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Abubaker M, Al Qasem W, Pilátová K, Ježdík P, Kvašňák E. Theta-gamma-coupling as predictor of working memory performance in young and elderly healthy people. Mol Brain 2024; 17:74. [PMID: 39415245 DOI: 10.1186/s13041-024-01149-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2024] [Accepted: 10/05/2024] [Indexed: 10/18/2024] Open
Abstract
The relationship between working memory (WM) and neuronal oscillations can be studied in detail using brain stimulation techniques, which provide a method for modulating these oscillations and thus influencing WM. The endogenous coupling between the amplitude of gamma oscillations and the phase of theta oscillations is crucial for cognitive control. Theta/gamma peak-coupled transcranial alternating current stimulation (TGCp-tACS) can modulate this coupling and thus influence WM performance. This study investigated the effects of TGCp-tACS on WM in older adults and compared their responses with those of younger participants from our previous work who underwent the same experimental design. Twenty-eight older subjects underwent both TGCp-tACS and sham stimulation sessions at least 72 h apart. Resting-state electroencephalography (EEG) was recorded before and after the interventions, and a WM task battery with five different WM tasks was performed during the interventions to assess various WM components. Outcomes measured included WM task performance (e.g., accuracy, reaction time (RT)) and changes in power spectral density (PSD) in different frequency bands. TGCp-tACS significantly decreased accuracy and RT on the 10- and 14-point Sternberg tasks and increased RT on the Digit Symbol Substitution Test in older adults. In contrast, younger participants showed a significant increase in accuracy only on the 14-item Sternberg task. Electrophysiological analysis revealed a decrease in delta and theta PSD and an increase in high gamma PSD in both younger and older participants after verum stimulation. In conclusion, theta-gamma coupling is essential for WM and modulation of this coupling affects WM performance. The effects of TGCp-tACS on WM vary with age due to natural brain changes. To better support older adults, the study suggests several strategies to improve cognitive function, including: Adjusting stimulation parameters, applying stimulation to two sites, conducting multiple sessions, and using brain imaging techniques for precise targeting.
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Affiliation(s)
- Mohammed Abubaker
- Department of Medical Biophysics and Medical Informatics, Third Faculty of Medicine, Charles University in Prague, Prague, Czechia.
| | - Wiam Al Qasem
- Department of Medical Biophysics and Medical Informatics, Third Faculty of Medicine, Charles University in Prague, Prague, Czechia
| | - Kateřina Pilátová
- Department of Information and Communication Technology in Medicine, Faculty of Biomedical Engineering, Czech Technical University in Prague, Prague, Czechia
| | - Petr Ježdík
- Department of Circuit Theory, Faculty of Electrical Engineering, Czech Technical University in Prague, Prague, Czechia
| | - Eugen Kvašňák
- Department of Medical Biophysics and Medical Informatics, Third Faculty of Medicine, Charles University in Prague, Prague, Czechia
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Al Qasem W, Abubaker M, Pilátová K, Ježdík P, Kvašňák E. Improving working memory by electrical stimulation and cross-frequency coupling. Mol Brain 2024; 17:72. [PMID: 39354549 PMCID: PMC11446076 DOI: 10.1186/s13041-024-01142-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2024] [Accepted: 09/12/2024] [Indexed: 10/03/2024] Open
Abstract
Working memory (WM) is essential for the temporary storage and processing of information required for complex cognitive tasks and relies on neuronal theta and gamma oscillations. Given the limited capacity of WM, researchers have investigated various methods to improve it, including transcranial alternating current stimulation (tACS), which modulates brain activity at specific frequencies. One particularly promising approach is theta-gamma peak-coupled-tACS (TGCp-tACS), which simulates the natural interaction between theta and gamma oscillations that occurs during cognitive control in the brain. The aim of this study was to improve WM in healthy young adults with TGCp-tACS, focusing on both behavioral and neurophysiological outcomes. Thirty-one participants completed five WM tasks under both sham and verum stimulation conditions. Electroencephalography (EEG) recordings before and after stimulation showed that TGCp-tACS increased power spectral density (PSD) in the high-gamma region at the stimulation site, while PSD decreased in the theta and delta regions throughout the cortex. From a behavioral perspective, although no significant changes were observed in most tasks, there was a significant improvement in accuracy in the 14-item Sternberg task, indicating an improvement in phonological WM. In conclusion, TGCp-tACS has the potential to promote and improve the phonological component of WM. To fully realize the cognitive benefits, further research is needed to refine the stimulation parameters and account for individual differences, such as baseline cognitive status and hormonal factors.
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Affiliation(s)
- Wiam Al Qasem
- Department of Medical Biophysics and Medical Informatics, Third Faculty of Medicine, Charles University in Prague, Prague, Czechia.
| | - Mohammed Abubaker
- Department of Medical Biophysics and Medical Informatics, Third Faculty of Medicine, Charles University in Prague, Prague, Czechia
| | - Kateřina Pilátová
- Department of Information and Communication Technology in Medicine, Faculty of Biomedical Engineering, Czech Technical University in Prague, Prague, Czechia
| | - Petr Ježdík
- Department of Circuit Theory, Faculty of Electrical Engineering, Czech Technical University in Prague, Prague, Czechia
| | - Eugen Kvašňák
- Department of Medical Biophysics and Medical Informatics, Third Faculty of Medicine, Charles University in Prague, Prague, Czechia
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Paßmann S, Baselgia S, Kasten FH, Herrmann CS, Rasch B. Differential online and offline effects of theta-tACS on memory encoding and retrieval. COGNITIVE, AFFECTIVE & BEHAVIORAL NEUROSCIENCE 2024; 24:894-911. [PMID: 39085585 PMCID: PMC11390785 DOI: 10.3758/s13415-024-01204-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 07/01/2024] [Indexed: 08/02/2024]
Abstract
Theta oscillations support memory formation, but their exact contribution to the communication between prefrontal cortex (PFC) and the hippocampus is unknown. We tested the functional relevance of theta oscillations as a communication link between both areas for memory formation using transcranial alternating current stimulation (tACS). Healthy, young participants learned two lists of Dutch-German word pairs and retrieved them immediately and with a 30-min delay. In the encoding group (N = 30), tACS was applied during the encoding of list 1. List 2 was used to test stimulation aftereffects. In the retrieval group (N = 23), we stimulated during the delayed recall. In both groups, we applied tACS bilaterally at prefrontal and tempo-parietal sites, using either individualized theta frequency or 15 Hz (as control), according to a within-subject design. Stimulation with theta-tACS did not alter overall learning performance. An exploratory analysis revealed that immediate recall improved when word-pairs were learned after theta-tACS (list 2). Applying theta-tACS during retrieval had detrimental effects on memory. No changes in the power of the respective frequency bands were observed. Our results do not support the notion that impacting the communication between PFC and the hippocampus during a task by bilateral tACS improves memory. However, we do find evidence that direct stimulation had a trend for negatively interfering effects during immediate and delayed recall. Hints for beneficial effects on memory only occurred with aftereffects of the stimulation. Future studies need to further examine the effects during and after stimulation on memory formation.
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Affiliation(s)
- Sven Paßmann
- Cognitive Biopsychology and Methods, Department of Psychology, Université Fribourg, Rue P.-A.-de-Faucigny 2, 1700, Fribourg, Switzerland.
- Department of Neurology, University Medicine Greifswald, Greifswald, Germany.
| | - Sandrine Baselgia
- Cognitive Biopsychology and Methods, Department of Psychology, Université Fribourg, Rue P.-A.-de-Faucigny 2, 1700, Fribourg, Switzerland
| | - Florian H Kasten
- Centre de Recherche Cerveau & Cognition, CNRS, Toulouse, France
- Université Toulouse III Paul Sabatier, Toulouse, France
| | - Christoph S Herrmann
- Experimental Psychology Lab, Department of Psychology, Carl Von Ossietzky Universität, Oldenburg, Germany
| | - Björn Rasch
- Cognitive Biopsychology and Methods, Department of Psychology, Université Fribourg, Rue P.-A.-de-Faucigny 2, 1700, Fribourg, Switzerland
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Pupíková M, Maceira-Elvira P, Harquel S, Šimko P, Popa T, Gajdoš M, Lamoš M, Nencha U, Mitterová K, Šimo A, Hummel FC, Rektorová I. Physiology-inspired bifocal fronto-parietal tACS for working memory enhancement. Heliyon 2024; 10:e37427. [PMID: 39315230 PMCID: PMC11417162 DOI: 10.1016/j.heliyon.2024.e37427] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2024] [Revised: 08/14/2024] [Accepted: 09/03/2024] [Indexed: 09/25/2024] Open
Abstract
Aging populations face significant cognitive challenges, particularly in working memory (WM). Transcranial alternating current stimulation (tACS) offer promising avenues for cognitive enhancement, especially when inspired by brain physiology. This study (NCT04986787) explores the effect of multifocal tACS on WM performance in healthy older adults, focusing on fronto-parietal network modulation. Individualized physiology-inspired tACS applied to the fronto-parietal network was investigated in two blinded cross-over experiments. The first experiment involved monofocal/bifocal theta-tACS to the fronto-parietal network, while in the second experiment cross-frequency theta-gamma interactions between these regions were explored. Participants have done online WM tasks under the stimulation conditions. Network connectivity was assessed via rs-fMRI and multichannel electroencephalography. Prefrontal monofocal theta tACS modestly improved WM accuracy over sham (d = 0.30). Fronto-parietal stimulation enhanced WM task processing speed, with the strongest effects for bifocal in-phase theta tACS (d = 0.41). Cross-frequency stimulations modestly boosted processing speed with or without impairing task accuracy depending on the stimulation protocol. This research adds to the understanding of physiology-inspired brain stimulation for cognitive enhancement in older subjects.
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Affiliation(s)
- Monika Pupíková
- Applied Neuroscience Research Group, Central European Institute of Technology, Masaryk University, Brno, Czech Republic
| | - Pablo Maceira-Elvira
- Neuro-X Institute (INX), École Polytechnique Fédérale de Lausanne (EPFL), Chemin des Mines 9, 1202, CH, Geneva, Switzerland
- Neuro-X Institute (INX), EPFL Valais, Clinique Romande de Réadaptation Sion, Switzerland
| | - Sylvain Harquel
- Neuro-X Institute (INX), École Polytechnique Fédérale de Lausanne (EPFL), Chemin des Mines 9, 1202, CH, Geneva, Switzerland
| | - Patrik Šimko
- Applied Neuroscience Research Group, Central European Institute of Technology, Masaryk University, Brno, Czech Republic
| | - Traian Popa
- Neuro-X Institute (INX), École Polytechnique Fédérale de Lausanne (EPFL), Chemin des Mines 9, 1202, CH, Geneva, Switzerland
- Neuro-X Institute (INX), EPFL Valais, Clinique Romande de Réadaptation Sion, Switzerland
| | - Martin Gajdoš
- International Clinical Research Center, Faculty of Medicine and St. Anne's University Hospital, Masaryk University, Brno, Czech Republic
- Brain and Mind Research, Central European Institute of Technology, Masaryk University, Brno, Czech Republic
- First Department of Neurology, Faculty of Medicine and St. Anne's University Hospital, Masaryk University, Brno, Czech Republic
| | - Martin Lamoš
- International Clinical Research Center, Faculty of Medicine and St. Anne's University Hospital, Masaryk University, Brno, Czech Republic
- Brain and Mind Research, Central European Institute of Technology, Masaryk University, Brno, Czech Republic
- First Department of Neurology, Faculty of Medicine and St. Anne's University Hospital, Masaryk University, Brno, Czech Republic
| | - Umberto Nencha
- Neuro-X Institute (INX), École Polytechnique Fédérale de Lausanne (EPFL), Chemin des Mines 9, 1202, CH, Geneva, Switzerland
- Clinical Neuroscience, University of Geneva Medical School, Geneva, Switzerland
| | - Kristína Mitterová
- Applied Neuroscience Research Group, Central European Institute of Technology, Masaryk University, Brno, Czech Republic
- International Clinical Research Center, Faculty of Medicine and St. Anne's University Hospital, Masaryk University, Brno, Czech Republic
| | - Adam Šimo
- First Department of Neurology, Faculty of Medicine and St. Anne's University Hospital, Masaryk University, Brno, Czech Republic
| | - Friedhelm C. Hummel
- Neuro-X Institute (INX), École Polytechnique Fédérale de Lausanne (EPFL), Chemin des Mines 9, 1202, CH, Geneva, Switzerland
- Neuro-X Institute (INX), EPFL Valais, Clinique Romande de Réadaptation Sion, Switzerland
- Clinical Neuroscience, University of Geneva Medical School, Geneva, Switzerland
| | - Irena Rektorová
- Applied Neuroscience Research Group, Central European Institute of Technology, Masaryk University, Brno, Czech Republic
- International Clinical Research Center, Faculty of Medicine and St. Anne's University Hospital, Masaryk University, Brno, Czech Republic
- First Department of Neurology, Faculty of Medicine and St. Anne's University Hospital, Masaryk University, Brno, Czech Republic
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Whittaker HT, Khayyat L, Fortier-Lavallée J, Laverdière M, Bélanger C, Zatorre RJ, Albouy P. Information-based rhythmic transcranial magnetic stimulation to accelerate learning during auditory working memory training: a proof-of-concept study. Front Neurosci 2024; 18:1355565. [PMID: 38638697 PMCID: PMC11024337 DOI: 10.3389/fnins.2024.1355565] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2023] [Accepted: 03/14/2024] [Indexed: 04/20/2024] Open
Abstract
Introduction Rhythmic transcranial magnetic stimulation (rhTMS) has been shown to enhance auditory working memory manipulation, specifically by boosting theta oscillatory power in the dorsal auditory pathway during task performance. It remains unclear whether these enhancements (i) persist beyond the period of stimulation, (ii) if they can accelerate learning and (iii) if they would accumulate over several days of stimulation. In the present study, we investigated the lasting behavioral and electrophysiological effects of applying rhTMS over the left intraparietal sulcus (IPS) throughout the course of seven sessions of cognitive training on an auditory working memory task. Methods A limited sample of 14 neurologically healthy participants took part in the training protocol with an auditory working memory task while being stimulated with either theta (5 Hz) rhTMS or sham TMS. Electroencephalography (EEG) was recorded before, throughout five training sessions and after the end of training to assess to effects of rhTMS on behavioral performance and on oscillatory entrainment of the dorsal auditory network. Results We show that this combined approach enhances theta oscillatory activity within the fronto-parietal network and causes improvements in auditoryworking memory performance. We show that compared to individuals who received sham stimulation, cognitive training can be accelerated when combined with optimized rhTMS, and that task performance benefits can outlast the training period by ∼ 3 days. Furthermore, we show that there is increased theta oscillatory power within the recruited dorsal auditory network during training, and that sustained EEG changes can be observed ∼ 3 days following stimulation. Discussion The present study, while underpowered for definitive statistical analyses, serves to improve our understanding of the causal dynamic interactions supporting auditory working memory. Our results constitute an important proof of concept for the potential translational impact of non-invasive brain stimulation protocols and provide preliminary data for developing optimized rhTMS and training protocols that could be implemented in clinical populations.
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Affiliation(s)
- Heather T. Whittaker
- Cognitive Neuroscience Unit, Montreal Neurological Institute, McGill University, Montréal, QC, Canada
- International Laboratory for Brain, Music and Sound Research (BRAMS) - Centre for Research on Brain Language and Music (CRBLM), Montreal, QC, Canada
| | - Lina Khayyat
- Cognitive Neuroscience Unit, Montreal Neurological Institute, McGill University, Montréal, QC, Canada
| | | | - Megan Laverdière
- CERVO Brain Research Centre, School of Psychology, Université Laval, Québec City, QC, Canada
| | - Carole Bélanger
- CERVO Brain Research Centre, School of Psychology, Université Laval, Québec City, QC, Canada
| | - Robert J. Zatorre
- Cognitive Neuroscience Unit, Montreal Neurological Institute, McGill University, Montréal, QC, Canada
- International Laboratory for Brain, Music and Sound Research (BRAMS) - Centre for Research on Brain Language and Music (CRBLM), Montreal, QC, Canada
| | - Philippe Albouy
- Cognitive Neuroscience Unit, Montreal Neurological Institute, McGill University, Montréal, QC, Canada
- International Laboratory for Brain, Music and Sound Research (BRAMS) - Centre for Research on Brain Language and Music (CRBLM), Montreal, QC, Canada
- CERVO Brain Research Centre, School of Psychology, Université Laval, Québec City, QC, Canada
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Ociepka M, Chinta SR, Basoń P, Chuderski A. No effects of the theta-frequency transcranial electrical stimulation for recall, attention control, and relation integration in working memory. Front Hum Neurosci 2024; 18:1354671. [PMID: 38439936 PMCID: PMC10910036 DOI: 10.3389/fnhum.2024.1354671] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Accepted: 02/05/2024] [Indexed: 03/06/2024] Open
Abstract
Introduction Recent studies have suggested that transcranial alternating current stimulation (tACS), and especially the theta-frequency tACS, can improve human performance on working memory tasks. However, evidence to date is mixed. Moreover, the two WM tasks applied most frequently, namely the n-back and change-detection tasks, might not constitute canonical measures of WM capacity. Method In a relatively large sample of young healthy participants (N = 62), we administered a more canonical WM task that required stimuli recall, as well as we applied two WM tasks tapping into other key WM functions: attention control (the antisaccade task) and relational integration (the graph mapping task). The participants performed these three tasks three times: during the left frontal 5.5-Hz and the left parietal 5.5-Hz tACS session as well as during the sham session, with a random order of sessions. Attentional vigilance and subjective experience were monitored. Results For each task administered, we observed significant gains in accuracy neither for the frontal tACS session nor for the parietal tACS session, as compared to the sham session. By contrast, the scores on each task positively inter-correlated across the three sessions. Discussion The results suggest that canonical measures of WM capacity are strongly stable in time and hardly affected by theta-frequency tACS. Either the tACS effects observed in the n-back and change detection tasks do not generalize onto other WM tasks, or the tACS method has limited effectiveness with regard to WM, and might require further methodological advancements.
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Affiliation(s)
- Michał Ociepka
- Department of Cognitive Science, Institute of Philosophy, Jagiellonian University, Kraków, Poland
| | | | - Paweł Basoń
- Department of Cognitive Science, Institute of Philosophy, Jagiellonian University, Kraków, Poland
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Fusco G, Scandola M, Lin H, Inzlicht M, Aglioti SM. Modulating preferences during intertemporal choices through exogenous midfrontal transcranial alternating current stimulation: A registered report. Cortex 2024; 171:435-464. [PMID: 38113613 DOI: 10.1016/j.cortex.2023.09.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Revised: 08/24/2023] [Accepted: 09/21/2023] [Indexed: 12/21/2023]
Abstract
Decision conflicts may arise when the costs and benefits of choices are evaluated as a function of outcomes predicted along a temporal dimension. Electrophysiology studies suggest that during performance monitoring a typical oscillatory activity in the theta rhythm, named midfrontal theta, may index conflict processing and resolution. In the present within-subject, sham controlled, cross-over preregistered study, we delivered online midfrontal transcranial Alternating Current Stimulation (tACS) to modulate electrocortical activity during intertemporal decisions. Participants were invited to select choice preference between economic offers at three different intermixed levels of conflict (i.e., low, medium, high) while receiving either theta -, gamma-, or sham tACS in separate blocks and sessions. At the end of each stimulation block, a Letter-Flanker task was also administered to measure behavioural aftereffects. We hypothesized that theta-tACS would have acted on the performance monitoring system inducing behavioural changes (i.e., faster decisions and more impulsive choices) in high conflicting trials, rather than gamma- and sham-tACS. Results very partially confirmed our predictions. Unexpectedly, both theta- and gamma-driven neuromodulation speeded-up decisions compared to sham. However, exploratory analyses revealed that such an effect was stronger in the high-conflict decisions during theta-tACS. These findings were independent from the influence of the sensations induced by the electrical stimulation. Moreover, further analyses highlighted a significant association during theta-tACS between the selection of immediate offers in high-conflict trials and attentional impulsiveness, suggesting that individual factors may account for the tACS effects during intertemporal decisions. Finally, we did not capture long-lasting behavioural changes following tACS in the Flanker task. Our findings may inform scholars to improve experimental designs and boost the knowledge toward a more effective application of tACS.
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Affiliation(s)
- Gabriele Fusco
- Sapienza University of Rome and CLNS@SAPIENZA, Istituto Italiano di Tecnologia, Italy; IRCCS Santa Lucia Foundation, Rome, Italy.
| | - Michele Scandola
- NPSY Lab-Vr, Department of Human Sciences, University of Verona, Verona, Italy
| | - Hause Lin
- Sloan School of Management, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Michael Inzlicht
- Department of Psychology, University of Toronto, Toronto, Canada
| | - Salvatore Maria Aglioti
- Sapienza University of Rome and CLNS@SAPIENZA, Istituto Italiano di Tecnologia, Italy; IRCCS Santa Lucia Foundation, Rome, Italy
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Wallace D, Cooper NR, Sel A, Russo R. Do non-traumatic stressful life events and ageing negatively impact working memory performance and do they interact to further impair working memory performance? PLoS One 2023; 18:e0290635. [PMID: 38019767 PMCID: PMC10686508 DOI: 10.1371/journal.pone.0290635] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2022] [Accepted: 08/13/2023] [Indexed: 12/01/2023] Open
Abstract
Stress and normal ageing produce allostatic load, which may lead to difficulties with cognition thereby degrading quality of life. The current study's objective was to assess whether ageing and cumulative stress interact to accelerate cognitive decline. With 60 participants, Marshall et al. found that ageing and cumulative stress interact significantly to impair working memory performance in older adults, suggesting vulnerability to the cumulative effects of life events beyond 60 years old. To replicate and extend this finding, we increased the sample size by conducting 3 independent studies with 156 participants and improved the statistical methods by conducting an iterative Bayesian meta-analysis with Bayes factors. Bayes factors deliver a more comprehensive result because they provide evidence for either the null hypothesis (H0), the alternative hypothesis (H1) or for neither hypothesis due to evidence not being sufficiently sensitive. Young (18-35 yrs) and older (60-85 yrs) healthy adults were categorised as high or low stress based on their life events score derived from the Life Events Scale for Students or Social Readjustment Rating Scale, respectively. We measured accuracy and reaction time on a 2-back working memory task to provide: a) Bayes factors and b) Bayesian meta-analysis, which iteratively added each study's effect sizes to evaluate the overall strength of evidence that ageing, cumulative stress and/or the combination of the two detrimentally affect working memory performance. Using a larger sample (N = 156 vs. N = 60) and a more powerful statistical approach, we did not replicate the robust age by cumulative stress interaction effect found by Marshall et al.. The effects of ageing and cumulative stress also fell within the anecdotal range (⅓
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Affiliation(s)
- Denise Wallace
- Department of Psychology and Centre for Brain Science, University of Essex, Colchester, Essex, United Kingdom
| | - Nicholas R. Cooper
- Department of Psychology and Centre for Brain Science, University of Essex, Colchester, Essex, United Kingdom
| | - Alejandra Sel
- Department of Psychology and Centre for Brain Science, University of Essex, Colchester, Essex, United Kingdom
| | - Riccardo Russo
- Department of Psychology and Centre for Brain Science, University of Essex, Colchester, Essex, United Kingdom
- Department of Behavioral and Brain Sciences, University of Pavia, Pavia, Italy
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Zhang C, Li Y, Yang L, Zhao H. Regulation of local alternating electric fields on synaptic plasticity in brain tissue. Biomed Eng Lett 2023; 13:391-396. [PMID: 37519881 PMCID: PMC10382455 DOI: 10.1007/s13534-023-00287-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Revised: 05/04/2023] [Accepted: 05/14/2023] [Indexed: 08/01/2023] Open
Abstract
Purpose External electric fields can regulate the neural network and change the excitability of the in-vivo cerebral cortex. Here, to prove the effect of alternating electric fields on the synaptic plasticity of ex-vivo tissues, the regular changes in the synaptic structure under alternating electric fields were studied. Methods This study applied alternating electric fields with a peak voltage of 20 V and frequencies of 5, 20, 50, and 80 Hz to the porcine cerebral cortex. Relying on transmission electron microscopy (TEM), the ultrastructure of synapses was observed, and the curvature radius of post-synaptic density (PSD) and the synaptic gap distance was quantified. Results The results indicated that under alternating electric fields, the average synaptic curvature of the PSD decreased by 30-59% with increasing frequency, and the average synaptic gap distance became narrower. Conclusion In ex-vivo brain tissue, synaptic plasticity can be regulated by alternating electric fields of different frequencies. This study can provide reference data for the storage and regulation of ex-vivo organs, as well as comparable data for in-vivo studies.
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Affiliation(s)
- Chi Zhang
- School of Mechanical & Aerospace Engineering, Jilin University, 5988 Renmin Street, Changchun, 130025 P. R. China
- Key Laboratory of CNC Equipment Reliability, Ministry of Education, Jilin University, 5988 Renmin Street, Changchun, 130025 P. R. China
| | - Yiqiang Li
- School of Mechanical & Aerospace Engineering, Jilin University, 5988 Renmin Street, Changchun, 130025 P. R. China
- Key Laboratory of CNC Equipment Reliability, Ministry of Education, Jilin University, 5988 Renmin Street, Changchun, 130025 P. R. China
| | - Li Yang
- Key Laboratory of Zoonosis Research, Ministry of Education, Institute of Zoonosis, College of Veterinary Medicine, Jilin University, Changchun, 130062 P. R. China
| | - Hongwei Zhao
- School of Mechanical & Aerospace Engineering, Jilin University, 5988 Renmin Street, Changchun, 130025 P. R. China
- Key Laboratory of CNC Equipment Reliability, Ministry of Education, Jilin University, 5988 Renmin Street, Changchun, 130025 P. R. China
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Rauh J, Müller ASM, Nolte G, Haaf M, Mußmann M, Steinmann S, Mulert C, Leicht G. Comparison of transcranial brain stimulation approaches: prefrontal theta alternating current stimulation enhances working memory performance. Front Psychiatry 2023; 14:1140361. [PMID: 37457770 PMCID: PMC10348840 DOI: 10.3389/fpsyt.2023.1140361] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2023] [Accepted: 06/05/2023] [Indexed: 07/18/2023] Open
Abstract
Introduction One of the most important cognitive functions in our everyday life is the working memory (WM). In several neuropsychiatric diseases such as ADHD or schizophrenia WM deficits can be observed, making it an attractive target for non-invasive brain stimulation methods like transcranial electrical stimulation (tES). However, the literature shows rather heterogeneous results of tES effects on WM performance. fMRI meta-analyses have identified a WM network including frontoparietal brain areas such as the dorsolateral prefrontal cortex (DLPFC) and the posterior parietal cortex (PPC). Neurophysiological studies revealed oscillatory activity in the theta band frequency range to be of crucial functional relevance for WM processes. Based on this, transcranial alternating current stimulation (tACS) in the theta frequency range targeting DLPFC and PPC in a spatially optimized way might further improve effects of tES on WM performance. Methods Sixteen healthy subjects were stimulated with varying stimulation settings on four different days in a counterbalanced within-subject design. These setups included the application of (1) tACS with a frequency of 5 Hz (theta frequency range) over the left DLPFC and (2) the right superior parietal cortex, (3) transcranial direct current stimulation (tDCS) of the DLPFC and (4) a sham stimulation condition during the online performance of a visual delayed-match-to-sample task with varying working memory load. We introduce a procedure to calculate an optimal tES model revealing optimized high-density setups for the present study for 3 cathodes and 1 anode and stimulation currents of 1.5 mA. Results A significant interaction effect of stimulation type and load condition on working memory capacity was found. This was reflected by a significant improvement of WM performance in the high load condition during tACS over the left DLPFC compared with sham stimulation, which was not the case for our parietal tACS or tDCS setup. Discussion Working memory performance can be improved with optimized high-definition tACS with a frequency of 5 Hz over the left DLPFC. The conception of different mechanisms underlying transcranial electrical stimulation with alternating and direct currents is supported by these results. Patients suffering from working memory impairments due to neuropsychiatric diseases might potentially benefit from this brain stimulation approach.
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Affiliation(s)
- Jonas Rauh
- Psychiatry Neuroimaging Branch, Department of Psychiatry and Psychotherapy, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Anne S. M. Müller
- Psychiatry Neuroimaging Branch, Department of Psychiatry and Psychotherapy, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Guido Nolte
- Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Moritz Haaf
- Psychiatry Neuroimaging Branch, Department of Psychiatry and Psychotherapy, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Marius Mußmann
- Psychiatry Neuroimaging Branch, Department of Psychiatry and Psychotherapy, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Saskia Steinmann
- Psychiatry Neuroimaging Branch, Department of Psychiatry and Psychotherapy, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Christoph Mulert
- Psychiatry Neuroimaging Branch, Department of Psychiatry and Psychotherapy, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- Center of Psychiatry, Justus-Liebig University, Giessen, Germany
| | - Gregor Leicht
- Psychiatry Neuroimaging Branch, Department of Psychiatry and Psychotherapy, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
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11
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Soutschek A, Nadporozhskaia L, Christian P. Brain stimulation over dorsomedial prefrontal cortex modulates effort-based decision making. COGNITIVE, AFFECTIVE & BEHAVIORAL NEUROSCIENCE 2022; 22:1264-1274. [PMID: 35729467 PMCID: PMC9622516 DOI: 10.3758/s13415-022-01021-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Accepted: 06/11/2022] [Indexed: 01/27/2023]
Abstract
Deciding whether to engage in strenuous mental activities requires trading-off the potential benefits against the costs of mental effort, but it is unknown which brain rhythms are causally involved in such cost-benefit calculations. We show that brain stimulation targeting midfrontal theta oscillations increases the engagement in goal-directed mental effort. Participants received transcranial alternating current stimulation over dorsomedial prefrontal cortex while deciding whether they are willing to perform a demanding working memory task for monetary rewards. Midfrontal theta tACS increased the willingness to exert mental effort for rewards while leaving working memory performance unchanged. Computational modelling using a hierarchical Bayesian drift diffusion model suggests that theta tACS shifts the starting bias before evidence accumulation towards high reward-high effort options without affecting the velocity of the evidence accumulation process. Our findings suggest that the motivation to engage in goal-directed mental effort can be increased via midfrontal tACS.
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Affiliation(s)
- Alexander Soutschek
- Department for Psychology, Ludwig Maximilian University Munich, Leopoldstr. 13, 80802, Munich, Germany.
| | - Lidiia Nadporozhskaia
- Department for Psychology, Ludwig Maximilian University Munich, Leopoldstr. 13, 80802, Munich, Germany
- Department of Biology, Graduate School for Systemic Neurosciences, Ludwig Maximilian University Munich, Munich, Germany
- Institute of Molecular and Clinical Ophthalmology, University of Basel, Basel, Switzerland
| | - Patricia Christian
- Department for Psychology, Ludwig Maximilian University Munich, Leopoldstr. 13, 80802, Munich, Germany
- Department of Biology, Graduate School for Systemic Neurosciences, Ludwig Maximilian University Munich, Munich, Germany
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12
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Bjekić J, Paunovic D, Živanović M, Stanković M, Griskova-Bulanova I, Filipović SR. Determining the Individual Theta Frequency for Associative Memory Targeted Personalized Transcranial Brain Stimulation. J Pers Med 2022; 12:jpm12091367. [PMID: 36143152 PMCID: PMC9506372 DOI: 10.3390/jpm12091367] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2022] [Revised: 08/05/2022] [Accepted: 08/19/2022] [Indexed: 11/16/2022] Open
Abstract
Non-invasive brain stimulation (NIBS) methods have gained increased interest in research and therapy of associative memory (AM) and its impairments. However, the one-size-fits-all approach yields inconsistent findings, thus putting forward the need for electroencephalography (EEG)-guided personalized frequency-modulated NIBS protocols to increase the focality and the effectiveness of the interventions. Still, extraction of individual frequency, especially in the theta band, turned out to be a challenging task. Here we present an approach to extracting the individual theta-band frequency (ITF) from EEG signals recorded during the AM task. The method showed a 93% success rate, good reliability, and the full range of variability of the extracted ITFs. This paper provides a rationale behind the adopted approach and critically evaluates it in comparison to the alternative methods that have been reported in the literature. Finally, we discuss how it could be used as an input parameter for personalized frequency-modulated NIBS approaches—transcranial alternating current stimulation (tACS) and transcranial oscillatory current stimulation (otDCS) directed at AM neuromodulation.
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Affiliation(s)
- Jovana Bjekić
- Human Neuroscience Group, Institute for Medical Research, University of Belgrade, 11000 Belgrade, Serbia
- Correspondence: (J.B.); (S.R.F.)
| | - Dunja Paunovic
- Human Neuroscience Group, Institute for Medical Research, University of Belgrade, 11000 Belgrade, Serbia
| | - Marko Živanović
- Institute of Psychology and Laboratory for Research of Individual Differences, Department of Psychology, Faculty of Philosophy, University of Belgrade, 11000 Belgrade, Serbia
| | - Marija Stanković
- Human Neuroscience Group, Institute for Medical Research, University of Belgrade, 11000 Belgrade, Serbia
| | - Inga Griskova-Bulanova
- Institute of Biosciences, Life Sciences Centre, Vilnius University, LT-10322 Vilnius, Lithuania
| | - Saša R. Filipović
- Human Neuroscience Group, Institute for Medical Research, University of Belgrade, 11000 Belgrade, Serbia
- Correspondence: (J.B.); (S.R.F.)
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13
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Preisig BC, Hervais-Adelman A. The Predictive Value of Individual Electric Field Modeling for Transcranial Alternating Current Stimulation Induced Brain Modulation. Front Cell Neurosci 2022; 16:818703. [PMID: 35273479 PMCID: PMC8901488 DOI: 10.3389/fncel.2022.818703] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Accepted: 02/02/2022] [Indexed: 11/13/2022] Open
Abstract
There is considerable individual variability in the reported effectiveness of non-invasive brain stimulation. This variability has often been ascribed to differences in the neuroanatomy and resulting differences in the induced electric field inside the brain. In this study, we addressed the question whether individual differences in the induced electric field can predict the neurophysiological and behavioral consequences of gamma band tACS. In a within-subject experiment, bi-hemispheric gamma band tACS and sham stimulation was applied in alternating blocks to the participants' superior temporal lobe, while task-evoked auditory brain activity was measured with concurrent functional magnetic resonance imaging (fMRI) and a dichotic listening task. Gamma tACS was applied with different interhemispheric phase lags. In a recent study, we could show that anti-phase tACS (180° interhemispheric phase lag), but not in-phase tACS (0° interhemispheric phase lag), selectively modulates interhemispheric brain connectivity. Using a T1 structural image of each participant's brain, an individual simulation of the induced electric field was computed. From these simulations, we derived two predictor variables: maximal strength (average of the 10,000 voxels with largest electric field values) and precision of the electric field (spatial correlation between the electric field and the task evoked brain activity during sham stimulation). We found considerable variability in the individual strength and precision of the electric fields. Importantly, the strength of the electric field over the right hemisphere predicted individual differences of tACS induced brain connectivity changes. Moreover, we found in both hemispheres a statistical trend for the effect of electric field strength on tACS induced BOLD signal changes. In contrast, the precision of the electric field did not predict any neurophysiological measure. Further, neither strength, nor precision predicted interhemispheric integration. In conclusion, we found evidence for the dose-response relationship between individual differences in electric fields and tACS induced activity and connectivity changes in concurrent fMRI. However, the fact that this relationship was stronger in the right hemisphere suggests that the relationship between the electric field parameters, neurophysiology, and behavior may be more complex for bi-hemispheric tACS.
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Affiliation(s)
- Basil C. Preisig
- Department of Psychology, Neurolinguistics, University of Zurich, Zurich, Switzerland
- Donders Institute for Cognitive Neuroimaging, Radboud University, Nijmegen, Netherlands
- Max Planck Institute for Psycholinguistics, Nijmegen, Netherlands
- Neuroscience Center Zurich, Eidgenössische Technische Hochschule Zurich, University of Zurich, Zurich, Switzerland
| | - Alexis Hervais-Adelman
- Department of Psychology, Neurolinguistics, University of Zurich, Zurich, Switzerland
- Neuroscience Center Zurich, Eidgenössische Technische Hochschule Zurich, University of Zurich, Zurich, Switzerland
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14
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Al Qasem W, Abubaker M, Kvašňák E. Working Memory and Transcranial-Alternating Current Stimulation-State of the Art: Findings, Missing, and Challenges. Front Psychol 2022; 13:822545. [PMID: 35237214 PMCID: PMC8882605 DOI: 10.3389/fpsyg.2022.822545] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Accepted: 01/19/2022] [Indexed: 12/06/2022] Open
Abstract
Working memory (WM) is a cognitive process that involves maintaining and manipulating information for a short period of time. WM is central to many cognitive processes and declines rapidly with age. Deficits in WM are seen in older adults and in patients with dementia, schizophrenia, major depression, mild cognitive impairment, Alzheimer's disease, etc. The frontal, parietal, and occipital cortices are significantly involved in WM processing and all brain oscillations are implicated in tackling WM tasks, particularly theta and gamma bands. The theta/gamma neural code hypothesis assumes that retained memory items are recorded via theta-nested gamma cycles. Neuronal oscillations can be manipulated by sensory, invasive- and non-invasive brain stimulations. Transcranial alternating-current stimulation (tACS) and repetitive transcranial magnetic stimulation (rTMS) are frequency-tuned non-invasive brain stimulation (NIBS) techniques that have been used to entrain endogenous oscillations in a frequency-specific manner. Compared to rTMS, tACS demonstrates superior cost, tolerability, portability, and safety profile, making it an attractive potential tool for improving cognitive performance. Although cognitive research with tACS is still in its infancy compared to rTMS, a number of studies have shown a promising WM enhancement effect, especially in the elderly and patients with cognitive deficits. This review focuses on the various methods and outcomes of tACS on WM in healthy and unhealthy human adults and highlights the established findings, unknowns, challenges, and perspectives important for translating laboratory tACS into realistic clinical settings. This will allow researchers to identify gaps in the literature and develop frequency-tuned tACS protocols with promising safety and efficacy outcomes. Therefore, research efforts in this direction should help to consider frequency-tuned tACS as a non-pharmacological tool of cognitive rehabilitation in physiological aging and patients with cognitive deficits.
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Affiliation(s)
- Wiam Al Qasem
- Department of Medical Biophysics and Medical Informatics, Third Faculty of Medicine, Charles University in Prague, Praha, Czechia
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15
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Pan L, Wu Y, Bao J, Guo D, Zhang X, Wang J, Deng M, Yu P, Wei G, Zhang L, Qin X, Song Y. Alterations in Neural Networks During Working Memory Encoding Related to Cognitive Impairment in Temporal Lobe Epilepsy. Front Hum Neurosci 2022; 15:770678. [PMID: 35069151 PMCID: PMC8766724 DOI: 10.3389/fnhum.2021.770678] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2021] [Accepted: 12/13/2021] [Indexed: 11/13/2022] Open
Abstract
Objective: The aim of the current study was to investigate the alterations in the neural networks of patients with temporal lobe epilepsy (TLE) during working memory (WM) encoding. Methods: Patients with TLE (n = 52) and healthy volunteers (n = 35) completed a WM task, during which 34-channel electroencephalogram signals were recorded. The neural networks during WM encoding were calculated in TLE patients with (TLE-WM) and without (TLE-N) WM deficits. Results: Functional connectivity strength decreased, and the theta network was altered in the TLE-WM group, although no significant differences in clinical features were observed between the TLE-N and TLE-WM groups. Conclusions: Not all patients with TLE present with cognitive impairments and alterations in the theta network were identified in TLE patients with functional cognitive deficits. Significance: The theta network may represent a sensitive measure of cognitive impairment and could predict cognitive outcomes among patients with TLE.
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Affiliation(s)
- Liping Pan
- General Medicine Department, Tianjin Medical University General Hospital, Tianjin, China
| | - Yakun Wu
- Department of Neurology, Tianjin Medical University General Hospital, Tianjin, China
- Department of Neurology, Tangshan Gongren Hospital, Tangshan, China
| | - Jie Bao
- Department of Rehabilitation Medicine, Tianjin Medical University General Hospital, Tianjin, China
| | - Dandan Guo
- Department of Neurology, Tianjin Medical University General Hospital, Tianjin, China
| | - Xin Zhang
- Department of Neurology, Tianjin Medical University General Hospital, Tianjin, China
| | - Jiajing Wang
- Department of Neurology, Tianjin Medical University General Hospital, Tianjin, China
| | - Meili Deng
- Department of Neurology, Tianjin Medical University General Hospital, Tianjin, China
| | - Peiran Yu
- School of Basic Medical Science, Tianjin Medical University, Tianjin, China
| | - Gaoxu Wei
- Department of Neurology, Tianjin Medical University General Hospital, Tianjin, China
| | - Lulin Zhang
- Department of Neurology, Tianjin Medical University General Hospital, Tianjin, China
- Department of Neurology, The First Affiliated Hospital of Fujian Medical University, Fuzhou, China
| | - Xiao Qin
- Department of Neurology, Tianjin Medical University General Hospital, Tianjin, China
| | - Yijun Song
- General Medicine Department, Tianjin Medical University General Hospital, Tianjin, China
- Key Laboratory of Central Nerve Injury Repair and Regeneration, Ministry of Education, Tianjin Neurological Institute, Tianjin, China
- *Correspondence: Yijun Song
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16
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Booth SJ, Taylor JR, Brown LJE, Pobric G. The effects of transcranial alternating current stimulation on memory performance in healthy adults: A systematic review. Cortex 2021; 147:112-139. [PMID: 35032750 DOI: 10.1016/j.cortex.2021.12.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Revised: 11/14/2021] [Accepted: 12/01/2021] [Indexed: 01/03/2023]
Abstract
The recent introduction of Transcranial Alternating Current stimulation (tACS) in research on memory modulation has yielded some exciting findings. Whilst evidence suggests small but significant modulatory effects of tACS on perception and cognition, it is unclear how effective tACS is at modulating memory, and the neural oscillations underlying memory. The aim of this systematic review was to determine the efficacy with which tACS, compared to sham stimulation, can modify working memory (WM) and long-term memory (LTM) performance in healthy adults. We examined how these effects may be moderated by specific tACS parameters and study/participant characteristics. Our secondary goal was to investigate the neural correlates of tACS' effects on memory performance in healthy adults. A systematic search of eight databases yielded 11,413 records, resulting in 34 papers that included 104 eligible studies. The results were synthesised by memory type (WM/LTM) and according to the specific parameters of frequency band, stimulation montage, individual variability, cognitive demand, and phase. A second synthesis examined the correspondence between tACS' effects on memory performance and the oscillatory features of electroencephalography (EEG) and magnetencephalography (MEG) recordings in a subset of 26 studies. The results showed a small-to-medium effect of tACS on WM and LTM performance overall. There was strong evidence to suggest that posterior theta-tACS modulates WM performance, whilst the modulation of LTM is achieved by anterior gamma-tACS. Moreover, there was a correspondence between tACS effects on memory performance and oscillatory outcomes at the stimulation frequency. We discuss limitations in the field and suggest ways to improve our understanding of tACS efficacy to ensure a transition of tACS from an investigative method to a therapeutic tool.
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Affiliation(s)
- Samantha J Booth
- Division of Neuroscience and Experimental Psychology, School of Biological Sciences, Faculty of Biology, Medicine, and Health, University of Manchester, Manchester Academic Health Science Centre, England, UK.
| | - Jason R Taylor
- Division of Neuroscience and Experimental Psychology, School of Biological Sciences, Faculty of Biology, Medicine, and Health, University of Manchester, Manchester Academic Health Science Centre, England, UK.
| | - Laura J E Brown
- Division of Psychology and Mental Health, School of Health Sciences, Faculty of Biology, Medicine, and Health, University of Manchester, Manchester Academic Health Science Centre, England, UK.
| | - Gorana Pobric
- Division of Neuroscience and Experimental Psychology, School of Biological Sciences, Faculty of Biology, Medicine, and Health, University of Manchester, Manchester Academic Health Science Centre, England, UK.
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17
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Biel AL, Sterner E, Röll L, Sauseng P. Modulating verbal working memory with fronto-parietal transcranial electric stimulation at theta frequency: Does it work? Eur J Neurosci 2021; 55:405-425. [PMID: 34902182 DOI: 10.1111/ejn.15563] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Revised: 11/22/2021] [Accepted: 11/29/2021] [Indexed: 11/29/2022]
Abstract
Oscillatory theta activity in a fronto-parietal network has been associated with working memory (WM) processes and may be directly related to WM performance. In their seminal study, Polanía et al. (2012) (de-)coupled a fronto-parietal theta-network by applying transcranial alternating current stimulation (tACS), and showed that anti-phase tACS led to slower and in-phase tACS to faster response times in a verbal WM task compared to placebo stimulation. In the literature, this 'synchronization-desynchronization' effect has only been partly replicated, and electric field modelling suggests that it might not be the fronto-parietal network that is primarily stimulated during in-phase tACS with a shared return electrode. This provides one possible reason for inconsistency in the literature. In this study, we aimed to reproduce the findings reported by Polanía et al. (2012). We also aimed to investigate whether in-phase theta tACS with multiple close-by return electrodes for focal stimulation of the frontal and the parietal cortex will have at least as much of a facilitatory effect as the in-phase stimulation as indicated by Polania et al. (2012). In a single-trial distributional analysis, we explored whether mean, variation and right-skewness of the response time distribution are affected. Against our hypothesis, we found no 'synchronization-desynchronization' effect by fronto-parietal theta tACS on response times using the same delayed letter discrimination task and stimulation parameters in two experiments, both between-subjects and within-subjects. However, we could show that in a more demanding 3-back task, fronto-parietal in-phase and in-phase focal theta tACS substantially improved task performance compared to placebo stimulation.
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Affiliation(s)
- Anna Lena Biel
- Department of Psychology, Ludwig-Maximilians-Universität München, Munich, Germany.,Graduate School of Systemic Neurosciences, Ludwig-Maximilians-Universität München, Planegg, Martinsried, Germany
| | - Elisabeth Sterner
- Department of Psychology, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Lukas Röll
- Department of Psychology, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Paul Sauseng
- Department of Psychology, Ludwig-Maximilians-Universität München, Munich, Germany.,Graduate School of Systemic Neurosciences, Ludwig-Maximilians-Universität München, Planegg, Martinsried, Germany
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18
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Abubaker M, Al Qasem W, Kvašňák E. Working Memory and Cross-Frequency Coupling of Neuronal Oscillations. Front Psychol 2021; 12:756661. [PMID: 34744934 PMCID: PMC8566716 DOI: 10.3389/fpsyg.2021.756661] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Accepted: 09/14/2021] [Indexed: 11/28/2022] Open
Abstract
Working memory (WM) is the active retention and processing of information over a few seconds and is considered an essential component of cognitive function. The reduced WM capacity is a common feature in many diseases, such as schizophrenia, attention deficit hyperactivity disorder (ADHD), mild cognitive impairment (MCI), and Alzheimer's disease (AD). The theta-gamma neural code is an essential component of memory representations in the multi-item WM. A large body of studies have examined the association between cross-frequency coupling (CFC) across the cerebral cortices and WM performance; electrophysiological data together with the behavioral results showed the associations between CFC and WM performance. The oscillatory entrainment (sensory, non-invasive electrical/magnetic, and invasive electrical) remains the key method to investigate the causal relationship between CFC and WM. The frequency-tuned non-invasive brain stimulation is a promising way to improve WM performance in healthy and non-healthy patients with cognitive impairment. The WM performance is sensitive to the phase and rhythm of externally applied stimulations. CFC-transcranial-alternating current stimulation (CFC-tACS) is a recent approach in neuroscience that could alter cognitive outcomes. The studies that investigated (1) the association between CFC and WM and (2) the brain stimulation protocols that enhanced WM through modulating CFC by the means of the non-invasive brain stimulation techniques have been included in this review. In principle, this review can guide the researchers to identify the most prominent form of CFC associated with WM processing (e.g., theta/gamma phase-amplitude coupling), and to define the previously published studies that manipulate endogenous CFC externally to improve WM. This in turn will pave the path for future studies aimed at investigating the CFC-tACS effect on WM. The CFC-tACS protocols need to be thoroughly studied before they can be considered as therapeutic tools in patients with WM deficits.
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Affiliation(s)
- Mohammed Abubaker
- Department of Medical Biophysics and Medical Informatics, Third Faculty of Medicine, Charles University in Prague, Prague, Czechia
| | - Wiam Al Qasem
- Department of Medical Biophysics and Medical Informatics, Third Faculty of Medicine, Charles University in Prague, Prague, Czechia
| | - Eugen Kvašňák
- Department of Medical Biophysics and Medical Informatics, Third Faculty of Medicine, Charles University in Prague, Prague, Czechia
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19
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Wei J, Zhang Z, Yao Z, Ming D, Zhou P. Modulation of Sustained Attention by Theta-tACS over the Lateral and Medial Frontal Cortices. Neural Plast 2021; 2021:5573471. [PMID: 34239553 PMCID: PMC8238627 DOI: 10.1155/2021/5573471] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Accepted: 05/29/2021] [Indexed: 11/25/2022] Open
Abstract
Theta oscillations over the posterior medial frontal cortex (pMFC) and lateral prefrontal cortex (LPFC) play vital roles in sustained attention. Specifically, pMFC power and pMFC-LPFC synchronization correlate with cognitive control in sustained-attention-related tasks, but the causal relationships remain unknown. In the present study, we first analyzed the correlation between EEG theta oscillations (characterized by time-frequency power and phase-based connectivity) and the level of sustained attention (Experiment 1) and then utilized transcranial alternating current stimulation (tACS) to modulate theta oscillations and in turn observed its effects on sustained attention (Experiment 2). In Experiment 1, two time-frequency regions of interest (ROIs) were determined, in which high/low time-frequency power and high/low phase-based connectivity corresponded to high/low-level sustained attention. In Experiment 2, time-frequency power and phase-based connectivity of theta oscillations were compared between the sham and tACS groups within the time-frequency ROIs determined in Experiment 1. Results showed that phase-based connectivity between pMFC and LPFC significantly decreased in the tACS group compared with the sham group during the first five minutes of the poststimulation period. Moreover, a marginal trend existed that sustained attention was downregulated by tACS in the same time interval, suggesting that theta phase synchronization between pMFC and LPFC may play a causal role in sustained attention.
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Affiliation(s)
- Jinwen Wei
- School of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin 300072, China
- School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen 518060, China
| | - Zhiguo Zhang
- School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen 518060, China
| | - Ziqing Yao
- Department of Psychology, The University of Hong Kong, Hong Kong S.A.R., China
| | - Dong Ming
- School of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin 300072, China
| | - Peng Zhou
- School of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin 300072, China
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20
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Wu L, Liu T, Wang J. Improving the Effect of Transcranial Alternating Current Stimulation (tACS): A Systematic Review. Front Hum Neurosci 2021; 15:652393. [PMID: 34163340 PMCID: PMC8215166 DOI: 10.3389/fnhum.2021.652393] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Accepted: 04/26/2021] [Indexed: 11/15/2022] Open
Abstract
With the development of electrical stimulation technology, traditional transcranial alternating current stimulation (tACS) technology has been found to have the drawback of not targeting a specific area accurately. Studies have shown that optimizing the number and position of electrodes during electrical stimulation has a very good effect on enhancing brain stimulation accuracy. At present, an increasing number of laboratories have begun to optimize tACS. However, there has been no study summarizing the optimization methods of tACS. Determining whether different optimization methods are effective and the optimization approach could provide information that could guide future tACS research. We describe the results of recent research on tACS optimization and integrate the optimization approaches of tACS in recent research. Optimization approaches can be classified into two groups: high-definition electrical stimulation and interference modulation electrical stimulation. The optimization methods can be divided into five categories: high-definition tACS, phase-shifted tACS, amplitude-modulated tACS, the temporally interfering (TI) method, and the intersectional short pulse (ISP) method. Finally, we summarize the latest research on hardware useful for tACS improvement and outline future directions.
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Affiliation(s)
- Linyan Wu
- The Key Laboratory of Biomedical Information Engineering of Ministry of Education, Institute of Health and Rehabilitation Science, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an, China.,National Engineering Research Center of Health Care and Medical Devices, Guangzhou, China.,The Key Laboratory of Neuro-informatics & Rehabilitation Engineering of Ministry of Civil Affairs, Xi'an, China
| | - Tian Liu
- The Key Laboratory of Biomedical Information Engineering of Ministry of Education, Institute of Health and Rehabilitation Science, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an, China.,National Engineering Research Center of Health Care and Medical Devices, Guangzhou, China.,The Key Laboratory of Neuro-informatics & Rehabilitation Engineering of Ministry of Civil Affairs, Xi'an, China
| | - Jue Wang
- The Key Laboratory of Biomedical Information Engineering of Ministry of Education, Institute of Health and Rehabilitation Science, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an, China.,National Engineering Research Center of Health Care and Medical Devices, Guangzhou, China.,The Key Laboratory of Neuro-informatics & Rehabilitation Engineering of Ministry of Civil Affairs, Xi'an, China
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21
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Meng A, Kaiser M, de Graaf TA, Dücker F, Sack AT, De Weerd P, van de Ven V. Transcranial alternating current stimulation at theta frequency to left parietal cortex impairs associative, but not perceptual, memory encoding. Neurobiol Learn Mem 2021; 182:107444. [PMID: 33895350 DOI: 10.1016/j.nlm.2021.107444] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Revised: 03/16/2021] [Accepted: 04/20/2021] [Indexed: 11/26/2022]
Abstract
Neural oscillations in the theta range (4-8 Hz) are thought to underlie associative memory function in the hippocampal-cortical network. While there is ample evidence supporting a role of theta oscillations in animal and human memory, most evidence is correlational. Non-invasive brain stimulation (NIBS) can be employed to modulate cortical oscillatory activity to influence brain activity, and possibly modulate deeper brain regions, such as hippocampus, through strong and reliable cortico-hippocampal functional connections. We applied focal transcranial alternating current stimulation (tACS) at 6 Hz over left parietal cortex to modulate brain activity in the putative cortico-hippocampal network to influence associative memory encoding. After encoding and brain stimulation, participants completed an associative memory and a perceptual recognition task. Results showed that theta tACS significantly decreased associative memory performance but did not affect perceptual memory performance. These results show that parietal theta tACS modulates associative processing separately from perceptual processing, and further substantiate the hypothesis that theta oscillations are implicated in the cortico-hippocampal network and associative encoding.
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Affiliation(s)
- Alyssa Meng
- Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, PO Box 616, 6200 MD Maastricht, the Netherlands
| | - Max Kaiser
- Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, PO Box 616, 6200 MD Maastricht, the Netherlands
| | - Tom A de Graaf
- Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, PO Box 616, 6200 MD Maastricht, the Netherlands; Maastricht Brain Imaging Center (MBIC), Maastricht University, PO Box 616, 6200 MD Maastricht, the Netherlands
| | - Felix Dücker
- Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, PO Box 616, 6200 MD Maastricht, the Netherlands; Maastricht Brain Imaging Center (MBIC), Maastricht University, PO Box 616, 6200 MD Maastricht, the Netherlands
| | - Alexander T Sack
- Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, PO Box 616, 6200 MD Maastricht, the Netherlands; Maastricht Brain Imaging Center (MBIC), Maastricht University, PO Box 616, 6200 MD Maastricht, the Netherlands
| | - Peter De Weerd
- Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, PO Box 616, 6200 MD Maastricht, the Netherlands; Maastricht Brain Imaging Center (MBIC), Maastricht University, PO Box 616, 6200 MD Maastricht, the Netherlands
| | - Vincent van de Ven
- Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, PO Box 616, 6200 MD Maastricht, the Netherlands; Maastricht Brain Imaging Center (MBIC), Maastricht University, PO Box 616, 6200 MD Maastricht, the Netherlands.
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22
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The Modulation of Cognitive Performance with Transcranial Alternating Current Stimulation: A Systematic Review of Frequency-Specific Effects. Brain Sci 2020; 10:brainsci10120932. [PMID: 33276533 PMCID: PMC7761592 DOI: 10.3390/brainsci10120932] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Revised: 11/20/2020] [Accepted: 11/29/2020] [Indexed: 12/21/2022] Open
Abstract
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.
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23
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Jones KT, Johnson EL, Berryhill ME. Frontoparietal theta-gamma interactions track working memory enhancement with training and tDCS. Neuroimage 2020; 211:116615. [PMID: 32044440 PMCID: PMC7733399 DOI: 10.1016/j.neuroimage.2020.116615] [Citation(s) in RCA: 61] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2019] [Revised: 01/14/2020] [Accepted: 02/05/2020] [Indexed: 01/17/2023] Open
Abstract
Despite considerable interest in enhancing, preserving, and rehabilitating working memory (WM), efforts to elicit sustained behavioral improvements have been met with limited success. Here, we paired WM training with transcranial direct current stimulation (tDCS) to the frontoparietal network over four days. Active tDCS enhanced WM performance by modulating interactions between frontoparietal theta oscillations and gamma activity, as measured by pre- and post-training high-density electroencephalography (EEG). Increased phase-amplitude coupling (PAC) between the prefrontal stimulation site and temporo-parietal gamma activity explained behavioral improvements, and was most effective when gamma occurred near the prefrontal theta peak. These results demonstrate for the first time that tDCS-linked WM training elicits lasting changes in behavior by optimizing the oscillatory substrates of prefrontal control.
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Affiliation(s)
- Kevin T Jones
- University of Nevada-Reno, Department of Psychology, Cognitive and Brain Sciences, Reno, NV, 89557, USA; University of California-San Francisco, Department of Neurology, Neuroscape, San Francisco, CA, 94158, USA
| | - Elizabeth L Johnson
- University of California-Berkeley, Helen Wills Neuroscience Institute, Berkeley, CA, 94720, USA; Wayne State University, Institute of Gerontology, Life-Span Cognitive Neuroscience Program, Detroit, MI, 48202, USA
| | - Marian E Berryhill
- University of Nevada-Reno, Department of Psychology, Cognitive and Brain Sciences, Reno, NV, 89557, USA.
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24
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Wischnewski M, Joergensen ML, Compen B, Schutter DJLG. Frontal Beta Transcranial Alternating Current Stimulation Improves Reversal Learning. Cereb Cortex 2020; 30:3286-3295. [PMID: 31898728 PMCID: PMC7197207 DOI: 10.1093/cercor/bhz309] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Electroencephalogram (EEG) studies suggest an association between beta (13-30 Hz) power and reversal learning performance. In search for direct evidence concerning the involvement of beta oscillations in reversal learning, transcranial alternating current stimulation (tACS) was applied in a double-blind, sham-controlled and between-subjects design. Exogenous oscillatory currents were administered bilaterally to the frontal cortex at 20 Hz with an intensity of 1 mA peak-to-peak and the effects on reward-punishment based reversal learning were evaluated in hundred-and-eight healthy volunteers. Pre- and post-tACS resting state EEG recordings were analyzed. Results showed that beta-tACS improved rule implementation during reversal learning and decreases left and right resting-state frontal theta/beta EEG ratios following tACS. Our findings provide the first behavioral and electrophysiological evidence for exogenous 20 Hz oscillatory electric field potentials administered over to the frontal cortex to improve reversal learning.
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Affiliation(s)
- Miles Wischnewski
- Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Nijmegen, 6537 RD, The Netherlands
| | - Mie L Joergensen
- Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Nijmegen, 6537 RD, The Netherlands
| | - Boukje Compen
- Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Nijmegen, 6537 RD, The Netherlands
| | - Dennis J L G Schutter
- Helmholtz Institute, Experimental Psychology, Utrecht University, Utrecht, 3584 CS, The Netherlands
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25
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Alekseichuk I, Falchier AY, Linn G, Xu T, Milham MP, Schroeder CE, Opitz A. Electric field dynamics in the brain during multi-electrode transcranial electric stimulation. Nat Commun 2019; 10:2573. [PMID: 31189931 PMCID: PMC6561925 DOI: 10.1038/s41467-019-10581-7] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Accepted: 05/20/2019] [Indexed: 11/29/2022] Open
Abstract
Neural oscillations play a crucial role in communication between remote brain areas. Transcranial electric stimulation with alternating currents (TACS) can manipulate these brain oscillations in a non-invasive manner. Recently, TACS using multiple electrodes with phase shifted stimulation currents were developed to alter long-range connectivity. Typically, an increase in coordination between two areas is assumed when they experience an in-phase stimulation and a disorganization through an anti-phase stimulation. However, the underlying biophysics of multi-electrode TACS has not been studied in detail. Here, we leverage direct invasive recordings from two non-human primates during multi-electrode TACS to characterize electric field magnitude and phase as a function of the phase of stimulation currents. Further, we report a novel "traveling wave" stimulation where the location of the electric field maximum changes over the stimulation cycle. Our results provide a mechanistic understanding of the biophysics of multi-electrode TACS and enable future developments of novel stimulation protocols.
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Affiliation(s)
- Ivan Alekseichuk
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, 55455, MN, USA
| | - Arnaud Y Falchier
- Center for Biomedical Imaging and Neuromodulation, Nathan Kline Institute for Psychiatric Research, Orangeburg, 10962, NY, USA
| | - Gary Linn
- Center for Biomedical Imaging and Neuromodulation, Nathan Kline Institute for Psychiatric Research, Orangeburg, 10962, NY, USA
| | - Ting Xu
- Center for the Developing Brain, Child Mind Institute, New York, 10022, NY, USA
| | - Michael P Milham
- Center for Biomedical Imaging and Neuromodulation, Nathan Kline Institute for Psychiatric Research, Orangeburg, 10962, NY, USA
- Center for the Developing Brain, Child Mind Institute, New York, 10022, NY, USA
| | - Charles E Schroeder
- Center for Biomedical Imaging and Neuromodulation, Nathan Kline Institute for Psychiatric Research, Orangeburg, 10962, NY, USA
- Departments of Neurological Surgery and Psychiatry, Columbia University College of Physicians and Surgeons, New York, 10032, NY, USA
| | - Alexander Opitz
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, 55455, MN, USA.
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26
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Vosskuhl J, Strüber D, Herrmann CS. Non-invasive Brain Stimulation: A Paradigm Shift in Understanding Brain Oscillations. Front Hum Neurosci 2018; 12:211. [PMID: 29887799 PMCID: PMC5980979 DOI: 10.3389/fnhum.2018.00211] [Citation(s) in RCA: 112] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Accepted: 05/07/2018] [Indexed: 11/13/2022] Open
Abstract
Cognitive neuroscience set out to understand the neural mechanisms underlying cognition. One central question is how oscillatory brain activity relates to cognitive processes. Up to now, most of the evidence supporting this relationship was correlative in nature. This situation changed dramatically with the recent development of non-invasive brain stimulation (NIBS) techniques, which open up new vistas for neuroscience by allowing researchers for the first time to validate their correlational theories by manipulating brain functioning directly. In this review, we focus on transcranial alternating current stimulation (tACS), an electrical brain stimulation method that applies sinusoidal currents to the intact scalp of human individuals to directly interfere with ongoing brain oscillations. We outline how tACS can impact human brain oscillations by employing different levels of observation from non-invasive tACS application in healthy volunteers and intracranial recordings in patients to animal studies demonstrating the effectiveness of alternating electric fields on neurons in vitro and in vivo. These findings likely translate to humans as comparable effects can be observed in human and animal studies. Neural entrainment and plasticity are suggested to mediate the behavioral effects of tACS. Furthermore, we focus on mechanistic theories about the relationship between certain cognitive functions and specific parameters of brain oscillaitons such as its amplitude, frequency, phase and phase coherence. For each of these parameters we present the current state of testing its functional relevance by means of tACS. Recent developments in the field of tACS are outlined which include the stimulation with physiologically inspired non-sinusoidal waveforms, stimulation protocols which allow for the observation of online-effects, and closed loop applications of tACS.
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Affiliation(s)
- Johannes Vosskuhl
- Experimental Psychology Lab, Center for Excellence “Hearing4all,” European Medical School, University of Oldenburg, Oldenburg, Germany
| | - Daniel Strüber
- Experimental Psychology Lab, Center for Excellence “Hearing4all,” European Medical School, University of Oldenburg, Oldenburg, Germany
- Research Center Neurosensory Science, University of Oldenburg, Oldenburg, Germany
| | - Christoph S. Herrmann
- Experimental Psychology Lab, Center for Excellence “Hearing4all,” European Medical School, University of Oldenburg, Oldenburg, Germany
- Research Center Neurosensory Science, University of Oldenburg, Oldenburg, Germany
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27
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Turi Z, Alekseichuk I, Paulus W. On ways to overcome the magical capacity limit of working memory. PLoS Biol 2018; 16:e2005867. [PMID: 29672569 PMCID: PMC5929568 DOI: 10.1371/journal.pbio.2005867] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Revised: 05/01/2018] [Indexed: 12/19/2022] Open
Abstract
The ability to simultaneously process and maintain multiple pieces of information is limited. Over the past 50 years, observational methods have provided a large amount of insight regarding the neural mechanisms that underpin the mental capacity that we refer to as "working memory." More than 20 years ago, a neural coding scheme was proposed for working memory. As a result of technological developments, we can now not only observe but can also influence brain rhythms in humans. Building on these novel developments, we have begun to externally control brain oscillations in order to extend the limits of working memory.
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Affiliation(s)
- Zsolt Turi
- Department of Clinical Neurophysiology, University Medical Center Goettingen, Georg-August University of Goettingen, Goettingen, Germany
| | - Ivan Alekseichuk
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Walter Paulus
- Department of Clinical Neurophysiology, University Medical Center Goettingen, Georg-August University of Goettingen, Goettingen, Germany
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