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Tuna AR, Pinto N, Fernandes A, Brardo FM, Pato MV. Can repetitive transcranial magnetic stimulation influence the visual cortex of adults with amblyopia? - systematic review. Clin Exp Optom 2024:1-7. [PMID: 39025787 DOI: 10.1080/08164622.2024.2363369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2023] [Accepted: 05/02/2024] [Indexed: 07/20/2024] Open
Abstract
Amblyopia is the most frequent cause of monocular vision loss. Transcranial Magnetic Stimulation (TMS) has been used to improve several vision parameters of the amblyopic eye in adulthood. This study is relevant in order to evaluate TMS effects and to raise awareness of the need for further research. Transcranial Magnetic Stimulation (TMS) is a neuromodulation technique capable of changing cortical excitability. In the last decade, it has been used to improve visual parameters in amblyopic patients. The main goal of this systematic review is to evaluate the influence of TMS in the amblyopic eye, in the visual parameters of amblyopic patients. Searches were done in PubMed and Embase databases, and a combined search strategy was performed using the following Mesh, EMBASE, and keywords: 'Amblyopia', 'Transcranial Magnetic Stimulation', and 'theta burst stimulation'. This review included randomised controlled studies, descriptive cases, and clinical case studies with adult amblyopes. All articles that had any of the following characteristics were excluded: children or animal studies, reviews, pathologies other than amblyopia, and other techniques rather than repetitive TMS (rTMS), or Theta Burst Stimulation (TBS). A total of 42 articles were found, of which only four studies (46 amblyopes) meet the criteria above. Three of the articles found significant improvement after one session of continuous TBS (cTBS) in visual parameters like visual acuity, contrast sensitivity, suppressive imbalance, and stereoacuity. One study found a significant visual improvement with 10 Hz rTMS. Only one stimulation-related dropout was reported. The few existing studies found in this review seem to show that through the usage of high-frequency rTMS and cTBS, it is possible to re-balance the eyes of an adult amblyope. However, despite the promising results, further research with larger randomised double-blind studies is needed for a better understanding of this process.
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Affiliation(s)
- Ana Rita Tuna
- Faculty of Health Sciences, University of Beira Interior, Covilhã, Portugal
- CICS-UBI-Health Sciences Research Centre, University of Beira Interior, Covilhã, Portugal
- GRUBI - Systematic Reviews Group, University of Beira Interior, Covilhã, Portugal
| | - Nuno Pinto
- Faculty of Health Sciences, University of Beira Interior, Covilhã, Portugal
- CICS-UBI-Health Sciences Research Centre, University of Beira Interior, Covilhã, Portugal
- GRUBI - Systematic Reviews Group, University of Beira Interior, Covilhã, Portugal
| | - Andresa Fernandes
- Faculty of Health Sciences, University of Beira Interior, Covilhã, Portugal
- CICS-UBI-Health Sciences Research Centre, University of Beira Interior, Covilhã, Portugal
- GRUBI - Systematic Reviews Group, University of Beira Interior, Covilhã, Portugal
- Department of Physics, University of Beira Interior, Covilhã, Portugal
| | - Francisco Miguel Brardo
- CICS-UBI-Health Sciences Research Centre, University of Beira Interior, Covilhã, Portugal
- GRUBI - Systematic Reviews Group, University of Beira Interior, Covilhã, Portugal
- Department of Physics, University of Beira Interior, Covilhã, Portugal
| | - Maria Vaz Pato
- Faculty of Health Sciences, University of Beira Interior, Covilhã, Portugal
- CICS-UBI-Health Sciences Research Centre, University of Beira Interior, Covilhã, Portugal
- GRUBI - Systematic Reviews Group, University of Beira Interior, Covilhã, Portugal
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Phylactou P, Pham TNM, Narskhani N, Diya N, Seminowicz DA, Schabrun SM. Phosphene and motor transcranial magnetic stimulation thresholds are correlated: A meta-analytic investigation. Prog Neuropsychopharmacol Biol Psychiatry 2024; 133:111020. [PMID: 38692474 DOI: 10.1016/j.pnpbp.2024.111020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2024] [Revised: 04/22/2024] [Accepted: 04/28/2024] [Indexed: 05/03/2024]
Abstract
Transcranial magnetic stimulation (TMS) is commonly delivered at an intensity defined by the resting motor threshold (rMT), which is thought to represent cortical excitability, even if the TMS target area falls outside of the motor cortex. This approach rests on the assumption that cortical excitability, as measured through the motor cortex, represents a 'global' measure of excitability. Another common approach to measure cortical excitability relies on the phosphene threshold (PT), measured through the visual cortex of the brain. However, it remains unclear whether either estimate can serve as a singular measure to infer cortical excitability across different brain regions. If PT and rMT can indeed be used to infer cortical excitability across brain regions, they should be correlated. To test this, we systematically identified previous studies that measured PT and rMT to calculate an overall correlation between the two estimates. Our results, based on 16 effect sizes from eight studies, indicated that PT and rMT are correlated (ρ = 0.4), and thus one measure could potentially serve as a measure to infer cortical excitability across brain regions. Three exploratory meta-analyses revealed that the strength of the correlation is affected by different methodologies, and that PT intensities are higher than rMT. Evidence for a PT-rMT correlation remained robust across all analyses. Further research is necessary for an in-depth understanding of how cortical excitability is reflected through TMS.
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Affiliation(s)
- P Phylactou
- School of Physical Therapy, Faculty of Health Sciences, University of Western Ontario, London, ON, Canada; The Gray Centre for Mobility and Activity, Parkwood Institute, London, ON, Canada.
| | - T N M Pham
- The Gray Centre for Mobility and Activity, Parkwood Institute, London, ON, Canada
| | - N Narskhani
- The Gray Centre for Mobility and Activity, Parkwood Institute, London, ON, Canada
| | - N Diya
- The Gray Centre for Mobility and Activity, Parkwood Institute, London, ON, Canada
| | - D A Seminowicz
- Department of Medical Biophysics, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Canada
| | - S M Schabrun
- School of Physical Therapy, Faculty of Health Sciences, University of Western Ontario, London, ON, Canada; The Gray Centre for Mobility and Activity, Parkwood Institute, London, ON, Canada
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Tik M, Vasileiadi M, Woletz M, Linhardt D, Schuler AL, Williams N, Windischberger C. Concurrent TMS/fMRI reveals individual DLPFC dose-response pattern. Neuroimage 2023; 282:120394. [PMID: 37805020 DOI: 10.1016/j.neuroimage.2023.120394] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2023] [Revised: 09/04/2023] [Accepted: 09/25/2023] [Indexed: 10/09/2023] Open
Abstract
BACKGROUND TMS is a valuable tool in both research and clinical settings, playing a crucial role in understanding brain-behavior relationships and providing treatment for various neurological and psychiatric conditions. Importantly, TMS over left DLPFC is an FDA approved treatment for MDD. Despite its potential, response variability to TMS remains a challenge, with stimulation parameters, particularly the stimulation intensity, being a primary contributor to these differences. OBJECTIVE The objective of this study was to establish dose-response relationships of TMS stimulation in DLPFC by means of concurrent TMS/fMRI. METHODS Here, we stimulated 15 subjects at different stimulation intensities of 80, 90, 100 and 110 % relative to the motor threshold during concurrent TMS/fMRI. The experiment comprised two sessions: one session to collect anatomical data in order to perform neuronavigation and one session dedicated to dose-response mapping. We calculated GLMs for each intensity level and each subject, as well as at a group-level per intensity. RESULTS On a group level, we show that the strongest BOLD-response was at 100 % stimulation. However, investigating individual dose response-relationships showed differences in response patterns across the group: subjects that responded to subthreshold stimulation, subjects that required above threshold stimulation in order to show a significant BOLD-response and atypical responders. CONCLUSIONS We observed qualitative inter-subject variability in terms of dose-response relationship to TMS over left DLPFC, which hints towards the motor threshold not being directly transferable to the excitability of the DLPFC. Concurrent TMS/fMRI might have the potential to improve response rates to rTMS applications. As such, it may be valuable in the future to consider implementing this approach prior to clinical TMS or validating more cost-effective methods to determine dose and target with respect to changes in clinical symptoms.
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Affiliation(s)
- Martin Tik
- MR Center of Excellence, Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Lazarettgasse 14, Vienna 1090, Austria; Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Palo Alto, CA, USA
| | - Maria Vasileiadi
- MR Center of Excellence, Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Lazarettgasse 14, Vienna 1090, Austria
| | - Michael Woletz
- MR Center of Excellence, Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Lazarettgasse 14, Vienna 1090, Austria
| | - David Linhardt
- MR Center of Excellence, Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Lazarettgasse 14, Vienna 1090, Austria
| | - Anna-Lisa Schuler
- MR Center of Excellence, Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Lazarettgasse 14, Vienna 1090, Austria
| | - Nolan Williams
- Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Palo Alto, CA, USA
| | - Christian Windischberger
- MR Center of Excellence, Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Lazarettgasse 14, Vienna 1090, Austria.
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Cash JJ, Bowden MG, Boan AD, McTeague LM, Kindred JH. Systematic Evaluation of the Effects of Voluntary Activation on Lower Extremity Motor Thresholds. J Clin Med 2023; 12:5993. [PMID: 37762933 PMCID: PMC10531833 DOI: 10.3390/jcm12185993] [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: 08/19/2023] [Revised: 09/09/2023] [Accepted: 09/12/2023] [Indexed: 09/29/2023] Open
Abstract
The purpose of this investigation was to elucidate the relationship between the resting motor threshold (rMT) and active motor threshold (aMT). A cross-sectional comparison of MTs measured at four states of lower extremity muscle activation was conducted: resting, 5% maximal voluntary contraction (MVC), 10%MVC, and standing. MTs were measured at the tibialis anterior in the ipsilesional and contralesional limbs in participants in the chronic phase (>6 months) of stroke (n = 11) and in the dominant limb of healthy controls (n = 11). To compare across activation levels, the responses were standardized using averaged peak-to-peak background electromyography (EMG) activity measured at 10%MVC + 2SD for each participant, in addition to the traditional 0.05 mV criterion for rMT (rMT50). In all participants, as muscle activation increased, the least square mean estimates of MTs decreased (contralesional: p = 0.008; ipsilesional: p = 0.0015, healthy dominant: p < 0.0001). In healthy controls, rMT50 was significantly different from all other MTs (p < 0.0344), while in stroke, there were no differences in either limb (p > 0.10). This investigation highlights the relationship between rMT and aMTs, which is important as many stroke survivors do not present with an rMT, necessitating the use of an aMT. Future works may consider the use of the standardized criterion that accounted for background EMG activity across activation levels.
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Affiliation(s)
- Jasmine J. Cash
- Department of Health Sciences and Research, Medical University of South Carolina, Charleston, SC 29425, USA;
| | - Mark G. Bowden
- Department of Clinical Integration and Research, Brooks Rehabilitation, Jacksonville, FL 32216, USA;
| | - Andrea D. Boan
- Department of Pediatrics, Medical University of South Carolina, Charleston, SC 29425, USA;
| | - Lisa M. McTeague
- Department of Psychiatry and Behavioral Sciences, Medical University of South Carolina, Charleston, SC 29425, USA;
- Ralph H Johnson VA Health Care System, Charleston, SC 29401, USA
| | - John H. Kindred
- Department of Health Sciences and Research, Medical University of South Carolina, Charleston, SC 29425, USA;
- Ralph H Johnson VA Health Care System, Charleston, SC 29401, USA
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Wang B, Peterchev AV, Goetz SM. Three novel methods for determining motor threshold with transcranial magnetic stimulation outperform conventional procedures. J Neural Eng 2023; 20:10.1088/1741-2552/acf1cc. [PMID: 37595573 PMCID: PMC10516469 DOI: 10.1088/1741-2552/acf1cc] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Accepted: 08/18/2023] [Indexed: 08/20/2023]
Abstract
Objective. Thresholding of neural responses is central to many applications of transcranial magnetic stimulation (TMS), but the stochastic aspect of neuronal activity and motor evoked potentials (MEPs) challenges thresholding techniques. We analyzed existing methods for obtaining TMS motor threshold and their variations, introduced new methods from other fields, and compared their accuracy and speed.Approach. In addition to existing relative-frequency methods, such as the five-out-of-ten method, we examined adaptive methods based on a probabilistic motor threshold model using maximum-likelihood (ML) or maximuma-posteriori(MAP) estimation. To improve the performance of these adaptive estimation methods, we explored variations in the estimation procedure and inclusion of population-level prior information. We adapted a Bayesian estimation method which iteratively incorporated information of the TMS responses into the probability density function. A family of non-parametric stochastic root-finding methods with different convergence criteria and stepping rules were explored as well. The performance of the thresholding methods was evaluated with an independent stochastic MEP model.Main Results. The conventional relative-frequency methods required a large number of stimuli, were inherently biased on the population level, and had wide error distributions for individual subjects. The parametric estimation methods obtained the thresholds much faster and their accuracy depended on the estimation method, with performance significantly improved when population-level prior information was included. Stochastic root-finding methods were comparable to adaptive estimation methods but were much simpler to implement and did not rely on a potentially inaccurate underlying estimation model.Significance. Two-parameter MAP estimation, Bayesian estimation, and stochastic root-finding methods have better error convergence compared to conventional single-parameter ML estimation, and all these methods require significantly fewer TMS pulses for accurate estimation than conventional relative-frequency methods. Stochastic root-finding appears particularly attractive due to the low computational requirements, simplicity of the algorithmic implementation, and independence from potential model flaws in the parametric estimators.
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Affiliation(s)
- Boshuo Wang
- Department of Psychiatry and Behavioral Sciences, School of Medicine, Duke University, Durham, NC, USA
| | - Angel V. Peterchev
- Department of Psychiatry and Behavioral Sciences, School of Medicine, Duke University, Durham, NC, USA
- Department of Electrical and Computer Engineering, School of Engineering, Duke University, Durham, NC, USA
- Department of Biomedical Engineering, School of Engineering, Duke University, Durham, NC, USA
- Department of Neurosurgery, School of Medicine, Duke University, Durham, NC, USA
| | - Stefan M. Goetz
- Department of Psychiatry and Behavioral Sciences, School of Medicine, Duke University, Durham, NC, USA
- Department of Electrical and Computer Engineering, School of Engineering, Duke University, Durham, NC, USA
- Department of Neurosurgery, School of Medicine, Duke University, Durham, NC, USA
- Department of Engineering, School of Technology, University of Cambridge, Cambridge, UK
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Kim HC, Lee W, Weisholtz DS, Yoo SS. Transcranial focused ultrasound stimulation of cortical and thalamic somatosensory areas in human. PLoS One 2023; 18:e0288654. [PMID: 37478086 PMCID: PMC10361523 DOI: 10.1371/journal.pone.0288654] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Accepted: 06/30/2023] [Indexed: 07/23/2023] Open
Abstract
The effects of transcranial focused ultrasound (FUS) stimulation of the primary somatosensory cortex and its thalamic projection (i.e., ventral posterolateral nucleus) on the generation of electroencephalographic (EEG) responses were evaluated in healthy human volunteers. Stimulation of the unilateral somatosensory circuits corresponding to the non-dominant hand generated EEG evoked potentials across all participants; however, not all perceived stimulation-mediated tactile sensations of the hand. These FUS-evoked EEG potentials (FEP) were observed from both brain hemispheres and shared similarities with somatosensory evoked potentials (SSEP) from median nerve stimulation. Use of a 0.5 ms pulse duration (PD) sonication given at 70% duty cycle, compared to the use of 1 and 2 ms PD, elicited more distinctive FEP peak features from the hemisphere ipsilateral to sonication. Although several participants reported hearing tones associated with FUS stimulation, the observed FEP were not likely to be confounded by the auditory sensation based on a separate measurement of auditory evoked potentials (AEP) to tonal stimulation (mimicking the same repetition frequency as the FUS stimulation). Off-line changes in resting-state functional connectivity (FC) associated with thalamic stimulation revealed that the FUS stimulation enhanced connectivity in a network of sensorimotor and sensory integration areas, which lasted for at least more than an hour. Clinical neurological evaluations, EEG, and neuroanatomical MRI did not reveal any adverse or unintended effects of sonication, attesting its safety. These results suggest that FUS stimulation may induce long-term neuroplasticity in humans, indicating its neurotherapeutic potential for various neurological and neuropsychiatric conditions.
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Affiliation(s)
- Hyun-Chul Kim
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Wonhye Lee
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Daniel S Weisholtz
- Department of Neurology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Seung-Schik Yoo
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
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Hernandez-Pavon JC, Veniero D, Bergmann TO, Belardinelli P, Bortoletto M, Casarotto S, Casula EP, Farzan F, Fecchio M, Julkunen P, Kallioniemi E, Lioumis P, Metsomaa J, Miniussi C, Mutanen TP, Rocchi L, Rogasch NC, Shafi MM, Siebner HR, Thut G, Zrenner C, Ziemann U, Ilmoniemi RJ. TMS combined with EEG: Recommendations and open issues for data collection and analysis. Brain Stimul 2023; 16:567-593. [PMID: 36828303 DOI: 10.1016/j.brs.2023.02.009] [Citation(s) in RCA: 24] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Revised: 02/10/2023] [Accepted: 02/19/2023] [Indexed: 02/25/2023] Open
Abstract
Transcranial magnetic stimulation (TMS) evokes neuronal activity in the targeted cortex and connected brain regions. The evoked brain response can be measured with electroencephalography (EEG). TMS combined with simultaneous EEG (TMS-EEG) is widely used for studying cortical reactivity and connectivity at high spatiotemporal resolution. Methodologically, the combination of TMS with EEG is challenging, and there are many open questions in the field. Different TMS-EEG equipment and approaches for data collection and analysis are used. The lack of standardization may affect reproducibility and limit the comparability of results produced in different research laboratories. In addition, there is controversy about the extent to which auditory and somatosensory inputs contribute to transcranially evoked EEG. This review provides a guide for researchers who wish to use TMS-EEG to study the reactivity of the human cortex. A worldwide panel of experts working on TMS-EEG covered all aspects that should be considered in TMS-EEG experiments, providing methodological recommendations (when possible) for effective TMS-EEG recordings and analysis. The panel identified and discussed the challenges of the technique, particularly regarding recording procedures, artifact correction, analysis, and interpretation of the transcranial evoked potentials (TEPs). Therefore, this work offers an extensive overview of TMS-EEG methodology and thus may promote standardization of experimental and computational procedures across groups.
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Affiliation(s)
- Julio C Hernandez-Pavon
- Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA; Legs + Walking Lab, Shirley Ryan AbilityLab, Chicago, IL, USA; Center for Brain Stimulation, Shirley Ryan AbilityLab, Chicago, IL, USA.
| | | | - Til Ole Bergmann
- Neuroimaging Center (NIC), Focus Program Translational Neuroscience (FTN), Johannes Gutenberg University Medical Center, Germany; Leibniz Institute for Resilience Research (LIR), Mainz, Germany
| | - Paolo Belardinelli
- Center for Mind/Brain Sciences - CIMeC, University of Trento, Rovereto, TN, Italy; Department of Neurology & Stroke, University of Tübingen, Tübingen, Germany
| | - Marta Bortoletto
- Neurophysiology Lab, IRCCS Istituto Centro San Giovanni di Dio Fatebenefratelli, Brescia, Italy
| | - Silvia Casarotto
- Department of Biomedical and Clinical Sciences, University of Milan, Milan, Italy; IRCCS Fondazione Don Carlo Gnocchi ONLUS, Milan, Italy
| | - Elias P Casula
- Department of Systems Medicine, University of Tor Vergata, Rome, Italy
| | - Faranak Farzan
- Simon Fraser University, School of Mechatronic Systems Engineering, Surrey, British Columbia, Canada
| | - Matteo Fecchio
- Center for Neurotechnology and Neurorecovery, Department of Neurology, Massachusetts General Hospital, Boston, MA, USA
| | - Petro Julkunen
- Department of Technical Physics, University of Eastern Finland, Kuopio, Finland; Department of Clinical Neurophysiology, Kuopio University Hospital, Kuopio, Finland
| | - Elisa Kallioniemi
- Department of Biomedical Engineering, New Jersey Institute of Technology, Newark, NJ, USA
| | - Pantelis Lioumis
- Department of Neuroscience and Biomedical Engineering, Aalto University, Espoo, Finland; BioMag Laboratory, HUS Medical Imaging Center, Helsinki University Hospital, Helsinki University and Aalto University School of Science, Helsinki, Finland
| | - Johanna Metsomaa
- Department of Neuroscience and Biomedical Engineering, Aalto University, Espoo, Finland; BioMag Laboratory, HUS Medical Imaging Center, Helsinki University Hospital, Helsinki University and Aalto University School of Science, Helsinki, Finland
| | - Carlo Miniussi
- Center for Mind/Brain Sciences - CIMeC, University of Trento, Rovereto, TN, Italy
| | - Tuomas P Mutanen
- Department of Neuroscience and Biomedical Engineering, Aalto University, Espoo, Finland; BioMag Laboratory, HUS Medical Imaging Center, Helsinki University Hospital, Helsinki University and Aalto University School of Science, Helsinki, Finland
| | - Lorenzo Rocchi
- Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, University College London, London, United Kingdom; Department of Medical Sciences and Public Health, University of Cagliari, Cagliari, Italy
| | - Nigel C Rogasch
- University of Adelaide, Adelaide, Australia; South Australian Health and Medical Research Institute, Adelaide, Australia; Monash University, Melbourne, Australia
| | - Mouhsin M Shafi
- Berenson-Allen Center for Noninvasive Brain Stimulation, Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
| | - Hartwig R Siebner
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital - Amager and Hvidovre, Copenhagen, Denmark; Department of Neurology, Copenhagen University Hospital Bispebjerg and Frederiksberg, Copenhagen, Denmark; Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Gregor Thut
- School of Psychology and Neuroscience, University of Glasgow, United Kingdom
| | - Christoph Zrenner
- Department of Neurology & Stroke, University of Tübingen, Tübingen, Germany; Temerty Centre for Therapeutic Brain Intervention, Centre for Addiction and Mental Health, Toronto, Canada; Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany; Department of Psychiatry, University of Toronto, Toronto, Canada
| | - Ulf Ziemann
- Department of Neurology & Stroke, University of Tübingen, Tübingen, Germany; Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
| | - Risto J Ilmoniemi
- Department of Neuroscience and Biomedical Engineering, Aalto University, Espoo, Finland; BioMag Laboratory, HUS Medical Imaging Center, Helsinki University Hospital, Helsinki University and Aalto University School of Science, Helsinki, Finland
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8
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Coetzee JP, Johnson MA, Lee Y, Wu AD, Iacoboni M, Monti MM. Dissociating Language and Thought in Human Reasoning. Brain Sci 2022; 13:brainsci13010067. [PMID: 36672048 PMCID: PMC9856203 DOI: 10.3390/brainsci13010067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Revised: 12/22/2022] [Accepted: 12/23/2022] [Indexed: 01/01/2023] Open
Abstract
What is the relationship between language and complex thought? In the context of deductive reasoning there are two main views. Under the first, which we label here the language-centric view, language is central to the syntax-like combinatorial operations of complex reasoning. Under the second, which we label here the language-independent view, these operations are dissociable from the mechanisms of natural language. We applied continuous theta burst stimulation (cTBS), a form of noninvasive neuromodulation, to healthy adult participants to transiently inhibit a subregion of Broca's area (left BA44) associated in prior work with parsing the syntactic relations of natural language. We similarly inhibited a subregion of dorsomedial frontal cortex (left medial BA8) which has been associated with core features of logical reasoning. There was a significant interaction between task and stimulation site. Post hoc tests revealed that performance on a linguistic reasoning task, but not deductive reasoning task, was significantly impaired after inhibition of left BA44, and performance on a deductive reasoning task, but not linguistic reasoning task, was decreased after inhibition of left medial BA8 (however not significantly). Subsequent linear contrasts supported this pattern. These novel results suggest that deductive reasoning may be dissociable from linguistic processes in the adult human brain, consistent with the language-independent view.
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Affiliation(s)
- John P. Coetzee
- Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, 401 Quarry Road, Stanford, CA 94305, USA
- VA Palo Alto Health Care System, Polytrauma Division, 3801 Miranda Avenue, Palo Alto, CA 94304, USA
| | - Micah A. Johnson
- Department of Psychology, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Youngzie Lee
- Department of Psychology, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Allan D. Wu
- Department of Neurology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095, USA
- Brain Research Institute (BRI), University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Marco Iacoboni
- Brain Research Institute (BRI), University of California Los Angeles, Los Angeles, CA 90095, USA
- Ahmanson-Lovelace Brain Mapping Center, University of California Los Angeles, Los Angeles, CA 90095, USA
- Department of Psychiatry and Biobehavioral Sciences, Semel Institute for Neuroscience and Human Behavior, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Martin M. Monti
- Department of Psychology, University of California Los Angeles, Los Angeles, CA 90095, USA
- Brain Research Institute (BRI), University of California Los Angeles, Los Angeles, CA 90095, USA
- Department of Psychiatry and Biobehavioral Sciences, Semel Institute for Neuroscience and Human Behavior, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095, USA
- Brain Injury Research Center (BIRC), Department of Neurosurgery, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
- Correspondence: ; Tel.: +1-310-825-8546
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9
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Siebner HR, Funke K, Aberra AS, Antal A, Bestmann S, Chen R, Classen J, Davare M, Di Lazzaro V, Fox PT, Hallett M, Karabanov AN, Kesselheim J, Beck MM, Koch G, Liebetanz D, Meunier S, Miniussi C, Paulus W, Peterchev AV, Popa T, Ridding MC, Thielscher A, Ziemann U, Rothwell JC, Ugawa Y. Transcranial magnetic stimulation of the brain: What is stimulated? - A consensus and critical position paper. Clin Neurophysiol 2022; 140:59-97. [PMID: 35738037 PMCID: PMC9753778 DOI: 10.1016/j.clinph.2022.04.022] [Citation(s) in RCA: 131] [Impact Index Per Article: 65.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2021] [Revised: 03/14/2022] [Accepted: 04/15/2022] [Indexed: 12/11/2022]
Abstract
Transcranial (electro)magnetic stimulation (TMS) is currently the method of choice to non-invasively induce neural activity in the human brain. A single transcranial stimulus induces a time-varying electric field in the brain that may evoke action potentials in cortical neurons. The spatial relationship between the locally induced electric field and the stimulated neurons determines axonal depolarization. The induced electric field is influenced by the conductive properties of the tissue compartments and is strongest in the superficial parts of the targeted cortical gyri and underlying white matter. TMS likely targets axons of both excitatory and inhibitory neurons. The propensity of individual axons to fire an action potential in response to TMS depends on their geometry, myelination and spatial relation to the imposed electric field and the physiological state of the neuron. The latter is determined by its transsynaptic dendritic and somatic inputs, intrinsic membrane potential and firing rate. Modeling work suggests that the primary target of TMS is axonal terminals in the crown top and lip regions of cortical gyri. The induced electric field may additionally excite bends of myelinated axons in the juxtacortical white matter below the gyral crown. Neuronal excitation spreads ortho- and antidromically along the stimulated axons and causes secondary excitation of connected neuronal populations within local intracortical microcircuits in the target area. Axonal and transsynaptic spread of excitation also occurs along cortico-cortical and cortico-subcortical connections, impacting on neuronal activity in the targeted network. Both local and remote neural excitation depend critically on the functional state of the stimulated target area and network. TMS also causes substantial direct co-stimulation of the peripheral nervous system. Peripheral co-excitation propagates centrally in auditory and somatosensory networks, but also produces brain responses in other networks subserving multisensory integration, orienting or arousal. The complexity of the response to TMS warrants cautious interpretation of its physiological and behavioural consequences, and a deeper understanding of the mechanistic underpinnings of TMS will be critical for advancing it as a scientific and therapeutic tool.
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Affiliation(s)
- Hartwig 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; Institute for Clinical Medicine, University of Copenhagen, Copenhagen, Denmark.
| | - Klaus Funke
- Department of Neurophysiology, Medical Faculty, Ruhr-University Bochum, Bochum, Germany
| | - Aman S Aberra
- Department of Biomedical Engineering, Duke University, Durham, NC, USA
| | - Andrea Antal
- Department of Clinical Neurophysiology, University Medical Center, Georg-August-University, Göttingen, Germany
| | - Sven Bestmann
- Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, University College London, London, United Kingdom; Wellcome Centre for Human Neuroimaging, UCL Queen Square Institute of Neurology, University College London, London, United Kingdom
| | - Robert Chen
- Krembil Brain Institute, University Health Network and Division of Neurology, University of Toronto, Toronto, Ontario, Canada
| | - Joseph Classen
- Department of Neurology, University of Leipzig, Leipzig, Germany
| | - Marco Davare
- Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, University College London, London, United Kingdom; Faculty of Life Sciences and Medicine, King's College London, London, United Kingdom
| | - Vincenzo Di Lazzaro
- Unit of Neurology, Neurophysiology, Neurobiology, Department of Medicine, Università Campus Bio-Medico di Roma, via Álvaro del Portillo 21, 00128 Rome, Italy
| | - Peter T Fox
- Research Imaging Institute, University of Texas Health Science Center at San Antonio, San Antonio, TX, United States
| | - Mark Hallett
- Human Motor Control Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - Anke N Karabanov
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark; Department of Nutrition and Exercise, University of Copenhagen, Copenhagen, Denmark
| | - Janine Kesselheim
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark
| | - Mikkel M Beck
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark
| | - Giacomo Koch
- Department of Neuroscience and Rehabilitation, University of Ferrara, Ferrara, Italy; Non-invasive Brain Stimulation Unit, Laboratorio di NeurologiaClinica e Comportamentale, Fondazione Santa Lucia IRCCS, Rome, Italy
| | - David Liebetanz
- Department of Clinical Neurophysiology, University Medical Center, Georg-August-University, Göttingen, Germany
| | - Sabine Meunier
- Sorbonne Université, Faculté de Médecine, INSERM U 1127, CNRS 4 UMR 7225, Institut du Cerveau, F-75013, Paris, France
| | - Carlo Miniussi
- Center for Mind/Brain Sciences (CIMeC), University of Trento, Italy; Cognitive Neuroscience Section, IRCCS Centro San Giovanni di DioFatebenefratelli, Brescia, Italy
| | - Walter Paulus
- Department of Clinical Neurophysiology, University Medical Center, Georg-August-University, Göttingen, Germany
| | - Angel V Peterchev
- Department of Biomedical Engineering, Duke University, Durham, NC, USA; Department of Psychiatry & Behavioral Sciences, School of Medicine, Duke University, Durham, NC, USA; Department of Electrical & Computer Engineering, Duke University, Durham, NC, USA; Department of Neurosurgery, School of Medicine, Duke University, Durham, NC, USA
| | - Traian Popa
- Center for Neuroprosthetics (CNP) and Brain Mind Institute (BMI), Swiss Federal Institute of Technology (EPFL), Geneva, Switzerland; Center for Neuroprosthetics (CNP) and Brain Mind Institute (BMI), Swiss Federal Institute of Technology (EPFL Valais), Clinique Romande de Réadaptation, Sion, Switzerland
| | - Michael C Ridding
- University of South Australia, IIMPACT in Health, Adelaide, Australia
| | - Axel Thielscher
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark; Department of Health Technology, Technical University of Denmark, Kgs. Lyngby, Denmark
| | - Ulf Ziemann
- Department of Neurology & Stroke, University Tübingen, Tübingen, Germany; Hertie Institute for Clinical Brain Research, University Tübingen, Tübingen, Germany
| | - John C Rothwell
- Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, University College London, London, United Kingdom
| | - Yoshikazu Ugawa
- Department of Neurology, Fukushima Medical University, Fukushima, Japan; Fukushima Global Medical Science Centre, Advanced Clinical Research Centre, Fukushima Medical University, Fukushima, Japan
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10
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Identifying novel biomarkers with TMS-EEG - Methodological possibilities and challenges. J Neurosci Methods 2022; 377:109631. [PMID: 35623474 DOI: 10.1016/j.jneumeth.2022.109631] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Revised: 05/09/2022] [Accepted: 05/21/2022] [Indexed: 12/17/2022]
Abstract
Biomarkers are essential for understanding the underlying pathologies in brain disorders and for developing effective treatments. Combined transcranial magnetic stimulation and electroencephalography (TMS-EEG) is an emerging neurophysiological tool that can be used for biomarker development. This method can identify biomarkers associated with the function and dynamics of the inhibitory and excitatory neurotransmitter systems and effective connectivity between brain areas. In this review, we outline the current state of the TMS-EEG biomarker field by summarizing the existing protocols and the possibilities and challenges associated with this methodology.
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11
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The Neurophysiological Impact of Subacute Stroke: Changes in Cortical Oscillations Evoked by Bimanual Finger Movement. Stroke Res Treat 2022; 2022:9772147. [PMID: 35154632 PMCID: PMC8831071 DOI: 10.1155/2022/9772147] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2021] [Revised: 12/08/2021] [Accepted: 12/29/2021] [Indexed: 11/17/2022] Open
Abstract
Introduction. To design more effective interventions, such as neurostimulation, for stroke rehabilitation, there is a need to understand early physiological changes that take place that may be relevant for clinical monitoring. We aimed to study changes in neurophysiology following recent ischemic stroke, both at rest and with motor planning and execution. Materials and Methods. We included 10 poststroke patients, between 7 and 10 days after stroke, and 20 age-matched controls to assess changes in cortical motor output via transcranial magnetic stimulation and in dynamics of oscillations, as recorded using electroencephalography (EEG). Results. We found significant differences in cortical oscillatory patterns comparing stroke patients with healthy participants, particularly in the beta rhythm during motor planning (
) and execution (
) of a complex movement with fingers from both hands simultaneously. Discussion. The stroke lesion induced a decrease in event-related desynchronization in patients, in comparison to controls, providing evidence for decreased disinhibition. Conclusions. After a stroke lesion, the dynamics of cortical oscillations is changed, with an increasing neural beta synchronization in the course of motor preparation and performance of complex bimanual finger tasks. The observed patterns may provide a potential functional measure that could be used to monitor and design interventional approaches in subacute stages.
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12
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Chakraborty A, Tran TT, Silva AE, Giaschi D, Thompson B. Continuous theta burst TMS of area MT+ impairs attentive motion tracking. Eur J Neurosci 2021; 54:7289-7300. [PMID: 34591329 DOI: 10.1111/ejn.15480] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Revised: 09/16/2021] [Accepted: 09/20/2021] [Indexed: 11/28/2022]
Abstract
Attentive motion tracking deficits measured using multiple object tracking (MOT) tasks have been identified in a number of neurodevelopmental disorders such as amblyopia and autism. These deficits are often attributed to the abnormal development of high-level attentional networks. However, neuroimaging evidence from amblyopia suggests that reduced MOT performance can be explained by impaired function in motion-sensitive area MT+ alone. To test the hypothesis that a subtle disruption of MT+ function could cause MOT impairment, we assessed whether continuous theta burst stimulation (cTBS) of MT+ influenced MOT task accuracy in individuals with normal vision. The MOT stimulus consisted of four target and four distractor dots and was presented at ±10° eccentricity (right/left hemifield). fMRI-guided cTBS was applied to left MT+. Participants (n = 13, age: 27 ± 3) attended separate active and sham cTBS sessions where the MOT task was completed before, 5-min post- and 30-min post-cTBS. Active cTBS significantly impaired MOT task accuracy relative to baseline for the right (stimulated) hemifield 5-min (10 ± 2% reduction) and 30-min (14 ± 3% reduction) post-stimulation. No impairment occurred within the left (control) hemifield after active cTBS or for either hemifield after sham cTBS. These results highlight the importance of lower level motion processing for MOT, suggesting that a minor disruption of MT+ function alone is sufficient to cause a deficit in MOT performance.
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Affiliation(s)
- Arijit Chakraborty
- School of Optometry and Vision Science, Faculty of Science, University of Waterloo, Waterloo, Ontario, Canada.,Chicago College of Optometry, Midwestern University, Downers Grove, Illinois, USA
| | - Tiffany T Tran
- School of Optometry and Vision Science, Faculty of Science, University of Waterloo, Waterloo, Ontario, Canada
| | - Andrew E Silva
- School of Optometry and Vision Science, Faculty of Science, University of Waterloo, Waterloo, Ontario, Canada
| | - Deborah Giaschi
- Department of Ophthalmology and Visual Sciences, University of British Columbia/B.C. Children's Hospital, Vancouver, British Columbia, Canada
| | - Benjamin Thompson
- School of Optometry and Vision Science, Faculty of Science, University of Waterloo, Waterloo, Ontario, Canada.,Centre for Eye and Vision Research (CEVR), Hong Kong, China.,Liggins Institute, University of Auckland, Auckland, New Zealand
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13
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Visual cortex cTBS increases mixed percept duration while a-tDCS has no effect on binocular rivalry. PLoS One 2021; 16:e0239349. [PMID: 33539443 PMCID: PMC7861428 DOI: 10.1371/journal.pone.0239349] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Accepted: 12/19/2020] [Indexed: 11/29/2022] Open
Abstract
Neuromodulation of the primary visual cortex using anodal transcranial direct current stimulation (a-tDCS) can alter visual perception and enhance neuroplasticity. However, the mechanisms that underpin these effects are currently unknown. When applied to the motor cortex, a-tDCS reduces the concentration of the inhibitory neurotransmitter gamma aminobutyric acid (GABA), an effect that has been linked to increased neuroplasticity. The aim of this study was to assess whether a-tDCS also reduces GABA-mediated inhibition when applied to the human visual cortex. Changes in visual cortex inhibition were measured using the mixed percept duration in binocular rivalry. Binocular rivalry mixed percept duration has recently been advocated as a direct and sensitive measure of visual cortex inhibition whereby GABA agonists decrease mixed percept durations and agonists of the excitatory neurotransmitter acetylcholine (ACH) increase them. Our hypothesis was that visual cortex a-tDCS would increase mixed percept duration by reducing GABA-mediated inhibition and increasing cortical excitation. In addition, we measured the effect of continuous theta-burst transcranial magnetic stimulation (cTBS) of the visual cortex on binocular rivalry dynamics. When applied to the motor or visual cortex, cTBS increases GABA concentration and we therefore hypothesized that visual cortex cTBS would decrease the mixed percept duration. Binocular rivalry dynamics were recorded before and after active and sham a-tDCS (N = 15) or cTBS (N = 15). Contrary to our hypotheses, a-tDCS had no effect, whereas cTBS increased mixed percepts during rivalry. These results suggest that the neurochemical mechanisms of a-tDCS may differ between the motor and visual cortices.
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14
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Davis NJ. Variance in cortical depth across the brain surface: Implications for transcranial stimulation of the brain. Eur J Neurosci 2020; 53:996-1007. [PMID: 32877015 DOI: 10.1111/ejn.14957] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2020] [Accepted: 08/20/2020] [Indexed: 01/12/2023]
Abstract
The distance between the surface of the scalp and the surface of the grey matter of the brain is a key factor in determining the effective dose of non-invasive brain stimulation for an individual person. The highly folded nature of the cortical surface means that the depth of a particular brain area is likely to vary between individuals. The question addressed here is: what is the variability of this measure of cortical depth? Ninety-four anatomical MRI images were taken from the OASIS database. For each image, the minimum distance from each point in the grey matter to the scalp surface was determined. Transforming these estimates into standard space meant that the coefficient of variation could be determined across the sample. The results indicated that depth variability is high across the cortical surface, even when taking sulcal depth into account. This was true even for the primary visual and motor areas, which are often used in setting TMS dosage. The correlation of the depth of these areas and the depth of other brain areas was low. The results suggest that dose setting of TMS based on visual or evoked potentials may offer poor reliability, and that individual brain images should be used when targeting non-primary brain areas.
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Affiliation(s)
- Nick J Davis
- Department of Psychology, Manchester Metropolitan University, Manchester, UK
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15
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Intensity- and timing-dependent modulation of motion perception with transcranial magnetic stimulation of visual cortex. Neuropsychologia 2020; 147:107581. [PMID: 32795456 DOI: 10.1016/j.neuropsychologia.2020.107581] [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: 06/03/2020] [Revised: 07/23/2020] [Accepted: 08/04/2020] [Indexed: 12/22/2022]
Abstract
Despite the widespread use of transcranial magnetic stimulation (TMS) in research and clinical care, the dose-response relations and neurophysiological correlates of modulatory effects remain relatively unexplored. To fill this gap, we studied modulation of visual processing as a function of TMS parameters. Our approach combined electroencephalography (EEG) with application of single pulse TMS to visual cortex as participants performed a motion perception task. During each participants' first visit, motion coherence thresholds, 64-channel visual evoked potentials (VEPs), and TMS resting motor thresholds (RMT) were measured. In second and third visits, single pulse TMS was delivered at one of two latencies, either 30 ms before the onset of motion or at the onset latency of the N2 VEP component derived from the first session. TMS was delivered at 0%, 80%, 100%, or 120% of RMT over the site of N2 peak activity, or at 120% over vertex. Behavioral results demonstrated a significant main effect of TMS timing on accuracy, with better performance when TMS was applied at the N2-Onset timing versus Pre-Onset, as well as a significant interaction, indicating that 80% intensity produced higher accuracy than other conditions at the N2-Onset. TMS effects on the P3 VEP showed reduced amplitudes in the 80% Pre-Onset condition, an increase for the 120% N2-Onset condition, and monotonic amplitude scaling with stimulation intensity. The N2 component was not affected by TMS. These findings reveal the influence of TMS intensity and timing on visual perception and electrophysiological responses, with optimal facilitation at stimulation intensities below RMT.
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16
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Shmuel D, Frank SM, Sharon H, Sasaki Y, Watanabe T, Censor N. Early Visual Cortex Stimulation Modifies Well-Consolidated Perceptual Gains. Cereb Cortex 2020; 31:138-146. [PMID: 32803241 DOI: 10.1093/cercor/bhaa215] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 07/15/2020] [Accepted: 07/15/2020] [Indexed: 11/15/2022] Open
Abstract
Perception thresholds can improve through repeated practice with visual tasks. Can an already acquired and well-consolidated perceptual skill be noninvasively neuromodulated, unfolding the neural mechanisms involved? Here, leveraging the susceptibility of reactivated memories ranging from synaptic to systems levels across learning and memory domains and animal models, we used noninvasive brain stimulation to neuromodulate well-consolidated reactivated visual perceptual learning and reveal the underlying neural mechanisms. Subjects first encoded and consolidated the visual skill memory by performing daily practice sessions with the task. On a separate day, the consolidated visual memory was briefly reactivated, followed by low-frequency, inhibitory 1 Hz repetitive transcranial magnetic stimulation over early visual cortex, which was individually localized using functional magnetic resonance imaging. Poststimulation perceptual thresholds were measured on the final session. The results show modulation of perceptual thresholds following early visual cortex stimulation, relative to control stimulation. Consistently, resting state functional connectivity between trained and untrained parts of early visual cortex prior to training predicted the magnitude of perceptual threshold modulation. Together, these results indicate that even previously consolidated human perceptual memories are susceptible to neuromodulation, involving early visual cortical processing. Moreover, the opportunity to noninvasively neuromodulate reactivated perceptual learning may have important clinical implications.
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Affiliation(s)
- Dean Shmuel
- Sagol School of Neuroscience and School of Psychological Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Sebastian M Frank
- Department of Cognitive, Linguistic, and Psychological Sciences, Brown University, Providence, RI 02912, USA
| | - Haggai Sharon
- Center for Brain Functions and Institute of Pain Medicine, Tel Aviv Sourasky Medical Center, Tel Aviv 62431, Israel
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
| | - Yuka Sasaki
- Department of Cognitive, Linguistic, and Psychological Sciences, Brown University, Providence, RI 02912, USA
| | - Takeo Watanabe
- Department of Cognitive, Linguistic, and Psychological Sciences, Brown University, Providence, RI 02912, USA
| | - Nitzan Censor
- Sagol School of Neuroscience and School of Psychological Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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17
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Yoon K, Lee W, Lee JE, Xu L, Croce P, Foley L, Yoo SS. Effects of sonication parameters on transcranial focused ultrasound brain stimulation in an ovine model. PLoS One 2019; 14:e0224311. [PMID: 31648261 PMCID: PMC6812789 DOI: 10.1371/journal.pone.0224311] [Citation(s) in RCA: 69] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Accepted: 10/10/2019] [Indexed: 01/01/2023] Open
Abstract
Low-intensity focused ultrasound (FUS) has significant potential as a non-invasive brain stimulation modality and novel technique for functional brain mapping, particularly with its advantage of greater spatial selectivity and depth penetration compared to existing non-invasive brain stimulation techniques. As previous studies, primarily carried out in small animals, have demonstrated that sonication parameters affect the stimulation efficiency, further investigation in large animals is necessary to translate this technique into clinical practice. In the present study, we examined the effects of sonication parameters on the transient modification of excitability of cortical and thalamic areas in an ovine model. Guided by anatomical and functional neuroimaging data specific to each animal, 250 kHz FUS was transcranially applied to the primary sensorimotor area associated with the right hind limb and its thalamic projection in sheep (n = 10) across multiple sessions using various combinations of sonication parameters. The degree of effect from FUS was assessed through electrophysiological responses, through analysis of electromyogram and electroencephalographic somatosensory evoked potentials for evaluation of excitatory and suppressive effects, respectively. We found that the modulatory effects were transient and reversible, with specific sonication parameters outperforming others in modulating regional brain activity. Magnetic resonance imaging and histological analysis conducted at different time points after the final sonication session, as well as behavioral observations, showed that repeated exposure to FUS did not damage the underlying brain tissue. Our results suggest that FUS-mediated, non-invasive, region-specific bimodal neuromodulation can be safely achieved in an ovine model, indicating its potential for translation into human studies.
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Affiliation(s)
- Kyungho Yoon
- Department of Radiology, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Wonhye Lee
- Department of Radiology, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Ji Eun Lee
- Department of Radiology, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Linda Xu
- Department of Radiology, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Phillip Croce
- Department of Radiology, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Lori Foley
- Translational Discovery Laboratory, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Seung-Schik Yoo
- Department of Radiology, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
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18
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A differential role for the posterior cerebellum in the adaptive control of convergence eye movements. Brain Stimul 2019; 13:215-228. [PMID: 31427273 DOI: 10.1016/j.brs.2019.07.025] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 06/15/2019] [Accepted: 07/26/2019] [Indexed: 11/21/2022] Open
Abstract
INTRODUCTION The vergence oculomotor system possesses two robust adaptive mechanisms; a fast "dynamic" and a slow "tonic" system that are both vital for single, clear and comfortable binocular vision. The neural substrates underlying these vergence adaptive mechanisms in humans is unclear. METHODS We investigated the role of the posterior cerebellum in convergence adaptation using inhibitory continuous theta-burst repetitive transcranial magnetic stimulation (cTBS) within a double-blind, sham controlled design while eye movements were recorded at 250hz via infrared oculography. RESULTS In a preliminary experiment we validated our stimulation protocols by reproducing results from previous work on saccadic adaptation during the classic double-step adaptive shortening paradigm. Following this, across a series of three separate experiments we observed a clear dissociation in the effect of cTBS on convergence adaptation. Dynamic adaptation was substantially reduced while tonic adaptation was unaffected. Baseline dynamic fusional vergence response were also unaffected by stimulation. CONCLUSIONS These results indicate a differential role for the posterior cerebellum in the adaptive control of convergence eye movements and provide initial evidence that repetitive transcranial magnetic stimulation is a viable tool to investigate the neurophysiology of vergence control. The results are discussed in the context of the current models of implicit motor adaptation of vergence and their application to clinical populations and technology design in virtual and augmented head mounted display architectures. SIGNIFICANCE STATEMENT The cerebellum plays a critical role in the adaptive control of motor systems. Vergence eye movements shift our gaze in depth allowing us to see in 3D and exhibit two distinct adaptive mechanisms that are engaged under a range of conditions including reading, wearing head-mounted displays and using a new spectacle prescription. It is unclear what role the cerebellum plays in these adaptive mechanisms. To answer this, we temporarily disrupted the function of the posterior cerebellum using non-invasive brain stimulation and report impairment of only one adaptive mechanism, providing evidence for neural compartmentalization. The results have implications for vergence control models and applications to comfort and experience studies in head-mounted displays and the rehabilitation of clinical populations exhibiting vergence dysfunctions.
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19
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Zacharias LR, Peres ASC, Souza VH, Conforto AB, Baffa O. Method to assess the mismatch between the measured and nominal parameters of transcranial magnetic stimulation devices. J Neurosci Methods 2019; 322:83-87. [PMID: 31014951 DOI: 10.1016/j.jneumeth.2019.03.021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Revised: 03/30/2019] [Accepted: 03/31/2019] [Indexed: 01/25/2023]
Abstract
BACKGROUND Small variations in TMS parameters, such as pulse frequency and amplitude may elicit distinct neurophysiological responses. Assessing the mismatch between nominal and experimental parameters of TMS stimulators is essential for safe application and comparisons of results across studies. NEW METHOD A search coil was used to assess exactness and precision errors of amplitude and timing parameters such as interstimulus interval, the period of pulse repetition, and intertrain interval of TMS devices. The method was validated using simulated pulses and applied to six commercial stimulators in single-pulse (spTMS), paired-pulse (ppTMS), and repetitive (rTMS) protocols, working at several combinations of intensities and frequencies. RESULTS In a simulated signal, the maximum exactness error was 1.7% for spTMS and the maximum precision error 1.9% for ppTMS. Three out of six TMS commercial devices showed exactness and precision errors in spTMS amplitude higher than 5%. Moreover, two devices showed amplitude exactness errors higher than 5% in rTMS with parameters suggested by the manufactures. COMPARISON WITH EXISTING METHODS Currently available tools allow characterization of induced electric field intensity and focality, and pulse waveforms of a single TMS pulse. Our method assesses the mismatch between nominal and experimental values in spTMS, ppTMS and rTMS protocols through the exactness and precision errors of amplitude and timing parameters. CONCLUSION This study highlights the importance of evaluating the physical characteristics of TMS devices and protocols, and provides a method for on-site quality assessment of multiple stimulation protocols in clinical and research environments.
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Affiliation(s)
- Leonardo Rakauskas Zacharias
- Departamento de Física, Faculdade de Filosofia Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil; Departamento de Neurociências e Ciências do Comportamento, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil.
| | - André Salles Cunha Peres
- Departamento de Física, Faculdade de Filosofia Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil; Instituto Internacional de Neurociências Edmond e Lily Safra, Instituto Santos Dumont, Macaíba, RN, Brazil; Instituto do Cérebro, Universidade Federal do Rio Grande do Norte, Natal, RN, Brazil
| | - Victor Hugo Souza
- Departamento de Física, Faculdade de Filosofia Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil
| | - Adriana Bastos Conforto
- Divisão de Clínica Neurológica, Hospital das Clínicas, Universidade de São Paulo, SP, Brazil; Instituto Israelita de Ensino e Pesquisa, Hospital Israelita Albert Einstein, São Paulo, SP, Brazil
| | - Oswaldo Baffa
- Departamento de Física, Faculdade de Filosofia Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil
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20
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Edwards G, Agosta S, Herpich F, Contò F, Parrott D, Tyler S, Grossman ED, Battelli L. Prolonged Neuromodulation of Cortical Networks Following Low-Frequency rTMS and Its Potential for Clinical Interventions. Front Psychol 2019; 10:529. [PMID: 30915006 PMCID: PMC6423083 DOI: 10.3389/fpsyg.2019.00529] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Accepted: 02/22/2019] [Indexed: 12/28/2022] Open
Abstract
Non-invasive brain stimulation safely induces persistent large-scale neural modulation in functionally connected brain circuits. Interruption models of repetitive transcranial magnetic stimulation (rTMS) capitalize on the acute impact of brain stimulation, which decays over minutes. However, rTMS also induces longer-lasting impact on cortical functions, evident by the use of multi-session rTMS in clinical population for therapeutic purposes. Defining the persistent cortical dynamics induced by rTMS is complicated by the complex balance of excitation and inhibition among functionally connected networks. Nonetheless, it is these neuronal dynamic responses that are essential for the development of new neuromodulatory protocols for translational applications. We will review evidence of prolonged changes of cortical response, tens of minutes following one session of low frequency rTMS over the cortex. We will focus on the different methods which resulted in prolonged behavioral and brain changes, such as the combination of brain stimulation techniques, and individually tailored stimulation protocols. We will also highlight studies which apply these methods in multi-session stimulation practices to extend stimulation impact into weeks and months. Our data and others' indicate that delayed cortical dynamics may persist much longer than previously thought and have potential as an extended temporal window during which cortical plasticity may be enhanced.
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Affiliation(s)
- Grace Edwards
- Center for Neuroscience and Cognitive Systems@UniTn, Istituto Italiano di Tecnologia, Rovereto, Italy
- Department of Psychology, Harvard University, Cambridge, MA, United States
| | - Sara Agosta
- Center for Neuroscience and Cognitive Systems@UniTn, Istituto Italiano di Tecnologia, Rovereto, Italy
| | - Florian Herpich
- Center for Neuroscience and Cognitive Systems@UniTn, Istituto Italiano di Tecnologia, Rovereto, Italy
| | - Federica Contò
- Center for Neuroscience and Cognitive Systems@UniTn, Istituto Italiano di Tecnologia, Rovereto, Italy
- Center for Mind/Brain Sciences, University of Trento, Trento, Italy
| | - Danielle Parrott
- Center for Neuroscience and Cognitive Systems@UniTn, Istituto Italiano di Tecnologia, Rovereto, Italy
- Center for Mind/Brain Sciences, University of Trento, Trento, Italy
| | - Sarah Tyler
- Center for Neuroscience and Cognitive Systems@UniTn, Istituto Italiano di Tecnologia, Rovereto, Italy
- Department of Psychology, University of California, San Diego, La Jolla, CA, United States
| | - Emily D. Grossman
- Department of Cognitive Sciences, University of California, Irvine, Irvine, CA, United States
| | - Lorella Battelli
- Center for Neuroscience and Cognitive Systems@UniTn, Istituto Italiano di Tecnologia, Rovereto, Italy
- Department of Psychology, Harvard University, Cambridge, MA, United States
- Department of Neurology, Berenson-Allen Center for Noninvasive Brain Stimulation, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, United States
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Saari J, Kallioniemi E, Tarvainen M, Julkunen P. Oscillatory TMS-EEG-Responses as a Measure of the Cortical Excitability Threshold. IEEE Trans Neural Syst Rehabil Eng 2019; 26:383-391. [PMID: 29432109 DOI: 10.1109/tnsre.2017.2779135] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Transcranial magnetic stimulation (TMS) is a non-invasive tool to perturb brain activity. In TMS studies, the stimulation intensity (SI) is commonly normalized to the resting motor threshold (rMT) that produces muscle responses in 50% of stimulations applied to the motor cortex (M1). Since rMT is influenced by spinal excitability and coil-to-cortex distance, responses recorded from the cortex, instead of a peripheral muscle, could provide a more accurate marker for cortical excitability. Combining TMS with electroencephalography (EEG) enables the measurement of brain-wide cortical reactivity to TMS. We quantified TMS-induced changes in oscillatory power and the phase of EEG with event-related spectral perturbation (ERSP) and inter-trial coherence (ITC). We studied the SI-dependency of ERSP and ITC responses by stimulating the dominant M1 of ten healthy volunteers using single-pulse TMS with 150 pulses at 60%, 80%, 100%, and 120% of rMT. We found SI-dependent ERSP and ITC responses in M1, most notably with the wide-band (8-70 Hz) early ITC responses averaged 20-60 ms after TMS. With approximately linear SI-dependence, the early ITC response was consistent between SIs (intraclass correlation = 0.78, ). Our results reveal the potential of oscillatory EEG responses, in place of rMT, as a measure of the cortical excitability threshold in M1.
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Soldati M, Mikkonen M, Laakso I, Murakami T, Ugawa Y, Hirata A. A multi-scale computational approach based on TMS experiments for the assessment of electro-stimulation thresholds of the brain at intermediate frequencies. ACTA ACUST UNITED AC 2018; 63:225006. [DOI: 10.1088/1361-6560/aae932] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Widhalm ML, Rose NS. How can transcranial magnetic stimulation be used to causally manipulate memory representations in the human brain? WILEY INTERDISCIPLINARY REVIEWS. COGNITIVE SCIENCE 2018; 10:e1469. [DOI: 10.1002/wcs.1469] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 04/21/2018] [Accepted: 05/14/2018] [Indexed: 11/12/2022]
Affiliation(s)
- Morgan L. Widhalm
- Department of Psychology University of Notre Dame Notre Dame Indiana
| | - Nathan S. Rose
- Department of Psychology University of Notre Dame Notre Dame Indiana
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TMS applied to V1 can facilitate reasoning. Exp Brain Res 2018; 236:2277-2286. [PMID: 29858917 DOI: 10.1007/s00221-018-5296-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Accepted: 05/22/2018] [Indexed: 10/14/2022]
Abstract
Visual mental imagery is the subjective experience of seeing objects or events in front of the 'inner eye', although they are not actually present. Previous research indicates that (1) visual images help to remember what has been experienced in the past or when objects need to be inspected or manipulated, and (2) visual images are correlated with neural activity in early visual cortices, demonstrating a possible overlap between visual imagery and visual perception. However, recent research revealed that visual imagery can also disrupt cognitive processes and impede thinking. In this transcranial magnetic stimulation (TMS) experiment, participants had to solve relational reasoning problems that varied in their imageability (easy or difficult to visualize as a mental image). While solving the problems, eight 10 Hz pulses were either applied to primary visual cortex (V1) or a control site (Vertex). Our findings suggest a causal link between mental imagery, primary visual cortex, and reasoning with visual problems. Moreover, participants exhibited much lower error rates when TMS was applied to V1. We conclude that the disruption of visual images in primary visual cortex can facilitate reasoning.
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Leitão J, Thielscher A, Tuennerhoff J, Noppeney U. Comparing TMS perturbations to occipital and parietal cortices in concurrent TMS-fMRI studies-Methodological considerations. PLoS One 2017; 12:e0181438. [PMID: 28767670 PMCID: PMC5540584 DOI: 10.1371/journal.pone.0181438] [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: 02/20/2017] [Accepted: 06/30/2017] [Indexed: 02/07/2023] Open
Abstract
Neglect and hemianopia are two neuropsychological syndromes that are associated with reduced awareness for visual signals in patients’ contralesional hemifield. They offer the unique possibility to dissociate the contributions of retino-geniculate and retino-colliculo circuitries in visual perception. Yet, insights from patient fMRI studies are limited by heterogeneity in lesion location and extent, long-term functional reorganization and behavioural compensation after stroke. Transcranial magnetic stimulation (TMS) has therefore been proposed as a complementary method to investigate the effect of transient perturbations on functional brain organization. This concurrent TMS-fMRI study applied TMS perturbation to occipital and parietal cortices with the aim to ‘mimick’ neglect and hemianopia. Based on the challenges and interpretational limitations of our own study we aim to provide tutorial guidance on how future studies should compare TMS to primary sensory and association areas that are governed by distinct computational principles, neural dynamics and functional architecture.
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Affiliation(s)
- Joana Leitão
- Max Planck Institute for biological Cybernetics, Tübingen, Germany
- Computational Neuroscience and Cognitive Robotics Centre, University of Birmingham, Birmingham, United Kingdom
- Laboratory for Behavioral Neurology and Imaging of Cognition, Department of Neuroscience, University of Geneva, Geneva, Switzerland
- * E-mail:
| | - Axel Thielscher
- Max Planck Institute for biological Cybernetics, Tübingen, Germany
- Department of Electrical Engineering, Technical University of Denmark, Lyngby, Denmark
- DRCMR, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark
| | - Johannes Tuennerhoff
- Max Planck Institute for biological Cybernetics, Tübingen, Germany
- University Clinic of Neurology, Tübingen, Germany
| | - Uta Noppeney
- Max Planck Institute for biological Cybernetics, Tübingen, Germany
- Computational Neuroscience and Cognitive Robotics Centre, University of Birmingham, Birmingham, United Kingdom
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Prause N, Siegle GJ, Deblieck C, Wu A, Iacoboni M. EEG to Primary Rewards: Predictive Utility and Malleability by Brain Stimulation. PLoS One 2016; 11:e0165646. [PMID: 27902711 PMCID: PMC5130195 DOI: 10.1371/journal.pone.0165646] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2016] [Accepted: 10/14/2016] [Indexed: 11/18/2022] Open
Abstract
Theta burst stimulation (TBS) is thought to affect reward processing mechanisms, which may increase and decrease reward sensitivity. To test the ability of TBS to modulate response to strong primary rewards, participants hypersensitive to primary rewards were recruited. Twenty men and women with at least two opposite-sex, sexual partners in the last year received two forms of TBS. Stimulations were randomized to avoid order effects and separated by 2 hours to reduce carryover. The two TBS forms have been demonstrated to inhibit (continuous) or excite (intermittent) the left dorsolateral prefrontal cortex using different pulse patterns, which links to brain areas associated with reward conditioning. After each TBS, participants completed tasks assessing their reward responsiveness to monetary and sexual rewards. Electroencephalography (EEG) was recorded. They also reported their number of orgasms in the weekend following stimulation. This signal was malleable by TBS, where excitatory TBS resulted in lower EEG alpha relative to inhibitory TBS to primary rewards. EEG responses to sexual rewards in the lab (following both forms of TBS) predicted the number of orgasms experienced over the forthcoming weekend. TBS may be useful in modifying hypersensitivity or hyposensitivity to primary rewards that predict sexual behaviors. Since TBS altered the anticipation of a sexual reward, TBS may offer a novel treatment for sexual desire problems.
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Affiliation(s)
- Nicole Prause
- Department of Psychiatry; University of California;Los Angeles, CA
- * E-mail:
| | - Greg J. Siegle
- Western Psychiatric Institute and Clinic, University of Pittsburgh, Pittsburgh, PA
| | - Choi Deblieck
- Ahmanson-Lovelace Brain Mapping Center, University of California, Los Angeles, Los Angeles, CA
| | - Allan Wu
- Ahmanson-Lovelace Brain Mapping Center, University of California, Los Angeles, Los Angeles, CA
| | - Marco Iacoboni
- Ahmanson-Lovelace Brain Mapping Center, University of California, Los Angeles, Los Angeles, CA
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Lagas AK, Black JM, Byblow WD, Fleming MK, Goodman LK, Kydd RR, Russell BR, Stinear CM, Thompson B. Fluoxetine Does Not Enhance Visual Perceptual Learning and Triazolam Specifically Impairs Learning Transfer. Front Hum Neurosci 2016; 10:532. [PMID: 27807412 PMCID: PMC5069436 DOI: 10.3389/fnhum.2016.00532] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2016] [Accepted: 10/06/2016] [Indexed: 01/17/2023] Open
Abstract
The selective serotonin reuptake inhibitor fluoxetine significantly enhances adult visual cortex plasticity within the rat. This effect is related to decreased gamma-aminobutyric acid (GABA) mediated inhibition and identifies fluoxetine as a potential agent for enhancing plasticity in the adult human brain. We tested the hypothesis that fluoxetine would enhance visual perceptual learning of a motion direction discrimination (MDD) task in humans. We also investigated (1) the effect of fluoxetine on visual and motor cortex excitability and (2) the impact of increased GABA mediated inhibition following a single dose of triazolam on post-training MDD task performance. Within a double blind, placebo controlled design, 20 healthy adult participants completed a 19-day course of fluoxetine (n = 10, 20 mg per day) or placebo (n = 10). Participants were trained on the MDD task over the final 5 days of fluoxetine administration. Accuracy for the trained MDD stimulus and an untrained MDD stimulus configuration was assessed before and after training, after triazolam and 1 week after triazolam. Motor and visual cortex excitability were measured using transcranial magnetic stimulation. Fluoxetine did not enhance the magnitude or rate of perceptual learning and full transfer of learning to the untrained stimulus was observed for both groups. After training was complete, trazolam had no effect on trained task performance but significantly impaired untrained task performance. No consistent effects of fluoxetine on cortical excitability were observed. The results do not support the hypothesis that fluoxetine can enhance learning in humans. However, the specific effect of triazolam on MDD task performance for the untrained stimulus suggests that learning and learning transfer rely on dissociable neural mechanisms.
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Affiliation(s)
- Alice K Lagas
- School of Optometry and Vision Science, University of AucklandAuckland, New Zealand; Centre for Brain Research, University of AucklandAuckland, New Zealand
| | - Joanna M Black
- School of Optometry and Vision Science, University of AucklandAuckland, New Zealand; Centre for Brain Research, University of AucklandAuckland, New Zealand
| | - Winston D Byblow
- Centre for Brain Research, University of AucklandAuckland, New Zealand; Department of Exercise Sciences, University of AucklandAuckland, New Zealand
| | - Melanie K Fleming
- Department of Exercise Sciences, University of AucklandAuckland, New Zealand; Centre of Human and Aerospace Physiological Sciences, King's College LondonLondon, UK
| | - Lucy K Goodman
- School of Optometry and Vision Science, University of AucklandAuckland, New Zealand; Centre for Brain Research, University of AucklandAuckland, New Zealand
| | - Robert R Kydd
- Centre for Brain Research, University of AucklandAuckland, New Zealand; Department of Psychological Medicine, University of AucklandAuckland, New Zealand
| | - Bruce R Russell
- School of Pharmacy, University of AucklandAuckland, New Zealand; National School of Pharmacy, University of OtagoDunedin, New Zealand
| | - Cathy M Stinear
- Centre for Brain Research, University of AucklandAuckland, New Zealand; Department of Medicine, University of AucklandAuckland, New Zealand
| | - Benjamin Thompson
- School of Optometry and Vision Science, University of AucklandAuckland, New Zealand; Centre for Brain Research, University of AucklandAuckland, New Zealand; School of Optometry and Vision Science, University of Waterloo, WaterlooON, Canada
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Lee W, Chung YA, Jung Y, Song IU, Yoo SS. Simultaneous acoustic stimulation of human primary and secondary somatosensory cortices using transcranial focused ultrasound. BMC Neurosci 2016; 17:68. [PMID: 27784293 PMCID: PMC5081675 DOI: 10.1186/s12868-016-0303-6] [Citation(s) in RCA: 103] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Accepted: 10/19/2016] [Indexed: 01/10/2023] Open
Abstract
Background Transcranial focused ultrasound (FUS) is gaining momentum as a novel non-invasive brain stimulation method, with promising potential for superior spatial resolution and depth penetration compared to transcranial magnetic stimulation or transcranial direct current stimulation. We examined the presence of tactile sensations elicited by FUS stimulation of two separate brain regions in humans—the primary (SI) and secondary (SII) somatosensory areas of the hand, as guided by individual-specific functional magnetic resonance imaging data. Results Under image-guidance, acoustic stimulations were delivered to the SI and SII areas either separately or simultaneously. The SII areas were divided into sub-regions that are activated by four types of external tactile sensations to the palmar side of the right hand—vibrotactile, pressure, warmth, and coolness. Across the stimulation conditions (SI only, SII only, SI and SII simultaneously), participants reported various types of tactile sensations that arose from the hand contralateral to the stimulation, such as the palm/back of the hand or as single/neighboring fingers. The type of tactile sensations did not match the sensations that are associated with specific sub-regions in the SII. The neuro-stimulatory effects of FUS were transient and reversible, and the procedure did not cause any adverse changes or discomforts in the subject’s mental/physical status. Conclusions The use of multiple FUS transducers allowed for simultaneous stimulation of the SI/SII in the same hemisphere and elicited various tactile sensations in the absence of any external sensory stimuli. Stimulation of the SII area alone could also induce perception of tactile sensations. The ability to stimulate multiple brain areas in a spatially restricted fashion can be used to study causal relationships between regional brain activities and their cognitive/behavioral outcomes. Electronic supplementary material The online version of this article (doi:10.1186/s12868-016-0303-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Wonhye Lee
- Incheon St. Mary's Hospital, The Catholic University of Korea, Incheon, Republic of Korea.,Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - Yong An Chung
- Incheon St. Mary's Hospital, The Catholic University of Korea, Incheon, Republic of Korea
| | - Yujin Jung
- Incheon St. Mary's Hospital, The Catholic University of Korea, Incheon, Republic of Korea
| | - In-Uk Song
- Incheon St. Mary's Hospital, The Catholic University of Korea, Incheon, Republic of Korea
| | - Seung-Schik Yoo
- Incheon St. Mary's Hospital, The Catholic University of Korea, Incheon, Republic of Korea. .,Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA.
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Combining non-invasive transcranial brain stimulation with neuroimaging and electrophysiology: Current approaches and future perspectives. Neuroimage 2016; 140:4-19. [DOI: 10.1016/j.neuroimage.2016.02.012] [Citation(s) in RCA: 197] [Impact Index Per Article: 24.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Revised: 01/26/2016] [Accepted: 02/07/2016] [Indexed: 12/23/2022] Open
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Transcranial focused ultrasound stimulation of human primary visual cortex. Sci Rep 2016; 6:34026. [PMID: 27658372 PMCID: PMC5034307 DOI: 10.1038/srep34026] [Citation(s) in RCA: 197] [Impact Index Per Article: 24.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Accepted: 09/06/2016] [Indexed: 12/20/2022] Open
Abstract
Transcranial focused ultrasound (FUS) is making progress as a new non-invasive mode of regional brain stimulation. Current evidence of FUS-mediated neurostimulation for humans has been limited to the observation of subjective sensory manifestations and electrophysiological responses, thus warranting the identification of stimulated brain regions. Here, we report FUS sonication of the primary visual cortex (V1) in humans, resulting in elicited activation not only from the sonicated brain area, but also from the network of regions involved in visual and higher-order cognitive processes (as revealed by simultaneous acquisition of blood-oxygenation-level-dependent functional magnetic resonance imaging). Accompanying phosphene perception was also reported. The electroencephalo graphic (EEG) responses showed distinct peaks associated with the stimulation. None of the participants showed any adverse effects from the sonication based on neuroimaging and neurological examinations. Retrospective numerical simulation of the acoustic profile showed the presence of individual variability in terms of the location and intensity of the acoustic focus. With exquisite spatial selectivity and capability for depth penetration, FUS may confer a unique utility in providing non-invasive stimulation of region-specific brain circuits for neuroscientific and therapeutic applications.
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Thompson B, Deblieck C, Wu A, Iacoboni M, Liu Z. Psychophysical and rTMS Evidence for the Presence of Motion Opponency in Human V5. Brain Stimul 2016; 9:876-881. [PMID: 27342938 DOI: 10.1016/j.brs.2016.05.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Revised: 04/22/2016] [Accepted: 05/30/2016] [Indexed: 10/21/2022] Open
Abstract
BACKGROUND Motion sensitive cells within macaque V5, but not V1, exhibit motion opponency whereby their firing is suppressed by motion in their anti-preferred direction. fMRI studies indicate the presence of motion opponent mechanisms in human V5. OBJECTIVE/HYPOTHESIS We tested two hypotheses. 1) Performance of a motion discrimination task would be poorer when stimuli were constructed from pairs of dots that moved in counter-phase vs. in-phase, because counter-phase dots would activate motion opponent mechanisms in V5. 2) Offline 1 Hz rTMS of V5 would impair discrimination performance for in-phase stimuli but not counter-phase stimuli, and the opposite effect would be found for rTMS of V1. METHODS Stimuli were constructed from 100 dot pairs. Paired dots moved along a fixed motion axis either in counter-phase (motion opponent stimulus) or in-phase (non-opponent motion stimulus). Motion axis orientation discrimination thresholds were measured for each stimulus. Blocks of 300 trials were then presented at 85% correct threshold and discrimination accuracy was measured before and after 1 Hz offline rTMS of either V1 or V5. Subjects were 8 healthy adults. RESULTS Discrimination thresholds were significantly larger (worse) for counter-phase than in-phase stimuli (p = 0.02). V5 rTMS mildly impaired discrimination accuracy for the in-phase dot stimuli (p = 0.02) but not the counter-phase dot stimuli. The opposite effect occurred for V1 rTMS (p = 0.05). CONCLUSIONS Opponent motion mechanisms are present within human V5 and activation of these mechanisms impairs motion discrimination. In addition, perception of the motion axis within opponent motion stimuli involves processing within V1.
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Affiliation(s)
- Benjamin Thompson
- School of Optometry and Vision Science, University of Waterloo, Canada; School of Optometry and Vision Science, University of Auckland, New Zealand.
| | - Choi Deblieck
- AcCENT (Academic Center for ECT and Neuromodulation), University Psychiatric Center - KU Leuven (University of Leuven) - Campus Kortenberg, Kortenberg, Belgium
| | - Allan Wu
- Ahmanson-Lovelace Brain Mapping Center, UCLA, Los Angeles, CA, USA; Department of Neurology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Marco Iacoboni
- Ahmanson-Lovelace Brain Mapping Center, UCLA, Los Angeles, CA, USA; Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA; Brain Research Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Zili Liu
- Department of Psychology, UCLA, Los Angeles, CA, USA
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Assessment of Effective Connectivity and Plasticity With Dual-Coil Transcranial Magnetic Stimulation. Brain Stimul 2016; 9:347-355. [DOI: 10.1016/j.brs.2016.02.010] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Revised: 12/14/2015] [Accepted: 02/16/2016] [Indexed: 12/30/2022] Open
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Lee W, Lee SD, Park MY, Foley L, Purcell-Estabrook E, Kim H, Fischer K, Maeng LS, Yoo SS. Image-Guided Focused Ultrasound-Mediated Regional Brain Stimulation in Sheep. ULTRASOUND IN MEDICINE & BIOLOGY 2016; 42:459-470. [PMID: 26525652 DOI: 10.1016/j.ultrasmedbio.2015.10.001] [Citation(s) in RCA: 134] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Revised: 09/17/2015] [Accepted: 10/01/2015] [Indexed: 06/05/2023]
Abstract
Non-invasive brain stimulation using focused ultrasound has largely been carried out in small animals. In the present study, we applied stimulatory focused ultrasound transcranially to the primary sensorimotor (SM1) and visual (V1) brain areas in sheep (Dorset, all female, n = 8), under the guidance of magnetic resonance imaging, and examined the electrophysiologic responses. By use of a 250-kHz focused ultrasound transducer, the area was sonicated in pulsed mode (tone-burst duration of 1 ms, duty cycle of 50%) for 300 ms. The acoustic intensity at the focal target was varied up to a spatial peak pulse-average intensity (Isppa) of 14.3 W/cm(2). Sonication of SM1 elicited electromyographic responses from the contralateral hind leg, whereas stimulation of V1 generated electroencephalographic potentials. These responses were detected only above a certain acoustic intensity, and the threshold intensity, as well as the degree of responses, varied among sheep. Post-sonication animal behavior was normal, but minor microhemorrhages were observed from the V1 areas exposed to highly repetitive sonication (every second for ≥500 times for electroencephalographic measurements, Isppa = 6.6-10.5 W/cm(2), mechanical index = 0.9-1.2). Our results suggest the potential translational utility of focused ultrasound as a new brain stimulation modality, yet also call for caution in the use of an excessive number of sonications.
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Affiliation(s)
- Wonhye Lee
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Stephanie D Lee
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Michael Y Park
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Lori Foley
- Invasive Cardiovascular Experimental Laboratory, Brigham and Women's Hospital, Boston, Massachusetts, USA
| | - Erin Purcell-Estabrook
- Invasive Cardiovascular Experimental Laboratory, Brigham and Women's Hospital, Boston, Massachusetts, USA
| | - Hyungmin Kim
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA; Center for Bionics, Korea Institute of Science and Technology, Seoul, Korea
| | - Krisztina Fischer
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Lee-So Maeng
- Incheon St. Mary's Hospital, The Catholic University of Korea, Incheon, Korea
| | - Seung-Schik Yoo
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA.
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Suppression of EEG visual-evoked potentials in rats through neuromodulatory focused ultrasound. Neuroreport 2015; 26:211-5. [PMID: 25646585 DOI: 10.1097/wnr.0000000000000330] [Citation(s) in RCA: 91] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
We investigated the use of pulsed low-intensity focused ultrasound (FUS) to suppress the visual neural response induced by light stimulation in rodents. FUS was administered transcranially to the rat visual cortex using different acoustic intensities and pulsing duty cycles. The visual-evoked potentials (VEPs) generated by an external strobe light stimulation were measured three times before, once during, and five times after the sonication. The VEP magnitude was suppressed during the sonication using a 5% duty cycle (pulse-repetition frequency of 100 Hz) and a spatial-peak pulse-average acoustic intensity of 3 W/cm; however, this suppressive effect was not present when a lower acoustic intensity and duty cycle were used. The application of a higher intensity and duty cycle resulted in a slight elevation in VEP magnitude, which suggested excitatory neuromodulation. Our findings demonstrate that the application of pulsed FUS to the region-specific brain area not only suppresses its excitability, but can also enhance the excitability depending on the acoustic intensity and the rate of energy deposition. This bimodal feature of FUS-mediated neuromodulation, which has been predicted by numerical models on neural membrane capacitance change by the external acoustic pressure waves, suggests its versatility for neurotherapeutic applications.
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cTBS delivered to the left somatosensory cortex changes its functional connectivity during rest. Neuroimage 2015; 114:386-397. [PMID: 25882754 DOI: 10.1016/j.neuroimage.2015.04.017] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2014] [Revised: 02/25/2015] [Accepted: 04/06/2015] [Indexed: 12/19/2022] Open
Abstract
The primary somatosensory cortex (SI) plays a critical role in somatosensation as well as in action performance and social cognition. Although the SI has been a major target of experimental and clinical research using non-invasive transcranial magnetic stimulation (TMS), to date information on the effect of TMS over the SI on its resting-state functional connectivity is very scant. Here, we explored whether continuous theta burst stimulation (cTBS), a repetitive TMS protocol, administered over the SI can change the functional connectivity of the brain at rest, as measured using resting-state functional magnetic resonance imaging (rs-fMRI). In a randomized order on two different days we administered active TMS or sham TMS over the left SI. TMS was delivered off-line before scanning by means of cTBS. The target area was selected previously and individually for each subject as the part of the SI activated both when the participant executes and observes actions. Three analytical approaches, both theory driven (partial correlations and seed based whole brain regression) and more data driven (Independent Component Analysis), indicated a reduction in functional connectivity between the stimulated part of the SI and several brain regions functionally associated with the SI including the dorsal premotor cortex, the cerebellum, basal ganglia, and anterior cingulate cortex. These findings highlight the impact of cTBS delivered over the SI on its functional connectivity at rest. Our data may have implications for experimental and therapeutic applications of cTBS over the SI.
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Rassovsky Y, Lee J, Nori P, Wu AD, Iacoboni M, Breitmeyer BG, Hellemann G, Green MF. Exploring facial emotion perception in schizophrenia using transcranial magnetic stimulation and spatial filtering. J Psychiatr Res 2014; 58:102-8. [PMID: 25106071 DOI: 10.1016/j.jpsychires.2014.07.017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2014] [Accepted: 07/17/2014] [Indexed: 12/14/2022]
Abstract
Schizophrenia patients have difficulty extracting emotional information from facial expressions. Perception of facial emotion can be examined by systematically altering the spatial frequency of stimuli and suppressing visual processing with temporal precision using transcranial magnetic stimulation (TMS). In the present study, we compared 25 schizophrenia patients and 27 healthy controls using a facial emotion identification task. Spatial processing was examined by presenting facial photographs that contained either high (HSF), low (LSF), or broadband/unfiltered (BSF) spatial frequencies. Temporal processing was manipulated using a single-pulse TMS delivered to the visual cortex either before (forward masking) or after (backward masking) photograph presentation. Consistent with previous studies, schizophrenia patients performed significantly below controls across all three spatial frequencies. A spatial frequency by forward/backward masking interaction effect demonstrated reduced performance in the forward masking component in the BSF condition and a reversed performance pattern in the HSF condition, with no significant differences between forward and backward masking in the LSF condition. However, the group by spatial frequency interaction was not significant. These findings indicate that manipulating visual suppression of emotional information at the level of the primary visual cortex results in comparable effects on both groups. This suggests that patients' deficits in facial emotion identification are not explained by low-level processes in the retino-geniculo-striate projection, but may rather depend on deficits of affect perception occurring at later integrative processing stages.
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Affiliation(s)
- Yuri Rassovsky
- Department of Psychology, Bar-Ilan University, Ramat-Gan, Israel; Gonda Multidisciplinary Brain Research Center, Bar-Ilan University, Ramat-Gan, Israel; Department of Psychiatry and Biobehavioral Sciences, UCLA Semel Institute for Neuroscience and Human Behavior, Los Angeles, CA, USA.
| | - Junghee Lee
- Department of Psychiatry and Biobehavioral Sciences, UCLA Semel Institute for Neuroscience and Human Behavior, Los Angeles, CA, USA
| | - Poorang Nori
- Department of Psychiatry and Biobehavioral Sciences, UCLA Semel Institute for Neuroscience and Human Behavior, Los Angeles, CA, USA
| | - Allan D Wu
- Department of Neurology, University of California, Los Angeles, USA
| | - Marco Iacoboni
- Department of Psychiatry and Biobehavioral Sciences, UCLA Semel Institute for Neuroscience and Human Behavior, Los Angeles, CA, USA; Ahmanson-Lovelace Brain Mapping Center, University of California, Los Angeles, USA
| | | | - Gerhard Hellemann
- Department of Psychiatry and Biobehavioral Sciences, UCLA Semel Institute for Neuroscience and Human Behavior, Los Angeles, CA, USA
| | - Michael F Green
- Department of Psychiatry and Biobehavioral Sciences, UCLA Semel Institute for Neuroscience and Human Behavior, Los Angeles, CA, USA; Department of Veteran Affairs VISN-22 Mental Illness Research Education Clinical Center, Los Angeles, CA, USA
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Tanaka LL, Dessing JC, Malik P, Prime SL, Crawford JD. The effects of TMS over dorsolateral prefrontal cortex on trans-saccadic memory of multiple objects. Neuropsychologia 2014; 63:185-93. [PMID: 25192630 DOI: 10.1016/j.neuropsychologia.2014.08.025] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Revised: 07/04/2014] [Accepted: 08/20/2014] [Indexed: 10/24/2022]
Abstract
Humans typically make several rapid eye movements (saccades) per second. It is thought that visual working memory can retain and spatially integrate three to four objects or features across each saccade but little is known about this neural mechanism. Previously we showed that transcranial magnetic stimulation (TMS) to the posterior parietal cortex and frontal eye fields degrade trans-saccadic memory of multiple object features (Prime, Vesia, & Crawford, 2008, Journal of Neuroscience, 28(27), 6938-6949; Prime, Vesia, & Crawford, 2010, Cerebral Cortex, 20(4), 759-772.). Here, we used a similar protocol to investigate whether dorsolateral prefrontal cortex (DLPFC), an area involved in spatial working memory, is also involved in trans-saccadic memory. Subjects were required to report changes in stimulus orientation with (saccade task) or without (fixation task) an eye movement in the intervening memory interval. We applied single-pulse TMS to left and right DLPFC during the memory delay, timed at three intervals to arrive approximately 100 ms before, 100 ms after, or at saccade onset. In the fixation task, left DLPFC TMS produced inconsistent results, whereas right DLPFC TMS disrupted performance at all three intervals (significantly for presaccadic TMS). In contrast, in the saccade task, TMS consistently facilitated performance (significantly for left DLPFC/perisaccadic TMS and right DLPFC/postsaccadic TMS) suggesting a dis-inhibition of trans-saccadic processing. These results are consistent with a neural circuit of trans-saccadic memory that overlaps and interacts with, but is partially separate from the circuit for visual working memory during sustained fixation.
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Affiliation(s)
- L L Tanaka
- Centre for Vision Research and Canadian Action and Perception Network, York University, Toronto, Canada; Neuroscience Graduate Diploma Program and Departments of Psychology, Biology, and Kinesiology and Health Sciences, York University, Toronto, Canada
| | - J C Dessing
- Centre for Vision Research and Canadian Action and Perception Network, York University, Toronto, Canada; School of Psychology, Queen׳s University Belfast, Northern Ireland
| | - P Malik
- Centre for Vision Research and Canadian Action and Perception Network, York University, Toronto, Canada; Neuroscience Graduate Diploma Program and Departments of Psychology, Biology, and Kinesiology and Health Sciences, York University, Toronto, Canada
| | - S L Prime
- Department of Psychology, University of Saskatchewan, Canada
| | - J D Crawford
- Centre for Vision Research and Canadian Action and Perception Network, York University, Toronto, Canada; Neuroscience Graduate Diploma Program and Departments of Psychology, Biology, and Kinesiology and Health Sciences, York University, Toronto, Canada.
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Vernet M, Quentin R, Chanes L, Mitsumasu A, Valero-Cabré A. Frontal eye field, where art thou? Anatomy, function, and non-invasive manipulation of frontal regions involved in eye movements and associated cognitive operations. Front Integr Neurosci 2014; 8:66. [PMID: 25202241 PMCID: PMC4141567 DOI: 10.3389/fnint.2014.00066] [Citation(s) in RCA: 102] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2014] [Accepted: 08/01/2014] [Indexed: 01/06/2023] Open
Abstract
The planning, control and execution of eye movements in 3D space relies on a distributed system of cortical and subcortical brain regions. Within this network, the Eye Fields have been described in animals as cortical regions in which electrical stimulation is able to trigger eye movements and influence their latency or accuracy. This review focuses on the Frontal Eye Field (FEF) a “hub” region located in Humans in the vicinity of the pre-central sulcus and the dorsal-most portion of the superior frontal sulcus. The straightforward localization of the FEF through electrical stimulation in animals is difficult to translate to the healthy human brain, particularly with non-invasive neuroimaging techniques. Hence, in the first part of this review, we describe attempts made to characterize the anatomical localization of this area in the human brain. The outcome of functional Magnetic Resonance Imaging (fMRI), Magneto-encephalography (MEG) and particularly, non-invasive mapping methods such a Transcranial Magnetic Stimulation (TMS) are described and the variability of FEF localization across individuals and mapping techniques are discussed. In the second part of this review, we will address the role of the FEF. We explore its involvement both in the physiology of fixation, saccade, pursuit, and vergence movements and in associated cognitive processes such as attentional orienting, visual awareness and perceptual modulation. Finally in the third part, we review recent evidence suggesting the high level of malleability and plasticity of these regions and associated networks to non-invasive stimulation. The exploratory, diagnostic, and therapeutic interest of such interventions for the modulation and improvement of perception in 3D space are discussed.
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Affiliation(s)
- Marine Vernet
- Centre de Recherche de l'Institut du Cerveau et de la Moelle Epinière, CNRS UMR 7225, INSERM UMRS 975 and Université Pierre et Marie Curie Paris, France
| | - Romain Quentin
- Centre de Recherche de l'Institut du Cerveau et de la Moelle Epinière, CNRS UMR 7225, INSERM UMRS 975 and Université Pierre et Marie Curie Paris, France
| | - Lorena Chanes
- Centre de Recherche de l'Institut du Cerveau et de la Moelle Epinière, CNRS UMR 7225, INSERM UMRS 975 and Université Pierre et Marie Curie Paris, France
| | - Andres Mitsumasu
- Centre de Recherche de l'Institut du Cerveau et de la Moelle Epinière, CNRS UMR 7225, INSERM UMRS 975 and Université Pierre et Marie Curie Paris, France
| | - Antoni Valero-Cabré
- Centre de Recherche de l'Institut du Cerveau et de la Moelle Epinière, CNRS UMR 7225, INSERM UMRS 975 and Université Pierre et Marie Curie Paris, France ; Laboratory for Cerebral Dynamics Plasticity and Rehabilitation, School of Medicine, Boston University Boston, MA, USA ; Cognitive Neuroscience and Information Technology Research Program, Open University of Catalonia Barcelona, Spain
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Sliwinska MW, Vitello S, Devlin JT. Transcranial magnetic stimulation for investigating causal brain-behavioral relationships and their time course. J Vis Exp 2014. [PMID: 25079670 PMCID: PMC4219631 DOI: 10.3791/51735] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Transcranial magnetic stimulation (TMS) is a safe, non-invasive brain stimulation technique that uses a strong electromagnet in order to temporarily disrupt information processing in a brain region, generating a short-lived "virtual lesion." Stimulation that interferes with task performance indicates that the affected brain region is necessary to perform the task normally. In other words, unlike neuroimaging methods such as functional magnetic resonance imaging (fMRI) that indicate correlations between brain and behavior, TMS can be used to demonstrate causal brain-behavior relations. Furthermore, by varying the duration and onset of the virtual lesion, TMS can also reveal the time course of normal processing. As a result, TMS has become an important tool in cognitive neuroscience. Advantages of the technique over lesion-deficit studies include better spatial-temporal precision of the disruption effect, the ability to use participants as their own control subjects, and the accessibility of participants. Limitations include concurrent auditory and somatosensory stimulation that may influence task performance, limited access to structures more than a few centimeters from the surface of the scalp, and the relatively large space of free parameters that need to be optimized in order for the experiment to work. Experimental designs that give careful consideration to appropriate control conditions help to address these concerns. This article illustrates these issues with TMS results that investigate the spatial and temporal contributions of the left supramarginal gyrus (SMG) to reading.
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Affiliation(s)
| | - Sylvia Vitello
- Cognitive, Perceptual & Brain Sciences, University College London
| | - Joseph T Devlin
- Cognitive, Perceptual & Brain Sciences, University College London
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Enhanced awareness followed reversible inhibition of human visual cortex: a combined TMS, MRS and MEG study. PLoS One 2014; 9:e100350. [PMID: 24956195 PMCID: PMC4067303 DOI: 10.1371/journal.pone.0100350] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Accepted: 05/23/2014] [Indexed: 11/19/2022] Open
Abstract
This series of experiments investigated the neural basis of conscious vision in humans using a form of transcranial magnetic stimulation (TMS) known as continuous theta burst stimulation (cTBS). Previous studies have shown that occipital TMS, when time-locked to the onset of visual stimuli, can induce a phenomenon analogous to blindsight in which conscious detection is impaired while the ability to discriminate ‘unseen’ stimuli is preserved above chance. Here we sought to reproduce this phenomenon using offline occipital cTBS, which has been shown to induce an inhibitory cortical aftereffect lasting 45–60 minutes. Contrary to expectations, our first experiment revealed the opposite effect: cTBS enhanced conscious vision relative to a sham control. We then sought to replicate this cTBS-induced potentiation of consciousness in conjunction with magnetoencephalography (MEG) and undertook additional experiments to assess its relationship to visual cortical excitability and levels of the inhibitory neurotransmitter γ-aminobutyric acid (GABA; via magnetic resonance spectroscopy, MRS). Occipital cTBS decreased cortical excitability and increased regional GABA concentration. No significant effects of cTBS on MEG measures were observed, although the results provided weak evidence for potentiation of event related desynchronisation in the β band. Collectively these experiments suggest that, through the suppression of noise, cTBS can increase the signal-to-noise ratio of neural activity underlying conscious vision. We speculate that gating-by-inhibition in the visual cortex may provide a key foundation of consciousness.
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Nardella A, Rocchi L, Conte A, Bologna M, Suppa A, Berardelli A. Inferior parietal lobule encodes visual temporal resolution processes contributing to the critical flicker frequency threshold in humans. PLoS One 2014; 9:e98948. [PMID: 24905987 PMCID: PMC4048231 DOI: 10.1371/journal.pone.0098948] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Accepted: 05/08/2014] [Indexed: 11/24/2022] Open
Abstract
The measurement of the Critical Flicker Frequency threshold is used to study the visual temporal resolution in healthy subjects and in pathological conditions. To better understand the role played by different cortical areas in the Critical Flicker Frequency threshold perception we used continuous Theta Burst Stimulation (cTBS), an inhibitory plasticity-inducing protocol based on repetitive transcranial magnetic stimulation. The Critical Flicker Frequency threshold was measured in twelve healthy subjects before and after cTBS applied over different cortical areas in separate sessions. cTBS over the left inferior parietal lobule altered the Critical Flicker Frequency threshold, whereas cTBS over the left mediotemporal cortex, primary visual cortex and right inferior parietal lobule left the Critical Flicker Frequency threshold unchanged. No statistical difference was found when the red or blue lights were used. Our findings show that left inferior parietal lobule is causally involved in the conscious perception of Critical Flicker Frequency and that Critical Flicker Frequency threshold can be modulated by plasticity-inducing protocols.
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Affiliation(s)
| | - Lorenzo Rocchi
- Department of Neurology and Psychiatry, "Sapienza", University of Rome, Rome, Italy
| | - Antonella Conte
- IRCCS Neuromed, Pozzilli, Isernia, Italy
- Department of Neurology and Psychiatry, "Sapienza", University of Rome, Rome, Italy
| | | | | | - Alfredo Berardelli
- IRCCS Neuromed, Pozzilli, Isernia, Italy
- Department of Neurology and Psychiatry, "Sapienza", University of Rome, Rome, Italy
- * E-mail:
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Schicktanz N, Schwegler K, Fastenrath M, Spalek K, Milnik A, Papassotiropoulos A, Nyffeler T, de Quervain DJF. Motor threshold predicts working memory performance in healthy humans. Ann Clin Transl Neurol 2013; 1:69-73. [PMID: 25356384 PMCID: PMC4207507 DOI: 10.1002/acn3.22] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Revised: 10/24/2013] [Accepted: 11/07/2013] [Indexed: 11/18/2022] Open
Abstract
Cognitive functions, such as working memory, depend on neuronal excitability in a distributed network of cortical regions. It is not known, however, if interindividual differences in cortical excitability are related to differences in working memory performance. In the present transcranial magnetic stimulation study, which included 188 healthy young subjects, we show that participants with lower resting motor threshold, which is related to higher corticospinal excitability, had increased 2-back working memory performance. The findings may help to better understand the link between cortical excitability and cognitive functions and may also have important clinical implications with regard to conditions of altered cortical excitability.
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Affiliation(s)
- Nathalie Schicktanz
- Division of Cognitive Neuroscience, Department of Psychology, University of Basel Basel, Switzerland ; Psychiatric University Clinics, University of Basel Basel, Switzerland
| | - Kyrill Schwegler
- Division of Cognitive Neuroscience, Department of Psychology, University of Basel Basel, Switzerland ; Psychiatric University Clinics, University of Basel Basel, Switzerland
| | - Matthias Fastenrath
- Division of Cognitive Neuroscience, Department of Psychology, University of Basel Basel, Switzerland
| | - Klara Spalek
- Division of Cognitive Neuroscience, Department of Psychology, University of Basel Basel, Switzerland
| | - Annette Milnik
- Division of Molecular Neuroscience, Department of Psychology, University of Basel Basel, Switzerland
| | - Andreas Papassotiropoulos
- Psychiatric University Clinics, University of Basel Basel, Switzerland ; Division of Molecular Neuroscience, Department of Psychology, University of Basel Basel, Switzerland ; Life Sciences Training Facility, Department Biozentrum, University of Basel Basel, Switzerland
| | - Thomas Nyffeler
- Departments of Neurology and Clinical Research, Perception and Eye Movement Laboratory Inselspital, Bern University Hospital, University of Bern Bern, Switzerland ; Center of Neurology and Neurorehabilitation, Luzerner Kantonsspital Luzern, Switzerland
| | - Dominique J-F de Quervain
- Division of Cognitive Neuroscience, Department of Psychology, University of Basel Basel, Switzerland ; Psychiatric University Clinics, University of Basel Basel, Switzerland
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Westin GG, Bassi BD, Lisanby SH, Luber B. Determination of motor threshold using visual observation overestimates transcranial magnetic stimulation dosage: safety implications. Clin Neurophysiol 2013; 125:142-147. [PMID: 23993680 DOI: 10.1016/j.clinph.2013.06.187] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Revised: 06/18/2013] [Accepted: 06/24/2013] [Indexed: 10/26/2022]
Abstract
OBJECTIVE While the standard has been to define motor threshold (MT) using EMG to measure motor cortex response to transcranial magnetic stimulation (TMS), another method of determining MT using visual observation of muscle twitch (OM-MT) has emerged in clinical and research use. We compared these two methods for determining MT. METHODS Left motor cortex MTs were found in 20 healthy subjects. Employing the commonly-used relative frequency procedure and beginning from a clearly suprathreshold intensity, two raters used motor evoked potentials and finger movements respectively to determine EMG-MT and OM-MT. RESULTS OM-MT was 11.3% higher than EMG-MT (p<0.001), ranging from 0% to 27.8%. In eight subjects, OM-MT was more than 10% higher than EMG-MT, with two greater than 25%. CONCLUSIONS These findings suggest using OM yields significantly higher MTs than EMG, and may lead to unsafe TMS in some individuals. In more than half of the subjects in the present study, use of their OM-MT for typical rTMS treatment of depression would have resulted in stimulation beyond safety limits. SIGNIFICANCE For applications that involve stimulation near established safety limits and in the presence of factors that could elevate risk such as concomitant medications, EMG-MT is advisable, given that safety guidelines for TMS parameters were based on EMG-MT.
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Affiliation(s)
- Gregory G Westin
- University of California Davis School of Medicine, Sacramento, CA, USA
| | - Bruce D Bassi
- University of Michigan Medical School, Ann Arbor, MI, USA
| | - Sarah H Lisanby
- Departments of Psychiatry and Behavioral Sciences, Duke School of Medicine, Duke University, Durham, NC, USA.,Psychology and Neuroscience, Duke University, Durham, NC, USA
| | - Bruce Luber
- Departments of Psychiatry and Behavioral Sciences, Duke School of Medicine, Duke University, Durham, NC, USA.,Psychology and Neuroscience, Duke University, Durham, NC, USA
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Salminen-Vaparanta N, Vanni S, Noreika V, Valiulis V, Móró L, Revonsuo A. Subjective Characteristics of TMS-Induced Phosphenes Originating in Human V1 and V2. Cereb Cortex 2013; 24:2751-60. [DOI: 10.1093/cercor/bht131] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Stokes MG, Barker AT, Dervinis M, Verbruggen F, Maizey L, Adams RC, Chambers CD. Biophysical determinants of transcranial magnetic stimulation: effects of excitability and depth of targeted area. J Neurophysiol 2012; 109:437-44. [PMID: 23114213 DOI: 10.1152/jn.00510.2012] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Safe and effective transcranial magnetic stimulation (TMS) requires accurate intensity calibration. Output is typically calibrated to individual motor cortex excitability and applied to nonmotor brain areas, assuming that it captures a site nonspecific factor of excitability. We tested this assumption by correlating the effect of TMS at motor and visual cortex. In 30 participants, we measured motor threshold (MT) and phosphene threshold (PT) at the scalp surface and at coil-scalp distances of 3.17, 5.63, and 9.03 mm. We also modeled the effect of TMS in a simple head model to test the effect of distance. Four independent tests confirmed a significant correlation between PT and MT. We also found similar effects of distance in motor and visual areas, which did not correlate across participants. Computational modeling suggests that the relationship between the effect of distance and the induced electric field is effectively linear within the range of distances that have been explored empirically. We conclude that MT-guided calibration is valid for nonmotor brain areas if coil-cortex distance is taken into account. For standard figure-of-eight TMS coils connected to biphasic stimulators, the effect of cortical distance should be adjusted using a general correction factor of 2.7% stimulator output per millimeter.
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Affiliation(s)
- Mark G Stokes
- Oxford Centre for Human Brain Activity, University of Oxford, Oxford, United Kingdom.
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Leitão J, Thielscher A, Werner S, Pohmann R, Noppeney U. Effects of parietal TMS on visual and auditory processing at the primary cortical level -- a concurrent TMS-fMRI study. ACTA ACUST UNITED AC 2012; 23:873-84. [PMID: 22490546 DOI: 10.1093/cercor/bhs078] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Accumulating evidence suggests that multisensory interactions emerge already at the primary cortical level. Specifically, auditory inputs were shown to suppress activations in visual cortices when presented alone but amplify the blood oxygen level-dependent (BOLD) responses to concurrent visual inputs (and vice versa). This concurrent transcranial magnetic stimulation-functional magnetic resonance imaging (TMS-fMRI) study applied repetitive TMS trains at no, low, and high intensity over right intraparietal sulcus (IPS) and vertex to investigate top-down influences on visual and auditory cortices under 3 sensory contexts: visual, auditory, and no stimulation. IPS-TMS increased activations in auditory cortices irrespective of sensory context as a result of direct and nonspecific auditory TMS side effects. In contrast, IPS-TMS modulated activations in the visual cortex in a state-dependent fashion: it deactivated the visual cortex under no and auditory stimulation but amplified the BOLD response to visual stimulation. However, only the response amplification to visual stimulation was selective for IPS-TMS, while the deactivations observed for IPS- and Vertex-TMS resulted from crossmodal deactivations induced by auditory activity to TMS sounds. TMS to IPS may increase the responses in visual (or auditory) cortices to visual (or auditory) stimulation via a gain control mechanism or crossmodal interactions. Collectively, our results demonstrate that understanding TMS effects on (uni)sensory processing requires a multisensory perspective.
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Affiliation(s)
- Joana Leitão
- Cognitive Neuroimaging Group, Max Planck Institute for Biological Cybernetics, 72076 Tübingen, Germany.
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Salminen-Vaparanta N, Noreika V, Revonsuo A, Koivisto M, Vanni S. Is selective primary visual cortex stimulation achievable with TMS? Hum Brain Mapp 2012; 33:652-65. [PMID: 21416561 PMCID: PMC6870472 DOI: 10.1002/hbm.21237] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2010] [Revised: 10/28/2010] [Accepted: 11/24/2010] [Indexed: 11/10/2022] Open
Abstract
The primary visual cortex (V1) has been the target of stimulation in a number of transcranial magnetic stimulation (TMS) studies. In this study, we estimated the actual sites of stimulation by modeling the cortical location of the TMS-induced electric field when participants reported visual phosphenes or scotomas. First, individual retinotopic areas were identified by multifocal functional magnetic resonance imaging (mffMRI). Second, during the TMS stimulation, the cortical stimulation sites were derived from electric field modeling. When an external anatomical landmark for V1 was used (2 cm above inion), the cortical stimulation landed in various functional areas in different individuals, the dorsal V2 being the most affected area at the group level. When V1 was specifically targeted based on the individual mffMRI data, V1 could be selectively stimulated in half of the participants. In the rest, the selective stimulation of V1 was obstructed by the intermediate position of the dorsal V2. We conclude that the selective stimulation of V1 is possible only if V1 happens to be favorably located in the individual anatomy. Selective and successful targeting of TMS pulses to V1 requires MRI-navigated stimulation, selection of participants and coil positions based on detailed retinotopic maps of individual functional anatomy, and computational modeling of the TMS-induced electric field distribution in the visual cortex. It remains to be resolved whether even more selective stimulation of V1 could be achieved by adjusting the coil orientation according to sulcal orientation of the target site.
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Comparison of transcranial magnetic stimulation measures obtained at rest and under active conditions and their reliability. J Neurosci Methods 2012; 205:65-71. [DOI: 10.1016/j.jneumeth.2011.12.012] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2011] [Revised: 12/14/2011] [Accepted: 12/20/2011] [Indexed: 11/18/2022]
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49
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Lefaucheur JP, André-Obadia N, Poulet E, Devanne H, Haffen E, Londero A, Cretin B, Leroi AM, Radtchenko A, Saba G, Thai-Van H, Litré CF, Vercueil L, Bouhassira D, Ayache SS, Farhat WH, Zouari HG, Mylius V, Nicolier M, Garcia-Larrea L. [French guidelines on the use of repetitive transcranial magnetic stimulation (rTMS): safety and therapeutic indications]. Neurophysiol Clin 2011; 41:221-95. [PMID: 22153574 DOI: 10.1016/j.neucli.2011.10.062] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2011] [Accepted: 10/18/2011] [Indexed: 12/31/2022] Open
Abstract
During the past decade, a large amount of work on transcranial magnetic stimulation (TMS) has been performed, including the development of new paradigms of stimulation, the integration of imaging data, and the coupling of TMS techniques with electroencephalography or neuroimaging. These accumulating data being difficult to synthesize, several French scientific societies commissioned a group of experts to conduct a comprehensive review of the literature on TMS. This text contains all the consensual findings of the expert group on the mechanisms of action, safety rules and indications of TMS, including repetitive TMS (rTMS). TMS sessions have been conducted in thousands of healthy subjects or patients with various neurological or psychiatric diseases, allowing a better assessment of risks associated with this technique. The number of reported side effects is extremely low, the most serious complication being the occurrence of seizures. In most reported seizures, the stimulation parameters did not follow the previously published recommendations (Wassermann, 1998) [430] and rTMS was associated to medication that could lower the seizure threshold. Recommendations on the safe use of TMS / rTMS were recently updated (Rossi et al., 2009) [348], establishing new limits for stimulation parameters and fixing the contraindications. The recommendations we propose regarding safety are largely based on this previous report with some modifications. By contrast, the issue of therapeutic indications of rTMS has never been addressed before, the present work being the first attempt of a synthesis and expert consensus on this topic. The use of TMS/rTMS is discussed in the context of chronic pain, movement disorders, stroke, epilepsy, tinnitus and psychiatric disorders. There is already a sufficient level of evidence of published data to retain a therapeutic indication of rTMS in clinical practice (grade A) in chronic neuropathic pain, major depressive episodes, and auditory hallucinations. The number of therapeutic indications of rTMS is expected to increase in coming years, in parallel with the optimisation of stimulation parameters.
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Affiliation(s)
- J-P Lefaucheur
- EA 4391, faculté de médecine, université Paris-Est-Créteil, 51, avenue du Maréchal-de-Lattre-de-Tassigny, 94010 Créteil, France
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Abstract
A recent study (Di Lazzaro et al. J Neurophysiol 105: 2150-2156, 2011) describes the findings from a rigorous comparison on the effects of several popular variations of transcranial magnetic stimulation (TMS) protocols. The results demonstrate that excitatory and inhibitory neural networks may be independently modulated based on TMS protocol selection. Moreover, the within-group replication of multiple between-group experiments suggests that independent evaluations of TMS parameters will continue to inform and guide future TMS research.
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Affiliation(s)
- Michael T Rubens
- Departments of Neurology and Physiology, University of California San Francisco, San Francisco, CA, USA.
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