1
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Cobos MI, Melcón M, Rodríguez-San Esteban P, Capilla A, Chica AB. The role of brain oscillations in feature integration. Psychophysiology 2024; 61:e14467. [PMID: 37990794 DOI: 10.1111/psyp.14467] [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: 01/17/2023] [Revised: 09/04/2023] [Accepted: 10/05/2023] [Indexed: 11/23/2023]
Abstract
Our sensory system is able to build a unified perception of the world, which although rich, is limited and inaccurate. Sometimes, features from different objects are erroneously combined. At the neural level, the role of the parietal cortex in feature integration is well-known. However, the brain dynamics underlying correct and incorrect feature integration are less clear. To explore the temporal dynamics of feature integration, we studied the modulation of different frequency bands in trials in which feature integration was correct or incorrect. Participants responded to the color of a shape target, surrounded by distractors. A calibration procedure ensured that accuracy was around 70% in each participant. To explore the role of expectancy in feature integration, we introduced an unexpected feature to the target in the last blocks of trials. Results demonstrated the contribution of several frequency bands to feature integration. Alpha and beta power was reduced for hits compared to illusions. Moreover, gamma power was overall larger during the experiment for participants who were aware of the unexpected target presented during the last blocks of trials (as compared to unaware participants). These results demonstrate that feature integration is a complex process that can go wrong at different stages of information processing and is influenced by top-down expectancies.
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Affiliation(s)
- M I Cobos
- Brain, Mind, and Behavior Research Center (CIMCYC), University of Granada (UGR), Granada, Spain
- Department of Experimental Psychology, University of Granada (UGR), Granada, Spain
| | - M Melcón
- Department of Biological and Health Psychology, Autonomous University of Madrid (UAM), Madrid, Spain
| | - P Rodríguez-San Esteban
- Brain, Mind, and Behavior Research Center (CIMCYC), University of Granada (UGR), Granada, Spain
- Department of Experimental Psychology, University of Granada (UGR), Granada, Spain
| | - A Capilla
- Department of Biological and Health Psychology, Autonomous University of Madrid (UAM), Madrid, Spain
| | - A B Chica
- Brain, Mind, and Behavior Research Center (CIMCYC), University of Granada (UGR), Granada, Spain
- Department of Experimental Psychology, University of Granada (UGR), Granada, Spain
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2
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Kraft JD, Hampstead BM. A Systematic Review of tACS Effects on Cognitive Functioning in Older Adults Across the Healthy to Dementia Spectrum. Neuropsychol Rev 2023:10.1007/s11065-023-09621-3. [PMID: 37882864 PMCID: PMC11045666 DOI: 10.1007/s11065-023-09621-3] [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: 11/09/2022] [Accepted: 09/26/2023] [Indexed: 10/27/2023]
Abstract
Transcranial alternating current stimulation (tACS) is a form of noninvasive brain stimulation that has experienced rapid growth within the aging population over the past decade due to its potential for modulating cognitive functioning across the "intact" to dementia spectrum. For this reason, we performed a systematic review of the literature to evaluate the efficacy of tACS on cognitive functioning in older adults, including those with cognitive impairment. Our review was completed in June 2023 using Psych INFO, Embase, PubMed, and Cochrane databases. Out of 479 screened articles, 21 met inclusion criteria and were organized according to clinical diagnoses. Seven out of nine studies targeted cognitively intact older adults and showed some type of cognitive improvement after stimulation, whereas nine out of twelve studies targeted clinical diagnoses and showed improved cognitive performance to varying degrees. Studies showed considerable heterogeneity in methodology, stimulation parameters, participant characteristics, choice of cognitive task, and analytic strategy, all of which reinforce the need for standardized reporting of tACS methods. Through this heterogeneity, multiple patterns are described, such as disease progression influencing tACS effects and the need for individualized tailoring. For clinical translation, it is imperative that the field (a) better understand the physiological effects of tACS in these populations, especially in respect to biomarkers, (b) document a causal relationship between tACS delivery and neurophysiological/cognitive effects, and (c) systematically establish dosing parameters (e.g., amplitude, stimulation frequency, number and duration of sessions, need for booster/maintenance sessions).
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Affiliation(s)
- Jacob D Kraft
- Research Program On Cognition and Neuromodulation Based Interventions, Department of Psychiatry, University of Michigan, 4250 Plymouth Rd, Ann Arbor, MI, 48105, USA.
- Department of Psychiatry &, Behavioral Health, The Ohio State University, Columbus, OH, 43210, USA.
| | - Benjamin M Hampstead
- Research Program On Cognition and Neuromodulation Based Interventions, Department of Psychiatry, University of Michigan, 4250 Plymouth Rd, Ann Arbor, MI, 48105, USA
- Mental Health Service, Neuropsychology Section, VA Ann Arbor Healthcare System, Ann Arbor, MI, 48105, USA
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3
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Janssens SEW, Oever ST, Sack AT, de Graaf TA. "Broadband Alpha Transcranial Alternating Current Stimulation": Exploring a new biologically calibrated brain stimulation protocol. Neuroimage 2022; 253:119109. [PMID: 35306159 DOI: 10.1016/j.neuroimage.2022.119109] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Revised: 03/09/2022] [Accepted: 03/15/2022] [Indexed: 11/26/2022] Open
Abstract
Transcranial alternating current stimulation (tACS) can be used to study causal contributions of oscillatory brain mechanisms to cognition and behavior. For instance, individual alpha frequency (IAF) tACS was reported to enhance alpha power and impact visuospatial attention performance. Unfortunately, such results have been inconsistent and difficult to replicate. In tACS, stimulation generally involves one frequency, sometimes individually calibrated to a peak value observed in an M/EEG power spectrum. Yet, the 'peak' actually observed in such power spectra often contains a broader range of frequencies, raising the question whether a biologically calibrated tACS protocol containing this fuller range of alpha-band frequencies might be more effective. Here, we introduce 'Broadband-alpha-tACS', a complex individually calibrated electrical stimulation protocol. We band-pass filtered left posterior resting-state EEG data around the IAF (± 2 Hz), and converted that time series into an electrical waveform for tACS stimulation of that same left posterior parietal cortex location. In other words, we stimulated a brain region with a 'replay' of its own alpha-band frequency content, based on spontaneous activity. Within-subjects (N = 24), we compared to a sham tACS session the effects of broadband-alpha tACS, power-matched spectral inverse ('alpha-removed') control tACS, and individual alpha frequency (IAF) tACS, on EEG alpha power and performance in an endogenous attention task previously reported to be affected by alpha tACS. Broadband-alpha-tACS significantly modulated attention task performance (i.e., reduced the rightward visuospatial attention bias in trials without distractors, and reduced attention benefits). Alpha-removed tACS also reduced the rightward visuospatial attention bias. IAF-tACS did not significantly modulate attention task performance compared to sham tACS, but also did not statistically significantly differ from broadband-alpha-tACS. This new broadband-alpha-tACS approach seems promising, but should be further explored and validated in future studies.
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Affiliation(s)
- Shanice E W Janssens
- Section Brain Stimulation and Cognition, Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, Netherlands; Maastricht Brain Imaging Centre (MBIC), Maastricht, Netherlands.
| | - Sanne Ten Oever
- Section Brain Stimulation and Cognition, Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, Netherlands; Language and Computation in Neural Systems Group, Max Planck Institute for Psycholinguistics, Nijmegen, Netherlands; Donders Centre for Cognitive Neuroimaging, Radboud University, Nijmegen, Netherlands
| | - Alexander T Sack
- Section Brain Stimulation and Cognition, Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, Netherlands; Maastricht Brain Imaging Centre (MBIC), Maastricht, Netherlands; Department of Psychiatry and Neuropsychology, School for Mental Health and Neuroscience (MHeNs), Brain+Nerve Centre, Maastricht University Medical Centre+ (MUMC+), Maastricht, Netherlands; Center for Integrative Neuroscience (CIN), Maastricht University, Maastricht, Netherlands
| | - Tom A de Graaf
- Section Brain Stimulation and Cognition, Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, Netherlands; Maastricht Brain Imaging Centre (MBIC), Maastricht, Netherlands; Center for Integrative Neuroscience (CIN), Maastricht University, Maastricht, Netherlands
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4
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Vogeti S, Boetzel C, Herrmann CS. Entrainment and Spike-Timing Dependent Plasticity – A Review of Proposed Mechanisms of Transcranial Alternating Current Stimulation. Front Syst Neurosci 2022; 16:827353. [PMID: 35283735 PMCID: PMC8909135 DOI: 10.3389/fnsys.2022.827353] [Citation(s) in RCA: 34] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 02/07/2022] [Indexed: 12/15/2022] Open
Abstract
Specific frequency bands of neural oscillations have been correlated with a range of cognitive and behavioral effects (e.g., memory and attention). The causal role of specific frequencies may be investigated using transcranial alternating current stimulation (tACS), a non-invasive brain stimulation method. TACS involves applying a sinusoidal current between two or more electrodes attached on the scalp, above neural regions that are implicated in cognitive processes of interest. The theorized mechanisms by which tACS affects neural oscillations have implications for the exact stimulation frequency used, as well as its anticipated effects. This review outlines two main mechanisms that are thought to underlie tACS effects – entrainment, and spike-timing dependent plasticity (STDP). Entrainment suggests that the stimulated frequency synchronizes the ongoing neural oscillations, and is thought to be most effective when the stimulated frequency is at or close to the endogenous frequency of the targeted neural network. STDP suggests that stimulation leads to synaptic changes based on the timing of neuronal firing in the target neural network. According to the principles of STDP, synaptic strength is thought to increase when pre-synaptic events occur prior to post-synaptic events (referred to as long-term potentiation, LTP). Conversely, when post-synaptic events occur prior to pre-synaptic events, synapses are thought to be weakened (referred to as long-term depression, LTD). In this review, we summarize the theoretical frameworks and critically review the tACS evidence for each hypothesis. We also discuss whether each mechanism alone can account for tACS effects or whether a combined account is necessary.
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Affiliation(s)
- Sreekari Vogeti
- Experimental Psychology Lab, Department of Psychology, European Medical School, Cluster for Excellence “Hearing for All”, Carl von Ossietzky University, Oldenburg, Germany
| | - Cindy Boetzel
- Experimental Psychology Lab, Department of Psychology, European Medical School, Cluster for Excellence “Hearing for All”, Carl von Ossietzky University, Oldenburg, Germany
| | - Christoph S. Herrmann
- Experimental Psychology Lab, Department of Psychology, European Medical School, Cluster for Excellence “Hearing for All”, Carl von Ossietzky University, Oldenburg, Germany
- Neuroimaging Unit, European Medical School, Carl von Ossietzky University, Oldenburg, Germany
- Research Center Neurosensory Science, Carl von Ossietzky University, Oldenburg, Germany
- *Correspondence: Christoph S. Herrmann,
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Kannen K, Aslan B, Boetzel C, Herrmann CS, Lux S, Rosen H, Selaskowski B, Wiebe A, Philipsen A, Braun N. P300 Modulation via Transcranial Alternating Current Stimulation in Adult Attention-Deficit/Hyperactivity Disorder: A Crossover Study. Front Psychiatry 2022; 13:928145. [PMID: 35923453 PMCID: PMC9339709 DOI: 10.3389/fpsyt.2022.928145] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Accepted: 06/16/2022] [Indexed: 11/13/2022] Open
Abstract
OBJECTIVE A repeated finding regarding event-related potentials (ERPs) is that patients with ADHD show a reduced P300 amplitude. This raises the question of whether the attention of ADHD patients can be increased by stabilizing the P300. Assuming that the P300 is generated by event-related oscillations (EROs) in the low frequency range (0-8 Hz), one approach to increase the P300 could be to stimulate the patient's P300 underlying ERO by means of transcranial alternating current stimulation (tACS). The aim of this follow-up study was to investigate this hypothesized mechanism of action in adult ADHD patients. MATERIALS AND METHODS Undergoing a crossover design, 20 adult ADHD patients (10 female) received an actual stimulation via tACS on one day and a sham stimulation on another day. Before and after each intervention, EEG characteristics (P300 amplitudes, low frequency power) and attention performances (d2 attention test, visual oddball task (VOT)) were recorded. RESULTS Electrophysiological analyses revealed no evidence for an enhanced P300 amplitude or low frequency power increase after actual stimulation compared to sham stimulation. Instead, a significant effect was found for a stronger N700 amplitude increase after actual stimulation compared to sham stimulation. Consistent with the P300 null results, none of the examined neuropsychological performance measures indicated a tACS-induced improvement in attentional ability. CONCLUSION Contrary to a previous study using tACS to modulate the P300 in adult ADHD patients, the current study yields no evidence that tACS can increase the P300 amplitude in adult ADHD patients and that such P300 enhancement can directly improve neuropsychological parameters of attention.
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Affiliation(s)
- Kyra Kannen
- Department of Psychiatry and Psychotherapy, University Hospital Bonn, Bonn, Germany
| | - Behrem Aslan
- Department of Psychiatry and Psychotherapy, University Hospital Bonn, Bonn, Germany
| | - Cindy Boetzel
- Experimental Psychology Lab, Department of Psychology, Carl von Ossietzky University, Oldenburg, Germany
| | - Christoph S Herrmann
- Experimental Psychology Lab, Department of Psychology, Carl von Ossietzky University, Oldenburg, Germany
| | - Silke Lux
- Department of Psychiatry and Psychotherapy, University Hospital Bonn, Bonn, Germany
| | - Helena Rosen
- Department of Psychiatry and Psychotherapy, University Hospital Bonn, Bonn, Germany
| | - Benjamin Selaskowski
- Department of Psychiatry and Psychotherapy, University Hospital Bonn, Bonn, Germany
| | - Annika Wiebe
- Department of Psychiatry and Psychotherapy, University Hospital Bonn, Bonn, Germany
| | - Alexandra Philipsen
- Department of Psychiatry and Psychotherapy, University Hospital Bonn, Bonn, Germany
| | - Niclas Braun
- Department of Psychiatry and Psychotherapy, University Hospital Bonn, Bonn, Germany
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6
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Saito K, Otsuru N, Yokota H, Inukai Y, Miyaguchi S, Kojima S, Onishi H. α-tACS over the somatosensory cortex enhances tactile spatial discrimination in healthy subjects with low alpha activity. Brain Behav 2021; 11:e02019. [PMID: 33405361 PMCID: PMC7994706 DOI: 10.1002/brb3.2019] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 10/28/2020] [Accepted: 12/17/2020] [Indexed: 12/15/2022] Open
Abstract
INTRODUCTION Spontaneous oscillations in the somatosensory cortex, especially of the alpha (8 - 14 Hz) and gamma (60 - 80 Hz) frequencies, affect tactile perception; moreover, these oscillations can be selectively modulated by frequency-matched transcranial alternating current stimulation (tACS) on the basis of ongoing oscillatory brain activity. To examine whether tACS can actually improve tactile perception via alpha and gamma modulation, we measured the effects of 10-Hz and 70-Hz tACS (α- and γ-tACS) on the left somatosensory cortex on right-finger tactile spatial orientation discrimination, and the associations between performance changes and individual alpha and gamma activities. METHODS Fifteen neurologically healthy subjects were recruited into this study. Electroencephalography (EEG) was performed before the first day, to assess the normal alpha- and gamma-activity levels. A grating orientation discrimination task was performed before and during 10-Hz and 70-Hz tACS. RESULTS The 10-Hz tACS protocol decreased the grating orientation discrimination threshold, primarily in subjects with low alpha event-related synchronization (ERS). In contrast, the 70-Hz tACS had no effect on the grating orientation discrimination threshold. CONCLUSIONS This study showed that 10-Hz tACS can improve tactile orientation discrimination in subjects with low alpha activity. Alpha-frequency tACS may help identify the contributions of these oscillations to other neurophysiological and pathological processes.
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Affiliation(s)
- Kei Saito
- Department of Physical Therapy, Niigata University of Health and Welfare, Niigata, Japan.,Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata, Japan
| | - Naofumi Otsuru
- Department of Physical Therapy, Niigata University of Health and Welfare, Niigata, Japan.,Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata, Japan
| | - Hirotake Yokota
- Department of Physical Therapy, Niigata University of Health and Welfare, Niigata, Japan.,Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata, Japan
| | - Yasuto Inukai
- Department of Physical Therapy, Niigata University of Health and Welfare, Niigata, Japan.,Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata, Japan
| | - Shota Miyaguchi
- Department of Physical Therapy, Niigata University of Health and Welfare, Niigata, Japan.,Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata, Japan
| | - Sho Kojima
- Department of Physical Therapy, Niigata University of Health and Welfare, Niigata, Japan.,Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata, Japan
| | - Hideaki Onishi
- Department of Physical Therapy, Niigata University of Health and Welfare, Niigata, Japan.,Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata, Japan
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7
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Zhuang W, Yin K, Zi Y, Liu Y. Non-Invasive Brain Stimulation: Augmenting the Training and Performance Potential in Esports Players. Brain Sci 2020; 10:brainsci10070454. [PMID: 32679797 PMCID: PMC7407750 DOI: 10.3390/brainsci10070454] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Revised: 07/10/2020] [Accepted: 07/12/2020] [Indexed: 11/16/2022] Open
Abstract
During the last two decades, esports, a highly competitive sporting activity, has gained increasing popularity. Both performance and competition in esports require players to have fine motor skills and physical and cognitive abilities in controlling and manipulating digital activities in a virtual environment. While strategies for building and improving skills and abilities are crucial for successful gaming performance, few effective training approaches exist in the fast-growing area of competitive esports. In this paper, we describe a non-invasive brain stimulation (NIBS) approach and highlight the relevance and potential areas for research while being cognizant of various technical, safety, and ethical issues related to NIBS when applied to esports.
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Affiliation(s)
| | | | | | - Yu Liu
- Correspondence: ; Tel.: +86-21-65507860
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8
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Kazemi R, Rostami R, Dehghan S, Nasiri Z, Lotfollahzadeh S, L Hadipour A, Khomami S, Ishii R, Ikeda S. Alpha frequency rTMS modulates theta lagged nonlinear connectivity in dorsal attention network. Brain Res Bull 2020; 162:271-281. [PMID: 32619694 DOI: 10.1016/j.brainresbull.2020.06.018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Revised: 05/14/2020] [Accepted: 06/26/2020] [Indexed: 11/24/2022]
Abstract
Dorsolateral prefrontal cortex (DLPFC) is a key structure in dorsal attention network (DAN) that facilitates sustained attention by modulating activity in task related and unrelated regions of the brain. Alpha and theta frequency bands enhance connectivity among different parts of the attention network and these connections are facilitated by long-range nonlinear connectivity in theta and alpha frequency bands. This study is an investigation of the behavioral and electrophysiological effects of alpha and theta frequency repetitive transcranial magnetic stimulation (rTMS) over RDLPFC. 20 healthy participants were randomly assigned to two groups of theta (n = 11, f = 6 Hz) and alpha (n = 9, f = 10 Hz) rTMS. Electroencephalogram (EEG) was recorded before and after each session while resting and performing tasks. Current source density (CSD) and functional connectivity (FC) in DAN and default mode network (DMN) and their correlations with rapid visual information processing task (RVIP) scores were calculated . Alpha frequency rTMS resulted in significant changes in RVIP scores. Active theta rTMS caused an increase in CSD in Postcentral gyrus and active alpha rTMS resulted in significant CSD changes in inferior parietal lobule (IPL). Theta lagged nonlinear connectivity was mudulated by alpha rTMSand FC changes were observed in DAN and DMN. Positive correlations were observed between DAN regions and RVIP scores in the alpha rTMS group. Increased activity in theta frequency band in left aPFC and left DLPFC correlated positively with higher total hits in RVIP. This study showed for the first time that theta and alpha frequency rTMS are able to modulate FC in DAN and DMN in a way that results in better performance in a sustained attention task.
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Affiliation(s)
- Reza Kazemi
- Cognitive Lab, Department of Psychology, University of Tehran, Tehran, Iran; Atieh Clinical Neuroscience Center, Tehran, Iran.
| | - Reza Rostami
- Department of Psychology, University of Tehran, Tehran, Iran
| | | | - Zahra Nasiri
- Atieh Clinical Neuroscience Center, Tehran, Iran
| | | | - Abed L Hadipour
- Atieh Clinical Neuroscience Center, Tehran, Iran; Department of Psychology, University of Tehran, Tehran, Iran
| | | | - Ryouhei Ishii
- Smart Rehabilitation Research Center, Osaka Prefecture University, Graduate School of Comprehensive Rehabilitation, Habikino, Japan; Department of Psychiatry, Osaka University, Graduate School of Medicine, Osaka, Japan
| | - Shunichiro Ikeda
- Department of Neuropsychiatry, Kansai Medical University, Osaka, Japan
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9
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Gundlach C, Moratti S, Forschack N, Müller MM. Spatial Attentional Selection Modulates Early Visual Stimulus Processing Independently of Visual Alpha Modulations. Cereb Cortex 2020; 30:3686-3703. [PMID: 31907512 DOI: 10.1093/cercor/bhz335] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Revised: 11/18/2019] [Accepted: 12/17/2019] [Indexed: 01/06/2023] Open
Abstract
The capacity-limited human brain is constantly confronted with a huge amount of sensory information. Selective attention is needed for biasing neural processing towards relevant information and consequently allows meaningful interaction with the environment. Activity in the alpha-band has been proposed to be related to top-down modulation of neural inhibition and could thus represent a viable candidate to control the priority of stimulus processing. It is, however, unknown whether modulations in the alpha-band directly relate to changes in the sensory gain control of the early visual cortex. Here, we used a spatial cueing paradigm while simultaneously measuring ongoing alpha-band oscillations and steady-state visual evoked potentials (SSVEPs) as a marker of continuous early sensory processing in the human visual cortex. Thereby, the effects of spatial attention for both of these signals and their potential interactions were assessed. As expected, spatial attention modulated both alpha-band and SSVEP responses. However, their modulations were independent of each other and the corresponding activity profiles differed across task demands. Thus, our results challenge the view that modulations of alpha-band activity represent a mechanism that directly alters or controls sensory gain. The potential role of alpha-band oscillations beyond sensory processing will be discussed in light of the present results.
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Affiliation(s)
- C Gundlach
- Experimental Psychology and Methods, Universität Leipzig, Leipzig, Germany.,Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - S Moratti
- Department of Experimental Psychology, Complutense University of Madrid, Madrid, Spain.,Laboratory for Clinical Neuroscience, Centre for Biomedical Technology, Universidad Politécnica de Madrid, Spain
| | - N Forschack
- Experimental Psychology and Methods, Universität Leipzig, Leipzig, Germany.,Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - M M Müller
- Experimental Psychology and Methods, Universität Leipzig, Leipzig, Germany
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10
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Transcranial alternating current stimulation of α but not β frequency sharpens multiple visual functions. Brain Stimul 2019; 13:343-352. [PMID: 31711878 DOI: 10.1016/j.brs.2019.10.022] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Revised: 09/23/2019] [Accepted: 10/31/2019] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND Transcranial alternating current stimulation (tACS) can entrain and enhance cortical oscillatory activity in a frequency-dependent manner. In our previous study (Nakazono et al., 2016), 20 Hz (β) tACS significantly increased excitability of primary motor cortex compared with 10 Hz (α) tACS. α oscillations are a prominent feature of the primary visual cortex (V1) in a resting electroencephalogram. Hence, we investigated whether α and β tACS can differentially influence multiple visual functions. METHODS Firstly, we evaluated the after-effects of α and β tACS on pattern-reversal (PR) and focal-flash (FF) visual evoked potentials (VEPs). Secondly, we determined the relationship between resting α oscillations and PR-VEPs modulated by tACS. Thirdly, the behavioral effects of tACS were assessed by contrast sensitivity. RESULTS α tACS modulated the amplitudes of PR-VEPs, compared with β tACS, but did not modulate the FF-VEPs. Time-frequency analysis revealed that α tACS facilitated event-related α phase synchronizations without increasing power, which consequently increased the PR-VEP amplitudes. There was a significant positive correlation between PR-VEP amplitudes and resting α oscillations. These findings suggested that α tACS modulated α oscillations, and affected visual functions of contrast and spatial frequency. Indeed, α tACS also improved subjects' contrast sensitivity at the behavioral level. Conversely, β tACS increased posterior α activity, but did not change VEP amplitudes. CONCLUSIONS α tACS can influence different neuronal populations from those influenced by β tACS. Thus, our results provide evidence that α tACS sharpens multiple visual functions by modulating α oscillations in V1.
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11
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Liu S, Ma R, Liu X, Zhang C, Chen Y, Jin C, Wang H, Cui J, Zhang X. Using Transcranial Alternating Current Stimulation (tACS) to Improve Romantic Relationships Can Be a Promising Approach. Front Psychol 2019; 10:365. [PMID: 30863342 PMCID: PMC6399378 DOI: 10.3389/fpsyg.2019.00365] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2018] [Accepted: 02/06/2019] [Indexed: 11/13/2022] Open
Abstract
The romantic relationship refers to the specific relationship in which partners are dependent upon each other to obtain satisfactory outcomes and facilitate the pursuit of their most important needs and goals. Satisfying romantic relationships is a strong predictor of better psychological well-being, better physical health, and longer life expectancy. However, romantic relationships are not all smooth-sailing and lovers are often confronted with a variety of unavoidable issues that constantly challenge the stability of their romantic relationships. Dissatisfying romantic relationships are harmful and even destructive. Dyads of lovers engage in a variety of efforts to protect and maintain their romantic relationships based on qualitative research methods including theories- and psychological consultation-based approaches. Unfortunately, those existing approaches do not seem to effectively improve romantic relationships. Thus, it is necessary to seek an efficient approach regulating dyads of lovers in romantic relationships simultaneously. Transcranial alternating current stimulation (tACS) with advantages over existing approaches satisfies this purpose. We discuss the practicability of tACS in detail, as well as why and how tACS can be utilized to improve romantic relationships. In summary, this review firstly introduced the concept of romantic relationship and the necessity of enhancing it. Then, it discussed methods to improve romantic relationships including some existing approaches. This review next discussed the practicability of using tACS to improve romantic relationships. Finally, it shone a spotlight on potential future directions for researches aiming to improve romantic relationships.
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Affiliation(s)
- Shen Liu
- School of Humanities and Social Science, University of Science and Technology of China, Hefei, China
| | - Ru Ma
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, China
| | - Xiaoming Liu
- School of Humanities and Social Science, University of Science and Technology of China, Hefei, China
- School of Foreign Languages, Anhui Jianzhu University, Hefei, China
| | - Chong Zhang
- Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, Hong Kong, China
| | - Yijun Chen
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, China
| | - Chenggong Jin
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, China
| | - Hangwei Wang
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, China
| | - Jiangtian Cui
- Centers for Biomedical Engineering, University of Science and Technology of China, Hefei, China
| | - Xiaochu Zhang
- School of Humanities and Social Science, University of Science and Technology of China, Hefei, China
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, China
- Hefei Medical Research Center on Alcohol Addiction, Anhui Mental Health Center, Hefei, China
- Academy of Psychology and Behavior, Tianjin Normal University, Tianjin, China
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Szymanski C, Müller V, Brick TR, von Oertzen T, Lindenberger U. Hyper-Transcranial Alternating Current Stimulation: Experimental Manipulation of Inter-Brain Synchrony. Front Hum Neurosci 2017; 11:539. [PMID: 29167638 PMCID: PMC5682643 DOI: 10.3389/fnhum.2017.00539] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2017] [Accepted: 10/24/2017] [Indexed: 01/29/2023] Open
Abstract
We walk together, we watch together, we win together: Interpersonally coordinated actions are omnipresent in everyday life, yet the associated neural mechanisms are not well understood. Available evidence suggests that the synchronization of oscillatory activity across brains may provide a mechanism for the temporal alignment of actions between two or more individuals. In an attempt to provide a direct test of this hypothesis, we applied transcranial alternating current stimulation simultaneously to two individuals (hyper-tACS) who were asked to drum in synchrony at a set pace. Thirty-eight female-female dyads performed the dyadic drumming in the course of 3 weeks under three different hyper-tACS stimulation conditions: same-phase-same-frequency; different-phase-different-frequency; sham. Based on available evidence and theoretical considerations, stimulation was applied over right frontal and parietal sites in the theta frequency range. We predicted that same-phase-same-frequency stimulation would improve interpersonal action coordination, expressed as the degree of synchrony in dyadic drumming, relative to the other two conditions. Contrary to expectations, both the same-phase-same-frequency and the different-phase-different-frequency conditions were associated with greater dyadic drumming asynchrony relative to the sham condition. No influence of hyper-tACS on behavioral performance was seen when participants were asked to drum separately in synchrony to a metronome. Individual and dyad preferred drumming tempo was also unaffected by hyper-tACS. We discuss limitations of the present version of the hyper-tACS paradigm, and suggest avenues for future research.
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Affiliation(s)
- Caroline Szymanski
- Center for Lifespan Psychology, Max Planck Institute for Human Development, Berlin, Germany.,Berlin School of Mind and Brain, Humboldt University of Berlin, Berlin, Germany
| | - Viktor Müller
- Center for Lifespan Psychology, Max Planck Institute for Human Development, Berlin, Germany
| | - Timothy R Brick
- Center for Lifespan Psychology, Max Planck Institute for Human Development, Berlin, Germany.,Department of Human Development and Family Studies, Pennsylvania State University, State College, PA, United States
| | - Timo von Oertzen
- Center for Lifespan Psychology, Max Planck Institute for Human Development, Berlin, Germany.,Department of Humanities, Universität der Bundeswehr München, München, Germany
| | - Ulman Lindenberger
- Center for Lifespan Psychology, Max Planck Institute for Human Development, Berlin, Germany.,European University Institute, Fiesole, Italy
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13
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Antal A, Alekseichuk I, Bikson M, Brockmöller J, Brunoni AR, Chen R, Cohen LG, Dowthwaite G, Ellrich J, Flöel A, Fregni F, George MS, Hamilton R, Haueisen J, Herrmann CS, Hummel FC, Lefaucheur JP, Liebetanz D, Loo CK, McCaig CD, Miniussi C, Miranda PC, Moliadze V, Nitsche MA, Nowak R, Padberg F, Pascual-Leone A, Poppendieck W, Priori A, Rossi S, Rossini PM, Rothwell J, Rueger MA, Ruffini G, Schellhorn K, Siebner HR, Ugawa Y, Wexler A, Ziemann U, Hallett M, Paulus W. Low intensity transcranial electric stimulation: Safety, ethical, legal regulatory and application guidelines. Clin Neurophysiol 2017; 128:1774-1809. [PMID: 28709880 PMCID: PMC5985830 DOI: 10.1016/j.clinph.2017.06.001] [Citation(s) in RCA: 679] [Impact Index Per Article: 97.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Revised: 05/29/2017] [Accepted: 06/06/2017] [Indexed: 12/11/2022]
Abstract
Low intensity transcranial electrical stimulation (TES) in humans, encompassing transcranial direct current (tDCS), transcutaneous spinal Direct Current Stimulation (tsDCS), transcranial alternating current (tACS), and transcranial random noise (tRNS) stimulation or their combinations, appears to be safe. No serious adverse events (SAEs) have been reported so far in over 18,000 sessions administered to healthy subjects, neurological and psychiatric patients, as summarized here. Moderate adverse events (AEs), as defined by the necessity to intervene, are rare, and include skin burns with tDCS due to suboptimal electrode-skin contact. Very rarely mania or hypomania was induced in patients with depression (11 documented cases), yet a causal relationship is difficult to prove because of the low incidence rate and limited numbers of subjects in controlled trials. Mild AEs (MAEs) include headache and fatigue following stimulation as well as prickling and burning sensations occurring during tDCS at peak-to-baseline intensities of 1-2mA and during tACS at higher peak-to-peak intensities above 2mA. The prevalence of published AEs is different in studies specifically assessing AEs vs. those not assessing them, being higher in the former. AEs are frequently reported by individuals receiving placebo stimulation. The profile of AEs in terms of frequency, magnitude and type is comparable in healthy and clinical populations, and this is also the case for more vulnerable populations, such as children, elderly persons, or pregnant women. Combined interventions (e.g., co-application of drugs, electrophysiological measurements, neuroimaging) were not associated with further safety issues. Safety is established for low-intensity 'conventional' TES defined as <4mA, up to 60min duration per day. Animal studies and modeling evidence indicate that brain injury could occur at predicted current densities in the brain of 6.3-13A/m2 that are over an order of magnitude above those produced by tDCS in humans. Using AC stimulation fewer AEs were reported compared to DC. In specific paradigms with amplitudes of up to 10mA, frequencies in the kHz range appear to be safe. In this paper we provide structured interviews and recommend their use in future controlled studies, in particular when trying to extend the parameters applied. We also discuss recent regulatory issues, reporting practices and ethical issues. These recommendations achieved consensus in a meeting, which took place in Göttingen, Germany, on September 6-7, 2016 and were refined thereafter by email correspondence.
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Affiliation(s)
- A Antal
- Department of Clinical Neurophysiology, University Medical Center Göttingen, Georg August University, Göttingen, Germany.
| | - I Alekseichuk
- Department of Clinical Neurophysiology, University Medical Center Göttingen, Georg August University, Göttingen, Germany
| | - M Bikson
- Department of Biomedical Engineering, The City College of New York, New York, USA
| | - J Brockmöller
- Department of Clinical Pharmacology, University Medical Center Goettingen, Germany
| | - A R Brunoni
- Service of Interdisciplinary Neuromodulation, Department and Institute of Psychiatry, Laboratory of Neurosciences (LIM-27) and Interdisciplinary Center for Applied Neuromodulation University Hospital, University of São Paulo, São Paulo, Brazil
| | - R Chen
- Division of Neurology, Department of Medicine, University of Toronto and Krembil Research Institute, Toronto, Ontario, Canada
| | - L G Cohen
- Human Cortical Physiology and Neurorehabilitation Section, National Institute of Neurological Disorders and Stroke NIH, Bethesda, USA
| | | | - J Ellrich
- Department of Health Science and Technology, Aalborg University, Aalborg, Denmark; Institute of Physiology and Pathophysiology, University of Erlangen-Nürnberg, Erlangen, Germany; EBS Technologies GmbH, Europarc Dreilinden, Germany
| | - A Flöel
- Universitätsmedizin Greifswald, Klinik und Poliklinik für Neurologie, Greifswald, Germany
| | - F Fregni
- Spaulding Neuromodulation Center, Spaulding Rehabilitation Hospital, Harvard Medical School, Boston, MA, USA
| | - M S George
- Brain Stimulation Division, Medical University of South Carolina, and Ralph H. Johnson Veterans Affairs Medical Center, Charleston, SC, USA
| | - R Hamilton
- Department of Neurology, University of Pennsylvania, Philadelphia, PA, USA
| | - J Haueisen
- Institute of Biomedical Engineering and Informatics, Technische Universität Ilmenau, Germany
| | - C S Herrmann
- Experimental Psychology Lab, Department of Psychology, European Medical School, Carl von Ossietzky Universität, Oldenburg, Germany
| | - F C Hummel
- Defitech Chair of Clinical Neuroengineering, Centre of Neuroprosthetics (CNP) and Brain Mind Institute, Swiss Federal Institute of Technology (EPFL), Geneva, Switzerland; Defitech Chair of Clinical Neuroengineering, Clinique Romande de Réadaptation, Swiss Federal Institute of Technology (EPFL Valais), Sion, Switzerland
| | - J P Lefaucheur
- Department of Physiology, Henri Mondor Hospital, Assistance Publique - Hôpitaux de Paris, and EA 4391, Nerve Excitability and Therapeutic Team (ENT), Faculty of Medicine, Paris Est Créteil University, Créteil, France
| | - D Liebetanz
- Department of Clinical Neurophysiology, University Medical Center Göttingen, Georg August University, Göttingen, Germany
| | - C K Loo
- School of Psychiatry & Black Dog Institute, University of New South Wales, Sydney, Australia
| | - C D McCaig
- Institute of Medical Sciences, University of Aberdeen, Aberdeen, Scotland, UK
| | - C Miniussi
- Center for Mind/Brain Sciences CIMeC, University of Trento, Rovereto, Italy; Cognitive Neuroscience Section, IRCCS Centro San Giovanni di Dio Fatebenefratelli, Brescia, Italy
| | - P C Miranda
- Institute of Biophysics and Biomedical Engineering, Faculdade de Ciências, Universidade de Lisboa, Lisboa, Portugal
| | - V Moliadze
- Institute of Medical Psychology and Medical Sociology, University Hospital of Schleswig-Holstein (UKSH), Campus Kiel, Christian-Albrechts-University, Kiel, Germany
| | - M A Nitsche
- Department of Psychology and Neurosciences, Leibniz Research Centre for Working Environment and Human Factors, Dortmund, Germany; Department of Neurology, University Hospital Bergmannsheil, Bochum, Germany
| | - R Nowak
- Neuroelectrics, Barcelona, Spain
| | - F Padberg
- Department of Psychiatry and Psychotherapy, Munich Center for Brain Stimulation, Ludwig-Maximilian University Munich, Germany
| | - A Pascual-Leone
- Division of Cognitive Neurology, Harvard Medical Center and Berenson-Allen Center for Noninvasive Brain Stimulation at Beth Israel Deaconess Medical Center, Boston, USA
| | - W Poppendieck
- Department of Information Technology, Mannheim University of Applied Sciences, Mannheim, Germany
| | - A Priori
- Center for Neurotechnology and Experimental Brain Therapeutich, Department of Health Sciences, University of Milan Italy; Deparment of Clinical Neurology, University Hospital Asst Santi Paolo E Carlo, Milan, Italy
| | - S Rossi
- Department of Medicine, Surgery and Neuroscience, Human Physiology Section and Neurology and Clinical Neurophysiology Section, Brain Investigation & Neuromodulation Lab, University of Siena, Italy
| | - P M Rossini
- Area of Neuroscience, Institute of Neurology, University Clinic A. Gemelli, Catholic University, Rome, Italy
| | | | - M A Rueger
- Department of Neurology, University Hospital of Cologne, Germany
| | | | | | - H R Siebner
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark; Department of Neurology, Copenhagen University Hospital Bispebjerg, Copenhagen, Denmark
| | - Y Ugawa
- Department of Neurology, Fukushima Medical University, Fukushima, Japan; Fukushima Global Medical Science Center, Advanced Clinical Research Center, Fukushima Medical University, Japan
| | - A Wexler
- Department of Science, Technology & Society, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - U Ziemann
- Department of Neurology & Stroke, and Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
| | - M Hallett
- Human Motor Control Section, National Institute of Neurological Disorders and Stroke, NIH, Bethesda, MD, USA
| | - W Paulus
- Department of Clinical Neurophysiology, University Medical Center Göttingen, Georg August University, Göttingen, Germany
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14
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Reteig LC, Talsma LJ, van Schouwenburg MR, Slagter HA. Transcranial Electrical Stimulation as a Tool to Enhance Attention. JOURNAL OF COGNITIVE ENHANCEMENT 2017. [DOI: 10.1007/s41465-017-0010-y] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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15
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Horwitz A, Dyhr Thomsen M, Wiegand I, Horwitz H, Klemp M, Nikolic M, Rask L, Lauritzen M, Benedek K. Visual steady state in relation to age and cognitive function. PLoS One 2017; 12:e0171859. [PMID: 28245274 PMCID: PMC5330460 DOI: 10.1371/journal.pone.0171859] [Citation(s) in RCA: 9] [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: 09/29/2016] [Accepted: 01/26/2017] [Indexed: 12/25/2022] Open
Abstract
Neocortical gamma activity is crucial for sensory perception and cognition. This study examines the value of using non-task stimulation-induced EEG oscillations to predict cognitive status in a birth cohort of healthy Danish males (Metropolit) with varying cognitive ability. In particular, we examine the steady-state VEP power response (SSVEP-PR) in the alpha (8Hz) and gamma (36Hz) bands in 54 males (avg. age: 62.0 years) and compare these with 10 young healthy participants (avg. age 27.6 years). Furthermore, we correlate the individual alpha-to-gamma difference in relative visual-area power (ΔRV) with cognitive scores for the older adults. We find that ΔRV decrease with age by just over one standard deviation when comparing young with old participants (p<0.01). Furthermore, intelligence is significantly negatively correlated with ΔRV in the older adult cohort, even when processing speed, global cognition, executive function, memory, and education (p<0.05). In our preferred specification, an increase in ΔRV of one standard deviation is associated with a reduction in intelligence of 48% of a standard deviation (p<0.01). Finally, we conclude that the difference in cerebral rhythmic activity between the alpha and gamma bands is associated with age and cognitive status, and that ΔRV therefore provide a non-subjective clinical tool with which to examine cognitive status in old age.
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Affiliation(s)
- Anna Horwitz
- Department of Neuroscience and Pharmacology, University of Copenhagen, Blegdamsvej 3, Copenhagen, Denmark
- Center for Healthy Aging, University of Copenhagen, Blegdamsvej 3, Copenhagen, Denmark
- Department of Clinical Neurophysiology, Rigshospitalet–Glostrup, Nordre Ringvej 57, Glostrup, Denmark
- * E-mail:
| | - Mia Dyhr Thomsen
- Department of Clinical Neurophysiology, Rigshospitalet–Glostrup, Nordre Ringvej 57, Glostrup, Denmark
| | - Iris Wiegand
- Department of Psychology, University of Copenhagen, Øster Farimagsgade 2A, Copenhagen, Denmark
| | - Henrik Horwitz
- Department of Clinical Pharmacology, Bispebjerg Hospital, Bispebjerg Bakke 23, København NV, Denmark
| | - Marc Klemp
- Department of Economics and Population Studies & Training Center, Brown University, Providence, Rhode Island, United States of America
- Department of Economics, University of Copenhagen, Øster Farimagsgade 5, Copenhagen, Denmark
| | - Miki Nikolic
- Department of Clinical Neurophysiology, Rigshospitalet–Glostrup, Nordre Ringvej 57, Glostrup, Denmark
| | - Lene Rask
- Department of Clinical Neurophysiology, Rigshospitalet–Glostrup, Nordre Ringvej 57, Glostrup, Denmark
| | - Martin Lauritzen
- Department of Neuroscience and Pharmacology, University of Copenhagen, Blegdamsvej 3, Copenhagen, Denmark
- Center for Healthy Aging, University of Copenhagen, Blegdamsvej 3, Copenhagen, Denmark
- Department of Clinical Neurophysiology, Rigshospitalet–Glostrup, Nordre Ringvej 57, Glostrup, Denmark
| | - Krisztina Benedek
- Department of Clinical Neurophysiology, Rigshospitalet–Glostrup, Nordre Ringvej 57, Glostrup, Denmark
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16
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Nakazono H, Ogata K, Kuroda T, Tobimatsu S. Phase and Frequency-Dependent Effects of Transcranial Alternating Current Stimulation on Motor Cortical Excitability. PLoS One 2016; 11:e0162521. [PMID: 27607431 PMCID: PMC5015848 DOI: 10.1371/journal.pone.0162521] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Accepted: 08/24/2016] [Indexed: 01/01/2023] Open
Abstract
Transcranial alternating current stimulation (tACS) can entrain ongoing brain oscillations and modulate the motor system in a frequency-dependent manner. Recent animal studies have demonstrated that the phase of a sinusoidal current also has an important role in modulation of neuronal activity. However, the phase effects of tACS on the human motor system are largely unknown. Here, we systematically investigated the effects of tACS phase and frequency on the primary motor cortex (M1) by using motor evoked potentials (MEPs) with transcranial magnetic stimulation (TMS). First, we compared the phase effects (90°, 180°, 270° or 360°) of 10 and 20 Hz tACS on MEPs. The 20 Hz tACS significantly increased M1 excitability compared with the 10 Hz tACS at 90° phase only. Second, we studied the 90° phase effect on MEPs at different tACS frequencies (5, 10, 20 or 40 Hz). The 20 vs. 10 Hz difference was again observed, but the 90° phase in 5 and 40 Hz tACS did not influence M1 excitability. Third, the 90° phase effects of 10 and 20 Hz tACS were compared with sham stimulation. The 90° phase of 20 Hz tACS enhanced MEP amplitudes compared with sham stimulation, but there was no significant effect of 10 Hz tACS. Taken together, we assume that the differential 90° phase effects on 20 Hz and 10 Hz tACS can be attributed to the neural synchronization modulated by tACS. Our results further underline that phase and frequency are the important factors in the effects of tACS on M1 excitability.
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Affiliation(s)
- Hisato Nakazono
- Department of Clinical Neurophysiology, Neurological Institute, Faculty of Medicine, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
- * E-mail:
| | - Katsuya Ogata
- Department of Clinical Neurophysiology, Neurological Institute, Faculty of Medicine, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Tsuyoshi Kuroda
- Faculty of Informatics, Shizuoka University, Shizuoka, Japan
| | - Shozo Tobimatsu
- Department of Clinical Neurophysiology, Neurological Institute, Faculty of Medicine, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
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