definition transcranial alternating current stimulation (hd-tACS) to manipulate the strength of coupling between sensory cortices. Here, we used a lateralized version of the task in which hd-tACS was applied either ipsilateral or contralateral to the hemisphere receiving sensory stimuli. Ipsilateral gamma, but not alpha stimulation slowed responses to congruent trials whereas responding to incongruent trials was not changed by tACS. We speculate that fast responding to congruent stimuli involves decoupling of sensory gamma oscillations, which was prevented by tACS. These results indicate that synchronization of gamma oscillations promotes direct communication between sensory modalities. The framework of coupled gamma oscillations underlying cortical communication might thus be generalizable from processing within sensory streams to interactions between sensory networks.Significance statementCortical gamma oscillations structure segregated neural activity and were suggested to represent a fundamental mechanism of network communication. While there is ample evidence for the role of long-range gamma synchronization in unisensory processing, its significance in multisensory networks is still unclear. We show that direct interactions between sensory cortices rely on synchronization of gamma band activity. To that end, we carried out two consecutive experiments using state-of-the-art high-density electroencephalography (EEG) and high-definition transcranial alternating current stimulation (hd-tACS). By complementing an observational with an interventional method, we provide novel evidence for the role of synchronized gamma oscillations in multisensory communication.

scholarly journals Modulating Inhibitory Control Processes Using Individualized High Definition Theta Transcranial Alternating Current Stimulation (HD θ-tACS) of the Anterior Cingulate and Medial Prefrontal Cortex

2021 ◽  
Vol 15 ◽  
Author(s):  
Monika Klírová ◽  
Veronika Voráčková ◽  
Jiří Horáček ◽  
Pavel Mohr ◽  
Juraj Jonáš ◽  
...  
Keyword(s):  
Prefrontal Cortex ◽  
Medial Prefrontal Cortex ◽  
Inhibitory Control ◽  
Alternating Current ◽  
Stroop Test ◽  
Anterior Cingulate ◽  
Stop Signal Task ◽  
Control Performance ◽  
High Definition ◽  
Transcranial Alternating Current Stimulation

Increased frontal midline theta activity generated by the anterior cingulate cortex (ACC) is induced by conflict processing in the medial frontal cortex (MFC). There is evidence that theta band transcranial alternating current stimulation (θ-tACS) modulates ACC function and alters inhibitory control performance during neuromodulation. Multi-electric (256 electrodes) high definition θ-tACS (HD θ-tACS) using computational modeling based on individual MRI allows precise neuromodulation targeting of the ACC via the medial prefrontal cortex (mPFC), and optimizes the required current density with a minimum impact on the rest of the brain. We therefore tested whether the individualized electrode montage of HD θ-tACS with the current flow targeted to the mPFC-ACC compared with a fixed montage (non-individualized) induces a higher post-modulatory effect on inhibitory control. Twenty healthy subjects were randomly assigned to a sequence of three HD θ-tACS conditions (individualized mPFC-ACC targeting; non-individualized MFC targeting; and a sham) in a double-blind cross-over study. Changes in the Visual Simon Task, Stop Signal Task, CPT III, and Stroop test were assessed before and after each session. Compared with non-individualized θ-tACS, the individualized HD θ-tACS significantly increased the number of interference words and the interference score in the Stroop test. The changes in the non-verbal cognitive tests did not induce a parallel effect. This is the first study to examine the influence of individualized HD θ-tACS targeted to the ACC on inhibitory control performance. The proposed algorithm represents a well-tolerated method that helps to improve the specificity of neuromodulation targeting of the ACC.

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