601
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Spiegel DP, Hansen BC, Byblow WD, Thompson B. Anodal transcranial direct current stimulation reduces psychophysically measured surround suppression in the human visual cortex. PLoS One 2012; 7:e36220. [PMID: 22563485 PMCID: PMC3341359 DOI: 10.1371/journal.pone.0036220] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2011] [Accepted: 03/30/2012] [Indexed: 02/01/2023] Open
Abstract
Transcranial direct current stimulation (tDCS) is a safe, non-invasive technique for transiently modulating the balance of excitation and inhibition within the human brain. It has been reported that anodal tDCS can reduce both GABA mediated inhibition and GABA concentration within the human motor cortex. As GABA mediated inhibition is thought to be a key modulator of plasticity within the adult brain, these findings have broad implications for the future use of tDCS. It is important, therefore, to establish whether tDCS can exert similar effects within non-motor brain areas. The aim of this study was to assess whether anodal tDCS could reduce inhibitory interactions within the human visual cortex. Psychophysical measures of surround suppression were used as an index of inhibition within V1. Overlay suppression, which is thought to originate within the lateral geniculate nucleus (LGN), was also measured as a control. Anodal stimulation of the occipital poles significantly reduced psychophysical surround suppression, but had no effect on overlay suppression. This effect was specific to anodal stimulation as cathodal stimulation had no effect on either measure. These psychophysical results provide the first evidence for tDCS-induced reductions of intracortical inhibition within the human visual cortex.
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Affiliation(s)
- Daniel P. Spiegel
- Department of Optometry and Vision Science, University of Auckland, Auckland, New Zealand
| | - Bruce C. Hansen
- Department of Psychology & Neuroscience Program, Colgate University, Hamilton, New York, United States of America
| | - Winston D. Byblow
- Department of Sport and Exercise Science, University of Auckland, Auckland, New Zealand
| | - Benjamin Thompson
- Department of Optometry and Vision Science, University of Auckland, Auckland, New Zealand
- * E-mail:
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602
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Foerster BR, Callaghan BC, Petrou M, Edden RAE, Chenevert TL, Feldman EL. Decreased motor cortex γ-aminobutyric acid in amyotrophic lateral sclerosis. Neurology 2012; 78:1596-600. [PMID: 22517106 DOI: 10.1212/wnl.0b013e3182563b57] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
OBJECTIVES To determine if there are in vivo differences in γ-aminobutyric acid (GABA) in the motor cortex and subcortical white matter of patients with amyotrophic lateral sclerosis (ALS) compared with healthy controls using proton magnetic resonance spectroscopy (1H-MRS). METHODS In this cross-sectional study, 10 patients with ALS and 9 age- and sex-matched healthy controls (HCs) underwent 3T edited 1H-MRS to quantify GABA centered on the motor cortex and the subcortical white matter. RESULTS Compared with healthy controls, patients with ALS had significantly lower levels of GABA in the left motor cortex (1.42 ± 0.27 arbitrary institutional units vs. 1.70 ± 0.24 arbitrary institutional units, p = 0.038). There was no significant difference in GABA levels between groups in the subcortical white matter (p > 0.05). CONCLUSION Decreased levels of GABA are present in the motor cortex of patients with ALS compared to HCs. Findings are consistent with prior reports of alterations in GABA receptors in the motor cortex as well as increased cortical excitability in the context of ALS. Larger, longitudinal studies are needed to confirm these findings and to further our understanding of the role of GABA in the pathogenesis of ALS.
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Affiliation(s)
- B R Foerster
- Department of Radiology, University of Michigan, Ann Arbor, USA.
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603
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Michels L, Martin E, Klaver P, Edden R, Zelaya F, Lythgoe DJ, Lüchinger R, Brandeis D, O'Gorman RL. Frontal GABA levels change during working memory. PLoS One 2012; 7:e31933. [PMID: 22485128 PMCID: PMC3317667 DOI: 10.1371/journal.pone.0031933] [Citation(s) in RCA: 89] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2011] [Accepted: 01/18/2012] [Indexed: 01/21/2023] Open
Abstract
Functional neuroimaging metrics are thought to reflect changes in neurotransmitter flux, but changes in neurotransmitter levels have not been demonstrated in humans during a cognitive task, and the relationship between neurotransmitter dynamics and hemodynamic activity during cognition has not yet been established. We evaluate the concentration of the major inhibitory (GABA) and excitatory (glutamate + glutamine: Glx) neurotransmitters and the cerebral perfusion at rest and during a prolonged delayed match-to-sample working memory task. Resting GABA levels in the dorsolateral prefrontal cortex correlated positively with the resting perfusion and inversely with the change in perfusion during the task. Further, only GABA increased significantly during the first working memory run and then decreased continuously across subsequent task runs. The decrease of GABA over time was paralleled by a trend towards decreased reaction times and higher task accuracy. These results demonstrate a link between neurotransmitter dynamics and hemodynamic activity during working memory, indicating that functional neuroimaging metrics depend on the balance of excitation and inhibition required for cognitive processing.
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Affiliation(s)
- Lars Michels
- Center for MR-Research, University Children's Hospital, Zurich, Switzerland.
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604
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List J, Duning T, Kürten J, Deppe M, Wilbers E, Flöel A. Cortical plasticity is preserved in nondemented older individuals with severe ischemic small vessel disease. Hum Brain Mapp 2012; 34:1464-76. [PMID: 22331645 DOI: 10.1002/hbm.22003] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2011] [Revised: 10/31/2011] [Accepted: 11/03/2011] [Indexed: 11/06/2022] Open
Abstract
Ischemic small vessel disease (SVD) is a common finding on routine scans in older people, but cognitive sequelae vary considerably. To improve understanding of mechanisms underlying decline or preservation of cognitive function in this condition, we assessed cognition and cortical plasticity in 20 elderly subjects with severe SVD and 20 age-matched controls without SVD, as rated on conventional MRI. Cognitive status was determined with a neuropsychological test battery, cortical plasticity induced with a paired associative stimulation protocol. Microstructural white matter changes were further analyzed for fractional anisotrophy using diffusion tensor imaging. We found that cortical plasticity as well as memory functions were preserved in severe SVD, while executive functions showed trendwise or significant decreases. Within the SVD group, lower white matter integrity in parahippocampal regions and posterior parts of the corpus callosum was associated with larger cortical plasticity, an association not seen for prefrontal white matter tracts. Enhanced cortical plasticity in subjects with lower white matter integrity in memory-relevant areas might thus indicate a compensatory mechanism to counteract memory decline in severe SVD.
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Affiliation(s)
- Jonathan List
- Department of Neurology, University Hospital of Münster, Charitéplatz 1, Münster, Germany
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605
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Puts NA, Edden RA. In vivo magnetic resonance spectroscopy of GABA: a methodological review. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2012; 60:29-41. [PMID: 22293397 PMCID: PMC3383792 DOI: 10.1016/j.pnmrs.2011.06.001] [Citation(s) in RCA: 273] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2011] [Accepted: 05/30/2011] [Indexed: 05/06/2023]
Affiliation(s)
- Nicolaas A.J. Puts
- Schools of Bioscience and Psychology, Cardiff University, Park Place, Cardiff, UK
| | - Richard A.E. Edden
- Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
- FM Kirby Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, USA
- Corresponding author. Address: Russell H. Morgan Department of Radiology and Radiological Science, 600 N Wolfe St., Park 367C, Baltimore, MD 21287, USA. Tel.: +1 410 614 3418. (R.A.E. Edden)
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606
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Jones KT, Berryhill ME. Parietal contributions to visual working memory depend on task difficulty. Front Psychiatry 2012; 3:81. [PMID: 22973241 PMCID: PMC3437464 DOI: 10.3389/fpsyt.2012.00081] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2012] [Accepted: 08/21/2012] [Indexed: 11/13/2022] Open
Abstract
The nature of parietal contributions to working memory (WM) remain poorly understood but of considerable interest. We previously reported that posterior parietal damage selectively impaired WM probed by recognition (Berryhill and Olson, 2008a). Recent studies provided support using a neuromodulatory technique, transcranial direct current stimulation (tDCS) applied to the right parietal cortex (P4). These studies confirmed parietal involvement in WM because parietal tDCS altered WM performance: anodal current tDCS improved performance in a change detection task, and cathodal current tDCS impaired performance on a sequential presentation task. Here, we tested whether these complementary results were due to different degrees of parietal involvement as a function of WM task demands, WM task difficulty, and/or participants' WM capacity. In Experiment 1, we applied cathodal and anodal tDCS to the right parietal cortex and tested participants on both previously used WM tasks. We observed an interaction between tDCS (anodal, cathodal), WM task difficulty, and participants' WM capacity. When the WM task was difficult, parietal stimulation (anodal or cathodal) improved WM performance selectively in participants with high WM capacity. In the low WM capacity group, parietal stimulation (anodal or cathodal) impaired WM performance. These nearly equal and opposite effects were only observed when the WM task was challenging, as in the change detection task. Experiment 2 probed the interplay of WM task difficulty and WM capacity in a parametric manner by varying set size in the WM change detection task. Here, the effect of parietal stimulation (anodal or cathodal) on the high WM capacity group followed a linear function as WM task difficulty increased with set size. The low WM capacity participants were largely unaffected by tDCS. These findings provide evidence that parietal involvement in WM performance depends on both WM capacity and WM task demands. We discuss these findings in terms of alternative WM strategies employed by low and high WM capacity individuals. We speculate that low WM capacity individuals do not recruit the posterior parietal lobe for WM tasks as efficiently as high WM capacity individuals. Consequently, tDCS provides greater benefit to individuals with high WM capacity.
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Affiliation(s)
- Kevin T Jones
- Memory and Brain Laboratory, Department of Psychology, University of Nevada Reno, NV, USA
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607
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Medeiros LF, de Souza ICC, Vidor LP, de Souza A, Deitos A, Volz MS, Fregni F, Caumo W, Torres ILS. Neurobiological effects of transcranial direct current stimulation: a review. Front Psychiatry 2012; 3:110. [PMID: 23293607 PMCID: PMC3531595 DOI: 10.3389/fpsyt.2012.00110] [Citation(s) in RCA: 167] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/05/2012] [Accepted: 12/04/2012] [Indexed: 12/20/2022] Open
Abstract
Transcranial Direct Current Stimulation (tDCS) is a non-invasive brain stimulation technique that is affordable and easy to operate compared to other neuromodulation techniques. Anodal stimulation increases cortical excitability, while the cathodal stimulation decreases it. Although tDCS is a promising treatment approach for chronic pain as well as for neuropsychiatric diseases and other neurological disorders, several complex neurobiological mechanisms that are not well understood are involved in its effect. The purpose of this systematic review is to summarize the current knowledge regarding the neurobiological mechanisms involved in the effects of tDCS. The initial search resulted in 171 articles. After applying inclusion and exclusion criteria, we screened 32 full-text articles to extract findings about the neurobiology of tDCS effects including investigation of cortical excitability parameters. Overall, these findings show that tDCS involves a cascade of events at the cellular and molecular levels. Moreover, tDCS is associated with glutamatergic, GABAergic, dopaminergic, serotonergic, and cholinergic activity modulation. Though these studies provide important advancements toward the understanding of mechanisms underlying tDCS effects, further studies are needed to integrate these mechanisms as to optimize clinical development of tDCS.
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Affiliation(s)
- Liciane Fernandes Medeiros
- Post-Graduate Program in Biological Sciences, Department of Physiology, Universidade Federal do Rio Grande do Sul Porto Alegre, Brazil ; Pharmacology Department, Institute of Basic Health Science, Universidade Federal do Rio Grande do Sul Porto Alegre, Brazil ; Laboratory of Pain and Neuromodulation, Hospital de Clínicas de Porto Alegre Porto Alegre, Brazil
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608
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Madhavan S, Shah B. Enhancing motor skill learning with transcranial direct current stimulation - a concise review with applications to stroke. Front Psychiatry 2012; 3:66. [PMID: 22807918 PMCID: PMC3395020 DOI: 10.3389/fpsyt.2012.00066] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2012] [Accepted: 06/15/2012] [Indexed: 02/04/2023] Open
Abstract
In the past few years, there has been a rapid increase in the application of non-invasive brain stimulation to study brain-behavior relations in an effort to potentially increase the effectiveness of neuro-rehabilitation. Transcranial direct current stimulation (tDCS), an emerging technique of non-invasive brain stimulation, has shown to produce beneficial neural effects in consequence with improvements in motor behavior. tDCS has gained popularity as it is economical, simple to use, portable, and increases corticospinal excitability without producing any serious side effects. As tDCS has been increasingly investigated as an effective tool for various disorders, numerous improvements, and developments have been proposed with respect to this technique. tDCS has been widely used to identify the functional relevance of particular brain regions in motor skill learning and also to facilitate activity in specific cortical areas involved in motor learning, in turn improving motor function. Understanding the interaction between tDCS and motor learning can lead to important implications for developing various rehabilitation approaches. This paper provides a concise overview of tDCS as a neuromodulatory technique and its interaction with motor learning. The paper further briefly goes through the application of this priming technique in the stroke population.
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609
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Hansen N. Action mechanisms of transcranial direct current stimulation in Alzheimer's disease and memory loss. Front Psychiatry 2012; 3:48. [PMID: 22615703 PMCID: PMC3351674 DOI: 10.3389/fpsyt.2012.00048] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2012] [Accepted: 04/24/2012] [Indexed: 01/01/2023] Open
Abstract
The pharmacological treatment of Alzheimer's disease (AD) is often limited and accompanied by drug side effects. Thus alternative therapeutic strategies such as non-invasive brain stimulation are needed. Few studies have demonstrated that transcranial direct current stimulation (tDCS), a method of neuromodulation with consecutive robust excitability changes within the stimulated cortex area, is beneficial in AD. There is also evidence that tDCS enhances memory function in cognitive rehabilitation in depressive patients, Parkinson's disease, and stroke. tDCS improves working and visual recognition memory in humans and object-recognition learning in the elderly. AD's neurobiological mechanisms comprise changes in neuronal activity and the cerebral blood flow (CBF) caused by altered microvasculature, synaptic dysregulation from ß-amyloid peptide accumulation, altered neuromodulation via degenerated modulatory amine transmitter systems, altered brain oscillations, and changes in network connectivity. tDCS alters (i) neuronal activity and (ii) human CBF, (iii) has synaptic and non-synaptic after-effects (iv), can modify neurotransmitters polarity-dependently, (v) and alter oscillatory brain activity and (vi) functional connectivity patterns in the brain. It thus is reasonable to use tDCS as a therapeutic instrument in AD as it improves cognitive function in manner based on a disease mechanism. Moreover, it could prove valuable in other types of dementia. Future large-scale clinical and mechanism-oriented studies may enable us to identify its therapeutic validity in other types of demential disorders.
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Affiliation(s)
- Niels Hansen
- Department of Neurophysiology, Ruhr University Bochum Bochum, Germany
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610
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Stagg CJ, Bachtiar V, O'Shea J, Allman C, Bosnell RA, Kischka U, Matthews PM, Johansen-Berg H. Cortical activation changes underlying stimulation-induced behavioural gains in chronic stroke. ACTA ACUST UNITED AC 2011; 135:276-84. [PMID: 22155982 PMCID: PMC3267983 DOI: 10.1093/brain/awr313] [Citation(s) in RCA: 127] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Transcranial direct current stimulation, a form of non-invasive brain stimulation, is showing increasing promise as an adjunct therapy in rehabilitation following stroke. However, although significant behavioural improvements have been reported in proof-of-principle studies, the underlying mechanisms are poorly understood. The rationale for transcranial direct current stimulation as therapy for stroke is that therapeutic stimulation paradigms increase activity in ipsilesional motor cortical areas, but this has not previously been directly tested for conventional electrode placements. This study was performed to test directly whether increases in ipsilesional cortical activation with transcranial direct current stimulation are associated with behavioural improvements in chronic stroke patients. Patients at least 6 months post-first stroke participated in a behavioural experiment (n = 13) or a functional magnetic resonance imaging experiment (n = 11), each investigating the effects of three stimulation conditions in separate sessions: anodal stimulation to the ipsilesional hemisphere; cathodal stimulation to the contralesional hemisphere; and sham stimulation. Anodal (facilitatory) stimulation to the ipsilesional hemisphere led to significant improvements (5–10%) in response times with the affected hand in both experiments. This improvement was associated with an increase in movement-related cortical activity in the stimulated primary motor cortex and functionally interconnected regions. Cathodal (inhibitory) stimulation to the contralesional hemisphere led to a functional improvement only when compared with sham stimulation. We show for the first time that the significant behavioural improvements produced by anodal stimulation to the ipsilesional hemisphere are associated with a functionally relevant increase in activity within the ipsilesional primary motor cortex in patients with a wide range of disabilities following stroke.
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Affiliation(s)
- Charlotte Jane Stagg
- Nuffield Department of Clinical Neurosciences, Oxford Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB), John Radcliffe Hospital, Oxford OX3 9DU, UK.
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611
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Brunoni AR, Fregni F, Pagano RL. Translational research in transcranial direct current stimulation (tDCS): a systematic review of studies in animals. Rev Neurosci 2011; 22:471-81. [PMID: 21819264 DOI: 10.1515/rns.2011.042] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Recent therapeutic human studies testing transcranial direct current stimulation (tDCS) has shown promising results, although many questions remain unanswered. Translational research with experimental animals is an appropriate framework for investigating its mechanisms of action that are still undetermined. Nevertheless, animal and human studies are often discordant. Our aim was to review tDCS animal studies, examining and comparing their main findings with human studies. We performed a systematic review in Medline and other databases, screening for animal studies in vivo that delivered tDCS. Studies in vitro and using other neuromodulatory techniques were excluded. We extracted data according to Animal Research: Reporting In Vivo Experiments (ARRIVE) guidelines for reporting in vivo animal research. Thus, we collected data on sample characteristics (size, gender, weight and specimen) and methodology (experimental procedures, experimental animals, housing and husbandry, as well as analysis). We also collected data on methods for delivering tDCS (location, size, current and current density of electrodes and electrode montage), experimental effects (polarity-, intensity- and after-effects) and safety. Only 12 of 48 potentially eligible studies met our inclusion criteria and were reviewed. Quality assessment reporting was only moderate and studies were heterogeneous regarding tDCS montage methodology, position of active and reference electrodes, and current density used. Nonetheless, almost all studies demonstrated that tDCS had positive immediate and long-lasting effects. Vis-à-vis human trials, animal studies applied higher current densities (34.2 vs. 0.4 A/m(2), respectively), preferred extra-cephalic positions for reference electrodes (60% vs. 10%, respectively) and used electrodes with different sizes more often. Potential implications for translational tDCS research are discussed.
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Affiliation(s)
- Andre Russowsky Brunoni
- Department of Neurosciences and Behavior, Institute of Psychology, University of São Paulo, Cidade Universitária, 05508-000 Butantã, São Paulo, Brazil.
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612
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Siniatchkin M, Sendacki M, Moeller F, Wolff S, Jansen O, Siebner H, Stephani U. Abnormal Changes of Synaptic Excitability in Migraine with Aura. Cereb Cortex 2011; 22:2207-16. [DOI: 10.1093/cercor/bhr248] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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613
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Boy F, Evans CJ, Edden RAE, Lawrence AD, Singh KD, Husain M, Sumner P. Dorsolateral prefrontal γ-aminobutyric acid in men predicts individual differences in rash impulsivity. Biol Psychiatry 2011; 70:866-72. [PMID: 21757187 PMCID: PMC3192031 DOI: 10.1016/j.biopsych.2011.05.030] [Citation(s) in RCA: 109] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2011] [Revised: 05/27/2011] [Accepted: 05/27/2011] [Indexed: 11/27/2022]
Abstract
BACKGROUND Impulsivity is a multifaceted personality construct associated with numerous psychiatric disorders. Recent research has characterized four facets of impulsivity: "urgency" (the tendency to act rashly especially in the context of distress or cravings); "lack of premeditation" (not envisaging the consequences of actions); "lack of perseverance" (not staying focused on a task); and "sensation seeking" (engaging in exciting activities). Urgency is particularly associated with clinical populations and problematic disinhibited behavior. METHODS We used magnetic resonance spectroscopy to measure concentration of the inhibitory neurotransmitter γ-aminobutyric acid (GABA) in the dorsolateral prefrontal cortex (DLPFC) in two cohorts of 12 and 13 participants. RESULTS We find that variation in trait urgency in healthy men correlates with GABA concentration in the DLPFC. The result was replicated in an independent cohort. More GABA predicted lower urgency scores, consistent with a role in self-control for GABA-mediated inhibitory mechanisms in DLPFC. CONCLUSIONS These findings help account for individual differences in self-control and thus clarify the relationship between GABA and a wide range of psychiatric disorders associated with impaired self-control.
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Affiliation(s)
- Frederic Boy
- Cardiff University Brain Research Imaging Centre, School of Psychology, Cardiff University, Cardiff, United Kingdom.
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614
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Stagg CJ, Bestmann S, Constantinescu AO, Moreno LM, Allman C, Mekle R, Woolrich M, Near J, Johansen-Berg H, Rothwell JC. Relationship between physiological measures of excitability and levels of glutamate and GABA in the human motor cortex. J Physiol 2011; 589:5845-55. [PMID: 22005678 PMCID: PMC3249054 DOI: 10.1113/jphysiol.2011.216978] [Citation(s) in RCA: 244] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Magnetic resonance spectroscopy (MRS) allows measurement of neurotransmitter concentrations within a region of interest in the brain. Inter-individual variation in MRS-measured GABA levels have been related to variation in task performance in a number of regions. However, it is not clear how MRS-assessed measures of GABA relate to cortical excitability or GABAergic synaptic activity. We therefore performed two studies investigating the relationship between neurotransmitter levels as assessed by MRS and transcranial magnetic stimulation (TMS) measures of cortical excitability and GABA synaptic activity in the primary motor cortex. We present uncorrected correlations, where the P value should therefore be considered with caution. We demonstrated a correlation between cortical excitability, as assessed by the slope of the TMS input-output curve and MRS-assessed glutamate levels (r = 0.803, P = 0.015) but no clear relationship between MRS-assessed GABA levels and TMS-assessed synaptic GABA(A) activity (2.5 ms inter-stimulus interval (ISI) short-interval intracortical inhibition (SICI); Experiment 1: r = 0.33, P = 0.31; Experiment 2: r = -0.23, P = 0.46) or GABA(B) activity (long-interval intracortical inhibition (LICI); Experiment 1: r = -0.47, P = 0.51; Experiment 2: r = 0.23, P = 0.47). We demonstrated a significant correlation between MRS-assessed GABA levels and an inhibitory TMS protocol (1 ms ISI SICI) with distinct physiological underpinnings from the 2.5 ms ISI SICI (r = -0.79, P = 0.018). Interpretation of this finding is challenging as the mechanisms of 1 ms ISI SICI are not well understood, but we speculate that our results support the possibility that 1 ms ISI SICI reflects a distinct GABAergic inhibitory process, possibly that of extrasynaptic GABA tone.
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Affiliation(s)
- C J Stagg
- Oxford Centre for Functional MRI of the Brain (FMRIB), Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK.
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615
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Dockery CA, Liebetanz D, Birbaumer N, Malinowska M, Wesierska MJ. Cumulative benefits of frontal transcranial direct current stimulation on visuospatial working memory training and skill learning in rats. Neurobiol Learn Mem 2011; 96:452-60. [DOI: 10.1016/j.nlm.2011.06.018] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2011] [Revised: 06/03/2011] [Accepted: 06/30/2011] [Indexed: 12/30/2022]
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616
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Polanía R, Paulus W, Nitsche MA. Modulating cortico-striatal and thalamo-cortical functional connectivity with transcranial direct current stimulation. Hum Brain Mapp 2011; 33:2499-508. [PMID: 21922602 DOI: 10.1002/hbm.21380] [Citation(s) in RCA: 287] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2011] [Revised: 04/19/2011] [Accepted: 05/18/2011] [Indexed: 11/08/2022] Open
Abstract
Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that has been shown to alter cortical excitability and activity via application of weak direct currents. Beyond intracortical effects, functional imaging as well as behavioral studies are suggesting additional tDCS-driven alterations of subcortical areas, however, direct evidence for such effects is scarce. We aimed to investigate the impact of tDCS on cortico-subcortical functional networks by seed functional connectivity analysis of different striatal and thalamic regions to prove tDCS-induced alterations of the cortico-striato-thalamic circuit. fMRI resting state data sets were acquired immediately before and after 10 min of bipolar tDCS during rest, with the anode/cathode placed over the left primary motor cortex (M1) and the cathode/anode over the contralateral frontopolar cortex. To control for possible placebo effects, an additional sham stimulation session was carried out. Functional coupling between the left thalamus and the ipsilateral primary motor cortex (M1) significantly increased following anodal stimulation over M1. Additionally, functional connectivity between the left caudate nucleus and parietal association cortices was significantly strengthened. In contrast, cathodal tDCS over M1 decreased functional coupling between left M1 and contralateral putamen. In summary, in this study, we show for the first time that tDCS modulates functional connectivity of cortico-striatal and thalamo-cortical circuits. Here we highlight that anodal tDCS over M1 is capable of modulating elements of the cortico-striato-thalamo-cortical functional motor circuit.
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Affiliation(s)
- Rafael Polanía
- Department of Clinical Neurophysiology, Georg-August University of Göttingen, 37075 Göttingen, Germany.
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617
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Fridriksson J. Measuring and inducing brain plasticity in chronic aphasia. JOURNAL OF COMMUNICATION DISORDERS 2011; 44:557-563. [PMID: 21620414 PMCID: PMC3162133 DOI: 10.1016/j.jcomdis.2011.04.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
UNLABELLED Brain plasticity associated with anomia recovery in aphasia is poorly understood. Here, I review four recent studies from my lab that focused on brain modulation associated with long-term anomia outcome, its behavioral treatment, and the use of transcranial brain stimulation to enhance anomia treatment success in individuals with chronic aphasia caused by left hemisphere stroke. In a study that included 15 participants with aphasia who were compared to a group of 10 normal control subjects, we found that improved naming ability was associated with increased left hemisphere activity. A separate study (N = 26) revealed similar results in that improved anomia treatment outcome was associated with increased left hemisphere recruitment. Taken together, these two studies suggest that improved naming in chronic aphasia relies on the damaged left hemisphere. Based on these findings, we conducted two studies to appreciate the effect of using low current transcranial electrical stimulation as an adjuvant to behavioral anomia treatment. Both studies yielded positive findings in that anomia treatment outcome was improved when it was coupled with real brain stimulation as compared with a placebo (sham) condition. Overall, these four studies support the notion that the intact cortex in the lesioned left hemisphere supports anomia recovery in aphasia. LEARNING OUTCOMES Readers will (a) be able to appreciate the possible influence of animal research upon the understanding of brain plasticity induced by aphasia treatment, (b) understand where functional changes associated with anomia treatment occur in the brain, (c) understand the basic principles of transcranial direct current stimulation, and (d) understand how brain stimulation coupled with aphasia treatment may potentially improve treatment outcome.
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Affiliation(s)
- Julius Fridriksson
- Department of Communication Sciences & Disorders, University of South Carolina, Columbia, SC 29208, USA.
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618
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Stagg CJ, Bachtiar V, Johansen-Berg H. What are we measuring with GABA magnetic resonance spectroscopy? Commun Integr Biol 2011; 4:573-5. [PMID: 22046466 DOI: 10.4161/cib.4.5.16213] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2011] [Accepted: 04/28/2011] [Indexed: 11/19/2022] Open
Abstract
A number of recent papers1-3 have demonstrated a relationship between in vivo concentration of GABA, as assessed using Magnetic Resonance Spectroscopy (MRS), and an individual's task performance, giving a unique insight into the relationship between physiology and behavior. However, interpretation of the functional significance of the MRS GABA measure is not straightforward. Here we discuss some of the outstanding questions as to how total concentration of GABA within a cortical region relates to phasic and tonic GABA activity within the cortical volume studied.
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Affiliation(s)
- Charlotte J Stagg
- Oxford Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB); Nuffield Department of Clinical Neurosciences; University of Oxford; Oxford, UK
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619
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Venkatakrishnan A, Sandrini M. Combining transcranial direct current stimulation and neuroimaging: novel insights in understanding neuroplasticity. J Neurophysiol 2011; 107:1-4. [PMID: 21832036 DOI: 10.1152/jn.00557.2011] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In recent years, noninvasive brain stimulation techniques like transcranial direct current stimulation (tDCS) have gained immense popularity owing to their effects on modulating cortical activity and consequently motor and cognitive performance. However, the neurophysiology underlying such neuroplastic changes is less understood. This article critically evaluates the contemporary approach of combined tDCS and neuroimaging as a means to provide novel insights in understanding the neurophysiological and neuroplastic processes modulated by this brain stimulation technique. We end by briefly suggesting further lines of inquiry.
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Affiliation(s)
- Anusha Venkatakrishnan
- Human Cortical Physiology and Stroke Neurorehabilitation Section, National Institute of Neurological Disorders and Stroke, NIH Bldg. 10, Rm. 7D52, Bethesda, MD 20892, USA.
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620
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Abstract
It has been hypothesized that the generalization patterns that accompany learning carry the signatures of the neural systems that are engaged in that learning. Reach adaptation in force fields has generalization patterns that suggest primary engagement of a neural system that encodes movements in the intrinsic coordinates of joints and muscles, and lesser engagement of a neural system that encodes movements in the extrinsic coordinates of the task. Among the cortical motor areas, the intrinsic coordinate system is most prominently represented in the primary sensorimotor cortices. Here, we used transcranial direct current stimulation (tDCS) to alter mechanisms of synaptic plasticity and found that when it was applied to the motor cortex, it increased generalization in intrinsic coordinates but not extrinsic coordinates. However, when tDCS was applied to the posterior parietal cortex, it had no effects on learning or generalization in the force field task. The results suggest that during force field adaptation, the component of learning that produces generalization in intrinsic coordinates depends on the plasticity in the sensorimotor cortex.
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621
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Bullard LM, Browning ES, Clark VP, Coffman BA, Garcia CM, Jung RE, van der Merwe AJ, Paulson KM, Vakhtin AA, Wootton CL, Weisend MP. Transcranial direct current stimulation’s effect on novice versus experienced learning. Exp Brain Res 2011; 213:9-14. [DOI: 10.1007/s00221-011-2764-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2010] [Accepted: 06/06/2011] [Indexed: 10/18/2022]
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622
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Zheng X, Alsop DC, Schlaug G. Effects of transcranial direct current stimulation (tDCS) on human regional cerebral blood flow. Neuroimage 2011; 58:26-33. [PMID: 21703350 DOI: 10.1016/j.neuroimage.2011.06.018] [Citation(s) in RCA: 248] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2011] [Revised: 05/21/2011] [Accepted: 06/08/2011] [Indexed: 12/21/2022] Open
Abstract
Transcranial direct current stimulation (tDCS) can up- and down-regulate cortical excitability depending on current direction, however our abilities to measure brain-tissue effects of the stimulation and its after-effects have been limited so far. We used regional cerebral blood flow (rCBF), a surrogate measure of brain activity, to examine regional brain-tissue and brain-network effects during and after tDCS. We varied the polarity (anodal and cathodal) as well as the current strength (0.8 to 2.0mA) of the stimulation. Fourteen healthy subjects were randomized into receiving either anodal or cathodal stimulation (two subjects received both, one week apart) while undergoing Arterial Spin Labeling (ASL) in the MRI scanner with an alternating off-on sampling paradigm. The stimulating, MRI-compatible electrode was placed over the right motor region and the reference electrode over the contralateral supra-orbital region. SPM5 was used to process and extract the rCBF data using a 10mm spherical volume of interest (VOI) placed in the motor cortex directly underneath the stimulating scalp electrode. Anodal stimulation induced a large increase (17.1%) in rCBF during stimulation, which returned to baseline after the current was turned off, but exhibited an increase in rCBF again in the post-stimulation period. Cathodal stimulation induced a smaller increase (5.6%) during stimulation, a significant decrease compared to baseline (-6.5%) after cessation, and a continued decrease in the post-stimulation period. These changes in rCBF were all significant when compared to the pre-stimulation baseline or to a control region. Furthermore, for anodal stimulation, there was a significant correlation between current strength and the increase in rCBF in the on-period relative to the pre-stimulation baseline. The differential rCBF after-effects of anodal (increase in resting state rCBF) and cathodal (decrease in resting state rCBF) tDCS support findings of behavioral and cognitive after-effects after cathodal and anodal tDCS. We also show that tDCS not only modulates activity in the brain region directly underlying the stimulating electrode but also in a network of brain regions that are functionally related to the stimulated area. Our results indicate that ASL may be an excellent tool to investigate the effects of tDCS and its stimulation parameters on brain activity.
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Affiliation(s)
- Xin Zheng
- Dept. of Neurology, Harvard Medical School, Boston, MA, USA
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623
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Stagg CJ, Nitsche MA. Physiological basis of transcranial direct current stimulation. Neuroscientist 2011; 17:37-53. [PMID: 21343407 DOI: 10.1177/1073858410386614] [Citation(s) in RCA: 1105] [Impact Index Per Article: 85.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Since the rediscovery of transcranial direct current stimulation (tDCS) about 10 years ago, interest in tDCS has grown exponentially. A noninvasive stimulation technique that induces robust excitability changes within the stimulated cortex, tDCS is increasingly being used in proof-of-principle and stage IIa clinical trials in a wide range of neurological and psychiatric disorders. Alongside these clinical studies, detailed work has been performed to elucidate the mechanisms underlying the observed effects. In this review, the authors bring together the results from these pharmacological, neurophysiological, and imaging studies to describe their current knowledge of the physiological effects of tDCS. In addition, the theoretical framework for how tDCS affects motor learning is proposed.
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Affiliation(s)
- Charlotte J Stagg
- Centre for Functional Magnetic Resonance Imaging of the Brain, University of Oxford, John Radcliffe Hospital, Oxford, UK.
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624
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Munneke MA, Stegeman DF, Hengeveld YA, Rongen JJ, Schelhaas HJ, Zwarts MJ. Transcranial direct current stimulation does not modulate motor cortex excitability in patients with amyotrophic lateral sclerosis. Muscle Nerve 2011; 44:109-14. [DOI: 10.1002/mus.22012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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625
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Clark VP, Coffman BA, Trumbo MC, Gasparovic C. Transcranial direct current stimulation (tDCS) produces localized and specific alterations in neurochemistry: a ¹H magnetic resonance spectroscopy study. Neurosci Lett 2011; 500:67-71. [PMID: 21683766 DOI: 10.1016/j.neulet.2011.05.244] [Citation(s) in RCA: 157] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2011] [Revised: 05/05/2011] [Accepted: 05/29/2011] [Indexed: 01/12/2023]
Abstract
Transcranial direct current stimulation (tDCS) has been found to produce significant changes in behavior, including a large increase of learning and performance for a difficult visual perceptual task (Clark et al., NeuroImage 2010). The mechanisms by which tDCS produces these behavioral effects are currently uncertain. One hypothesis is that anodal tDCS leads to increased metabolic activity in the brain, which enhances cognitive and memory processes. Here we examined the neuronal mechanisms by which tDCS influences learning by measuring changes in brain metabolite concentrations using proton magnetic resonance spectroscopy (¹H MRS). As perception and learning can also influence neurochemistry, here we applied tDCS during rest. MRS data was obtained before and after 2.0 mA of anodal tDCS was applied for 30 min over electrode site P4, with the cathode placed on the contralateral arm. MRS data were acquired from the right parietal lobe beneath the anodal tDCS electrode, and from the homologous regions of the left hemisphere once before and once after tDCS. Significantly higher combined glutamate and glutamine levels were found in right parietal cortex, beneath the stimulating electrode, with non-significant increases in homologous regions of the opposite hemisphere. In addition, a significant interaction between hemispheres was found for tDCS effects on tNAA. These results suggest that changes in glutamatergic activity and tNAA may be related to the mechanisms by which tDCS influences learning and behavior.
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Affiliation(s)
- Vincent P Clark
- Department of Psychology, University of New Mexico, Albuquerque, NM 87131, USA.
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626
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Stagg CJ, Bachtiar V, Johansen-Berg H. The role of GABA in human motor learning. Curr Biol 2011; 21:480-4. [PMID: 21376596 PMCID: PMC3063350 DOI: 10.1016/j.cub.2011.01.069] [Citation(s) in RCA: 418] [Impact Index Per Article: 32.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2010] [Revised: 12/08/2010] [Accepted: 01/28/2011] [Indexed: 11/29/2022]
Abstract
GABA modification plays an important role in motor cortical plasticity [1–4]. We therefore hypothesized that interindividual variation in the responsiveness of the GABA system to modification influences learning capacity in healthy adults. We assessed GABA responsiveness by transcranial direct current stimulation (tDCS), an intervention known to decrease GABA [5, 6]. The magnitude of M1 GABA decrease induced by anodal tDCS correlated positively with both the degree of motor learning and the degree of fMRI signal change within the left M1 during learning. This study therefore suggests that the responsiveness of the GABAergic system to modification may be relevant to short-term motor learning behavior and learning-related brain activity.
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Affiliation(s)
- Charlotte J Stagg
- Oxford Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB), Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DU, UK.
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627
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628
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Prefrontal direct current stimulation modulates resting EEG and event-related potentials in healthy subjects: A standardized low resolution tomography (sLORETA) study. Neuroimage 2011; 55:644-57. [DOI: 10.1016/j.neuroimage.2010.12.004] [Citation(s) in RCA: 212] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2010] [Revised: 11/03/2010] [Accepted: 12/02/2010] [Indexed: 11/17/2022] Open
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629
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Stagg CJ, Jayaram G, Pastor D, Kincses ZT, Matthews PM, Johansen-Berg H. Polarity and timing-dependent effects of transcranial direct current stimulation in explicit motor learning. Neuropsychologia 2011; 49:800-804. [PMID: 21335013 PMCID: PMC3083512 DOI: 10.1016/j.neuropsychologia.2011.02.009] [Citation(s) in RCA: 323] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2010] [Revised: 10/28/2010] [Accepted: 02/07/2011] [Indexed: 11/21/2022]
Abstract
Transcranial direct current stimulation (tDCS) is attracting increasing interest as a therapeutic tool for neurorehabilitation, particularly after stroke, because of its potential to modulate local excitability and therefore promote functional plasticity. Previous studies suggest that timing is important in determining the behavioural effects of brain stimulation. Regulatory metaplastic mechanisms exist to modulate the effects of a stimulation intervention in a manner dependent on prior cortical excitability, thereby preventing destabilization of existing cortical networks. The importance of such timing dependence has not yet been fully explored for tDCS. Here, we describe the results of a series of behavioural experiments in healthy controls to determine the importance of the relative timing of tDCS for motor performance. Application of tDCS during an explicit sequence-learning task led to modulation of behaviour in a polarity specific manner: relative to sham stimulation, anodal tDCS was associated with faster learning and cathodal tDCS with slower learning. Application of tDCS prior to performance of the sequence-learning task led to slower learning after both anodal and cathodal tDCS. By contrast, regardless of the polarity of stimulation, tDCS had no significant effect on performance of a simple reaction time task. These results are consistent with the idea that anodal tDCS interacts with subsequent motor learning in a metaplastic manner and suggest that anodal stimulation modulates cortical excitability in a manner similar to motor learning.
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Affiliation(s)
- C J Stagg
- Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB), Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK.
| | - G Jayaram
- Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB), Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK; Department of Biomedical Engineering, Johns Hopkins University School of Medicine, 720 Rutland Avenue, Baltimore, MD 21205, USA
| | - D Pastor
- Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB), Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK; INSERM, U864, Espace et Action, 16 avenue Lépine, Bron F-69676, France
| | - Z T Kincses
- Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB), Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - P M Matthews
- Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB), Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK; Department of Clinical Neurosciences, Imperial College London, and GSK Clinical Imaging Centre, Hammersmith Hospital, London, UK
| | - H Johansen-Berg
- Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB), Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
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630
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Ziemann U. Transcranial magnetic stimulation at the interface with other techniques: a powerful tool for studying the human cortex. Neuroscientist 2011; 17:368-81. [PMID: 21311054 DOI: 10.1177/1073858410390225] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Transcranial magnetic stimulation (TMS) has developed into a very powerful tool in the hands of basic and clinical neuroscientists alike to study function and dysfunction of the human brain noninvasively and painlessly. However, as a stand-alone technique, the potential of TMS to gain knowledge is relatively limited. This potential can be strongly enhanced by combining TMS with simultaneous measurements in other electrophysiological (EEG) or imaging modalities (PET, fMRI, NIRS, MRS) or by combining TMS with exposure to neuroactive drugs (pharmaco-TMS). This review provides an up-to-date synopsis of these combined approaches and highlights important examples that have advanced our understanding of how TMS interacts with neuronal networks in the human brain.
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Affiliation(s)
- Ulf Ziemann
- Department of Neurology, Goethe University Frankfurt, Frankfurt am Main, Germany.
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631
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Cogiamanian F, Vergari M, Schiaffi E, Marceglia S, Ardolino G, Barbieri S, Priori A. Transcutaneous spinal cord direct current stimulation inhibits the lower limb nociceptive flexion reflex in human beings. Pain 2011; 152:370-375. [DOI: 10.1016/j.pain.2010.10.041] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2010] [Revised: 09/27/2010] [Accepted: 10/28/2010] [Indexed: 10/18/2022]
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632
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Abstract
A new study using transcranial direct current stimulation shows that modulating parietal cortex activity during the learning of abstract numerical material can enhance numerical competency for up to six months.
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Affiliation(s)
- Jean-François Lepage
- Département de psychologie and Centre Hospitalier Universitaire Sainte-Justine, CP 6128, Succ. Centre-Ville, Montréal, QC, H3C3J7, Canada
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633
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Cohen Kadosh R, Soskic S, Iuculano T, Kanai R, Walsh V. Modulating neuronal activity produces specific and long-lasting changes in numerical competence. Curr Biol 2010; 20:2016-20. [PMID: 21055945 PMCID: PMC2990865 DOI: 10.1016/j.cub.2010.10.007] [Citation(s) in RCA: 217] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2010] [Revised: 09/20/2010] [Accepted: 10/04/2010] [Indexed: 01/29/2023]
Abstract
Around 20% of the population exhibits moderate to severe numerical disabilities [1-3], and a further percentage loses its numerical competence during the lifespan as a result of stroke or degenerative diseases [4]. In this work, we investigated the feasibility of using noninvasive stimulation to the parietal lobe during numerical learning to selectively improve numerical abilities. We used transcranial direct current stimulation (TDCS), a method that can selectively inhibit or excitate neuronal populations by modulating GABAergic (anodal stimulation) and glutamatergic (cathodal stimulation) activity [5, 6]. We trained subjects for 6 days with artificial numerical symbols, during which we applied concurrent TDCS to the parietal lobes. The polarity of the brain stimulation specifically enhanced or impaired the acquisition of automatic number processing and the mapping of number into space, both important indices of numerical proficiency [7-9]. The improvement was still present 6 months after the training. Control tasks revealed that the effect of brain stimulation was specific to the representation of artificial numerical symbols. The specificity and longevity of TDCS on numerical abilities establishes TDCS as a realistic tool for intervention in cases of atypical numerical development or loss of numerical abilities because of stroke or degenerative illnesses.
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Affiliation(s)
- Roi Cohen Kadosh
- Department of Experimental Psychology and Oxford Centre for Functional MRI of the Brain, University of Oxford, Oxford OX1 3UD, UK.
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634
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Brunoni AR, Valiengo L, Baccaro A, Zanao TA, de Oliveira JF, Vieira GP, Bueno VF, Goulart AC, Boggio PS, Lotufo PA, Bensenor IM, Fregni F. Sertraline vs. ELectrical Current Therapy for Treating Depression Clinical Trial--SELECT TDCS: design, rationale and objectives. Contemp Clin Trials 2010; 32:90-8. [PMID: 20854930 DOI: 10.1016/j.cct.2010.09.007] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2010] [Revised: 09/12/2010] [Accepted: 09/14/2010] [Indexed: 10/19/2022]
Abstract
BACKGROUND Despite significant advancements in psychopharmacology, treating major depressive disorder (MDD) is still a challenge considering the efficacy, tolerability, safety, and economical costs of most antidepressant drugs. One approach that has been increasingly investigated is modulation of cortical activity with tools of non-invasive brain stimulation - such as transcranial magnetic stimulation and transcranial direct current stimulation (tDCS). Due to its profile, tDCS seems to be a safe and affordable approach. METHODS AND DESIGN The SELECT TDCS trial aims to compare sertraline vs. tDCS in a double-blinded, randomized, factorial trial enrolling 120 participants to be allocated to four groups to receive sertraline+tDCS, sertraline, tDCS or placebo. Eligibility criteria are moderate-to-severe unipolar depression (Hamilton Depression Rating Scale >17) not currently on sertraline treatment. Treatment will last 6weeks and the primary outcome is depression change in the Montgomery-Asberg Depression Rating Score (MADRS). Potential biological markers that mediate response, such as BDNF serum levels, Val66Met BDNF polymorphism, and heart rate variability will also be examined. A neuropsychological battery with a focus on executive functioning will be administered. DISCUSSION With this design we will be able to investigate whether tDCS is more effective than placebo in a sample of patients free of antidepressants and in addition, we will be able to secondarily compare the effect sizes of sertraline vs. tDCS and also the comparison between tDCS and combination of tDCS and sertraline.
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635
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Fritsch B, Reis J, Martinowich K, Schambra HM, Ji Y, Cohen LG, Lu B. Direct current stimulation promotes BDNF-dependent synaptic plasticity: potential implications for motor learning. Neuron 2010; 66:198-204. [PMID: 20434997 DOI: 10.1016/j.neuron.2010.03.035] [Citation(s) in RCA: 973] [Impact Index Per Article: 69.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/11/2010] [Indexed: 12/13/2022]
Abstract
Despite its increasing use in experimental and clinical settings, the cellular and molecular mechanisms underlying transcranial direct current stimulation (tDCS) remain unknown. Anodal tDCS applied to the human motor cortex (M1) improves motor skill learning. Here, we demonstrate in mouse M1 slices that DCS induces a long-lasting synaptic potentiation (DCS-LTP), which is polarity specific, NMDA receptor dependent, and requires coupling of DCS with repetitive low-frequency synaptic activation (LFS). Combined DCS and LFS enhance BDNF-secretion and TrkB activation, and DCS-LTP is absent in BDNF and TrkB mutant mice, suggesting that BDNF is a key mediator of this phenomenon. Moreover, the BDNF val66met polymorphism known to partially affect activity-dependent BDNF secretion impairs motor skill acquisition in humans and mice. Motor learning is enhanced by anodal tDCS, as long as activity-dependent BDNF secretion is in place. We propose that tDCS may improve motor skill learning through augmentation of synaptic plasticity that requires BDNF secretion and TrkB activation within M1.
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Affiliation(s)
- Brita Fritsch
- Epilepsy Research Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
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636
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Weiss SA, Faber DS. Field effects in the CNS play functional roles. Front Neural Circuits 2010; 4:15. [PMID: 20508749 PMCID: PMC2876880 DOI: 10.3389/fncir.2010.00015] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2010] [Accepted: 04/23/2010] [Indexed: 11/22/2022] Open
Abstract
An endogenous electrical field effect, i.e., ephaptic transmission, occurs when an electric field associated with activity occurring in one neuron polarizes the membrane of another neuron. It is well established that field effects occur during pathological conditions, such as epilepsy, but less clear if they play a functional role in the healthy brain. Here, we describe the principles of field effect interactions, discuss identified field effects in diverse brain structures from the teleost Mauthner cell to the mammalian cortex, and speculate on the function of these interactions. Recent evidence supports that relatively weak endogenous and exogenous field effects in laminar structures reach significance because they are amplified by network interactions. Such interactions may be important in rhythmogenesis for the cortical slow wave and hippocampal sharp wave-ripple, and also during transcranial stimulation.
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Affiliation(s)
- Shennan A. Weiss
- Department of Neuroscience, Albert Einstein College of MedicineBronx, NY, USA
| | - Donald S. Faber
- Department of Neuroscience, Albert Einstein College of MedicineBronx, NY, USA
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637
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Transcranial direct current stimulation facilitates decision making in a probabilistic guessing task. J Neurosci 2010; 30:4241-5. [PMID: 20335459 DOI: 10.1523/jneurosci.2924-09.2010] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In a random sequence of binary events where one alternative occurs more often than the other, humans tend to guess which of the two alternatives will occur next by trying to match the frequencies of previous occurrences. Based on split-brain and unilaterally damaged patients' performances, it has been proposed that the left hemisphere (LH) tends to match the frequencies, while the right hemisphere (RH) tends toward maximizing and always choosing the most frequent alternative. The current study used transcranial direct current stimulation (tDCS) to test this hemispheric asymmetry hypothesis by stimulating the dorsolateral prefrontal cortex of each hemisphere and simultaneously inhibiting the corresponding region in the homotopic hemisphere, while participants were engaged in a probabilistic guessing task. Results showed no difference in strategy between the three groups (RH anodal/LH cathodal, LH anodal/RH cathodal, no stimulation) as participants predominantly matched the frequencies of the two alternatives. However, when anodal tDCS was applied to the LH and cathodal tDCS applied to the RH, participants became quicker to select the most frequent alternative. This finding is in line with previous evidence on the involvement of the LH in probabilistic learning and reasoning and adds to a number of demonstrations of anodal tDCS leading to some behavioral enhancement or change in bias.
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638
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Cheeran B, Koch G, Stagg C, Baig F, Teo J. Transcranial Magnetic Stimulation: From Neurophysiology to Pharmacology, Molecular Biology and Genomics. Neuroscientist 2010; 16:210-21. [DOI: 10.1177/1073858409349901] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Noninvasive plasticity paradigms, both physiologically induced and artificially induced, have come into their own in the study of the effects of genetic variation on human cortical plasticity. These techniques have the singular advantage that they enable one to study the effects of genetic variation in its natural and most relevant context, that of the awake intact human cortex, in both health and disease. This review aims to introduce the currently available artificially induced plasticity paradigms, their putative mechanisms—both in the traditional language of the systems neurophysiologist and in the evolving (and perhaps more relevant for the purposes of stimulation genomics) reinterpretation in terms of molecular neurochemistry, and highlights recent studies employing these techniques by way of examples of applications.
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Affiliation(s)
- B. Cheeran
- Department of Neurology, John Radcliffe Hospital, Headington, Oxford, UK, , Sobell Dept, Institute of Neurology, Queen Square, London, UK
| | - G. Koch
- Laboratorio di Neurologia Clinica e Comportamentale, Fondazione Santa Lucia IRCCS, and Dipartimento di Neuroscienze, Università di Roma Tor Vergata, Rome, Italy
| | - C.J. Stagg
- FMRIB Centre, University of Oxford, Department of Clinical Neurology, John Radcliffe Hospital, Headington, Oxford, UK
| | - F. Baig
- Department of Neurology, John Radcliffe Hospital, Headington, Oxford, UK
| | - J. Teo
- Sobell Dept, Institute of Neurology, Queen Square, London, UK
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639
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Hecht D. Transcranial direct current stimulation in the treatment of anorexia. Med Hypotheses 2010; 74:1044-7. [PMID: 20096507 DOI: 10.1016/j.mehy.2009.12.032] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2009] [Accepted: 12/27/2009] [Indexed: 11/29/2022]
Abstract
Transcranial direct current stimulation (tDCS) is a non-invasive technique for brain stimulation and it increasingly being used in the treatments of some neurological/psychiatric conditions (e.g. chronic pain, epilepsy, depression, motor rehabilitation after stroke and Parkinson's disease). With tDCS, cortical neurons excitability increases in the vicinity of the anodal electrode and suppressed near the cathodal electrode. There is evidence that anorexia is associated with hyperactivity in right-hemisphere frontal regions. tDCS, therefore has a promising potential in facilitating inter-hemispheric balance. A tDCS protocol is proposed: the anode electrode placed over the left prefrontal cortex and the cathode electrode located, either on the right homotopic region for non-SSRI-medicated anorexics, or on a non-cephalic site for SSRI-medicated anorexics. Together with nutritional supplements, psychotherapy and other treatments, tDCS have a good potential, as a complementary tool, in the treatment of anorexia.
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Affiliation(s)
- David Hecht
- Institute of Cognitive Neuroscience, University College London, London WC1N 3AR, UK.
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640
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Jefferson S, Mistry S, Singh S, Rothwell J, Hamdy S. Characterizing the application of transcranial direct current stimulation in human pharyngeal motor cortex. Am J Physiol Gastrointest Liver Physiol 2009; 297:G1035-40. [PMID: 19815630 PMCID: PMC2850087 DOI: 10.1152/ajpgi.00294.2009] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Transcranial direct current stimulation (tDCS) is a novel intervention that can modulate brain excitability in health and disease; however, little is known about its effects on bilaterally innervated systems such as pharyngeal motor cortex. Here, we assess the effects of differing doses of tDCS on the physiology of healthy human pharyngeal motor cortex as a prelude to designing a therapeutic intervention in dysphagic patients. Healthy subjects (n = 17) underwent seven regimens of tDCS (anodal 10 min 1 mA, cathodal 10 min 1 mA, anodal 10 min 1.5 mA, cathodal 10 min 1.5 mA, anodal 20 min 1 mA, cathodal 20 min 1 mA, Sham) on separate days, in a double blind randomized order. Bihemispheric motor evoked potential (MEP) responses to single-pulse transcranial magnetic stimulation (TMS) as well as intracortical facilitation (ICF) and inhibition (ICI) were recorded using a swallowed pharyngeal catheter before and up to 60 min following the tDCS. Compared with sham, both 10 min 1.5 mA and 20 min 1 mA anodal stimulation induced increases in cortical excitability in the stimulated hemisphere (+44 +/- 17% and +59 +/- 16%, respectively; P < 0.005) whereas only 10 min 1.5 mA cathodal stimulation induced inhibition (-26 +/- 4%, P = 0.02). There were neither contralateral hemisphere changes nor any evidence for ICI or ICF in driving the ipsilateral effects. In conclusion, anodal tDCS can alter pharyngeal motor cortex excitability in an intensity-dependent manner, with little evidence for transcallosal spread. Anodal stimulation may therefore provide a useful means of stimulating pharyngeal cortex and promoting recovery in dysphagic patients.
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Affiliation(s)
- Samantha Jefferson
- 1Department of Gastrointestinal Sciences, Salford Royal Foundation Trust, University of Manchester, Manchester; and
| | - Satish Mistry
- 1Department of Gastrointestinal Sciences, Salford Royal Foundation Trust, University of Manchester, Manchester; and
| | - Salil Singh
- 1Department of Gastrointestinal Sciences, Salford Royal Foundation Trust, University of Manchester, Manchester; and
| | - John Rothwell
- 2Sobell Department of Neurophysiology, Institute of Neurology, University College London, London, United Kingdom
| | - Shaheen Hamdy
- 1Department of Gastrointestinal Sciences, Salford Royal Foundation Trust, University of Manchester, Manchester; and
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641
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Stagg CJ, O'Shea J, Kincses ZT, Woolrich M, Matthews PM, Johansen-Berg H. Modulation of movement-associated cortical activation by transcranial direct current stimulation. Eur J Neurosci 2009; 30:1412-23. [PMID: 19788568 DOI: 10.1111/j.1460-9568.2009.06937.x] [Citation(s) in RCA: 132] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Transcranial direct current stimulation (tDCS) is currently attracting increasing interest as a tool for neurorehabilitation. However, local and distant effects of tDCS on motor-related cortical activation patterns remain poorly defined, limiting the rationale for its use. Here we describe the results of a functional magnetic resonance imaging (MRI) experiment designed to characterize local and distant effects on cortical motor activity following excitatory anodal stimulation and inhibitory cathodal stimulation. Fifteen right-handed subjects performed a visually cued serial reaction time task with their right hand in a 3-T MRI scanner both before and after 10 min of 1-mA tDCS applied to the left primary motor cortex (M1). Relative to sham stimulation, anodal tDCS led to short-lived activation increases in the M1 and the supplementary motor area (SMA) within the stimulated hemisphere. The increase in activation in the SMA with anodal stimulation was found also when directly comparing anodal with cathodal stimulation. Relative to sham stimulation, cathodal tDCS led to an increase in activation in the contralateral M1 and dorsal premotor cortex (PMd), as well as an increase in functional connectivity between these areas and the stimulated left M1. These increases were also found when directly comparing cathodal with anodal stimulation. Significant within-session linear decreases in activation occurred in all scan sessions. The after-effects of anodal tDCS arose primarily from a change in the slope of these decreases. In addition, following sham stimulation compared with baseline, a between-session decrease in task-related activity was found. The effects of cathodal tDCS arose primarily from a reduction of this normal decrease.
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Affiliation(s)
- C J Stagg
- Centre for Functional MRI of the Brain, Department of Clinical Neurology, University of Oxford, John Radcliffe Hospital, Oxford UK.
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642
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Stagg CJ, Wylezinska M, Matthews PM, Johansen-Berg H, Jezzard P, Rothwell JC, Bestmann S. Neurochemical effects of theta burst stimulation as assessed by magnetic resonance spectroscopy. J Neurophysiol 2009; 101:2872-7. [PMID: 19339458 PMCID: PMC2694115 DOI: 10.1152/jn.91060.2008] [Citation(s) in RCA: 203] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2008] [Accepted: 03/24/2009] [Indexed: 11/22/2022] Open
Abstract
Continuous theta burst stimulation (cTBS) is a novel transcranial stimulation technique that causes significant inhibition of synaptic transmission for
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Affiliation(s)
- C J Stagg
- Centre for Functional Resonance Imaging of the Brain, University of Oxford, Oxford, United Kingdom.
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