scholarly journals Effects of Transcranial Alternating Current Stimulation on Cognitive Functions in Healthy Young and Older Adults

2016 ◽  
Vol 2016 ◽  
pp. 1-13 ◽  
Author(s):  
Daria Antonenko ◽  
Miriam Faxel ◽  
Ulrike Grittner ◽  
Michal Lavidor ◽  
Agnes Flöel
Keyword(s):  
Older Adults ◽  
Language Learning ◽  
Cognitive Functions ◽  
Alternating Current ◽  
Future Research ◽  
Brain Oscillations ◽  
Specific Patient ◽  
Transcranial Alternating Current Stimulation ◽  
Young Subjects ◽  
Interaction With Age

Recently, transcranial alternating current stimulation (tACS) has emerged as a tool to enhance human cognitive processes. Here, we provide a brief summary of the rationale behind tACS-induced effects on task-relevant brain oscillations and associated cognitive functions and review previous studies in young subjects that have applied tACS in cognitive paradigms. Additionally, we present pilot data where we administered theta-tACS (6 Hz) over the temporoparietal cortex and a supraorbital reference for 20 min during implicit language learning in healthy young (mean/SD age: 22/2) and older (mean/SD age: 66/4) adults, in a sham-controlled crossover design. Linear mixed models revealed significantly increased retrieval accuracy following tACS-accompanied associative learning, after controlling for session order and learning success. These data provide the first implementation of tACS during cognitive performance in older adults and support recent studies suggesting that tACS in the theta frequency range may serve as a tool to enhance cognition, possibly through direct modulation of task-relevant brain oscillations. So far, studies have been heterogeneous in their designs, leaving a number of issues to be addressed in future research, including the setup of electrodes and optimal stimulation frequencies to be employed, as well as the interaction with age and underlying brain pathologies in specific patient populations.

scholarly journals Probing the Link Between Perception and Oscillations: Lessons from Transcranial Alternating Current Stimulation

2019 ◽  
Vol 26 (1) ◽  
pp. 57-73 ◽  
Author(s):  
Yuranny Cabral-Calderin ◽  
Melanie Wilke
Keyword(s):  
Time Windows ◽  
Gamma Oscillations ◽  
Alternating Current ◽  
Brain Regions ◽  
Causal Link ◽  
Brain Oscillations ◽  
Promising Tool ◽  
Transcranial Alternating Current Stimulation ◽  
Close Time ◽  
Auditory Cortices

Brain oscillations are regarded as important for perception as they open and close time windows for neural spiking to enable the effective communication within and across brain regions. In the past, studies on perception primarily relied on the use of electrophysiological techniques for probing a correlative link between brain oscillations and perception. The emergence of noninvasive brain stimulation techniques such as transcranial alternating current stimulation (tACS) provides the possibility to study the causal contribution of specific oscillatory frequencies to perception. Here, we review the studies on visual, auditory, and somatosensory perception that employed tACS to probe the causality of brain oscillations for perception. The current literature is consistent with a causal role of alpha and gamma oscillations in parieto-occipital regions for visual perception and theta and gamma oscillations in auditory cortices for auditory perception. In addition, the sensory gating by alpha oscillations applies not only to the visual but also to the somatosensory domain. We conclude that albeit more refined perceptual paradigms and individualized stimulation practices remain to be systematically adopted, tACS is a promising tool for establishing a causal link between neural oscillations and perception.

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 Transcranial alternating current stimulation (tACS): from basic mechanisms towards first applications in psychiatry

2020 ◽  
Author(s):  
Osama Elyamany ◽  
Gregor Leicht ◽  
Christoph S. Herrmann ◽  
Christoph Mulert
Keyword(s):  
Psychiatric Disorders ◽  
Cortical Neurons ◽  
Alternating Current ◽  
Brain Network ◽  
Brain Oscillations ◽  
Serious Adverse Events ◽  
Double Blind ◽  
Response Predictors ◽  
Transcranial Alternating Current Stimulation ◽  
The Brain

AbstractTranscranial alternating current stimulation (tACS) is a unique form of non-invasive brain stimulation. Sinusoidal alternating electric currents are delivered to the scalp to affect mostly cortical neurons. tACS is supposed to modulate brain function and, in turn, cognitive processes by entraining brain oscillations and inducing long-term synaptic plasticity. Therefore, tACS has been investigated in cognitive neuroscience, but only recently, it has been also introduced in psychiatric clinical trials. This review describes current concepts and first findings of applying tACS as a potential therapeutic tool in the field of psychiatry. The current understanding of its mechanisms of action is explained, bridging cellular neuronal activity and the brain network mechanism. Revisiting the relevance of altered brain oscillations found in six major psychiatric disorders, putative targets for the management of mental disorders using tACS are discussed. A systematic literature search on PubMed was conducted to report findings of the clinical studies applying tACS in patients with psychiatric conditions. In conclusion, the initial results may support the feasibility of tACS in clinical psychiatric populations without serious adverse events. Moreover, these results showed the ability of tACS to reset disturbed brain oscillations, and thus to improve behavioural outcomes. In addition to its potential therapeutic role, the reactivity of the brain circuits to tACS could serve as a possible tool to determine the diagnosis, classification or prognosis of psychiatric disorders. Future double-blind randomised controlled trials are necessary to answer currently unresolved questions. They may aim to detect response predictors and control for various confounding factors.

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 Is Transcranial Alternating Current Stimulation Effective in Modulating Brain Oscillations?

PLoS ONE ◽  
2013 ◽  
Vol 8 (2) ◽  
pp. e56589 ◽  
Author(s):  
Debora Brignani ◽  
Manuela Ruzzoli ◽  
Piercarlo Mauri ◽  
Carlo Miniussi
Keyword(s):  
Alternating Current ◽  
Brain Oscillations ◽  
Transcranial Alternating Current Stimulation

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 Can Machines Find the Bilingual Advantage? Machine Learning Algorithms Find No Evidence to Differentiate Between Lifelong Bilingual and Monolingual Cognitive Profiles

2021 ◽  
Vol 15 ◽  
Author(s):  
Samuel Kyle Jones ◽  
Jodie Davies-Thompson ◽  
Jeremy Tree
Keyword(s):  
Machine Learning ◽  
Older Adults ◽  
Cognitive Functions ◽  
Machine Learning Algorithms ◽  
Future Research ◽  
Cognitive Profiles ◽  
Bilingual Advantage ◽  
Domain Specific ◽  
Wide Range ◽  
Key Variables

Bilingualism has been identified as a potential cognitive factor linked to delayed onset of dementia as well as boosting executive functions in healthy individuals. However, more recently, this claim has been called into question following several failed replications. It remains unclear whether these contradictory findings reflect how bilingualism is defined between studies, or methodological limitations when measuring the bilingual effect. One key issue is that despite the claims that bilingualism yields general protection to cognitive processes (i.e., the cognitive reserve hypothesis), studies reporting putative bilingual differences are often focused on domain specific experimental paradigms. This study chose a broader approach, by considering the consequences of bilingualism on a wide range of cognitive functions within individuals. We utilised 19 measures of different cognitive functions commonly associated with bilingual effects, to form a “cognitive profile” for 215 non-clinical participants. We recruited Welsh speakers, who as a group of bilinguals were highly homogeneous, as means of isolating the bilingualism criterion. We sought to determine if such analyses would independently classify bilingual/monolingual participant groups based on emergent patterns driven by collected cognitive profiles, such that population differences would emerge. Multiple predictive models were trained to independently recognise the cognitive profiles of bilinguals, older adults (60-90 years of age) and higher education attainment. Despite managing to successfully classify cognitive profiles based on age and education, the model failed to differentiate between bilingual and monolingual cognitive ability at a rate greater than that of chance. Repeated modelling using alternative definitions of bilingualism, and just the older adults, yielded similar results. In all cases then, using our “bottom–up” analytical approach, there was no evidence that bilingualism as a variable indicated differential cognitive performance – as a consequence, we conclude that bilinguals are not cognitively different from their monolingual counterparts, even in older demographics. We suggest that studies that have reported a bilingual advantage (typically recruiting immigrant populations) could well have confounded other key variables that may be driving reported advantages. We recommend that future research refine the machine learning methods used in this study to further investigate the complex relationship between bilingualism and cognition.

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