1
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Vogeti S, Faramarzi M, Herrmann CS. Alpha transcranial alternating current stimulation modulates auditory perception. Brain Stimul 2023; 16:1646-1652. [PMID: 37949295 DOI: 10.1016/j.brs.2023.11.002] [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: 05/03/2023] [Revised: 10/30/2023] [Accepted: 11/02/2023] [Indexed: 11/12/2023] Open
Abstract
BACKGROUND Studies using transcranial alternating current stimulation (tACS), a type of non-invasive brain stimulation, have demonstrated a relationship between the positive versus negative phase of both alpha and delta/theta oscillations with variable near-threshold auditory perception. These findings have not been directly compared before. Furthermore, as perception was better in the positive versus negative phase of two different frequencies, it is unclear whether changes in polarity (independent of a specific frequency) could also modulate auditory perception. OBJECTIVE We investigated whether auditory perception depends on the phase of alpha, delta/theta, or polarity alone. METHODS We stimulated participants with alpha, delta, and positive and negative direct current (DC) over temporal and central scalp sites while they identified near-threshold tones-in-noise. A Sham condition without tACS served as a control condition. A repeated-measures analysis of variance was used to assess differences in proportions of hits between conditions and polarities. Permutation-based circular-logistic regressions were used to assess the relationship between circular-predictors and single-trial behavioral responses. An exploratory analysis compared the full circular-logistic regression model to the intercept-only model. RESULTS Overall, there were a greater proportion of hits in the Alpha condition in comparison to Delta, DC, and Sham conditions. We also found an interaction between polarity and stimulation condition; post-hoc analyses revealed a greater proportion of hits in the positive versus negative phase of Alpha tACS. In contrast, no significant differences were found in the Delta, DC, or Sham conditions. The permutation-based circular-logistic regressions did not reveal a statistically significant difference between the obtained RMS of the sine and cosine coefficients and the mean of the surrogate distribution for any of the conditions. However, our exploratory analysis revealed that circular-predictors explained the behavioral data significantly better than an intercept-only model for the Alpha condition, and not the other three conditions. CONCLUSION These findings suggest that alpha tACS, and not delta nor polarity alone, modulates auditory perception.
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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
| | - Maryam Faramarzi
- 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.
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2
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Chalas N, Daube C, Kluger DS, Abbasi O, Nitsch R, Gross J. Multivariate analysis of speech envelope tracking reveals coupling beyond auditory cortex. Neuroimage 2022; 258:119395. [PMID: 35718023 DOI: 10.1016/j.neuroimage.2022.119395] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Revised: 05/16/2022] [Accepted: 06/14/2022] [Indexed: 11/19/2022] Open
Abstract
The systematic alignment of low-frequency brain oscillations with the acoustic speech envelope signal is well established and has been proposed to be crucial for actively perceiving speech. Previous studies investigating speech-brain coupling in source space are restricted to univariate pairwise approaches between brain and speech signals, and therefore speech tracking information in frequency-specific communication channels might be lacking. To address this, we propose a novel multivariate framework for estimating speech-brain coupling where neural variability from source-derived activity is taken into account along with the rate of envelope's amplitude change (derivative). We applied it in magnetoencephalographic (MEG) recordings while human participants (male and female) listened to one hour of continuous naturalistic speech, showing that a multivariate approach outperforms the corresponding univariate method in low- and high frequencies across frontal, motor, and temporal areas. Systematic comparisons revealed that the gain in low frequencies (0.6 - 0.8 Hz) was related to the envelope's rate of change whereas in higher frequencies (from 0.8 to 10 Hz) it was mostly related to the increased neural variability from source-derived cortical areas. Furthermore, following a non-negative matrix factorization approach we found distinct speech-brain components across time and cortical space related to speech processing. We confirm that speech envelope tracking operates mainly in two timescales (δ and θ frequency bands) and we extend those findings showing shorter coupling delays in auditory-related components and longer delays in higher-association frontal and motor components, indicating temporal differences of speech tracking and providing implications for hierarchical stimulus-driven speech processing.
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Affiliation(s)
- Nikos Chalas
- Institute for Biomagnetism and Biosignal Analysis, University of Münster, Münster, Germany; Otto-Creutzfeldt-Center for Cognitive and Behavioral Neuroscience, University of Münster, Münster, Germany.
| | - Christoph Daube
- Centre for Cognitive Neuroimaging, University of Glasgow, Glasgow, UK
| | - Daniel S Kluger
- Institute for Biomagnetism and Biosignal Analysis, University of Münster, Münster, Germany; Otto-Creutzfeldt-Center for Cognitive and Behavioral Neuroscience, University of Münster, Münster, Germany
| | - Omid Abbasi
- Institute for Biomagnetism and Biosignal Analysis, University of Münster, Münster, Germany
| | - Robert Nitsch
- Institute for Translational Neuroscience, University of Münster, Münster, Germany
| | - Joachim Gross
- Institute for Biomagnetism and Biosignal Analysis, University of Münster, Münster, Germany; Otto-Creutzfeldt-Center for Cognitive and Behavioral Neuroscience, University of Münster, Münster, Germany
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3
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Keitel C, Ruzzoli M, Dugué L, Busch NA, Benwell CSY. Rhythms in cognition: The evidence revisited. Eur J Neurosci 2022; 55:2991-3009. [PMID: 35696729 PMCID: PMC9544967 DOI: 10.1111/ejn.15740] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2022] [Revised: 05/27/2022] [Accepted: 05/30/2022] [Indexed: 12/27/2022]
Affiliation(s)
| | - Manuela Ruzzoli
- Basque Center on Cognition, Brain and Language (BCBL), Donostia/San Sebastian, Spain.,Ikerbasque, Basque Foundation for Science, Bilbao, Spain
| | - Laura Dugué
- Université Paris Cité, INCC UMR 8002, CNRS, Paris, France.,Institut Universitaire de France (IUF), Paris, France
| | - Niko A Busch
- Institute for Psychology, University of Münster, Münster, Germany
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4
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Ma R, Xia X, Zhang W, Lu Z, Wu Q, Cui J, Song H, Fan C, Chen X, Zha R, Wei J, Ji GJ, Wang X, Qiu B, Zhang X. High Gamma and Beta Temporal Interference Stimulation in the Human Motor Cortex Improves Motor Functions. Front Neurosci 2022; 15:800436. [PMID: 35046771 PMCID: PMC8761631 DOI: 10.3389/fnins.2021.800436] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2021] [Accepted: 11/29/2021] [Indexed: 12/14/2022] Open
Abstract
Background: Temporal interference (TI) stimulation is a new technique of non-invasive brain stimulation. Envelope-modulated waveforms with two high-frequency carriers can activate neurons in target brain regions without stimulating the overlying cortex, which has been validated in mouse brains. However, whether TI stimulation can work on the human brain has not been elucidated. Objective: To assess the effectiveness of the envelope-modulated waveform of TI stimulation on the human primary motor cortex (M1). Methods: Participants attended three sessions of 30-min TI stimulation during a random reaction time task (RRTT) or a serial reaction time task (SRTT). Motor cortex excitability was measured before and after TI stimulation. Results: In the RRTT experiment, only 70 Hz TI stimulation had a promoting effect on the reaction time (RT) performance and excitability of the motor cortex compared to sham stimulation. Meanwhile, compared with the sham condition, only 20 Hz TI stimulation significantly facilitated motor learning in the SRTT experiment, which was significantly positively correlated with the increase in motor evoked potential. Conclusion: These results indicate that the envelope-modulated waveform of TI stimulation has a significant promoting effect on human motor functions, experimentally suggesting the effectiveness of TI stimulation in humans for the first time and paving the way for further explorations.
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Affiliation(s)
- Ru Ma
- Hefei National Laboratory for Physical Sciences at the Microscale, Division of Life Science and Medicine, Department of Radiology, The First Affiliated Hospital of USTC, School of Life Science, University of Science and Technology of China, Hefei, China
| | - Xinzhao Xia
- Centers for Biomedical Engineering, School of Information Science and Technology, University of Science and Technology of China, Hefei, China
| | - Wei Zhang
- Hefei National Laboratory for Physical Sciences at the Microscale, Division of Life Science and Medicine, Department of Radiology, The First Affiliated Hospital of USTC, School of Life Science, University of Science and Technology of China, Hefei, China
| | - Zhuo Lu
- Centers for Biomedical Engineering, School of Information Science and Technology, University of Science and Technology of China, Hefei, China
| | - Qianying Wu
- Hefei National Laboratory for Physical Sciences at the Microscale, Division of Life Science and Medicine, Department of Radiology, The First Affiliated Hospital of USTC, School of Life Science, University of Science and Technology of China, Hefei, China.,Division of the Humanities and Social Sciences, California Institute of Technology, Pasadena, CA, United States
| | - Jiangtian Cui
- Centers for Biomedical Engineering, School of Information Science and Technology, University of Science and Technology of China, Hefei, China.,School of Optometry and Vision Sciences, Cardiff University, Cardiff, United Kingdom
| | - Hongwen Song
- Hefei National Laboratory for Physical Sciences at the Microscale, Division of Life Science and Medicine, Department of Radiology, The First Affiliated Hospital of USTC, School of Life Science, University of Science and Technology of China, Hefei, China
| | - Chuan Fan
- Centers for Biomedical Engineering, School of Information Science and Technology, University of Science and Technology of China, Hefei, China
| | - Xueli Chen
- Hefei National Laboratory for Physical Sciences at the Microscale, Division of Life Science and Medicine, Department of Radiology, The First Affiliated Hospital of USTC, School of Life Science, University of Science and Technology of China, Hefei, China
| | - Rujing Zha
- Hefei National Laboratory for Physical Sciences at the Microscale, Division of Life Science and Medicine, Department of Radiology, The First Affiliated Hospital of USTC, School of Life Science, University of Science and Technology of China, Hefei, China
| | - Junjie Wei
- Department of Neurology, The First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Gong-Jun Ji
- Department of Neurology, The First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Xiaoxiao Wang
- Centers for Biomedical Engineering, School of Information Science and Technology, University of Science and Technology of China, Hefei, China
| | - Bensheng Qiu
- Centers for Biomedical Engineering, School of Information Science and Technology, University of Science and Technology of China, Hefei, China
| | - Xiaochu Zhang
- Hefei National Laboratory for Physical Sciences at the Microscale, Division of Life Science and Medicine, Department of Radiology, The First Affiliated Hospital of USTC, School of Life Science, University of Science and Technology of China, Hefei, China.,Centers for Biomedical Engineering, School of Information Science and Technology, University of Science and Technology of China, Hefei, China.,Department of Psychology, School of Humanities and Social Science, University of Science and Technology of China, Hefei, China.,Biomedical Sciences and Health Laboratory of Anhui Province, University of Science and Technology of China, Hefei, China
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5
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Fiene M, Radecke JO, Misselhorn J, Sengelmann M, Herrmann CS, Schneider TR, Schwab BC, Engel AK. tACS phase-specifically biases brightness perception of flickering light. Brain Stimul 2022; 15:244-253. [PMID: 34990876 DOI: 10.1016/j.brs.2022.01.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Revised: 12/08/2021] [Accepted: 01/01/2022] [Indexed: 11/02/2022] Open
Abstract
BACKGROUND Visual phenomena like brightness illusions impressively demonstrate the highly constructive nature of perception. In addition to physical illumination, the subjective experience of brightness is related to temporal neural dynamics in visual cortex. OBJECTIVE Here, we asked whether biasing the temporal pattern of neural excitability in visual cortex by transcranial alternating current stimulation (tACS) modulates brightness perception of concurrent rhythmic visual stimuli. METHODS Participants performed a brightness discrimination task of two flickering lights, one of which was targeted by same-frequency electrical stimulation at varying phase shifts. tACS was applied with an occipital and a periorbital active control montage, based on simulations of electrical currents using finite element head models. RESULTS Experimental results reveal that flicker brightness perception is modulated dependent on the phase shift between sensory and electrical stimulation, solely under occipital tACS. Phase-specific modulatory effects by tACS were dependent on flicker-evoked neural phase stability at the tACS-targeted frequency, recorded prior to electrical stimulation. Further, the optimal timing of tACS application leading to enhanced brightness perception was correlated with the neural phase delay of the cortical flicker response. CONCLUSIONS Our results corroborate the role of temporally coordinated neural activity in visual cortex for brightness perception of rhythmic visual input in humans. Phase-specific behavioral modulations by tACS emphasize its efficacy to transfer perceptually relevant temporal information to the cortex. These findings provide an important step towards understanding the basis of visual perception and further confirm electrical stimulation as a tool for advancing controlled modulations of neural activity and related behavior.
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Affiliation(s)
- Marina Fiene
- Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, Hamburg, 20246, Germany.
| | - Jan-Ole Radecke
- Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, Hamburg, 20246, Germany
| | - Jonas Misselhorn
- Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, Hamburg, 20246, Germany
| | - Malte Sengelmann
- Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, Hamburg, 20246, Germany
| | - Christoph S Herrmann
- Experimental Psychology Lab, Department of Psychology, Cluster of Excellence "Hearing4all", European Medical School, Carl von Ossietzky University Oldenburg, Oldenburg, 26129, Germany; Research Center Neurosensory Science, Carl von Ossietzky University Oldenburg, Oldenburg, 26129, Germany
| | - Till R Schneider
- Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, Hamburg, 20246, Germany
| | - Bettina C Schwab
- Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, Hamburg, 20246, Germany
| | - Andreas K Engel
- Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, Hamburg, 20246, Germany
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6
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Coldea A, Morand S, Veniero D, Harvey M, Thut G. Parietal alpha tACS shows inconsistent effects on visuospatial attention. PLoS One 2021; 16:e0255424. [PMID: 34351972 PMCID: PMC8341497 DOI: 10.1371/journal.pone.0255424] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Accepted: 07/15/2021] [Indexed: 11/19/2022] Open
Abstract
Transcranial alternating current stimulation (tACS) is a popular technique that has been used for manipulating brain oscillations and inferring causality regarding the brain-behaviour relationship. Although it is a promising tool, the variability of tACS results has raised questions regarding the robustness and reproducibility of its effects. Building on recent research using tACS to modulate visuospatial attention, we here attempted to replicate findings of lateralized parietal tACS at alpha frequency to induce a change in attention bias away from the contra- towards the ipsilateral visual hemifield. 40 healthy participants underwent tACS in two separate sessions where either 10 Hz tACS or sham was applied via a high-density montage over the left parietal cortex at 1.5 mA for 20 min, while performance was assessed in an endogenous attention task. Task and tACS parameters were chosen to match those of previous studies reporting positive effects. Unlike these studies, we did not observe lateralized parietal alpha tACS to affect attention deployment or visual processing across the hemifields as compared to sham. Likewise, additional resting electroencephalography immediately offline to tACS did not reveal any notable effects on individual alpha power or frequency. Our study emphasizes the need for more replication studies and systematic investigations of the factors that drive tACS effects.
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Affiliation(s)
- Andra Coldea
- Centre for Cognitive Neuroimaging, Institute of Neuroscience and Psychology, University of Glasgow, Glasgow, United Kingdom
| | - Stephanie Morand
- School of Life Sciences, MVLS College, University of Glasgow, Glasgow, United Kingdom
| | - Domenica Veniero
- School of Psychology, University of Nottingham, Nottingham, United Kingdom
| | - Monika Harvey
- Centre for Cognitive Neuroimaging, Institute of Neuroscience and Psychology, University of Glasgow, Glasgow, United Kingdom
| | - Gregor Thut
- Centre for Cognitive Neuroimaging, Institute of Neuroscience and Psychology, University of Glasgow, Glasgow, United Kingdom
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7
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Erkens J, Schulte M, Vormann M, Wilsch A, Herrmann CS. Hearing Impaired Participants Improve More Under Envelope-Transcranial Alternating Current Stimulation When Signal to Noise Ratio Is High. Neurosci Insights 2021; 16:2633105520988854. [PMID: 33709079 PMCID: PMC7907945 DOI: 10.1177/2633105520988854] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Accepted: 12/31/2020] [Indexed: 11/16/2022] Open
Abstract
An issue commonly expressed by hearing aid users is a difficulty to understand speech in complex hearing scenarios, that is, when speech is presented together with background noise or in situations with multiple speakers. Conventional hearing aids are already designed with these issues in mind, using beamforming to only enhance sound from a specific direction, but these are limited in solving these issues as they can only modulate incoming sound at the cochlear level. However, evidence exists that age-related hearing loss might partially be caused later in the hearing processes due to brain processes slowing down and becoming less efficient. In this study, we tested whether it would be possible to improve the hearing process at the cortical level by improving neural tracking of speech. The speech envelopes of target sentences were transformed into an electrical signal and stimulated onto elderly participants' cortices using transcranial alternating current stimulation (tACS). We compared 2 different signal to noise ratios (SNRs) with 5 different delays between sound presentation and stimulation ranging from 50 ms to 150 ms, and the differences in effects between elderly normal hearing and elderly hearing impaired participants. When the task was performed at a high SNR, hearing impaired participants appeared to gain more from envelope-tACS compared to when the task was performed at a lower SNR. This was not the case for normal hearing participants. Furthermore, a post-hoc analysis of the different time-lags suggest that elderly were significantly better at a stimulation time-lag of 150 ms when the task was presented at a high SNR. In this paper, we outline why these effects are worth exploring further, and what they tell us about the optimal tACS time-lag.
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Affiliation(s)
- Jules Erkens
- Department of Psychology, Cluster of
Excellence “Hearing4All,” European Medical School, Carl von Ossietzky University,
Oldenburg, Germany
| | | | | | - Anna Wilsch
- Department of Psychology, Cluster of
Excellence “Hearing4All,” European Medical School, Carl von Ossietzky University,
Oldenburg, Germany
| | - Christoph S Herrmann
- Department of Psychology, Cluster of
Excellence “Hearing4All,” European Medical School, Carl von Ossietzky University,
Oldenburg, Germany
- Research Center Neurosensory Science,
Carl von Ossietzky University, Oldenburg, Germany
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8
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Zhang M, Amon A, Hanssen S, Wu M, Bonte M, Riecke L. No evidence for modulation of sound rise-time perception by 4-Hz brain oscillations. Brain Stimul 2021; 14:364-365. [PMID: 33581282 DOI: 10.1016/j.brs.2021.02.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Accepted: 02/07/2021] [Indexed: 10/22/2022] Open
Affiliation(s)
- Manli Zhang
- Maastricht Brain Imaging Center, Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, 6229 EV, Maastricht, the Netherlands
| | - Anita Amon
- Maastricht Brain Imaging Center, Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, 6229 EV, Maastricht, the Netherlands
| | - Saskia Hanssen
- Maastricht Brain Imaging Center, Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, 6229 EV, Maastricht, the Netherlands; Faculty of Health Medicine and Life Sciences, Maastricht University, 6229 EV, Maastricht, the Netherlands
| | - Min Wu
- Maastricht Brain Imaging Center, Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, 6229 EV, Maastricht, the Netherlands
| | - Milene Bonte
- Maastricht Brain Imaging Center, Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, 6229 EV, Maastricht, the Netherlands
| | - Lars Riecke
- Maastricht Brain Imaging Center, Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, 6229 EV, Maastricht, the Netherlands.
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9
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Ronconi L, Melcher D, Junghöfer M, Wolters CH, Busch NA. Testing the effect of tACS over parietal cortex in modulating endogenous alpha rhythm and temporal integration windows in visual perception. Eur J Neurosci 2020; 55:3438-3450. [PMID: 33098112 PMCID: PMC9542321 DOI: 10.1111/ejn.15017] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 10/14/2020] [Accepted: 10/15/2020] [Indexed: 11/29/2022]
Abstract
Neural oscillations in the alpha band (8-12 Hz) have been proposed as a key mechanism for the temporal resolution of visual perception. Higher alpha frequencies have been related to improved segregation of visual events over time, whereas lower alpha frequencies have been related to improved temporal integration. Similarly, also the phase of ongoing alpha has been shown to correlate with temporal integration/segregation. To test a causal relationship between alpha oscillations and perception, we here employed multi-channel transcranial alternating current stimulation (mc-tACS) over the right parietal cortex, whereas participants performed a visual temporal integration/segregation task that used identical stimuli with different instructions. Before and after mc-tACS we recorded the resting-state electroencephalogram (EEG) to extract the individual alpha frequency (IAF) and delivered electrical stimulation at slightly slower and faster frequencies (IAF±2 Hz). We hypothesized that this would not only drive endogenous alpha rhythms, but also affect temporal integration and segregation in an opposite way. However, the mc-tACS protocol used here did not consistently increase or decrease the IAF after the stimulation and did not affect temporal integration/segregation accuracy as expected. Although we found some preliminary evidence for an influence of tACS phase on temporal integration accuracy, the ongoing phase of mc-tACS oscillations did not reliably modulate temporal integration/segregation accuracy in a sinusoidal way as would have been predicted by an effective entrainment of brain oscillations. These findings may guide future studies using different stimulation montages for investigating the role of cortical alpha oscillations for human vision.
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Affiliation(s)
- Luca Ronconi
- School of Psychology, Vita-Salute San Raffaele University, Milan, Italy.,Division of Neuroscience, Scientific Institute IRCCS San Raffaele, Milan, Italy.,Center for Mind/Brain Sciences and Department of Psychology and Cognitive Science, University of Trento, Rovereto, Italy
| | - David Melcher
- Center for Mind/Brain Sciences and Department of Psychology and Cognitive Science, University of Trento, Rovereto, Italy.,Department of Psychology, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
| | - Markus Junghöfer
- Institute for Biomagnetism and Biosignalanalysis, University of Münster, Münster, Germany.,Otto Creutzfeldt Center for Cognitive and Behavioral Neuroscience, University of Münster, Münster, Germany
| | - Carsten H Wolters
- Institute for Biomagnetism and Biosignalanalysis, University of Münster, Münster, Germany.,Otto Creutzfeldt Center for Cognitive and Behavioral Neuroscience, University of Münster, Münster, Germany
| | - Niko A Busch
- Otto Creutzfeldt Center for Cognitive and Behavioral Neuroscience, University of Münster, Münster, Germany.,Institute of Psychology, University of Münster, Münster, Germany
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10
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Kasten FH, Herrmann CS. Discrete sampling in perception via neuronal oscillations-Evidence from rhythmic, non-invasive brain stimulation. Eur J Neurosci 2020; 55:3402-3417. [PMID: 33048382 DOI: 10.1111/ejn.15006] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Revised: 10/07/2020] [Accepted: 10/08/2020] [Indexed: 11/26/2022]
Abstract
A variety of perceptual phenomena suggest that, in contrast to our everyday experience, our perception may be discrete rather than continuous. The possibility of such discrete sampling processes inevitably prompts the question of how such discretization is implemented in the brain. Evidence from neurophysiological measurements suggest that neural oscillations, particularly in the lower frequencies, may provide a mechanism by which such discretization can be implemented. It is hypothesized that cortical excitability is rhythmically enhanced or reduced along the positive and negative half-cycle of such oscillations. In recent years, rhythmic non-invasive brain stimulation approaches such as rhythmic transcranial magnetic stimulation (rTMS) and transcranial alternating current stimulation (tACS) are increasingly used to test this hypothesis. Both methods are thought to entrain endogenous brain oscillations, allowing them to alter their power, frequency, and phase in order to study their roles in perception. After a brief introduction to the core mechanisms of both methods, we will provide an overview of rTMS and tACS studies probing the role of brain oscillations for discretized perception in different domains and will contrast these results with unsuccessful attempts. Further, we will discuss methodological pitfalls and challenges associated with the methods.
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Affiliation(s)
- Florian H Kasten
- Experimental Psychology Lab, Department of Psychology, Cluster of Excellence "Hearing for All", European Medical School, Carl von Ossietzky University, Oldenburg, Germany.,Neuroimaging Unit, European Medical School, Carl von Ossietzky University, Oldenburg, Germany
| | - Christoph S Herrmann
- Experimental Psychology Lab, Department of Psychology, Cluster of Excellence "Hearing for All", European Medical School, 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
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11
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van der Plas M, Hanslmayr S. Entraining neurons via noninvasive electric stimulation improves cognition. PLoS Biol 2020; 18:e3000931. [PMID: 33091011 PMCID: PMC7654821 DOI: 10.1371/journal.pbio.3000931] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Revised: 11/10/2020] [Indexed: 11/19/2022] Open
Abstract
Transcranial Alternating Current Stimulation (tACS) is a method that injects rhythmic currents into the human brain via electrodes attached to the scalp of a participant. This technique allows researchers to control naturally occurring brain rhythms and study their causal relevance for cognition. Recent findings, however, cast doubts on the effectiveness of tACS to stimulate the brain and its mode of action. Two new studies by Vieira and colleagues and Marchesotti and colleagues reported in the current issue report promising new results in showing that tACS can entrain single neuron activity and improve reading abilities in dyslexic individuals.
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Affiliation(s)
- Mircea van der Plas
- School of Psychology, University of Birmingham, Birmingham, United Kingdom
- Centre for Human Brain Health, University of Birmingham, United Kingdom
- Institute for Neuroscience and Psychology, University of Glasgow, Glasgow, United Kingdom
| | - Simon Hanslmayr
- Institute for Neuroscience and Psychology, University of Glasgow, Glasgow, United Kingdom
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12
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Erkens J, Schulte M, Vormann M, Herrmann CS. Lacking Effects of Envelope Transcranial Alternating Current Stimulation Indicate the Need to Revise Envelope Transcranial Alternating Current Stimulation Methods. Neurosci Insights 2020; 15:2633105520936623. [PMID: 32685924 PMCID: PMC7343360 DOI: 10.1177/2633105520936623] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Accepted: 05/28/2020] [Indexed: 12/13/2022] Open
Abstract
In recent years, several studies have reported beneficial effects of transcranial alternating current stimulation (tACS) in experiments regarding sound and speech perception. A new development in this field is envelope-tACS: The goal of this method is to improve cortical entrainment to the speech signal by stimulating with a waveform based on the speech envelope. One challenge of this stimulation method is timing; the electrical stimulation needs to be phase-aligned with the naturally occurring cortical entrainment to the auditory stimuli. Due to individual differences in anatomy and processing speed, the optimal time-lag between presentation of sound and applying envelope-tACS varies between participants. To better investigate the effects of envelope-tACS, we performed a speech comprehension task with a larger amount of time-lags than previous experiments, as well as an equal amount of sham conditions. No significant difference between optimal stimulation time-lag condition and best sham condition was found. Further investigation of the data revealed a significant difference between the positive and negative half-cycles of the stimulation conditions but not for sham. However, we also found a significant learning effect over the course of the experiment which was of comparable size to the effects of envelope-tACS found in previous auditory tACS studies. In this article, we discuss possible explanations for why our findings did not match up with those of previous studies and the issues that come with researching and developing envelope-tACS.
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Affiliation(s)
- Jules Erkens
- Experimental Psychology Lab, Department of Psychology, Cluster of Excellence 'Hearing4All', European Medical School, Carl von Ossietzky University of Oldenburg, Oldenburg, Germany
| | | | | | - Christoph S Herrmann
- Experimental Psychology Lab, Department of Psychology, Cluster of Excellence 'Hearing4All', European Medical School, Carl von Ossietzky University of Oldenburg, Oldenburg, Germany.,Research Center Neurosensory Science, Carl von Ossietzky University of Oldenburg, Oldenburg, Germany
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Kadir S, Kaza C, Weissbart H, Reichenbach T. Modulation of Speech-in-Noise Comprehension Through Transcranial Current Stimulation With the Phase-Shifted Speech Envelope. IEEE Trans Neural Syst Rehabil Eng 2019; 28:23-31. [PMID: 31751277 PMCID: PMC7001147 DOI: 10.1109/tnsre.2019.2939671] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Neural activity tracks the envelope of a speech signal at latencies from 50 ms to 300 ms. Modulating this neural tracking through transcranial alternating current stimulation influences speech comprehension. Two important variables that can affect this modulation are the latency and the phase of the stimulation with respect to the sound. While previous studies have found an influence of both variables on speech comprehension, the interaction between both has not yet been measured. We presented 17 subjects with speech in noise coupled with simultaneous transcranial alternating current stimulation. The currents were based on the envelope of the target speech but shifted by different phases, as well as by two temporal delays of 100 ms and 250 ms. We also employed various control stimulations, and assessed the signal-to-noise ratio at which the subject understood half of the speech. We found that, at both latencies, speech comprehension is modulated by the phase of the current stimulation. However, the form of the modulation differed between the two latencies. Phase and latency of neurostimulation have accordingly distinct influences on speech comprehension. The different effects at the latencies of 100 ms and 250 ms hint at distinct neural processes for speech processing.
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Zoefel B, Davis MH, Valente G, Riecke L. How to test for phasic modulation of neural and behavioural responses. Neuroimage 2019; 202:116175. [PMID: 31499178 PMCID: PMC6773602 DOI: 10.1016/j.neuroimage.2019.116175] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Revised: 07/31/2019] [Accepted: 09/05/2019] [Indexed: 12/30/2022] Open
Abstract
Research on whether perception or other processes depend on the phase of neural oscillations is rapidly gaining popularity. However, it is unknown which methods are optimally suited to evaluate the hypothesized phase effect. Using a simulation approach, we here test the ability of different methods to detect such an effect on dichotomous (e.g., "hit" vs "miss") and continuous (e.g., scalp potentials) response variables. We manipulated parameters that characterise the phase effect or define the experimental approach to test for this effect. For each parameter combination and response variable, we identified an optimal method. We found that methods regressing single-trial responses on circular (sine and cosine) predictors perform best for all of the simulated parameters, regardless of the nature of the response variable (dichotomous or continuous). In sum, our study lays a foundation for optimized experimental designs and analyses in future studies investigating the role of phase for neural and behavioural responses. We provide MATLAB code for the statistical methods tested.
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Affiliation(s)
- Benedikt Zoefel
- MRC Cognition and Brain Sciences Unit, University of Cambridge, UK.
| | - Matthew H Davis
- MRC Cognition and Brain Sciences Unit, University of Cambridge, UK
| | - Giancarlo Valente
- Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, 6229, EV Maastricht, the Netherlands
| | - Lars Riecke
- Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, 6229, EV Maastricht, the Netherlands
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Zoefel B, Allard I, Anil M, Davis MH. Perception of Rhythmic Speech Is Modulated by Focal Bilateral Transcranial Alternating Current Stimulation. J Cogn Neurosci 2019; 32:226-240. [PMID: 31659922 DOI: 10.1162/jocn_a_01490] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Several recent studies have used transcranial alternating current stimulation (tACS) to demonstrate a causal role of neural oscillatory activity in speech processing. In particular, it has been shown that the ability to understand speech in a multi-speaker scenario or background noise depends on the timing of speech presentation relative to simultaneously applied tACS. However, it is possible that tACS did not change actual speech perception but rather auditory stream segregation. In this study, we tested whether the phase relation between tACS and the rhythm of degraded words, presented in silence, modulates word report accuracy. We found strong evidence for a tACS-induced modulation of speech perception, but only if the stimulation was applied bilaterally using ring electrodes (not for unilateral left hemisphere stimulation with square electrodes). These results were only obtained when data were analyzed using a statistical approach that was identified as optimal in a previous simulation study. The effect was driven by a phasic disruption of word report scores. Our results suggest a causal role of neural entrainment for speech perception and emphasize the importance of optimizing stimulation protocols and statistical approaches for brain stimulation research.
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Bland NS, Sale MV. Current challenges: the ups and downs of tACS. Exp Brain Res 2019; 237:3071-3088. [DOI: 10.1007/s00221-019-05666-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Accepted: 10/09/2019] [Indexed: 02/08/2023]
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Synchronization of Sensory Gamma Oscillations Promotes Multisensory Communication. eNeuro 2019; 6:ENEURO.0101-19.2019. [PMID: 31601635 PMCID: PMC6873160 DOI: 10.1523/eneuro.0101-19.2019] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Revised: 09/03/2019] [Accepted: 09/16/2019] [Indexed: 01/15/2023] Open
Abstract
Rhythmic neuronal activity in the gamma range is a signature of cortical processing and its synchronization across distant sites has been proposed as a fundamental mechanism of network interactions. While this has been shown within sensory streams, we tested whether cross talk between the senses relies on similar mechanisms. Direct sensory interactions in humans (male and female) were studied with a visual-tactile amplitude matching paradigm. In this task, congruent stimuli are associated with behavioral benefits, which are proposed to be mediated by increased binding between sensory cortices through coherent gamma oscillations. We tested this hypothesis by applying 4-in-1 multi-electrode transcranial alternating current stimulation (tACS) with 40 Hz over visual and somatosensory cortices. In phase stimulation (0°) was expected to strengthen binding and thereby enhance the congruence effect, while anti-phase (180°) stimulation was expected to have opposite effects. Gamma tACS was controlled by alpha (10 Hz) and sham stimulation, as well as by applying tACS unilaterally while visual-tactile stimuli were presented lateralized. Contrary to our expectations, gamma tACS over the relevant hemisphere delayed responses to congruent trials. Additionally, reanalysis of EEG data revealed decoupling of sensory gamma oscillations during congruent trials. We propose that gamma tACS prevented sensory decoupling and thereby limited the congruence effect. Together, our results favor the perspective that processing multisensory congruence involves corticocortical communication rather than feature binding. Furthermore, we found control stimulation over the irrelevant hemisphere to speed responses under alpha stimulation and to delay responses under gamma stimulation, consistent with the idea that contralateral alpha/gamma dynamics regulate cortical excitability.
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