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Millard SK, Speis DB, Skippen P, Chiang AKI, Chang WJ, Lin AJ, Furman AJ, Mazaheri A, Seminowicz DA, Schabrun SM. Can non-invasive brain stimulation modulate peak alpha frequency in the human brain? A systematic review and meta-analysis. Eur J Neurosci 2024; 60:4182-4200. [PMID: 38779808 DOI: 10.1111/ejn.16424] [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: 11/13/2023] [Revised: 04/18/2024] [Accepted: 05/06/2024] [Indexed: 05/25/2024]
Abstract
Peak alpha frequency (PAF), the dominant oscillatory frequency within the alpha range (8-12 Hz), is associated with cognitive function and several neurological conditions, including chronic pain. Manipulating PAF could offer valuable insight into the relationship between PAF and various functions and conditions, potentially providing new treatment avenues. This systematic review aimed to comprehensively synthesise effects of non-invasive brain stimulation (NIBS) on PAF speed. Relevant studies assessing PAF pre- and post-NIBS in healthy adults were identified through systematic searches of electronic databases (Embase, PubMed, PsychINFO, Scopus, The Cochrane Library) and trial registers. The Cochrane risk-of-bias tool was employed for assessing study quality. Quantitative analysis was conducted through pairwise meta-analysis when possible; otherwise, qualitative synthesis was performed. The review protocol was registered with PROSPERO (CRD42020190512) and the Open Science Framework (https://osf.io/2yaxz/). Eleven NIBS studies were included, all with a low risk-of-bias, comprising seven transcranial alternating current stimulation (tACS), three repetitive transcranial magnetic stimulation (rTMS), and one transcranial direct current stimulation (tDCS) study. Meta-analysis of active tACS conditions (eight conditions from five studies) revealed no significant effects on PAF (mean difference [MD] = -0.12, 95% CI = -0.32 to 0.08, p = 0.24). Qualitative synthesis provided no evidence that tDCS altered PAF and moderate evidence for transient increases in PAF with 10 Hz rTMS. However, it is crucial to note that small sample sizes were used, there was substantial variation in stimulation protocols, and most studies did not specifically target PAF alteration. Further studies are needed to determine NIBS's potential for modulating PAF.
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Affiliation(s)
- Samantha K Millard
- Faculty of Medicine, Wallace Wurth Building, University of New South Wales (UNSW), Kensington, NSW, Australia
- Centre for Pain IMPACT, Neuroscience Research Australia (NeuRA), Sydney, NSW, Australia
| | - Darrah B Speis
- Department of Neural and Pain Sciences, University of Maryland School of Dentistry, Baltimore, MD, USA
- Center to Advance Chronic Pain Research, University of Maryland Baltimore, Baltimore, MD, USA
| | - Patrick Skippen
- Centre for Pain IMPACT, Neuroscience Research Australia (NeuRA), Sydney, NSW, Australia
- Hunter Medical Research Institute, Newcastle, NSW, Australia
- School of Medicine and Public Health, College of Health, Medicine and Wellbeing, University of Newcastle, Callaghan, NSW, Australia
| | - Alan K I Chiang
- Faculty of Medicine, Wallace Wurth Building, University of New South Wales (UNSW), Kensington, NSW, Australia
- Centre for Pain IMPACT, Neuroscience Research Australia (NeuRA), Sydney, NSW, Australia
| | - Wei-Ju Chang
- Centre for Pain IMPACT, Neuroscience Research Australia (NeuRA), Sydney, NSW, Australia
- School of Health Science, College of Health, Medicine and Wellbeing, University of Newcastle, Callaghan, NSW, Australia
| | - Andrew J Lin
- Centre for Pain IMPACT, Neuroscience Research Australia (NeuRA), Sydney, NSW, Australia
| | - Andrew J Furman
- Department of Neural and Pain Sciences, University of Maryland School of Dentistry, Baltimore, MD, USA
- Center to Advance Chronic Pain Research, University of Maryland Baltimore, Baltimore, MD, USA
- Department of Radiology and Nuclear Medicine, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Ali Mazaheri
- School of Psychology, University of Birmingham, Birmingham, UK
- Centre for Human Brain Health (CHBH), University of Birmingham, Birmingham, UK
| | - David A Seminowicz
- Centre for Pain IMPACT, Neuroscience Research Australia (NeuRA), Sydney, NSW, Australia
- Department of Neural and Pain Sciences, University of Maryland School of Dentistry, Baltimore, MD, USA
- Center to Advance Chronic Pain Research, University of Maryland Baltimore, Baltimore, MD, USA
- Department of Medical Biophysics, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Siobhan M Schabrun
- Centre for Pain IMPACT, Neuroscience Research Australia (NeuRA), Sydney, NSW, Australia
- School of Physical Therapy, University of Western Ontario, London, Ontario, Canada
- The Gray Centre for Mobility and Activity, Parkwood Institute, London, Ontario, Canada
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2
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Chen L, Jiang Y. Distinct Contributions of Alpha and Beta Oscillations to Context-Dependent Visual Size Perception. Neurosci Bull 2024:10.1007/s12264-024-01257-4. [PMID: 39078596 DOI: 10.1007/s12264-024-01257-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Accepted: 03/15/2024] [Indexed: 07/31/2024] Open
Abstract
Previous studies have proposed two cognitive mechanisms responsible for the Ebbinghaus illusion effect, i.e., contour interaction and size contrast. However, the neural underpinnings of these two mechanisms are largely unexplored. The present study introduced binocular depth to the Ebbinghaus illusion configuration and made the central target appear either in front of or behind the surrounding inducers in order to disturb size contrast instead of contour interaction. The results showed that the illusion effect, though persisted, was significantly reduced under the binocular depth conditions. Notably, the target with a larger perceived size reduced early alpha-band power (8-13 Hz, 0-100 ms after stimulus onset) at centroparietal sites irrespective of the relative depth of the target and the inducers, with the parietal alpha power negatively correlated with the illusion effect. Moreover, the target with a larger perceived size increased the occipito-parietal beta-band power (14-25 Hz, 200-300 ms after stimulus onset) under the no-depth condition, and the beta power was positively correlated with the illusion effect when the depth conditions were subtracted from the no-depth condition. The findings provided neurophysiological evidence in favor of the two cognitive mechanisms of the Ebbinghaus illusion by revealing that early alpha power is associated with low-level contour interaction and late beta power is linked to high-level size contrast, supporting the claim that neural oscillations at distinct frequency bands dynamically support different aspects of visual processing.
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Affiliation(s)
- Lihong Chen
- State Key Laboratory of Brain and Cognitive Science, Institute of Psychology, Chinese Academy of Sciences, Beijing, 100101, China
- Department of Psychology, University of Chinese Academy of Sciences, Beijing, 100049, China
- Research Center of Brain and Cognitive Neuroscience, Liaoning Normal University, Dalian, 116029, China
- Key Laboratory of Brain and Cognitive Neuroscience, Dalian, 116029, Liaoning Province, China
| | - Yi Jiang
- State Key Laboratory of Brain and Cognitive Science, Institute of Psychology, Chinese Academy of Sciences, Beijing, 100101, China.
- Department of Psychology, University of Chinese Academy of Sciences, Beijing, 100049, China.
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Jensen O. Distractor inhibition by alpha oscillations is controlled by an indirect mechanism governed by goal-relevant information. COMMUNICATIONS PSYCHOLOGY 2024; 2:36. [PMID: 38665356 PMCID: PMC11041682 DOI: 10.1038/s44271-024-00081-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/19/2023] [Accepted: 03/25/2024] [Indexed: 04/28/2024]
Abstract
The role of alpha oscillations (8-13 Hz) in cognition is intensively investigated. While intracranial animal recordings demonstrate that alpha oscillations are associated with decreased neuronal excitability, it is been questioned whether alpha oscillations are under direct control from frontoparietal areas to suppress visual distractors. We here point to a revised mechanism in which alpha oscillations are controlled by an indirect mechanism governed by the load of goal-relevant information - a view compatible with perceptual load theory. We will outline how this framework can be further tested and discuss the consequences for network dynamics and resource allocation in the working brain.
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Affiliation(s)
- Ole Jensen
- Centre for Human Brain Health, School of Psychology, University of Birmingham, Birmingham, B152TT UK
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Zhao Z, Shirinpour S, Tran H, Wischnewski M, Opitz A. intensity- and frequency-specific effects of transcranial alternating current stimulation are explained by network dynamics. J Neural Eng 2024; 21:026024. [PMID: 38530297 DOI: 10.1088/1741-2552/ad37d9] [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: 09/19/2023] [Accepted: 03/26/2024] [Indexed: 03/27/2024]
Abstract
Objective. Transcranial alternating current stimulation (tACS) can be used to non-invasively entrain neural activity and thereby cause changes in local neural oscillatory power. Despite its increased use in cognitive and clinical neuroscience, the fundamental mechanisms of tACS are still not fully understood.Approach. We developed a computational neuronal network model of two-compartment pyramidal neurons (PY) and inhibitory interneurons, which mimic the local cortical circuits. We modeled tACS with electric field strengths that are achievable in human applications. We then simulated intrinsic network activity and measured neural entrainment to investigate how tACS modulates ongoing endogenous oscillations.Main results. The intensity-specific effects of tACS are non-linear. At low intensities (<0.3 mV mm-1), tACS desynchronizes neural firing relative to the endogenous oscillations. At higher intensities (>0.3 mV mm-1), neurons are entrained to the exogenous electric field. We then further explore the stimulation parameter space and find that the entrainment of ongoing cortical oscillations also depends on stimulation frequency by following an Arnold tongue. Moreover, neuronal networks can amplify the tACS-induced entrainment via synaptic coupling and network effects. Our model shows that PY are directly entrained by the exogenous electric field and drive the inhibitory neurons.Significance. The results presented in this study provide a mechanistic framework for understanding the intensity- and frequency-specific effects of oscillating electric fields on neuronal networks. This is crucial for rational parameter selection for tACS in cognitive studies and clinical applications.
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Affiliation(s)
- Zhihe Zhao
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, United States of America
| | - Sina Shirinpour
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, United States of America
| | - Harry Tran
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, United States of America
| | - Miles Wischnewski
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, United States of America
| | - Alexander Opitz
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, United States of America
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Fresnoza S, Ischebeck A. Probing Our Built-in Calculator: A Systematic Narrative Review of Noninvasive Brain Stimulation Studies on Arithmetic Operation-Related Brain Areas. eNeuro 2024; 11:ENEURO.0318-23.2024. [PMID: 38580452 PMCID: PMC10999731 DOI: 10.1523/eneuro.0318-23.2024] [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: 08/25/2023] [Revised: 02/06/2024] [Accepted: 02/26/2024] [Indexed: 04/07/2024] Open
Abstract
This systematic review presented a comprehensive survey of studies that applied transcranial magnetic stimulation and transcranial electrical stimulation to parietal and nonparietal areas to examine the neural basis of symbolic arithmetic processing. All findings were compiled with regard to the three assumptions of the triple-code model (TCM) of number processing. Thirty-seven eligible manuscripts were identified for review (33 with healthy participants and 4 with patients). Their results are broadly consistent with the first assumption of the TCM that intraparietal sulcus both hold a magnitude code and engage in operations requiring numerical manipulations such as subtraction. However, largely heterogeneous results conflicted with the second assumption of the TCM that the left angular gyrus subserves arithmetic fact retrieval, such as the retrieval of rote-learned multiplication results. Support is also limited for the third assumption of the TCM, namely, that the posterior superior parietal lobule engages in spatial operations on the mental number line. Furthermore, results from the stimulation of brain areas outside of those postulated by the TCM show that the bilateral supramarginal gyrus is involved in online calculation and retrieval, the left temporal cortex in retrieval, and the bilateral dorsolateral prefrontal cortex and cerebellum in online calculation of cognitively demanding arithmetic problems. The overall results indicate that multiple cortical areas subserve arithmetic skills.
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Affiliation(s)
- Shane Fresnoza
- Department of Psychology, University of Graz, 8010 Graz, Austria
- BioTechMed, 8010 Graz, Austria
| | - Anja Ischebeck
- Department of Psychology, University of Graz, 8010 Graz, Austria
- BioTechMed, 8010 Graz, Austria
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Deng X, Chen X, Li Y, Zhang B, Xu W, Wang J, Zang Y, Dong Q, Chen C, Li J. Online and offline effects of parietal 10 Hz repetitive transcranial magnetic stimulation on working memory in healthy controls. Hum Brain Mapp 2024; 45:e26636. [PMID: 38488458 PMCID: PMC10941606 DOI: 10.1002/hbm.26636] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Revised: 10/30/2023] [Accepted: 02/12/2024] [Indexed: 03/18/2024] Open
Abstract
Parietal alpha activity shows a specific pattern of phasic changes during working memory. It decreases during the encoding and recall phases but increases during the maintenance phase. This study tested whether online rTMS delivered to the parietal cortex during the maintenance phase of a working memory task would increase alpha activity and hence improve working memory. Then, 46 healthy volunteers were randomly assigned to two groups to receive 3-day parietal 10 Hz online rTMS (either real or sham, 3600 pulses in total) that were time-locked to the maintenance phase of a spatial span task (180 trials in total). Behavioral performance on another spatial span task and EEG signals during a change detection task were recorded on the day before the first rTMS (pretest) and the day after the last rTMS (posttest). We found that rTMS improved performance on both online and offline spatial span tasks. For the offline change detection task, rTMS enhanced alpha activity within the maintenance phase and improved interference control of working memory at both behavioral (K score) and neural (contralateral delay activity) levels. These results suggested that rTMS with alpha frequency time-locked to the maintenance phase is a promising way to boost working memory.
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Affiliation(s)
- Xinping Deng
- State Key Laboratory of Cognitive Neuroscience and Learning & IDG/McGovern Institute for Brain ResearchBeijing Normal UniversityBeijingP.R. China
| | - Xiongying Chen
- The National Clinical Research Center for Mental Disorders & Beijing Key Laboratory of Mental Disorders & the Advanced Innovation Center for Human Brain Protection, Beijing Anding Hospital, School of Mental HealthCapital Medical UniversityBeijingChina
| | - Yang Li
- State Key Laboratory of Cognitive Neuroscience and Learning & IDG/McGovern Institute for Brain ResearchBeijing Normal UniversityBeijingP.R. China
| | - Bofan Zhang
- State Key Laboratory of Cognitive Neuroscience and Learning & IDG/McGovern Institute for Brain ResearchBeijing Normal UniversityBeijingP.R. China
| | - Wending Xu
- State Key Laboratory of Cognitive Neuroscience and Learning & IDG/McGovern Institute for Brain ResearchBeijing Normal UniversityBeijingP.R. China
| | - Jue Wang
- Institute of Sports Medicine and HealthChengdu Sport UniversityChengduChina
| | - Yu‐Feng Zang
- Institute of Psychological SciencesHangzhou Normal UniversityHangzhouChina
- Center for Cognition and Brain DisordersHangzhou Normal University Affiliated HospitalHangzhouChina
| | - Qi Dong
- State Key Laboratory of Cognitive Neuroscience and Learning & IDG/McGovern Institute for Brain ResearchBeijing Normal UniversityBeijingP.R. China
| | - Chuansheng Chen
- Department of Psychological ScienceUniversity of CaliforniaIrvineCaliforniaUSA
| | - Jun Li
- State Key Laboratory of Cognitive Neuroscience and Learning & IDG/McGovern Institute for Brain ResearchBeijing Normal UniversityBeijingP.R. China
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Trajkovic J, Sack AT, Romei V. EEG-based biomarkers predict individual differences in TMS-induced entrainment of intrinsic brain rhythms. Brain Stimul 2024; 17:224-232. [PMID: 38428585 DOI: 10.1016/j.brs.2024.02.016] [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: 10/26/2023] [Revised: 02/23/2024] [Accepted: 02/24/2024] [Indexed: 03/03/2024] Open
Abstract
BACKGROUND Entrainment (increase) and modulation (shift) of intrinsic brain oscillations via rhythmic-TMS (rh-TMS) enables to either increase the amplitude of the individual peak oscillatory frequency, or experimentally slowing/accelerating this intrinsic peak oscillatory frequency by slightly shifting it. Both entrainment, and modulation of brain oscillations can lead to different measurable perceptual and cognitive changes. However, there are noticeable between-participant differences in such experimental entrainment outcomes. OBJECTIVE/HYPOTHESIS The current study aimed at explaining these inter-individual differences in entrainment/frequency shift success. Here we hypothesize that the width and the height of the Arnold tongue, i.e., the frequency offsets that can still lead to oscillatory change, can be individually modelled via resting-state neural markers, and may explain and predict efficacy and limitation of successful rhythmic-TMS (rh-TMS) manipulation. METHODS Spectral decomposition of resting-state data was used to extract the spectral curve of alpha activity, serving as a proxy of an individual Arnold tongue. These parameters were then used as predictors of the rh-TMS outcome, when increasing alpha-amplitude (i.e., applying pulse train tuned to the individual alpha frequency, IAF), or modulating the alpha-frequency (i.e., making alpha faster or slower by stimulating at IAF±1Hz frequencies). RESULTS Our results showed that the height of the at-rest alpha curve predicted how well the entrainment increased the intrinsic oscillatory peak frequency, with a higher at-rest spectral curve negatively predicting amplitude-enhancement during entrainment selectively during IAF-stimulation. In contrast, the wider the resting-state alpha curve, the higher the modulation effects aiming to shift the intrinsic frequency towards faster or slower rhythms. CONCLUSION These results not only offer a theoretical and experimental model for explaining the variance across different rh-TMS studies reporting heterogenous rh-TMS outcomes, but also introduce a potential biomarker and corresponding evaluative tool to develop most optimal and personalized rh-TMS protocols, both in research and clinical applications.
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Affiliation(s)
- Jelena Trajkovic
- Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, 6229 ER, the Netherlands; Centro studi e ricerche in Neuroscienze Cognitive, Dipartimento di Psicologia, Alma Mater Studiorum - Università di Bologna, Campus di Cesena, Cesena, 47521, Italy.
| | - Alexander T Sack
- Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, 6229 ER, the Netherlands
| | - Vincenzo Romei
- Centro studi e ricerche in Neuroscienze Cognitive, Dipartimento di Psicologia, Alma Mater Studiorum - Università di Bologna, Campus di Cesena, Cesena, 47521, Italy; Facultad de Lenguas y Educación, Universidad Antonio de Nebrija, Madrid, 28015, Spain.
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8
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Landry M, da Silva Castanheira J, Raz A, Baillet S, Sackur J. A lateralized alpha-band marker of the interference of exogenous attention over endogenous attention. Cereb Cortex 2024; 34:bhad457. [PMID: 38044466 PMCID: PMC10793586 DOI: 10.1093/cercor/bhad457] [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: 08/28/2023] [Revised: 10/27/2023] [Accepted: 10/27/2023] [Indexed: 12/05/2023] Open
Abstract
Current theories of attention differentiate exogenous from endogenous orienting of visuospatial attention. While both forms of attention orienting engage different functional systems, endogenous and exogenous attention are thought to share resources, as shown by empirical evidence of their functional interactions. The present study aims to uncover the neurobiological basis of how salient events that drive exogenous attention disrupts endogenous attention processes. We hypothesize that interference from exogenous attention over endogenous attention involves alpha-band activity, a neural marker of visuospatial attention. To test this hypothesis, we contrast the effects of endogenous attention across two experimental tasks while we recorded electroencephalography (n = 32, both sexes): a single cueing task where endogenous attention is engaged in isolation, and a double cueing task where endogenous attention is concurrently engaged with exogenous attention. Our results confirm that the concurrent engagement of exogenous attention interferes with endogenous attention processes. We also found that changes in alpha-band activity mediate the relationship between endogenous attention and its effect on task performance, and that the interference of exogenous attention on endogenous attention occurs via the moderation of this indirect effect. Altogether, our results substantiate a model of attention, whereby endogenous and exogenous attentional processes involve the same neurophysiological resources. SIGNIFICANCE STATEMENT Scientists differentiate top-down from bottom-up visuospatial attention processes. While bottom-up attention is rapidly engaged by emerging demands from the environment, top-down attention in contrast reflects slow voluntary shifts of spatial attention. Several lines of research substantiate the idea that top-down and bottom-up attentional processes involve distinct functional systems. An increasing number of studies, however, argue that both attention systems share brain processing resources. The current study examines how salient visual events that engage bottom-up processes interfere with top-down attentional processes. Using neurophysiological recordings and multivariate pattern classification techniques, the authors show that these patterns of interference occur within the alpha-band of neural activity (8-12 Hz), which implies that bottom-up and top-down attention processes share this narrow-band frequency brain resource. The results further demonstrate that patterns of alpha-band activity explains, in part, the interference between top-down and bottom-up attention at the behavioral level.
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Affiliation(s)
- Mathieu Landry
- Laboratoire de Sciences Cognitives et Psycholinguistique, ENS, PSL University, EHESS, CNRS, Paris 75005, France
| | | | - Amir Raz
- Institute for Interdisciplinary Behavioral and Brain Sciences, Chapman University, Irvine, CA, 92618, USA
| | - Sylvain Baillet
- Montreal Neurological Institute, McGill University, Montreal, Qc, H3A 2B4, Canada
| | - Jérôme Sackur
- Laboratoire de Sciences Cognitives et Psycholinguistique, ENS, PSL University, EHESS, CNRS, Paris 75005, France
- École Polytechnique, Palaiseau 91120, France
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Akaiwa M, Matsuda Y, Kurokawa R, Sugawara Y, Kosuge R, Saito H, Shibata E, Sasaki T, Sugawara K, Kozuka N. Does 20 Hz Transcranial Alternating Current Stimulation over the Human Primary Motor Cortex Modulate Beta Rebound Following Voluntary Movement? Brain Sci 2024; 14:74. [PMID: 38248289 PMCID: PMC10813667 DOI: 10.3390/brainsci14010074] [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: 12/11/2023] [Revised: 01/04/2024] [Accepted: 01/09/2024] [Indexed: 01/23/2024] Open
Abstract
Beta frequency oscillations originating from the primary motor cortex increase in amplitude following the initiation of voluntary movement, a process termed beta rebound. The strength of beta rebound has been reported to predict the recovery of motor function following stroke, suggesting therapeutic applications of beta rebound modulation. The present study examined the effect of 20 Hz transcranial alternating current stimulation (tACS) on the beta rebound induced by self-paced voluntary movement. Electroencephalograms (EEGs) and electromyograms (EMGs) were recorded from 16 healthy adults during voluntary movements performed before and after active or sham tACS. There was no significant change in average beta rebound after active tACS. However, the beta rebound amplitude was significantly enhanced in a subset of participants, and the magnitude of the increase across all participants was negatively correlated with the difference between individual peak beta frequency and tACS frequency. Thus, matching the stimulus frequency of tACS with individual beta frequency may facilitate therapeutic enhancement for motor rehabilitation.
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Affiliation(s)
- Mayu Akaiwa
- Graduate School of Health Sciences, Sapporo Medical University, Sapporo 060-8556, Japan
| | - Yuya Matsuda
- Graduate School of Health Sciences, Sapporo Medical University, Sapporo 060-8556, Japan
| | - Ryo Kurokawa
- Graduate School of Health Sciences, Sapporo Medical University, Sapporo 060-8556, Japan
| | - Yasushi Sugawara
- Graduate School of Health Sciences, Sapporo Medical University, Sapporo 060-8556, Japan
| | - Rin Kosuge
- Graduate School of Health Sciences, Sapporo Medical University, Sapporo 060-8556, Japan
| | - Hidekazu Saito
- Department of Occupational Therapy, School of Health Sciences, Sapporo Medical University, Sapporo 060-8556, Japan
| | - Eriko Shibata
- Major of Physical Therapy, Department of Rehabilitation, Faculty of Healthcare and Science, Hokkaido Bunkyo University, Eniwa 061-1449, Japan;
| | - Takeshi Sasaki
- Department of Physical Therapy, School of Health Sciences, Sapporo Medical University, Sapporo 060-8556, Japan; (T.S.); (K.S.); (N.K.)
| | - Kazuhiro Sugawara
- Department of Physical Therapy, School of Health Sciences, Sapporo Medical University, Sapporo 060-8556, Japan; (T.S.); (K.S.); (N.K.)
| | - Naoki Kozuka
- Department of Physical Therapy, School of Health Sciences, Sapporo Medical University, Sapporo 060-8556, Japan; (T.S.); (K.S.); (N.K.)
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Radecke JO, Fiene M, Misselhorn J, Herrmann CS, Engel AK, Wolters CH, Schneider TR. Personalized alpha-tACS targeting left posterior parietal cortex modulates visuo-spatial attention and posterior evoked EEG activity. Brain Stimul 2023; 16:1047-1061. [PMID: 37353071 DOI: 10.1016/j.brs.2023.06.013] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Revised: 06/04/2023] [Accepted: 06/20/2023] [Indexed: 06/25/2023] Open
Abstract
BACKGROUND Covert visuo-spatial attention is marked by the anticipatory lateralization of neuronal alpha activity in the posterior parietal cortex. Previous applications of transcranial alternating current stimulation (tACS) at the alpha frequency, however, were inconclusive regarding the causal contribution of oscillatory activity during visuo-spatial attention. OBJECTIVE Attentional shifts of behavior and electroencephalography (EEG) after-effects were assessed in a cued visuo-spatial attention paradigm. We hypothesized that parietal alpha-tACS shifts attention relative to the ipsilateral visual hemifield. Furthermore, we assumed that modulations of behavior and neurophysiology are related to individual electric field simulations. METHODS We applied personalized tACS at alpha and gamma frequencies to elucidate the role of oscillatory neuronal activity for visuo-spatial attention. Personalized tACS montages were algorithmically optimized to target individual left and right parietal regions that were defined by an EEG localizer. RESULTS Behavioral performance in the left hemifield was specifically increased by alpha-tACS compared to gamma-tACS targeting the left parietal cortex. This hemisphere-specific effect was observed despite the symmetry of simulated electric fields. In addition, visual event-related potential (ERP) amplitudes showed a reduced lateralization over posterior sites induced by left alpha-tACS. Neuronal sources of this effect were localized in the left premotor cortex. Interestingly, accuracy modulations induced by left parietal alpha-tACS were directly related to electric field magnitudes in the left premotor cortex. CONCLUSION Overall, results corroborate the notion that alpha lateralization plays a causal role in covert visuo-spatial attention and indicate an increased susceptibility of parietal and premotor brain regions of the left dorsal attention network to subtle tACS-neuromodulation.
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Affiliation(s)
- Jan-Ole Radecke
- Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, 20246, Hamburg, Germany.
| | - Marina Fiene
- Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, 20246, Hamburg, Germany
| | - Jonas Misselhorn
- Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, 20246, Hamburg, Germany
| | - Christoph S Herrmann
- Experimental Psychology Lab, Department of Psychology, University of Oldenburg, 26111, Oldenburg, Germany; Research Center Neurosensory Science, University of Oldenburg, 26111, Oldenburg, Germany; Cluster of Excellence "Hearing4all", Germany
| | - Andreas K Engel
- Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, 20246, Hamburg, Germany
| | - Carsten H Wolters
- Institute for Biomagnetism and Biosignalanalysis, University of Münster, 48149, Münster, Germany; Otto Creutzfeldt Center for Cognitive and Behavioral Neuroscience, University of Münster, 48149, Münster, Germany
| | - Till R Schneider
- Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, 20246, Hamburg, Germany
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Davis MC, Fitzgerald PB, Bailey NW, Sullivan C, Stout JC, Hill AT, Hoy KE. Effects of medial prefrontal transcranial alternating current stimulation on neural activity and connectivity in people with Huntington's disease and neurotypical controls. Brain Res 2023; 1811:148379. [PMID: 37121424 DOI: 10.1016/j.brainres.2023.148379] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2022] [Revised: 03/30/2023] [Accepted: 04/25/2023] [Indexed: 05/02/2023]
Abstract
We investigated the effects of transcranial alternating current stimulation (tACS) targeted to the medial prefrontal cortex (mPFC) on resting electroencephalographic (EEG) indices of oscillatory power, aperiodic exponent and offset, and functional connectivity in 22 late premanifest and early manifest stage individuals with HD and 20 neurotypical controls. Participants underwent three 20-minute sessions of tACS at least 72 hours apart; one session at alpha frequency (either each participant's Individualised Alpha Frequency (IAF), or 10Hz when an IAF was not detected); one session at delta frequency (2Hz); and a session of sham tACS. Session order was randomised and counterbalanced across participants. EEG recordings revealed a reduction of the spectral exponent ('flattening' of the 1/f slope) of the eyes-open aperiodic signal in participants with HD following alpha-tACS, suggestive of an enhancement in excitatory tone. Contrary to expectation, there were no changes in oscillatory power or functional connectivity in response to any of the tACS conditions in the participants with HD. By contrast, alpha-tACS increased delta power in neurotypical controls, who further demonstrated significant increases in theta power and theta functional connectivity in response to delta-tACS. This study contributes to the rapidly growing literature on the potential experimental and therapeutic applications of tACS by examining neurophysiological outcome measures in people with HD as well as neurotypical controls.
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Affiliation(s)
- Marie-Claire Davis
- Central Clinical School, Department of Psychiatry, Monash University, Victoria, Australia; Statewide Progressive Neurological Disease Service, Calvary Health Care Bethlehem, Victoria Australia.
| | - Paul B Fitzgerald
- School of Medicine and Psychology, Australian National University, Canberra, ACT, Australia
| | - Neil W Bailey
- Central Clinical School, Department of Psychiatry, Monash University, Victoria, Australia; School of Medicine and Psychology, Australian National University, Canberra, ACT, Australia; Monarch Research Institute Monarch Mental Health Group, Sydney, NSW, Australia
| | - Caley Sullivan
- Central Clinical School, Department of Psychiatry, Monash University, Victoria, Australia
| | - Julie C Stout
- School of Psychological Sciences, Turner Institute for Brain and Mental Health, Monash University, Melbourne, Victoria, Australia
| | - Aron T Hill
- Central Clinical School, Department of Psychiatry, Monash University, Victoria, Australia; Cognitive Neuroscience Unit, School of Psychology, Deakin University, Melbourne, Australia
| | - Kate E Hoy
- Central Clinical School, Department of Psychiatry, Monash University, Victoria, Australia; The Bionics Institute of Australia, 384-388 Albert St, East Melbourne, VIC, 3002, Australia
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Davis MC, Hill AT, Fitzgerald PB, Bailey NW, Sullivan C, Stout JC, Hoy KE. Medial prefrontal transcranial alternating current stimulation for apathy in Huntington's disease. Prog Neuropsychopharmacol Biol Psychiatry 2023; 126:110776. [PMID: 37120005 DOI: 10.1016/j.pnpbp.2023.110776] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/28/2022] [Revised: 04/19/2023] [Accepted: 04/21/2023] [Indexed: 05/01/2023]
Abstract
We investigated the effects of transcranial alternating current stimulation (tACS) targeted to the bilateral medial prefrontal cortex (mPFC) and administered at either delta or alpha frequencies, on brain activity and apathy in people with Huntington's disease (HD) (n = 17). Given the novelty of the protocol, neurotypical controls (n = 20) were also recruited. All participants underwent three 20-min sessions of tACS; one session at alpha frequency (Individualised Alpha Frequency (IAF), or 10 Hz when an IAF was not detected); one session at delta frequency (2 Hz); and a session of sham tACS. Participants completed the Monetary Incentive Delay (MID) task with simultaneous recording of EEG immediately before and after each tACS condition. The MID task presents participants with cues signalling potential monetary gains or losses that increase activity in key regions of the cortico-basal ganglia-thalamocortical networks, with dysfunction of the latter network being implicated in the pathophysiology of apathy. We used the P300 and Contingent Negative Variation (CNV) event-related potentials elicited during the MID task as markers of mPFC engagement. HD participants' CNV amplitude significantly increased in response to alpha-tACS, but not delta-tACS or sham. Neurotypical controls' P300 and CNV were not modulated by any of the tACS conditions, but they did demonstrate a significant decrease in post-target response times following alpha-tACS. We present this as preliminary evidence of the ability of alpha-tACS to modulate brain activity associated with apathy in HD.
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Affiliation(s)
- Marie-Claire Davis
- Central Clinical School, Department of Psychiatry, Monash University, Victoria, Australia; Statewide Progressive Neurological Disease Service, Calvary Health Care Bethlehem, Victoria, Australia.
| | - Aron T Hill
- Central Clinical School, Department of Psychiatry, Monash University, Victoria, Australia; Cognitive Neuroscience Unit, School of Psychology, Deakin University, Melbourne, Australia
| | - Paul B Fitzgerald
- Central Clinical School, Department of Psychiatry, Monash University, Victoria, Australia; School of Medicine and Psychology, Australian National University, Canberra, ACT, Australia
| | - Neil W Bailey
- Central Clinical School, Department of Psychiatry, Monash University, Victoria, Australia; School of Medicine and Psychology, Australian National University, Canberra, ACT, Australia; Monarch Research Institute Monarch Mental Health Group, Sydney, NSW, Australia
| | - Caley Sullivan
- Central Clinical School, Department of Psychiatry, Monash University, Victoria, Australia
| | - Julie C Stout
- School of Psychological Sciences, Turner Institute for Brain and Mental Health, Monash University, Melbourne, Victoria, Australia
| | - Kate E Hoy
- Central Clinical School, Department of Psychiatry, Monash University, Victoria, Australia; The Bionics Institute of Australia, 384-388 Albert St, East Melbourne, VIC 3002, Australia
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Li D, Hu Y, Qi M, Zhao C, Jensen O, Huang J, Song Y. Prioritizing flexible working memory representations through retrospective attentional strengthening. Neuroimage 2023; 269:119902. [PMID: 36708973 DOI: 10.1016/j.neuroimage.2023.119902] [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: 10/09/2022] [Revised: 01/14/2023] [Accepted: 01/24/2023] [Indexed: 01/26/2023] Open
Abstract
Previous work has proposed two potential benefits of retrospective attention on working memory (WM): target strengthening and non-target inhibition. It remains unknown which hypothesis contributes to the improved WM performance, yet the neural mechanisms responsible for this attentional benefit are unclear. Here, we recorded electroencephalography (EEG) signals while 33 participants performed a retrospective-cue WM task. Multivariate pattern classification analysis revealed that only representations of target features were enhanced by valid retrospective attention during retention, supporting the target strengthening hypothesis. Further univariate analysis found that mid-frontal theta inter-trial phase coherence (ITPC) and ERP components were modulated by valid retrospective attention and correlated with individual differences and moment-to-moment fluctuations on behavioral outcomes, suggesting that both trait- and state-level variability in attentional preparatory processes influence goal-directed behavior. Furthermore, task-irrelevant target spatial location could be decoded from EEG signals, indicating that enhanced spatial binding of target representation is vital to high WM precision. Importantly, frontoparietal theta-alpha phase-amplitude coupling was increased by valid retrospective attention and predicted the reduced random guessing rates. This long-range connection supported top-down information flow in the engagement of frontoparietal networks, which might organize attentional states to integrate target features. Altogether, these results provide neurophysiological bases that retrospective attention improves WM precision by enhancing flexible target representation and emphasize the critical role of the frontoparietal attentional network in the control of WM representations.
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Affiliation(s)
- Dongwei Li
- State Key Laboratory of Cognitive Neuroscience and Learning & IDG/McGovern Institute for Brain Research, Beijing Normal University, Beijing, China; Centre for Human Brain Health, University of Birmingham, Birmingham, UK
| | - Yiqing Hu
- State Key Laboratory of Cognitive Neuroscience and Learning & IDG/McGovern Institute for Brain Research, Beijing Normal University, Beijing, China
| | - Mengdi Qi
- State Key Laboratory of Cognitive Neuroscience and Learning & IDG/McGovern Institute for Brain Research, Beijing Normal University, Beijing, China
| | - Chenguang Zhao
- State Key Laboratory of Cognitive Neuroscience and Learning & IDG/McGovern Institute for Brain Research, Beijing Normal University, Beijing, China; Center for Cognition and Neuroergonomics, State Key Laboratory of Cognitive Neuroscience and Learning, Beijing Normal University, Zhuhai, China
| | - Ole Jensen
- Centre for Human Brain Health, University of Birmingham, Birmingham, UK
| | - Jing Huang
- Center for Cognition and Neuroergonomics, State Key Laboratory of Cognitive Neuroscience and Learning, Beijing Normal University, Zhuhai, China.
| | - Yan Song
- State Key Laboratory of Cognitive Neuroscience and Learning & IDG/McGovern Institute for Brain Research, Beijing Normal University, Beijing, China; Center for Collaboration and Innovation in Brain and Learning Sciences, Beijing Normal University, Beijing, China.
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14
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Li Y, Chen X, Zhang Q, Xu W, Li J, Ji F, Dong Q, Chen C, Li J. Effects of working memory span training on top-down attentional asymmetry at both neural and behavioral levels. Cereb Cortex 2023; 33:5937-5946. [PMID: 36617305 DOI: 10.1093/cercor/bhac472] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Revised: 11/07/2022] [Accepted: 11/08/2022] [Indexed: 01/09/2023] Open
Abstract
The leftward asymmetry of the visual field and posterior brain regions, a feature of the normal attention process, can be strengthened by brain stimulation, e.g. administering alpha frequency stimulation to the left posterior cortex. However, whether it can be strengthened by cognitive training, especially with nonlateralized tasks, is unknown. We used a dataset from a 2-month-long randomized controlled trial and compared the control group with 2 training groups trained with backward or forward memory span tasks. A lateralized change detection task with varied memory loads was administered as the pre-, mid-, and post-tests with simultaneous electroencephalographic recording. Intrasubject response variability (IRV) and the alpha modulation index (MI) were calculated. Analysis of IRV showed more enhanced leftward attentional bias in the backward group than in the other groups. Consistently, analysis of MI found that its enhancements in the left hemisphere (but not the right hemisphere) of the backward group were significantly higher than those of the other groups. Further analysis revealed that left MI changes predicted left IRV improvement. All of these results indicated that backward memory span training enhanced leftward attentional asymmetry at both the behavioral and neural levels.
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Affiliation(s)
- Yang Li
- State Key Laboratory of Cognitive Neuroscience and Learning & IDG/McGovern Institute for Brain Research, Beijing Normal University, No.19, Xinjiekouwai Street, Haidian District, Beijing 100875, P.R. China
| | - Xiongying Chen
- The National Clinical Research Center for Mental Disorders & Beijing Key Laboratory of Mental Disorders, Beijing Anding Hospital & the Advanced Innovation Center for Human Brain Protection, Capital Medical University, No.5, Ankang Hutong, Xicheng District, Beijing 100088, P.R. China
| | - Qiumei Zhang
- School of Mental Health, Jining Medical University, 45# Jianshe South Road, Jining, Shandong 272013, P.R. China
| | - Wending Xu
- State Key Laboratory of Cognitive Neuroscience and Learning & IDG/McGovern Institute for Brain Research, Beijing Normal University, No.19, Xinjiekouwai Street, Haidian District, Beijing 100875, P.R. China
| | - Jin Li
- Brainnetome Center, Institute of Automation, Chinese Academy of Sciences, No. 95 Zhongguancun East Road, Haidian District, Beijing 100190, P.R. China.,National Laboratory of Pattern Recognition, Institute of Automation, Chinese Academy of Sciences, No. 95 Zhongguancun East Road, Haidian District, Beijing 100190, P.R. China
| | - Feng Ji
- School of Mental Health, Jining Medical University, 45# Jianshe South Road, Jining, Shandong 272013, P.R. China
| | - Qi Dong
- State Key Laboratory of Cognitive Neuroscience and Learning & IDG/McGovern Institute for Brain Research, Beijing Normal University, No.19, Xinjiekouwai Street, Haidian District, Beijing 100875, P.R. China
| | - Chuansheng Chen
- Department of Psychological Science, University of California, Irvine, 4201 Social & Behavioral Sciences Gateway,CA 92697, United States
| | - Jun Li
- State Key Laboratory of Cognitive Neuroscience and Learning & IDG/McGovern Institute for Brain Research, Beijing Normal University, No.19, Xinjiekouwai Street, Haidian District, Beijing 100875, P.R. China
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Schuhmann T, Duecker F, Middag-van Spanje M, Gallotto S, van Heugten C, Schrijnemaekers AC, van Oostenbrugge R, Sack AT. Transcranial alternating brain stimulation at alpha frequency reduces hemispatial neglect symptoms in stroke patients. Int J Clin Health Psychol 2022; 22:100326. [PMID: 35990733 PMCID: PMC9364103 DOI: 10.1016/j.ijchp.2022.100326] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Accepted: 07/18/2022] [Indexed: 12/03/2022] Open
Abstract
Background/Objective Non-invasive brain stimulation techniques such as transcranial alternating current stimulation (tACS) may help alleviate attention deficits in stroke patients with hemispatial neglect by modulating oscillatory brain activity. We applied high-definition (HD)-tACS at alpha frequency over the contralesional hemisphere to support unilateral oscillatory alpha activity and correct for the pathologically altered attention bias in neglect patients. Methods We performed a within-subject, placebo-controlled study in which sixteen stroke patients with hemispatial neglect underwent 10 Hz (alpha) as well as sham (placebo) stimulation targeting the contralesional posterior parietal cortex. Attentional bias was measured with a computerized visual detection paradigm and two standard paper-and-pencil neglect tests. Results We revealed a significant shift of attentional resources after alpha-HD-tACS, but not sham tACS, toward the ipsilateral and thus contralesional hemifield leading to a reduction in neglect symptoms, measured with a computerized visual detection paradigm and a widely used standard paper and pencil neglect tests. Conclusions We showed a significant alpha-HD-tACS-induced shift of attentional resources toward the contralesional hemifield, thus leading to a reduction in neglect symptoms. Importantly, HD-tACS effects persisted after the stimulation itself had ended. This tACS protocol, based on intrinsic oscillatory processes, may be an effective and well-tolerated treatment option for neglect.
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Affiliation(s)
- Teresa Schuhmann
- Section Brain Stimulation and Cognition, Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, the Netherlands.,Maastricht Brain Imaging Centre (MBIC), Maastricht University, Maastricht, the Netherlands
| | - Felix Duecker
- Section Brain Stimulation and Cognition, Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, the Netherlands.,Maastricht Brain Imaging Centre (MBIC), Maastricht University, Maastricht, the Netherlands
| | - Marij Middag-van Spanje
- Section Brain Stimulation and Cognition, Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, the Netherlands.,Maastricht Brain Imaging Centre (MBIC), Maastricht University, Maastricht, the Netherlands.,InteraktContour, Nunspeet, the Netherlands
| | - Stefano Gallotto
- Section Brain Stimulation and Cognition, Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, the Netherlands.,Maastricht Brain Imaging Centre (MBIC), Maastricht University, Maastricht, the Netherlands.,EEG and Epilepsy Unit, University Hospitals and Faculty of Medicine of Geneva, University of Geneva, Geneva, Switzerland
| | - Caroline van Heugten
- Limburg Brain Injury Center, the Netherlands.,Department of Neuropsychology & Psychopharmacology, Faculty of Psychology and Neuroscience (FPN), Maastricht University, the Netherlands.,School for Mental Health and Neuroscience, Department of Psychiatry & Neuropsychology, Faculty of Health, Medicine and Life Sciences (FHML), Maastricht University Medical Center, the Netherlands
| | - Anne-Claire Schrijnemaekers
- Adelante Rehabilitation Centre, Department of Brain Injury, Hoensbroek, the Netherlands.,Mondriaan Mental Health Centre, Department of Adult Psychiatry, Heerlen, the Netherlands
| | - Robert van Oostenbrugge
- Department of Neurology, School for Mental Health and Neuroscience, Maastricht University Medical Center, Maastricht, the Netherlands
| | - Alexander T Sack
- Section Brain Stimulation and Cognition, Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, the Netherlands.,Maastricht Brain Imaging Centre (MBIC), Maastricht University, Maastricht, the Netherlands.,Centre for Integrative Neuroscience, Faculty of Psychology and Neuroscience, Faculty of Health, Medicine and Life Sciences, Maastricht University, Maastricht, the Netherlands
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Aktürk T, de Graaf TA, Güntekin B, Hanoğlu L, Sack AT. Enhancing memory capacity by experimentally slowing theta frequency oscillations using combined EEG-tACS. Sci Rep 2022; 12:14199. [PMID: 35987918 PMCID: PMC9392784 DOI: 10.1038/s41598-022-18665-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Accepted: 08/17/2022] [Indexed: 11/09/2022] Open
Abstract
The coupling of gamma oscillation (~ 40+ Hz) amplitude to the phase of ongoing theta (~ 6 Hz) oscillations has been proposed to be directly relevant for memory performance. Current theories suggest that memory capacity scales with number of gamma cycles that can be fitted into the preferred phase of a theta cycle. Following this logic, transcranial alternating current stimulation (tACS) may be used to adjust theta cycles (increasing/decreasing theta frequency) to decrease or increase memory performance during stimulation. Here, we used individualized EEG-informed theta tACS to (1) experimentally “slow down” individual theta frequency (ITF), (2) evaluate cognitive after effects on a battery of memory and learning tasks, and (3) link the cognitive performance changes to tACS-induced effects on theta-band oscillations as measured by post EEG. We found frequency- and task-specific tACS after effects demonstrating a specific enhancement in memory capacity. This tACS-induced cognitive enhancement was specific to the visual memory task performed immediately after tACS offset, and specific to the ITF-1 Hz (slowing) stimulation condition and thus following a protocol specifically designed to slow down theta frequency to enhance memory capacity. Follow-up correlation analyses in this group linked the enhanced memory performance to increased left frontal-parietal theta-band connectivity. Interestingly, resting-state theta power immediately after tACS offset revealed a theta power increase not for the ITF-1 Hz group, but only for the ITF group where the tACS frequency was ‘optimal’ for entrainment. These results suggest that while individually calibrated tACS at peak frequency maximally modulates resting-state oscillatory power, tACS stimulation slightly below this optimal peak theta frequency is better suited to enhance memory capacity performance. Importantly, our results further suggest that such cognitive enhancement effects can last beyond the period of stimulation and are linked to increased network connectivity, opening the door towards more clinical and applied relevance of using tACS in cognitive rehabilitation and/or neurocognitive enhancement.
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