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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 2024:10.3758/s13415-024-01204-w. [PMID: 39085585 DOI: 10.3758/s13415-024-01204-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [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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2
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Wynn SC, Marshall TR, Nyhus E. Utilizing tACS to enhance memory confidence and EEG to predict individual differences in brain stimulation efficacy. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.27.596015. [PMID: 38854074 PMCID: PMC11160642 DOI: 10.1101/2024.05.27.596015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2024]
Abstract
The information transfer necessary for successful memory retrieval is believed to be mediated by theta and gamma oscillations. These oscillations have been linked to memory processes in electrophysiological studies, which were correlational in nature. In the current study, we used transcranial alternating current stimulation (tACS) to externally modulate brain oscillations to examine its direct effects on memory performance. Participants received sham, theta (4 Hz), and gamma (50 Hz) tACS over frontoparietal regions while retrieving information in a source memory paradigm. Linear regression models were used to investigate the direct effects of oscillatory non-invasive brain stimulation (NIBS) on memory accuracy and confidence. Our results indicate that both theta and gamma tACS altered memory confidence. Specifically, theta tACS seemed to lower the threshold for confidence in retrieved information, while gamma tACS appeared to alter the memory confidence bias. Furthermore, the individual differences in tACS effects could be predicted from electroencephalogram (EEG) measures recorded prior to stimulation, suggesting that EEG could be a useful tool for predicting individual variability in the efficacy of NIBS.
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Affiliation(s)
- Syanah C Wynn
- Neuroimaging Center, Johannes Gutenberg University Medical Center Mainz, Mainz, Germany
- Department of Psychology and Program in Neuroscience, Bowdoin College, Brunswick, ME, United States
- Centre for Human Brain Health, School of Psychology, University of Birmingham, Birmingham, UK
| | - Tom R Marshall
- Centre for Human Brain Health, School of Psychology, University of Birmingham, Birmingham, UK
| | - Erika Nyhus
- Department of Psychology and Program in Neuroscience, Bowdoin College, Brunswick, ME, United States
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3
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Baselgia S, Kasten FH, Herrmann CS, Rasch B, Paβmann S. No Benefit in Memory Performance after Nocturnal Memory Reactivation Coupled with Theta-tACS. Clocks Sleep 2024; 6:211-233. [PMID: 38651390 PMCID: PMC11036246 DOI: 10.3390/clockssleep6020015] [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: 01/12/2024] [Revised: 03/14/2024] [Accepted: 03/19/2024] [Indexed: 04/25/2024] Open
Abstract
Targeted memory reactivation (TMR) is an effective technique to enhance sleep-associated memory consolidation. The successful reactivation of memories by external reminder cues is typically accompanied by an event-related increase in theta oscillations, preceding better memory recall after sleep. However, it remains unclear whether the increase in theta oscillations is a causal factor or an epiphenomenon of successful TMR. Here, we used transcranial alternating current stimulation (tACS) to examine the causal role of theta oscillations for TMR during non-rapid eye movement (non-REM) sleep. Thirty-seven healthy participants learned Dutch-German word pairs before sleep. During non-REM sleep, we applied either theta-tACS or control-tACS (23 Hz) in blocks (9 min) in a randomised order, according to a within-subject design. One group of participants received tACS coupled with TMR time-locked two seconds after the reminder cue (time-locked group). Another group received tACS in a continuous manner while TMR cues were presented (continuous group). Contrary to our predictions, we observed no frequency-specific benefit of theta-tACS coupled with TMR during sleep on memory performance, neither for continuous nor time-locked stimulation. In fact, both stimulation protocols blocked the TMR-induced memory benefits during sleep, resulting in no memory enhancement by TMR in both the theta and control conditions. No frequency-specific effect was found on the power analyses of the electroencephalogram. We conclude that tACS might have an unspecific blocking effect on memory benefits typically observed after TMR during non-REM sleep.
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Affiliation(s)
- Sandrine Baselgia
- Cognitive Biopsychology and Methods, Department of Psychology, Université de Fribourg, 1700 Fribourg, Switzerland;
| | - Florian H. Kasten
- Centre de Recherche Cerveau & Cognition, CNRS & Université Toulouse III Paul Sabatier, 31062 Toulouse, France;
| | - Christoph S. Herrmann
- Experimental Psychology Lab, Department of Psychology, Carl von Ossietzky Universität, 26129 Oldenburg, Germany;
| | - Björn Rasch
- Cognitive Biopsychology and Methods, Department of Psychology, Université de Fribourg, 1700 Fribourg, Switzerland;
| | - Sven Paβmann
- Cognitive Biopsychology and Methods, Department of Psychology, Université de Fribourg, 1700 Fribourg, Switzerland;
- Department of Neurology, University Medicine Greifswald, 17475 Greifswald, Germany
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4
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Wischnewski M, Tran H, Zhao Z, Shirinpour S, Haigh ZJ, Rotteveel J, Perera ND, Alekseichuk I, Zimmermann J, Opitz A. Induced neural phase precession through exogenous electric fields. Nat Commun 2024; 15:1687. [PMID: 38402188 PMCID: PMC10894208 DOI: 10.1038/s41467-024-45898-5] [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: 05/05/2023] [Accepted: 02/06/2024] [Indexed: 02/26/2024] Open
Abstract
The gradual shifting of preferred neural spiking relative to local field potentials (LFPs), known as phase precession, plays a prominent role in neural coding. Correlations between the phase precession and behavior have been observed throughout various brain regions. As such, phase precession is suggested to be a global neural mechanism that promotes local neuroplasticity. However, causal evidence and neuroplastic mechanisms of phase precession are lacking so far. Here we show a causal link between LFP dynamics and phase precession. In three experiments, we modulated LFPs in humans, a non-human primate, and computational models using alternating current stimulation. We show that continuous stimulation of motor cortex oscillations in humans lead to a gradual phase shift of maximal corticospinal excitability by ~90°. Further, exogenous alternating current stimulation induced phase precession in a subset of entrained neurons (~30%) in the non-human primate. Multiscale modeling of realistic neural circuits suggests that alternating current stimulation-induced phase precession is driven by NMDA-mediated synaptic plasticity. Altogether, the three experiments provide mechanistic and causal evidence for phase precession as a global neocortical process. Alternating current-induced phase precession and consequently synaptic plasticity is crucial for the development of novel therapeutic neuromodulation methods.
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Affiliation(s)
- Miles Wischnewski
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, USA.
| | - Harry Tran
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, USA
| | - Zhihe Zhao
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, USA
| | - Sina Shirinpour
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, USA
| | - Zachary J Haigh
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, USA
| | - Jonna Rotteveel
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, USA
| | - Nipun D Perera
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, USA
| | - Ivan Alekseichuk
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, USA
| | - Jan Zimmermann
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, USA
- Department of Neuroscience, University of Minnesota, Minneapolis, MN, USA
- Department of Radiology, Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, USA
| | - Alexander Opitz
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, USA.
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5
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Lee S, Shirinpour S, Alekseichuk I, Perera N, Linn G, Schroeder CE, Falchier AY, Opitz A. Predicting the phase distribution during multi-channel transcranial alternating current stimulation in silico and in vivo. Comput Biol Med 2023; 166:107516. [PMID: 37769460 PMCID: PMC10955626 DOI: 10.1016/j.compbiomed.2023.107516] [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: 06/15/2023] [Revised: 08/22/2023] [Accepted: 09/19/2023] [Indexed: 09/30/2023]
Abstract
BACKGROUND Transcranial alternating current stimulation (tACS) is a widely used noninvasive brain stimulation (NIBS) technique to affect neural activity. TACS experiments have been coupled with computational simulations to predict the electromagnetic fields within the brain. However, existing simulations are focused on the magnitude of the field. As the possibility of inducing the phase gradient in the brain using multiple tACS electrodes arises, a simulation framework is necessary to investigate and predict the phase gradient of electric fields during multi-channel tACS. OBJECTIVE Here, we develop such a framework for phasor simulation using phasor algebra and evaluate its accuracy using in vivo recordings in monkeys. METHODS We extract the phase and amplitude of electric fields from intracranial recordings in two monkeys during multi-channel tACS and compare them to those calculated by phasor analysis using finite element models. RESULTS Our findings demonstrate that simulated phases correspond well to measured phases (r = 0.9). Further, we systematically evaluated the impact of accurate electrode placement on modeling and data agreement. Finally, our framework can predict the amplitude distribution in measurements given calibrated tissues' conductivity. CONCLUSIONS Our validated general framework for simulating multi-phase, multi-electrode tACS provides a streamlined tool for principled planning of multi-channel tACS experiments.
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Affiliation(s)
- Sangjun Lee
- Department of Biomedical Engineering, University of Minnesota, MN, USA.
| | - Sina Shirinpour
- Department of Biomedical Engineering, University of Minnesota, MN, USA
| | - Ivan Alekseichuk
- Department of Biomedical Engineering, University of Minnesota, MN, USA
| | - Nipun Perera
- Department of Biomedical Engineering, University of Minnesota, MN, USA
| | - Gary Linn
- Translational Neuroscience Lab Division, Center for Biomedical Imaging and Neuromodulation, The Nathan S. Kline Institute for Psychiatric Research, Orangeburg, NY, USA; Department of Psychiatry NYU Grossman School of Medicine, New York City, NY, USA
| | - Charles E Schroeder
- Translational Neuroscience Lab Division, Center for Biomedical Imaging and Neuromodulation, The Nathan S. Kline Institute for Psychiatric Research, Orangeburg, NY, USA; Departments of Neurological Surgery and Psychiatry, Columbia University College of Physicians and Surgeons, NY, USA
| | - Arnaud Y Falchier
- Translational Neuroscience Lab Division, Center for Biomedical Imaging and Neuromodulation, The Nathan S. Kline Institute for Psychiatric Research, Orangeburg, NY, USA; Department of Psychiatry NYU Grossman School of Medicine, New York City, NY, USA
| | - Alexander Opitz
- Department of Biomedical Engineering, University of Minnesota, MN, USA.
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6
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Wischnewski M, Tran H, Zhao Z, Shirinpour S, Haigh Z, Rotteveel J, Perera N, Alekseichuk I, Zimmermann J, Opitz A. Induced neural phase precession through exogeneous electric fields. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.31.535073. [PMID: 37034780 PMCID: PMC10081336 DOI: 10.1101/2023.03.31.535073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/20/2023]
Abstract
The gradual shifting of preferred neural spiking relative to local field potentials (LFPs), known as phase precession, plays a prominent role in neural coding. Correlations between the phase precession and behavior have been observed throughout various brain regions. As such, phase precession is suggested to be a global neural mechanism that promotes local neuroplasticity. However, causal evidence and neuroplastic mechanisms of phase precession are lacking so far. Here we show a causal link between LFP dynamics and phase precession. In three experiments, we modulated LFPs in humans, a non-human primate, and computational models using alternating current stimulation. We show that continuous stimulation of motor cortex oscillations in humans lead to a gradual phase shift of maximal corticospinal excitability by ~90°. Further, exogenous alternating current stimulation induced phase precession in a subset of entrained neurons (~30%) in the non-human primate. Multiscale modeling of realistic neural circuits suggests that alternating current stimulation-induced phase precession is driven by NMDA-mediated synaptic plasticity. Altogether, the three experiments provide mechanistic and causal evidence for phase precession as a global neocortical process. Alternating current-induced phase precession and consequently synaptic plasticity is crucial for the development of novel therapeutic neuromodulation methods.
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Affiliation(s)
- M. Wischnewski
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, USA
| | - H. Tran
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, USA
| | - Z. Zhao
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, USA
| | - S. Shirinpour
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, USA
| | - Z.J. Haigh
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, USA
| | - J. Rotteveel
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, USA
| | - N.D. Perera
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, USA
| | - I. Alekseichuk
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, USA
| | - J. Zimmermann
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, USA
- Department of Neuroscience, University of Minnesota, Minneapolis, MN, USA
- Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, USA
| | - A. Opitz
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, USA
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7
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Nissim NR, McAfee DC, Edwards S, Prato A, Lin JX, Lu Z, Coslett HB, Hamilton RH. Efficacy of Transcranial Alternating Current Stimulation in the Enhancement of Working Memory Performance in Healthy Adults: A Systematic Meta-Analysis. Neuromodulation 2023; 26:728-737. [PMID: 36759231 PMCID: PMC10257732 DOI: 10.1016/j.neurom.2022.12.014] [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: 09/23/2022] [Revised: 12/22/2022] [Accepted: 12/29/2022] [Indexed: 02/10/2023]
Abstract
BACKGROUND Transcranial alternating current stimulation (tACS)-a noninvasive brain stimulation technique that modulates cortical oscillations in the brain-has shown the capacity to enhance working memory (WM) abilities in healthy individuals. The efficacy of tACS in the improvement of WM performance in healthy individuals is not yet fully understood. OBJECTIVE/HYPOTHESIS This meta-analysis aimed to systematically evaluate the efficacy of tACS in the enhancement of WM in healthy individuals and to assess moderators of response to stimulation. We hypothesized that active tACS would significantly enhance WM compared with sham. We further hypothesized that it would do so in a task-dependent manner and that differing stimulation parameters would affect response to tACS. MATERIALS AND METHODS Ten tACS studies met the inclusion criteria and provided 32 effects in the overall analysis. Random-effect models assessed mean change scores on WM tasks from baseline to poststimulation. The included studies involved varied in stimulation parameters, between-subject and within-subject study designs, and online vs offline tACS. RESULTS We observed a significant, heterogeneous, and moderate effect size for active tACS in the enhancement of WM performance over sham (Cohen's d = 0.5). Cognitive load, task domain, session number, and stimulation region showed a significant relationship between active tACS and enhanced WM behavior over sham. CONCLUSIONS Our findings indicate that active tACS enhances WM performance in healthy individuals compared with sham. Future randomized controlled trials are needed to further explore key parameters, including personalized stimulation vs standardized electroencephalography frequencies and maintenance of tACS effects, and whether tACS-induced effects translate to populations with WM impairments.
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Affiliation(s)
- Nicole R Nissim
- Laboratory for Cognition and Neural Stimulation, Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA; Moss Rehabilitation Research Institute, Einstein Medical Center, Elkins Park, PA, USA.
| | - Darrian C McAfee
- Laboratory for Cognition and Neural Stimulation, Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Shanna Edwards
- Laboratory for Cognition and Neural Stimulation, Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Amara Prato
- Laboratory for Cognition and Neural Stimulation, Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Jennifer X Lin
- Laboratory for Cognition and Neural Stimulation, Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Zhiye Lu
- Laboratory for Cognition and Neural Stimulation, Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - H Branch Coslett
- Laboratory for Cognition and Neural Stimulation, Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA; Moss Rehabilitation Research Institute, Einstein Medical Center, Elkins Park, PA, USA
| | - Roy H Hamilton
- Laboratory for Cognition and Neural Stimulation, Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA; Moss Rehabilitation Research Institute, Einstein Medical Center, Elkins Park, PA, USA
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8
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Lee S, Shirinpour S, Alekseichuk I, Perera N, Linn G, Schroeder CE, Falchier AY, Opitz A. Experimental validation of computational models for the prediction of phase distribution during multi-channel transcranial alternating current stimulation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.07.536090. [PMID: 37066288 PMCID: PMC10104155 DOI: 10.1101/2023.04.07.536090] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/18/2023]
Abstract
Transcranial alternating current stimulation (tACS) is a widely used noninvasive brain stimulation (NIBS) technique to affect neural activity. Neural oscillations exhibit phase-dependent associations with cognitive functions, and tools to manipulate local oscillatory phases can affect communication across remote brain regions. A recent study demonstrated that multi-channel tACS can generate electric fields with a phase gradient or traveling waves in the brain. Computational simulations using phasor algebra can predict the phase distribution inside the brain and aid in informing parameters in tACS experiments. However, experimental validation of computational models for multi-phase tACS is still lacking. Here, we develop such a framework for phasor simulation and evaluate its accuracy using in vivo recordings in nonhuman primates. We extract the phase and amplitude of electric fields from intracranial recordings in two monkeys during multi-channel tACS and compare them to those calculated by phasor analysis using finite element models. Our findings demonstrate that simulated phases correspond well to measured phases (r = 0.9). Further, we systematically evaluated the impact of accurate electrode placement on modeling and data agreement. Finally, our framework can predict the amplitude distribution in measurements given calibrated tissues’ conductivity. Our validated general framework for simulating multi-phase, multi-electrode tACS provides a streamlined tool for principled planning of multi-channel tACS experiments.
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9
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Wischnewski M, Alekseichuk I, Opitz A. Neurocognitive, physiological, and biophysical effects of transcranial alternating current stimulation. Trends Cogn Sci 2023; 27:189-205. [PMID: 36543610 PMCID: PMC9852081 DOI: 10.1016/j.tics.2022.11.013] [Citation(s) in RCA: 37] [Impact Index Per Article: 37.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Revised: 11/23/2022] [Accepted: 11/26/2022] [Indexed: 12/23/2022]
Abstract
Transcranial alternating current stimulation (tACS) can modulate human neural activity and behavior. Accordingly, tACS has vast potential for cognitive research and brain disorder therapies. The stimulation generates oscillating electric fields in the brain that can bias neural spike timing, causing changes in local neural oscillatory power and cross-frequency and cross-area coherence. tACS affects cognitive performance by modulating underlying single or nested brain rhythms, local or distal synchronization, and metabolic activity. Clinically, stimulation tailored to abnormal neural oscillations shows promising results in alleviating psychiatric and neurological symptoms. We summarize the findings of tACS mechanisms, its use for cognitive applications, and novel developments for personalized stimulation.
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Affiliation(s)
- Miles Wischnewski
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, USA
| | - Ivan Alekseichuk
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, USA.
| | - Alexander Opitz
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, USA.
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10
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Lee TL, Lee H, Kang N. A meta-analysis showing improved cognitive performance in healthy young adults with transcranial alternating current stimulation. NPJ SCIENCE OF LEARNING 2023; 8:1. [PMID: 36593247 PMCID: PMC9807644 DOI: 10.1038/s41539-022-00152-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Accepted: 12/12/2022] [Indexed: 06/17/2023]
Abstract
Transcranial alternating current stimulation (tACS) is a non-invasive brain stimulation used for improving cognitive functions via delivering weak electrical stimulation with a certain frequency. This systematic review and meta-analysis investigated the effects of tACS protocols on cognitive functions in healthy young adults. We identified 56 qualified studies that compared cognitive functions between tACS and sham control groups, as indicated by cognitive performances and cognition-related reaction time. Moderator variable analyses specified effect size according to (a) timing of tACS, (b) frequency band of simulation, (c) targeted brain region, and (b) cognitive domain, respectively. Random-effects model meta-analysis revealed small positive effects of tACS protocols on cognitive performances. The moderator variable analyses found significant effects for online-tACS with theta frequency band, online-tACS with gamma frequency band, and offline-tACS with theta frequency band. Moreover, cognitive performances were improved in online- and offline-tACS with theta frequency band on either prefrontal and posterior parietal cortical regions, and further both online- and offline-tACS with theta frequency band enhanced executive function. Online-tACS with gamma frequency band on posterior parietal cortex was effective for improving cognitive performances, and the cognitive improvements appeared in executive function and perceptual-motor function. These findings suggested that tACS protocols with specific timing and frequency band may effectively improve cognitive performances.
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Affiliation(s)
- Tae Lee Lee
- Department of Human Movement Science, Incheon National University, Incheon, South Korea
- Neuromechanical Rehabilitation Research Laboratory, Incheon National University, Incheon, South Korea
| | - Hanall Lee
- Department of Human Movement Science, Incheon National University, Incheon, South Korea
- Neuromechanical Rehabilitation Research Laboratory, Incheon National University, Incheon, South Korea
| | - Nyeonju Kang
- Department of Human Movement Science, Incheon National University, Incheon, South Korea.
- Neuromechanical Rehabilitation Research Laboratory, Incheon National University, Incheon, South Korea.
- Division of Sport Science & Sport Science Institute, Incheon National University, Incheon, South Korea.
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11
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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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12
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The application of the spot the difference teaching method in clinical skills training for residents. BMC MEDICAL EDUCATION 2022; 22:542. [PMID: 35836172 PMCID: PMC9281025 DOI: 10.1186/s12909-022-03612-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/10/2021] [Accepted: 07/08/2022] [Indexed: 02/08/2023]
Abstract
BACKGROUND Clinical skill training (CST) is indispensable for first-year surgical residents. It can usually be carried out through video-based flipped learning (FL) within a web-based learning environment. However, we found that residents lack the process of reflection, blindly imitating results in losing interest and passion for learning in the traditional teaching pattern. The teaching method of "spot the difference" (SDTM), which is based on the fundamentals of the popular game of "spot the difference," is designed to improve students' participation and reflective learning during skill training. This study aimed to evaluate this novel educational model's short-term and long-term effectiveness for surgical residents in China. METHODS First-year residents who required a three-month rotation in the head and neck surgery department were recruited to participate in a series of CSTs. They were randomized into SDTM and traditional FL (control) groups. Clinical skill performance was assessed with validated clinical skill scoring criteria. Evaluations were conducted by comparing the scores that contain departmental rotation skill examinations and the first China medical licensing examination (CMLE) performance on practical skills. In addition, two-way subjective evaluations were also implemented as a reference for the training results. Training effects were assessed using t tests, Mann-Whitney-Wilcoxon tests, chi-square tests, and Cohen' s effect size (d). The Cohen' s d value was considered to be small (<0.2), medium (0.2-0.8), or large (>0.8). RESULTS The SDTM group was significantly superior to the control group in terms of after-department skill examination (t=2.179, p<0.05, d=0.5), taking medical history (t=2.665, p<0.05, d=0.59), and CMLE performance on practical skill (t=2.103, p<0.05, d=0.47). The SDTM members rated the curriculum more highly than the control on the items relating to interestingness and participation (p < 0.05) with large effect sizes (d >0.8). There were no significant differences between the two groups on clinical competence (t=0.819, p=0.415, d=0.18), the first-time pass rate for CMLE (χ2 =1.663, p=0.197, d=0.29), and short-term operational skills improvement (t=1.747, p=0.084, d=0.39). CONCLUSIONS SDTM may be an effective method for enhancing residents' clinical skills, and the effect is significant both short- and long-term. The improvement effect seemed to be more significant in the peer-involved SDTM than training alone. However, despite positive objective results, SDTM still risks student learning burnout. TRIAL REGISTRATION ISRCTN registry, ISRCTN10598469 , 02/04/2022,retrospectively registered.
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Personalized Frequency Modulated Transcranial Electrical Stimulation for Associative Memory Enhancement. Brain Sci 2022; 12:brainsci12040472. [PMID: 35448003 PMCID: PMC9025454 DOI: 10.3390/brainsci12040472] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2022] [Revised: 03/28/2022] [Accepted: 03/28/2022] [Indexed: 12/25/2022] Open
Abstract
Associative memory (AM) is the ability to remember the relationship between previously unrelated items. AM is significantly affected by normal aging and neurodegenerative conditions, thus there is a growing interest in applying non-invasive brain stimulation (NIBS) techniques for AM enhancement. A growing body of studies identifies posterior parietal cortex (PPC) as the most promising cortical target for both transcranial magnetic stimulation (TMS) and transcranial electrical stimulation (tES) to modulate a cortico-hippocampal network that underlines AM. In that sense, theta frequency oscillatory tES protocols, targeted towards the hallmark oscillatory activity within the cortico-hippocampal network, are increasingly coming to prominence. To increase precision and effectiveness, the need for EEG guided individualization of the tES protocols is proposed. Here, we present the study protocol in which two types of personalized oscillatory tES–transcranial alternating current stimulation (tACS) and oscillatory transcranial direct current stimulation (otDCS), both frequency-modulated to the individual theta-band frequency (ITF), are compared to the non-oscillatory transcranial direct current stimulation (tDCS) and to the sham stimulation. The study has cross-over design with four tES conditions (tACS, otDCS, tDCS, sham), and the comprehensive set of neurophysiological (resting state EEG and AM-evoked EEG) and behavioral outcomes, including AM tasks (short-term associative memory, face–word, face–object, object-location), as well as measures of other cognitive functions (cognitive control, verbal fluency, and working memory).
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14
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Wynn SC, Nyhus E. Brain activity patterns underlying memory confidence. Eur J Neurosci 2022; 55:1774-1797. [PMID: 35304774 PMCID: PMC9314063 DOI: 10.1111/ejn.15649] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 02/15/2022] [Accepted: 03/14/2022] [Indexed: 11/26/2022]
Abstract
The primary aim of this review is to examine the brain activity patterns that are related to subjectively perceived memory confidence. We focus on the main brain regions involved in episodic memory: the medial temporal lobe (MTL), prefrontal cortex (PFC), and posterior parietal cortex (PPC), and relate activity in their subregions to memory confidence. How this brain activity in both the encoding and retrieval phase is related to (subsequent) memory confidence ratings will be discussed. Specifically, encoding related activity in MTL regions and ventrolateral PFC mainly shows a positive linear increase with subsequent memory confidence, while dorsolateral and ventromedial PFC activity show mixed patterns. In addition, encoding-related PPC activity seems to only have indirect effects on memory confidence ratings. Activity during retrieval in both the hippocampus and parahippocampal cortex increases with memory confidence, especially during high-confident recognition. Retrieval-related activity in the PFC and PPC show mixed relationships with memory confidence, likely related to post-retrieval monitoring and attentional processes, respectively. In this review, these MTL, PFC, and PPC activity patterns are examined in detail and related to their functional roles in memory processes. This insight into brain activity that underlies memory confidence is important for our understanding of brain-behaviour relations and memory-guided decision making.
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Affiliation(s)
- Syanah C Wynn
- Department of Psychology and Program in Neuroscience, Bowdoin College, Brunswick, ME, United States
| | - Erika Nyhus
- Department of Psychology and Program in Neuroscience, Bowdoin College, Brunswick, ME, United States
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15
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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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16
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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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17
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Benussi A, Cantoni V, Cotelli MS, Cotelli M, Brattini C, Datta A, Thomas C, Santarnecchi E, Pascual-Leone A, Borroni B. Exposure to gamma tACS in Alzheimer's disease: A randomized, double-blind, sham-controlled, crossover, pilot study. Brain Stimul 2021; 14:531-540. [PMID: 33762220 DOI: 10.1016/j.brs.2021.03.007] [Citation(s) in RCA: 58] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Revised: 03/05/2021] [Accepted: 03/11/2021] [Indexed: 12/12/2022] Open
Abstract
OBJECTIVE To assess whether exposure to non-invasive brain stimulation with transcranial alternating current stimulation at γ frequency (γ-tACS) applied over Pz (an area overlying the medial parietal cortex and the precuneus) can improve memory and modulate cholinergic transmission in mild cognitive impairment due to Alzheimer's disease (MCI-AD). METHODS In this randomized, double-blind, sham controlled, crossover pilot study, participants were assigned to a single 60 min treatment with exposure to γ-tACS over Pz or sham tACS. Each subject underwent a clinical evaluation including assessment of episodic memory pre- and post-γ-tACS or sham stimulation. Indirect measures of cholinergic transmission evaluated using transcranial magnetic stimulation (TMS) pre- and post-γ-tACS or sham tACS were evaluated. RESULTS Twenty MCI-AD participants completed the study. No tACS-related side effects were observed, and the intervention was well tolerated in all participants. We observed a significant improvement at the Rey auditory verbal learning (RAVL) test total recall (5.7 [95% CI, 4.0 to 7.4], p < 0.001) and long delayed recall scores (1.3 [95% CI, 0.4 to 2.1], p = 0.007) after γ-tACS but not after sham tACS. Face-name associations scores improved during γ-tACS (4.3 [95% CI, 2.8 to 5.8], p < 0.001) but not after sham tACS. Short latency afferent inhibition, an indirect measure of cholinergic transmission evaluated with TMS, increased only after γ-tACS (0.31 [95% CI, 0.24 to 0.38], p < 0.001) but not after sham tACS. CONCLUSIONS exposure to γ-tACS over Pz showed a significant improvement of memory performances, along with restoration of intracortical connectivity measures of cholinergic neurotransmission, compared to sham tACS.
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Affiliation(s)
- Alberto Benussi
- Neurology Unit, Department of Clinical and Experimental Sciences, University of Brescia, Brescia, Italy; Neurology Unit, Department of Neurological and Vision Sciences, ASST Spedali Civili, Brescia, Italy
| | - Valentina Cantoni
- Neurology Unit, Department of Clinical and Experimental Sciences, University of Brescia, Brescia, Italy
| | | | - Maria Cotelli
- Neuropsychology Unit, IRCCS Istituto Centro San Giovanni di Dio Fatebenefratelli, Brescia, Italy
| | - Chiara Brattini
- Neurology Unit, Department of Neurological and Vision Sciences, ASST Spedali Civili, Brescia, Italy
| | - Abhishek Datta
- Research & Development, Soterix Medical, Inc., New York, USA
| | - Chris Thomas
- Research & Development, Soterix Medical, Inc., New York, USA
| | - Emiliano Santarnecchi
- Berenson-Allen Center for Non-Invasive Brain Stimulation, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA; Department of Neurology, Harvard Medical School, Boston, MA, USA
| | - Alvaro Pascual-Leone
- Department of Neurology, Harvard Medical School, Boston, MA, USA; Hinda and Arthur Marcus Institute for Aging Research and Center for Memory Health, Hebrew SeniorLife, Boston, MA, USA; Guttmann Brain Health Institut, Institut Guttmann, Universitat Autonoma Barcelona, Spain
| | - Barbara Borroni
- Neurology Unit, Department of Clinical and Experimental Sciences, University of Brescia, Brescia, Italy; Neurology Unit, Department of Neurological and Vision Sciences, ASST Spedali Civili, Brescia, Italy.
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18
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Vulić K, Bjekić J, Paunović D, Jovanović M, Milanović S, Filipović SR. Theta-modulated oscillatory transcranial direct current stimulation over posterior parietal cortex improves associative memory. Sci Rep 2021; 11:3013. [PMID: 33542344 PMCID: PMC7862221 DOI: 10.1038/s41598-021-82577-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Accepted: 01/19/2021] [Indexed: 01/30/2023] Open
Abstract
Associative memory (AM) reflects the ability to remember and retrieve multiple pieces of information bound together thus enabling complex episodic experiences. Despite growing interest in the use of transcranial direct current stimulation (tDCS) for the modulation of AM, there are inconsistent evidence regarding its benefits. An alternative to standard constant tDCS could be the application of frequency-modulated tDCS protocols, that mimic natural function-relevant brain rhythms. Here, we show the effects of anodal tDCS oscillating in theta rhythm (5 Hz; 1.5 ± 0.1 mA) versus constant anodal tDCS and sham over left posterior parietal cortex on cued recall of face-word associations. In a crossover design, each participant completed AM assessment immediately following 20-min theta-oscillatory, constant, and sham tDCS, as well as 1 and 5 days after. Theta oscillatory tDCS increased initial AM performance in comparison to sham, and so did constant tDCS. On the group level, no differences between oscillatory and constant tDCS were observed, but individual-level analysis revealed that some participants responded to theta-oscillatory but not to constant tDCS, and vice versa, which could be attributed to their different physiological modes of action. This study shows the potential of oscillatory tDCS protocols for memory enhancement to produce strong and reliable memory-modulating effects which deserve to be investigated further.
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Affiliation(s)
- Katarina Vulić
- grid.7149.b0000 0001 2166 9385Department for Human Neuroscience, Institute for Medical Research, University of Belgrade, Belgrade, Serbia
| | - Jovana Bjekić
- grid.7149.b0000 0001 2166 9385Department for Human Neuroscience, Institute for Medical Research, University of Belgrade, Belgrade, Serbia
| | - Dunja Paunović
- grid.7149.b0000 0001 2166 9385Department for Human Neuroscience, Institute for Medical Research, University of Belgrade, Belgrade, Serbia
| | - Miloš Jovanović
- grid.445141.1The School of Computing, Union University, Belgrade, Serbia
| | - Slađan Milanović
- grid.7149.b0000 0001 2166 9385Department for Biomedical Engineering and Biophysics, Institute for Medical Research, University of Belgrade, Belgrade, Serbia
| | - Saša R. Filipović
- grid.7149.b0000 0001 2166 9385Department for Human Neuroscience, Institute for Medical Research, University of Belgrade, Belgrade, Serbia
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19
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Ergo K, De Loof E, Debra G, Pastötter B, Verguts T. Failure to modulate reward prediction errors in declarative learning with theta (6 Hz) frequency transcranial alternating current stimulation. PLoS One 2020; 15:e0237829. [PMID: 33270685 PMCID: PMC7714179 DOI: 10.1371/journal.pone.0237829] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Accepted: 11/18/2020] [Indexed: 12/26/2022] Open
Abstract
Recent evidence suggests that reward prediction errors (RPEs) play an important role in declarative learning, but its neurophysiological mechanism remains unclear. Here, we tested the hypothesis that RPEs modulate declarative learning via theta-frequency oscillations, which have been related to memory encoding in prior work. For that purpose, we examined the interaction between RPE and transcranial Alternating Current Stimulation (tACS) in declarative learning. Using a between-subject (real versus sham stimulation group), single-blind stimulation design, 76 participants learned 60 Dutch-Swahili word pairs, while theta-frequency (6 Hz) tACS was administered over the medial frontal cortex (MFC). Previous studies have implicated MFC in memory encoding. We replicated our previous finding of signed RPEs (SRPEs) boosting declarative learning; with larger and more positive RPEs enhancing memory performance. However, tACS failed to modulate the SRPE effect in declarative learning and did not affect memory performance. Bayesian statistics supported evidence for an absence of effect. Our study confirms a role of RPE in declarative learning, but also calls for standardized procedures in transcranial electrical stimulation.
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Affiliation(s)
- Kate Ergo
- Department of Experimental Psychology, Ghent University, Ghent, Belgium
| | - Esther De Loof
- Department of Experimental Psychology, Ghent University, Ghent, Belgium
| | - Gillian Debra
- Department of Experimental Psychology, Ghent University, Ghent, Belgium
| | | | - Tom Verguts
- Department of Experimental Psychology, Ghent University, Ghent, Belgium
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20
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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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21
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Johnson L, Alekseichuk I, Krieg J, Doyle A, Yu Y, Vitek J, Johnson M, Opitz A. Dose-dependent effects of transcranial alternating current stimulation on spike timing in awake nonhuman primates. SCIENCE ADVANCES 2020; 6:eaaz2747. [PMID: 32917605 PMCID: PMC7467690 DOI: 10.1126/sciadv.aaz2747] [Citation(s) in RCA: 108] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Accepted: 07/16/2020] [Indexed: 05/07/2023]
Abstract
Weak extracellular electric fields can influence spike timing in neural networks. Approaches to noninvasively impose these fields on the brain have high therapeutic potential in neurology and psychiatry. Transcranial alternating current stimulation (TACS) is hypothesized to affect spike timing and cause neural entrainment. However, the conditions under which these effects occur in vivo are unknown. Here, we recorded single-unit activity in the neocortex in awake nonhuman primates during TACS and found dose-dependent neural entrainment to the stimulation waveform. Cluster analysis of changes in interspike intervals identified two main types of neural responses to TACS-increased burstiness and phase entrainment. Our results uncover key mechanisms of TACS and show that the stimulation affects spike timing in the awake primate brain at intensities feasible in humans. Thus, novel TACS protocols tailored to ongoing brain activity may be a tool to normalize spike timing in maladaptive brain networks and neurological disease.
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Affiliation(s)
- Luke Johnson
- Department of Neurology, University of Minnesota, Minneapolis, MN 55455, USA
| | - Ivan Alekseichuk
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN 55455, USA
| | - Jordan Krieg
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN 55455, USA
| | - Alex Doyle
- Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA
| | - Ying Yu
- Department of Neurology, University of Minnesota, Minneapolis, MN 55455, USA
| | - Jerrold Vitek
- Department of Neurology, University of Minnesota, Minneapolis, MN 55455, USA
| | - Matthew Johnson
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN 55455, USA
| | - Alexander Opitz
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN 55455, USA.
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