The Experts below are selected from a list of 39939 Experts worldwide ranked by ideXlab platform
Marom Bikson - One of the best experts on this subject based on the ideXlab platform.
-
Methodology for tDCS integration with fMRI.
Human Brain Mapping, 2019Co-Authors: Zeinab Esmaeilpour, Marom Bikson, Abhishek Datta, Adam J Woods, A. Duke Shereen, Peyman Ghobadi‐azbari, Maria Ironside, Jacinta O'shea, Ulrich Kirk, Hamed EkhtiariAbstract:Understanding and reducing variability of response to transcranial direct current stimulation (tDCS) requires measuring what factors predetermine sensitivity to tDCS and tracking individual response to tDCS. Human trials, animal models, and computational models suggest structural traits and functional states of neural systems are the major sources of this variance. There are 118 published tDCS studies (up to October 1, 2018) that used fMRI as a proxy measure of neural activation to answer mechanistic, predictive, and localization questions about how brain activity is modulated by tDCS. FMRI can potentially contribute as: a measure of cognitive state-level variance in baseline brain activation before tDCS; inform the design of stimulation montages that aim to target functional networks during specific tasks; and act as an outcome measure of functional response to tDCS. In this systematic review, we explore methodological parameter space of tDCS integration with fMRI spanning: (a) fMRI timing relative to tDCS (pre, post, concurrent); (b) study design (parallel, crossover); (c) control condition (sham, active control); (d) number of tDCS sessions; (e) number of follow up scans; (f) stimulation dose and combination with task; (g) functional imaging sequence (BOLD, ASL, resting); and (h) additional behavioral (cognitive, clinical) or quantitative (neurophysiological, biomarker) measurements. Existing tDCS-fMRI literature shows little replication across these permutations; few studies used comparable study designs. Here, we use a representative sample study with both task and resting state fMRI before and after tDCS in a crossover design to discuss methodological confounds. We further outline how computational models of current flow should be combined with imaging data to understand sources of variability. Through the representative sample study, we demonstrate how modeling and imaging methodology can be integrated for individualized analysis. Finally, we discuss the importance of conducting tDCS-fMRI with stimulation equipment certified as safe to use inside the MR scanner, and of correcting for image artifacts caused by tDCS. tDCS-fMRI can address important questions on the functional mechanisms of tDCS action (e.g., target engagement) and has the potential to support enhancement of behavioral interventions, provided studies are designed rationally.
-
Beyond the target area: an integrative view of tDCS-induced motor cortex modulation in patients and athletes
Journal of NeuroEngineering and Rehabilitation, 2019Co-Authors: Edgard Morya, Zeinab Esmaeilpour, Claudinei Eduardo Biazoli, Raaj Chatterjee, Katia Monte-silva, André Fonseca, Faranak Farzan, Tommaso Bocci, Marom Bikson, Jeffrey M HausdorffAbstract:Transcranial Direct Current Stimulation (tDCS) is a non-invasive technique used to modulate neural tissue. Neuromodulation apparently improves cognitive functions in several neurologic diseases treatment and sports performance. In this study, we present a comprehensive, integrative review of tDCS for motor rehabilitation and motor learning in healthy individuals, athletes and multiple neurologic and neuropsychiatric conditions. We also report on neuromodulation mechanisms, main applications, current knowledge including areas such as language, embodied cognition, functional and social aspects, and future directions. We present the use and perspectives of new developments in tDCS technology, namely high-definition tDCS (HD-tDCS) which promises to overcome one of the main tDCS limitation (i.e., low focality) and its application for neurological disease, pain relief, and motor learning/rehabilitation. Finally, we provided information regarding the Transcutaneous Spinal Direct Current Stimulation (tsDCS) in clinical applications, Cerebellar tDCS (ctDCS) and its influence on motor learning, and TMS combined with electroencephalography (EEG) as a tool to evaluate tDCS effects on brain function.
-
Methodology for tDCS integration with fMRI
2019Co-Authors: Zeinab Esmaeilpour, Marom Bikson, Abhishek Datta, Adam J Woods, A. Duke Shereen, Peyman Ghobadi‐azbari, Maria Ironside, Jacinta O'shea, Ulrich Kirk, Hamed EkhtiariAbstract:Integration of tDCS with fMRI holds promise for investigation the underlying mechanism of stimulation effect. There are 118 published tDCS studies (up to 1st Oct 2018) that used fMRI as a proxy measure of neural activation to answer mechanistic, predictive, and localization questions about how brain activity is modulated by tDCS. FMRI can potentially contribute as: a measure of cognitive state-level variance in baseline brain activation before tDCS; inform the design of stimulation montages that aim to target functional networks during specific tasks; and act as an outcome measure of functional response to tDCS. In this systematic review we explore methodological parameter space of tDCS integration with fMRI. Existing tDCS-fMRI literature shows little replication across these permutations; few studies used comparable study designs. Here, we use a case study with both task and resting state fMRI before and after tDCS in a cross-over design to discuss methodological confounds. We further outline how computational models of current flow should be combined with imaging data to understand sources of variability in responsiveness. Through the case study, we demonstrate how modeling and imaging methodology can be integrated for individualized analysis. Finally, we discuss the importance of conducting tDCS-fMRI with stimulation equipment certified as safe to use inside the MR scanner, and of correcting for image artifacts caused by tDCS. tDCS-fMRI can address important questions on the functional mechanisms of tDCS action (e.g. target engagement) and has the potential to support enhancement of behavioral interventions, provided studies are designed rationally.
-
Language boosting by transcranial stimulation in progressive supranuclear palsy
Neurology, 2019Co-Authors: Dr Valero-cabré, Marom Bikson, Antoni Valero-cabré, Clara Sanches, Juliette Godard, Oriane Fracchia, Bruno Dubois, Richard Levy, Dennis Truong, Marc TeichmannAbstract:Objective To explore whether transcranial direct current stimulation (tDCS) over the dorsolateral pre-frontal cortex (DLPFC) can improve language capacities in patients with progressive supra-nuclear palsy (PSP). Methods We used a sham-controlled double-blind crossover design to assess the efficiency of tDCS over the DLPFC in a cohort of 12 patients with PSP. In 3 separate sessions, we evaluated the ability to boost the left DLPFC via left-anodal (excitatory) and right-cathodal (inhibitory) tDCS, while comparing them to sham tDCS. Tasks assessing lexical access (letter fluency task) and semantic access (category judgment task) were applied immediately before and after the tDCS sessions to provide a marker of potential language modulation. Results The comparison with healthy controls showed that patients with PSP were impaired on both tasks at baseline. Contrasting poststimulation vs prestimulation performance across tDCS conditions revealed language improvement in the category judgment task following right-cathodal tDCS, and in the letter fluency task following left-anodal tDCS. A computational finite element model of current distribution corroborated the intended effect of left-anodal and right-cathodal tDCS on the targeted DLPFC. Conclusions Our results demonstrate tDCS-driven language improvement in PSP. They provide proof-of-concept for the use of tDCS in PSP and set the stage for future multiday stimulation regimens, which might lead to longer-lasting therapeutic effects promoted by neuroplasticity. Classification of evidence This study provides Class III evidence that for patients with PSP, tDCS over the DLPFC improves performance in some language tasks.
-
sham tDCS a hidden source of variability reflections for further blinded controlled trials
Brain Stimulation, 2019Co-Authors: Clara Fonteneau, Marom Bikson, Andre R Brunoni, Marine Mondino, Martijn Arns, Chris Baeken, Matthew J Burke, Tuomas Neuvonen, Frank PadbergAbstract:Abstract Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique increasingly used to modulate neural activity in the living brain. In order to establish the neurophysiological, cognitive or clinical effects of tDCS, most studies compare the effects of active tDCS to those observed with a sham tDCS intervention. In most cases, sham tDCS consists in delivering an active stimulation for a few seconds to mimic the sensations observed with active tDCS and keep participants blind to the intervention. However, to date, sham-controlled tDCS studies yield inconsistent results, which might arise in part from sham inconsistencies. Indeed, a multiplicity of sham stimulation protocols is being used in the tDCS research field and might have different biological effects beyond the intended transient sensations. Here, we seek to enlighten the scientific community to this possible confounding factor in order to increase reproducibility of neurophysiological, cognitive and clinical tDCS studies.
Monica Christova - One of the best experts on this subject based on the ideXlab platform.
-
ID 298 – Timing – Dependant effects of anodal tDCS on motor memory following pegboard test training
Clinical Neurophysiology, 2016Co-Authors: Monica Christova, Dietmar Rafolt, S Fresnoza, E GallaschAbstract:Objective Facilitating effect of anodal transcranial direct current stimulation (atDCS) on motor learning and memory has been demonstrated.The present study examines whether the motor memory gains depend on the timing of stimulation in relation to the ongoing motor task. Methods Five study groups ( n = 70) were trained on the grooved pegboard test (GPT) in a randomized, between-subjects design: sham stimulation during training, atDCS prior training, atDCS during training, atDCS after training, atDCS 15 min after training. The tDCS was applied to the contralateral motor cortex for 15 min. Motor performance was assessed by GPT completion time and retested 14 days later to determine the task consolidation. Results Preliminary results showed shorter performance times at retest for the stimulated groups compared to sham. Final results concerning the specific effect of different timings of stimulation will be reported. Conclusions Anodal tDCS improves motor memory following pegboard test training. As the task consolidation occurs in the first minutes after the end of the motor training, we assume that atDCS applied post GPT ameliorates motor memory more effectively. Key message Effect of timing of tDCS application should be considered when designing brain stimulation protocols.
-
id 298 timing dependant effects of anodal tDCS on motor memory following pegboard test training
Clinical Neurophysiology, 2016Co-Authors: Monica Christova, Dietmar Rafolt, S Fresnoza, E GallaschAbstract:Objective Facilitating effect of anodal transcranial direct current stimulation (atDCS) on motor learning and memory has been demonstrated.The present study examines whether the motor memory gains depend on the timing of stimulation in relation to the ongoing motor task. Methods Five study groups ( n = 70) were trained on the grooved pegboard test (GPT) in a randomized, between-subjects design: sham stimulation during training, atDCS prior training, atDCS during training, atDCS after training, atDCS 15 min after training. The tDCS was applied to the contralateral motor cortex for 15 min. Motor performance was assessed by GPT completion time and retested 14 days later to determine the task consolidation. Results Preliminary results showed shorter performance times at retest for the stimulated groups compared to sham. Final results concerning the specific effect of different timings of stimulation will be reported. Conclusions Anodal tDCS improves motor memory following pegboard test training. As the task consolidation occurs in the first minutes after the end of the motor training, we assume that atDCS applied post GPT ameliorates motor memory more effectively. Key message Effect of timing of tDCS application should be considered when designing brain stimulation protocols.
-
cumulative effects of anodal and priming cathodal tDCS on pegboard test performance and motor cortical excitability
Behavioural Brain Research, 2015Co-Authors: Monica Christova, Dietmar Rafolt, E GallaschAbstract:Abstract Transcranial direct current stimulation (tDCS) protocols applied over the primary motor cortex are associated with changes in motor performance. This transcranial magnetic stimulation (TMS) study examines whether cathodal tDCS prior to motor training, combined with anodal tDCS during motor training improves motor performance and off-line learning. Three study groups ( n = 36) were trained on the grooved pegboard test (GPT) in a randomized, between-subjects design: SHAM—sham stimulation prior and during training, STIM1—sham stimulation prior and atDCS during training, STIM2—ctDCS stimulation prior and atDCS during training. Motor performance was assessed by GPT completion time and retested 14 days later to determine off-line learning. Cortical excitability was assessed via TMS at baseline (T0), prior training (T1), after training (T2), and 60 min after training (T3). Motor evoked potentials (MEP) were recorded from m. abductor pollicis brevis of the active left hand. GPT completion time was reduced for both stimulated groups compared to SHAM. For STIM2 this reduction in time was significantly higher than for STIM1 and further off-line learning occurred after STIM2. After ctDCS at T1, MEP amplitude and intracortical facilitation was decreased and intracortical inhibition was increased. After atDCS at T2, an opposite effect was observed for STIM1 and STIM2. For STIM2 these neuromodulatory effects were retained until T3. It is concluded that application of atDCS during the training improves pegboard performance and that additional priming with ctDCS has a positive effect on off-line learning. These cumulative behavioral gains were indicated by the preceding neuromodulatory changes.
E Gallasch - One of the best experts on this subject based on the ideXlab platform.
-
ID 298 – Timing – Dependant effects of anodal tDCS on motor memory following pegboard test training
Clinical Neurophysiology, 2016Co-Authors: Monica Christova, Dietmar Rafolt, S Fresnoza, E GallaschAbstract:Objective Facilitating effect of anodal transcranial direct current stimulation (atDCS) on motor learning and memory has been demonstrated.The present study examines whether the motor memory gains depend on the timing of stimulation in relation to the ongoing motor task. Methods Five study groups ( n = 70) were trained on the grooved pegboard test (GPT) in a randomized, between-subjects design: sham stimulation during training, atDCS prior training, atDCS during training, atDCS after training, atDCS 15 min after training. The tDCS was applied to the contralateral motor cortex for 15 min. Motor performance was assessed by GPT completion time and retested 14 days later to determine the task consolidation. Results Preliminary results showed shorter performance times at retest for the stimulated groups compared to sham. Final results concerning the specific effect of different timings of stimulation will be reported. Conclusions Anodal tDCS improves motor memory following pegboard test training. As the task consolidation occurs in the first minutes after the end of the motor training, we assume that atDCS applied post GPT ameliorates motor memory more effectively. Key message Effect of timing of tDCS application should be considered when designing brain stimulation protocols.
-
id 298 timing dependant effects of anodal tDCS on motor memory following pegboard test training
Clinical Neurophysiology, 2016Co-Authors: Monica Christova, Dietmar Rafolt, S Fresnoza, E GallaschAbstract:Objective Facilitating effect of anodal transcranial direct current stimulation (atDCS) on motor learning and memory has been demonstrated.The present study examines whether the motor memory gains depend on the timing of stimulation in relation to the ongoing motor task. Methods Five study groups ( n = 70) were trained on the grooved pegboard test (GPT) in a randomized, between-subjects design: sham stimulation during training, atDCS prior training, atDCS during training, atDCS after training, atDCS 15 min after training. The tDCS was applied to the contralateral motor cortex for 15 min. Motor performance was assessed by GPT completion time and retested 14 days later to determine the task consolidation. Results Preliminary results showed shorter performance times at retest for the stimulated groups compared to sham. Final results concerning the specific effect of different timings of stimulation will be reported. Conclusions Anodal tDCS improves motor memory following pegboard test training. As the task consolidation occurs in the first minutes after the end of the motor training, we assume that atDCS applied post GPT ameliorates motor memory more effectively. Key message Effect of timing of tDCS application should be considered when designing brain stimulation protocols.
-
cumulative effects of anodal and priming cathodal tDCS on pegboard test performance and motor cortical excitability
Behavioural Brain Research, 2015Co-Authors: Monica Christova, Dietmar Rafolt, E GallaschAbstract:Abstract Transcranial direct current stimulation (tDCS) protocols applied over the primary motor cortex are associated with changes in motor performance. This transcranial magnetic stimulation (TMS) study examines whether cathodal tDCS prior to motor training, combined with anodal tDCS during motor training improves motor performance and off-line learning. Three study groups ( n = 36) were trained on the grooved pegboard test (GPT) in a randomized, between-subjects design: SHAM—sham stimulation prior and during training, STIM1—sham stimulation prior and atDCS during training, STIM2—ctDCS stimulation prior and atDCS during training. Motor performance was assessed by GPT completion time and retested 14 days later to determine off-line learning. Cortical excitability was assessed via TMS at baseline (T0), prior training (T1), after training (T2), and 60 min after training (T3). Motor evoked potentials (MEP) were recorded from m. abductor pollicis brevis of the active left hand. GPT completion time was reduced for both stimulated groups compared to SHAM. For STIM2 this reduction in time was significantly higher than for STIM1 and further off-line learning occurred after STIM2. After ctDCS at T1, MEP amplitude and intracortical facilitation was decreased and intracortical inhibition was increased. After atDCS at T2, an opposite effect was observed for STIM1 and STIM2. For STIM2 these neuromodulatory effects were retained until T3. It is concluded that application of atDCS during the training improves pegboard performance and that additional priming with ctDCS has a positive effect on off-line learning. These cumulative behavioral gains were indicated by the preceding neuromodulatory changes.
Michael A. Nitsche - One of the best experts on this subject based on the ideXlab platform.
-
differential tDCS and tacs effects on working memory related neural activity and resting state connectivity
Frontiers in Neuroscience, 2020Co-Authors: Kilian Abellanedaperez, Michael A. Nitsche, Lidia Vaquealcazar, Ruben Perellonalfonso, Nuria Bargallo, Minfang Kuo, Alvaro Pascualleone, David BartresfazAbstract:Transcranial direct and alternating current stimulation (tDCS and tACS, respectively) entail capability to modulate human brain dynamics and cognition. However, the comparability of these approaches at the level of large-scale functional networks has not been thoroughly investigated. In this study, 44 subjects were randomly assigned to receive sham (N = 15), tDCS (N = 15), or tACS (N = 14). The first electrode (anode in tDCS) was positioned over the left dorsolateral prefrontal cortex, the target area, and the second electrode (cathode in tDCS) was placed over the right supraorbital region. tDCS was delivered with a constant current of 2 mA. tACS was fixed to 2 mA peak-to-peak with 6 Hz frequency. Stimulation was applied concurrently with functional magnetic resonance imaging (fMRI) acquisitions, both at rest and during the performance of a verbal working memory (WM) task. After stimulation, subjects repeated the fMRI WM task. Our results indicated that at rest, tDCS increased functional connectivity particularly within the default-mode network (DMN), while tACS decreased it. When comparing both fMRI WM tasks, it was observed that tDCS displayed decreased brain activity post-stimulation as compared to online. Conversely, tACS effects were driven by neural increases online as compared to post-stimulation. Interestingly, both effects primarily occurred within DMN-related areas. Regarding the differences in each fMRI WM task, during the online fMRI WM task, tACS engaged distributed neural resources which did not overlap with the WM-dependent activity pattern, but with some posterior DMN regions. In contrast, during the post-stimulation fMRI WM task, tDCS strengthened prefrontal DMN deactivations, being these activity reductions associated with faster responses. Furthermore, it was observed that tDCS neural responses presented certain consistency across distinct fMRI modalities, while tACS did not. In sum, tDCS and tACS modulate fMRI-derived network dynamics differently. However, both effects seem to focus on DMN regions and the WM network-DMN shift, which are highly affected in aging and disease. Thus, albeit exploratory and needing further replication with larger samples, our results might provide a refined understanding of how the DMN functioning can be externally modulated through commonly used non-invasive brain stimulation techniques, which may be of eventual clinical relevance.
-
Basic science of tDCS
Frontiers in Psychology, 2014Co-Authors: Michael A. NitscheAbstract:Neuroplasticity, and functional connectivity are important physiological derivates of cognition, and behaviour. Recently introduced non-invasive brain stimulation techniques are suited to induce, and modulate respective physiological alterations. One of these techniques is transcranial direct current stimulation (tDCS). Its primary mechanism of action is a polarity-dependent subthreshold shift of resting membrane potentials, the after-effects of stimulation depend on the glutamatergic system. Beyond these regional effects, tDCS has been shown recently to alter cortical, as well as cortico-subcortical functional network connectivity. This talk will give an overview about the physiological effects of tDCS, including animal data, and will cover functional consequences of tDCS. Furthermore, new developments with regard to optimization strategies, and the complex interaction of physiological and cognitive processes, will be presented and it will be discussed how tDCS relates to other non-invasive brain stimulation techniques, like transcranial magnetic stimulation (TMS), transcranial alternating current stimulation (tACS), and paired associative stimulation (PAS)
-
behavioral effects of transcranial direct current stimulation tDCS induced dorsolateral prefrontal cortex plasticity in alcohol dependence
Journal of Physiology-paris, 2013Co-Authors: Morgana Croce Da Silva, Michael A. Nitsche, Felipe Fregni, Catarine Lima Conti, Jaisa Klauss, Luana Gaburro Alves, Henrique Mineiro Do Nascimento Cavalcante, Ester Miyuki NakamurapalaciosAbstract:Abstract Transcranial Direct Current Stimulation (tDCS) has been shown to reduce acute substance craving in drug addicts, and improve cognition in neuropsychiatric patients. Here we aimed to explore further tDCS induced behavioral and neurophysiological modulation including assessment of relapse rate over a prolonged time course in alcoholism. We examined the effects of repeated anodal tDCS (2 mA, 35 cm 2 , 20 min) over the left dorsolateral prefrontal cortex (DLPFC) on relapse to the use of alcohol in alcoholics from outpatient services, who received additional routine clinical treatment. Furthermore, event related potentials (ERPs), cognitive and frontal executive processes, craving, depressive and anxiety symptoms were obtained before and after treatment. From thirteen alcoholic subjects, seven were randomized to sham-tDCS and six to real tDCS treatment (once a week for five consecutive weeks). Depressive symptoms and craving were reduced to a larger extent in the tDCS group compared to the sham group ( p = 0.005 and p = 0.015, respectively). On the other hand, active tDCS was able to block the increase in neural activation triggered by alcohol related and neutral cues in prefrontal cortex (PFC) as indexed by ERP as seen in the sham-tDCS group. Finally, there was a trend for increased change in executive function in the tDCS group compared to the sham-tDCS group ( p = 0.082), and, similarly, a trend for more relapses in the tDCS group compared to sham tDCS (four alcoholic subjects (66.7%) vs. one (14.3%), p = 0.053).These results confirm the previous findings of tDCS effects on craving in alcoholism and also extend these findings as we showed also tDCS-related mood improvement. However, potential increase in relapse is possible; thus the clinical value of an increase in craving and improvement in depression and executive function needs to be carefully assessed in further studies; including investigation of optimal parameters of stimulation.
-
Is Motor Learning Mediated by tDCS Intensity
PLoS ONE, 2013Co-Authors: Koen Cuypers, Daphnie Leenus, Femke Van Den Berg, Michael A. Nitsche, Herbert Thijs, Nicole Wenderoth, Raf MeesenAbstract:Although tDCS has been shown to improve motor learning, previous studies reported rather small effects. Since physiological effects of tDCS depend on intensity, the present study evaluated this parameter in order to enhance the effect of tDCS on skill acquisition. The effect of different stimulation intensities of anodal tDCS (atDCS) was investigated in a double blind, sham controlled crossover design. In each condition, thirteen healthy subjects were instructed to perform a unimanual motor (sequence) learning task. Our results showed (1) a significant increase in the slope of the learning curve and (2) a significant improvement in motor performance at retention for 1.5 mA atDCS as compared to sham tDCS. No significant differences were reported between 1 mA atDCS and sham tDCS; and between 1.5 mA atDCS and 1 mA atDCS.
-
repeated sessions of noninvasive brain dc stimulation is associated with motor function improvement in stroke patients
Restorative Neurology and Neuroscience, 2007Co-Authors: Paulo S Boggio, Michael A. Nitsche, Alvaro Pascualleone, Alice Nunes, Sergio P Rigonatti, Felipe FregniAbstract:Purpose: Recent evidence has suggested that a simple technique of noninvasive brain stimulation - transcranial direct current stimulation (tDCS) - is associated with a significant motor function improvement in stroke patients. Methods: We tested the motor performance improvement in stroke patients following 4 weekly sessions of sham, anodal- and cathodal tDCS (experiment 1) and the effects of 5 consecutive daily sessions of cathodal tDCS (experiment 2). A blinded rater evaluated motor function using the Jebsen-Taylor Hand Function Test. Results: There was a significant main effect of stimulation condition ( p = 0.009) in experiment 1. Furthermore there was a significant motor function improvement after either cathodal tDCS of the unaffected hemisphere ( p = 0.016) or anodal tDCS of the affected hemisphere (p = 0.046) when compared to sham tDCS. There was no cumulative effect associated with weekly sessions of tDCS, however consecutive daily sessions of tDCS (experiment 2) were associated with a significant effect on time ( p< 0.0001) that lasted for 2 weeks after treatment. Conclusions: The findings of our study support previous research showing that tDCS is significantly associated with motor function improvement in stroke patients; and support that consecutive daily sessions of tDCS might increase its behavioral effects. Because the technique of tDCS is simple, safe and non-expensive; our findings support further research on the use of this technique for the rehabilitation of patients with stroke.
Felipe Fregni - One of the best experts on this subject based on the ideXlab platform.
-
a technical guide to tDCS and related non invasive brain stimulation tools
Clinical Neurophysiology, 2016Co-Authors: Adam J Woods, Marom Bikson, Christoph Herrmann, Leonardo G Cohen, Felipe Fregni, Andrea Antal, Paulo S Boggio, Andre R Brunoni, Pablo A Celnik, Emily S KappenmanAbstract:Transcranial electrical stimulation (tES), including transcranial direct and alternating current stimulation (tDCS, tACS) are non-invasive brain stimulation techniques increasingly used for modulation of central nervous system excitability in humans. Here we address methodological issues required for tES application. This review covers technical aspects of tES, as well as applications like exploration of brain physiology, modelling approaches, tES in cognitive neurosciences, and interventional approaches. It aims to help the reader to appropriately design and conduct studies involving these brain stimulation techniques, understand limitations and avoid shortcomings, which might hamper the scientific rigor and potential applications in the clinical domain.
-
Exogenously induced brain activation regulates neuronal activity by top-down modulation: conceptualized model for electrical brain stimulation
Experimental Brain Research, 2015Co-Authors: Lauren Naomi Spezia Adachi, Alexandre Silva Quevedo, Andressa Souza, Vanessa Leal Scarabelot, Joanna Ripoll Rozisky, Carla Oliveira, Paulo Ricardo Marques Filho, Liciane Fernandes Medeiros, Felipe Fregni, Wolnei CaumoAbstract:Physiological and exogenous factors are able to adjust sensory processing by modulating activity at different levels of the nervous system hierarchy. Accordingly, transcranial direct current stimulation (tDCS) may use top-down mechanisms to control the access for incoming information along the neuroaxis. To test the hypothesis that brain activation induced by tCDS is able to initiate top-down modulation and that chronic stress disrupts this effect, 60-day-old male Wistar rats ( n = 78) were divided into control; control + tDCS; control + sham-tDCS; stress; stress + tDCS; and stress + sham-tDCS. Chronic stress was induced using a restraint stress model for 11 weeks, and then, the treatment was applied over 8 days. BDNF levels were used to assess neuronal activity at spinal cord, brainstem, and hippocampus. Mechanical pain threshold was assessed by von Frey test immediately and 24 h after the last tDCS-intervention. tDCS was able to decrease BDNF levels in the structures involved in the descending systems (spinal cord and brainstem) only in unstressed animals. The treatment was able to reverse the stress-induced allodynia and to increase the pain threshold in unstressed animals. Furthermore, there was an inverse relation between pain sensitivity and spinal cord BDNF levels. Accordingly, we propose the addition of descending systems in the current brain electrical modulation model.
-
behavioral effects of transcranial direct current stimulation tDCS induced dorsolateral prefrontal cortex plasticity in alcohol dependence
Journal of Physiology-paris, 2013Co-Authors: Morgana Croce Da Silva, Michael A. Nitsche, Felipe Fregni, Catarine Lima Conti, Jaisa Klauss, Luana Gaburro Alves, Henrique Mineiro Do Nascimento Cavalcante, Ester Miyuki NakamurapalaciosAbstract:Abstract Transcranial Direct Current Stimulation (tDCS) has been shown to reduce acute substance craving in drug addicts, and improve cognition in neuropsychiatric patients. Here we aimed to explore further tDCS induced behavioral and neurophysiological modulation including assessment of relapse rate over a prolonged time course in alcoholism. We examined the effects of repeated anodal tDCS (2 mA, 35 cm 2 , 20 min) over the left dorsolateral prefrontal cortex (DLPFC) on relapse to the use of alcohol in alcoholics from outpatient services, who received additional routine clinical treatment. Furthermore, event related potentials (ERPs), cognitive and frontal executive processes, craving, depressive and anxiety symptoms were obtained before and after treatment. From thirteen alcoholic subjects, seven were randomized to sham-tDCS and six to real tDCS treatment (once a week for five consecutive weeks). Depressive symptoms and craving were reduced to a larger extent in the tDCS group compared to the sham group ( p = 0.005 and p = 0.015, respectively). On the other hand, active tDCS was able to block the increase in neural activation triggered by alcohol related and neutral cues in prefrontal cortex (PFC) as indexed by ERP as seen in the sham-tDCS group. Finally, there was a trend for increased change in executive function in the tDCS group compared to the sham-tDCS group ( p = 0.082), and, similarly, a trend for more relapses in the tDCS group compared to sham tDCS (four alcoholic subjects (66.7%) vs. one (14.3%), p = 0.053).These results confirm the previous findings of tDCS effects on craving in alcoholism and also extend these findings as we showed also tDCS-related mood improvement. However, potential increase in relapse is possible; thus the clinical value of an increase in craving and improvement in depression and executive function needs to be carefully assessed in further studies; including investigation of optimal parameters of stimulation.
-
repeated sessions of noninvasive brain dc stimulation is associated with motor function improvement in stroke patients
Restorative Neurology and Neuroscience, 2007Co-Authors: Paulo S Boggio, Michael A. Nitsche, Alvaro Pascualleone, Alice Nunes, Sergio P Rigonatti, Felipe FregniAbstract:Purpose: Recent evidence has suggested that a simple technique of noninvasive brain stimulation - transcranial direct current stimulation (tDCS) - is associated with a significant motor function improvement in stroke patients. Methods: We tested the motor performance improvement in stroke patients following 4 weekly sessions of sham, anodal- and cathodal tDCS (experiment 1) and the effects of 5 consecutive daily sessions of cathodal tDCS (experiment 2). A blinded rater evaluated motor function using the Jebsen-Taylor Hand Function Test. Results: There was a significant main effect of stimulation condition ( p = 0.009) in experiment 1. Furthermore there was a significant motor function improvement after either cathodal tDCS of the unaffected hemisphere ( p = 0.016) or anodal tDCS of the affected hemisphere (p = 0.046) when compared to sham tDCS. There was no cumulative effect associated with weekly sessions of tDCS, however consecutive daily sessions of tDCS (experiment 2) were associated with a significant effect on time ( p< 0.0001) that lasted for 2 weeks after treatment. Conclusions: The findings of our study support previous research showing that tDCS is significantly associated with motor function improvement in stroke patients; and support that consecutive daily sessions of tDCS might increase its behavioral effects. Because the technique of tDCS is simple, safe and non-expensive; our findings support further research on the use of this technique for the rehabilitation of patients with stroke.
