Littérature scientifique sur le sujet « Cathodal tDCS »

Transcranial direct current stimulation (tDCS) of the human cerebral cortex modulates cortical excitability noninvasively in a polarity-specific manner: anodal tDCS leads to lasting facilitation and cathodal tDCS to inhibition of motor cortex excitability. To further elucidate the underlying physiological mechanisms, we recorded corticospinal volleys evoked by single-pulse transcranial magnetic stimulation of the primary motor cortex before and after a 5-min period of anodal or cathodal tDCS in eight conscious patients who had electrodes implanted in the cervical epidural space for the control of pain. The effects of anodal tDCS were evaluated in six subjects and the effects of cathodal tDCS in five subjects. Three subjects were studied with both polarities. Anodal tDCS increased the excitability of cortical circuits generating I waves in the corticospinal system, including the earliest wave (I1 wave), whereas cathodal tDCS suppressed later I waves. The motor evoked potential (MEP) amplitude changes immediately following tDCS periods were in agreement with the effects produced on intracortical circuitry. The results deliver additional evidence that tDCS changes the excitability of cortical neurons.

Objective: This study examined effects of transcranial direct current stimulation (tDCS) over the dorsolateral prefrontal cortex (DLPFC) and orbitofrontal cortex (OFC) on major executive functions (EFs), including response inhibition, executive control, working memory (WM), and cognitive flexibility/task switching in ADHD. Method: ADHD children received (a) left anodal/right cathodal DLPFC tDCS and (b) sham stimulation in Experiment 1 and (a) left anodal DLPFC/right cathodal OFC tDCS, (b) left cathodal DLPFC/right anodal OFC tDCS, and (c) sham stimulation in Experiment 2. The current intensity was 1 mA for 15 min with a 72-hr interval between sessions. Participants underwent Go/No-Go task, N-back test, Wisconsin Card Sorting Test (WCST), and Stroop task after each tDCS condition. Results: Anodal left DLPFC tDCS most clearly affected executive control functions (e.g., WM, interference inhibition), while cathodal left DLPFC tDCS improved inhibitory control. Cognitive flexibility/task switching benefited from combined DLPFC-OFC, but not DLPFC stimulation alone. Conclusion: Task-specific stimulation protocols can improve EFs in ADHD.

Noninvasive brain stimulation techniques such as transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) can induce long-term potentiation-like facilitation, but whether the combination of TMS and tDCS has additive effects is unclear. To address this issue, in this randomized crossover study, we investigated the effect of preconditioning with cathodal high-definition (HD) tDCS on intermittent theta burst stimulation- (iTBS-) induced plasticity in the left motor cortex. A total of 24 healthy volunteers received preconditioning with cathodal HD-tDCS or sham intervention prior to iTBS in a random order with a washout period of 1 week. The amplitude of motor evoked potentials (MEPs) was measured at baseline and at several time points (5, 10, 15, and 30 min) after iTBS to determine the effects of the intervention on cortical plasticity. Preconditioning with cathodal HD-tDCS followed by iTBS showed a greater increase in MEP amplitude than sham cathodal HD-tDCS preconditioning and iTBS at each time postintervention point, with longer-lasting after-effects on cortical excitability. These results demonstrate that preintervention with cathodal HD-tDCS primes the motor cortex for long-term potentiation induced by iTBS and is a potential strategy for improving the clinical outcome to guide therapeutic decisions.

The role of the cerebellum in cognitive processing is increasingly recognized but still poorly understood. A recent study in this field applied cerebellar Transcranial Direct Current Stimulation (c-tDCS) to the right cerebellum to investigate the role of prefrontal-cerebellar loops in language aspects of cognition. Results showed that the improvement in participants’ verbal response times on a verb generation task was facilitated immediately after cathodal c-tDCS, compared to anodal or sham c-tDCS. The primary aim of the present study is to replicate these findings and additionally to investigate possible longer term effects. A crossover within-subject design was used, comparing cathodal and sham c-tDCS. The experiment consisted of two visits with an interval of one week. Our results show no direct contribution of cathodal c-tDCS over the cerebellum to language task performance. However, one week later, the group receiving cathodal c-tDCS in the first visit show less improvement and increased variability in their verbal response times during the second visit, compared to the group receiving sham c-tDCS in the first visit. These findings suggest a potential negative effect of c-tDCS and warrant further investigation into long term effects of c-tDCS before undertaking clinical studies with poststroke patients with aphasia.

Background Working memory, as a complex system, consists of two independent components: manipulation and maintenance process, which are defined as executive control and storage process. Previous studies mainly focused on the overall effect of transcranial direct current stimulation (tDCS) on working memory. However, little has been known about the segregative effects of tDCS on the sub-processes within working memory. Method Transcranial direct current stimulation, as one of the non-invasive brain stimulation techniques, is being widely used to modulate the cortical activation of local brain areas. This study modified a spatial n-back experiment with anodal and cathodal tDCS exertion on the right dorsolateral prefrontal cortex (DLPFC), aiming to investigate the effects of tDCS on the two sub-processes of working memory: manipulation (updating) and maintenance. Meanwhile, considering the separability of tDCS effects, we further reconfirmed the causal relationship between the right DLPFC and the sub-processes of working memory with different tDCS conditions. Results The present study showed that cathodal tDCS on the right DLPFC selectively improved the performance of the modified 2-back task in the difficult condition, whereas anodal tDCS significantly reduced the performance of subjects and showed an speeding-up tendency of response time. More precisely, the results of discriminability index and criterion showed that only cathodal tDCS enhanced the performance of maintenance in the difficult condition. Neither of the two tDCS conditions affected the performance of manipulation (updating). Conclusion These findings provide evidence that cathodal tDCS of the right DLPFC selectively affects maintenance capacity. Besides, cathodal tDCS also serves as an interference suppressor to reduce the irrelevant interference, thereby indirectly improving the working memory capacity. Moreover, the right DLPFC is not the unique brain regions for working memory manipulation (updating).

Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that induces changes in cortical excitability: anodal stimulation increases while cathodal stimulation reduces excitability. Imaging studies performed after unilateral stimulation have shown conflicting results regarding the effects of tDCS on surrogate markers of neuronal activity. The aim of this study was to directly measure these effects on activation-induced changes in regional cerebral blood flow (⊿rBF) using positron emission tomography (PET) during bilateral tDCS. Nine healthy subjects underwent repeated rCBF measurements with 15O-water and PET during a simple motor task while receiving tDCS or sham stimulation over the primary motor cortex (M1). Motor evoked potentials (MEPs) were also assessed before and after real and sham stimulation. During tDCS with active movement, ⊿rBF in M1 was significantly lower on the cathodal than the anodal side when compared with sham stimulation. This decrease in ⊿rBF was accompanied by a decrease in MEP amplitude on the cathodal side. No effect was observed on resting or activated rCBF relative to sham stimulation. We thus conclude that it is the interaction of cathodal tDCS with activation-induced ⊿rBF rather than the effect on resting or activated rCBF itself which constitutes the physiological imaging correlate of tDCS.

ObjectiveTo explore whether transcranial direct current stimulation (tDCS) over the dorsolateral prefrontal cortex (DLPFC) can improve language capacities in patients with progressive supranuclear palsy (PSP).MethodsWe 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.ResultsThe 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.ConclusionsOur 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 evidenceThis study provides Class III evidence that for patients with PSP, tDCS over the DLPFC improves performance in some language tasks.

Proliferative diabetic retinopathy (PDR) is a severe complication of diabetes. PDR-related retinal hemorrhages often lead to severe vision loss. The main goals of management are to prevent visual impairment progression and improve residual vision. We explored the potential of transcranial direct current stimulation (tDCS) to enhance residual vision. tDCS applied to the primary visual cortex (V1) may improve visual input processing from PDR patients’ retinas. Eleven PDR patients received cathodal tDCS stimulation of V1 (1 mA for 10 min), and another eleven patients received sham stimulation (1 mA for 30 s). Visual acuity (logarithm of the minimum angle of resolution (LogMAR) scores) and number acuity (reaction times (RTs) and accuracy rates (ARs)) were measured before and immediately after stimulation. The LogMAR scores and the RTs of patients who received cathodal tDCS decreased significantly after stimulation. Cathodal tDCS has no significant effect on ARs. There were no significant changes in the LogMAR scores, RTs, and ARs of PDR patients who received sham stimulation. The results are compatible with our proposal that neuronal noise aggravates impaired visual function in PDR. The therapeutic effect indicates the potential of tDCS as a safe and effective vision rehabilitation tool for PDR patients.

People with schizophrenia (SZ) exhibit visual processing abnormalities that affect their daily functioning and remediating these deficits might help to improve functioning. Transcranial direct current stimulation (tDCS) is a potential tool for perceptual enhancement for this purpose, though there are no reports of tDCS applied to visual cortex in SZ. In a within-subject, crossover design, we evaluated the effects of tDCS on visual processing in 27 SZ. All patients received anodal, cathodal, or sham stimulation over the central occipital region in 3 visits separated by 1 week. In each visit, a backward masking task and an electroencephalography measure of visual neuroplasticity were administered after tDCS. Neuroplasticity was assessed with visual evoked potentials before and after tetanizing visual high-frequency stimulation. Masking performance was significantly poorer in the anodal and cathodal conditions compared with sham. Both anodal and cathodal stimulation increased the amplitude of P1 but did not change the plasticity index. We found significant plasticity effects of tDCS for only one waveform for one stimulation condition (P2 for anodal tDCS) which did not survive correction for multiple comparisons. The reason for the lack of tDCS stimulation effects on plasticity may be because tDCS was not delivered simultaneously with the tetanizing visual stimulus. The present findings emphasize the need for more research on the relevant parameters for stimulation of visual processing regions in clinical populations.

Transcranial direct current stimulation (tDCS) is a noninvasive technique for modulating neural plasticity and is considered to have therapeutic potential in neurological disorders. For the purpose of translational neuroscience research, a suitable animal model can be ideal for providing a stable condition for identifying mechanisms that can help to explore therapeutic strategies. Here, we developed a tDCS protocol for modulating motor excitability in anesthetized rats. To examine the responses of tDCS-elicited plasticity, the motor evoked potential (MEP) and MEP input-output (IO) curve elicited by epidural motor cortical electrical stimulus were evaluated at baseline and after 30 min of anodal tDCS or cathodal tDCS. Furthermore, a paired-pulse cortical electrical stimulus was applied to assess changes in the inhibitory network by measuring long-interval intracortical inhibition (LICI) before and after tDCS. In the results, analogous to those observed in humans, the present study demonstrates long-term potentiation- (LTP-) and long-term depression- (LTD-) like plasticity can be induced by tDCS protocol in anesthetized rats. We found that the MEPs were significantly enhanced immediately after anodal tDCS at 0.1 mA and 0.8 mA and remained enhanced for 30 min. Similarly, MEPs were suppressed immediately after cathodal tDCS at 0.8 mA and lasted for 30 min. No effect was noted on the MEP magnitude under sham tDCS stimulation. Furthermore, the IO curve slope was elevated following anodal tDCS and presented a trend toward diminished slope after cathodal tDCS. No significant differences in the LICI ratio of pre- to post-tDCS were observed. These results indicated that developed tDCS schemes can produce consistent, rapid, and controllable electrophysiological changes in corticomotor excitability in rats. This newly developed tDCS animal model could be useful to further explore mechanical insights and may serve as a translational platform bridging human and animal studies, establishing new therapeutic strategies for neurological disorders.

La Stimolazione transcranica a Corrente Diretta continua (tDCS) è una tecnica di neurostimolazione non invasiva in grado di generare alterazioni dell’eccitabilità neuronale dipendenti dalla plasticità. Negli ultimi anni si sta assistendo a un crescente interesse nell’utilizzo di questa tecnica, sia in settings clinici che sperimentali. In particolare, la possibilità di indurre effetti a lungo termine rende la tDCS interessante nel trattamento di deficit cognitivi associati a disturbi sia neuropsicologici che psichiatrici. Nonostante la sua crescente diffusione, si sa ancora poco riguardo i meccanismi neurofisiologici alla base del suo funzionamento, soprattutto per quanto riguarda gli effetti su regioni cerebrali che sottostanno a funzioni cognitive di ordine superiore. Una conoscenza più approfondita dei meccanismi alla base della tDCS potrebbe quindi essere cruciale per riuscire a definire e migliorare i protocolli di stimolazione sia clinici che di ricerca. A questo scopo, uno studio sistematico degli effetti corticali della tDCS appare ancora più necessario. In questo progetto abbiamo quindi esplorato gli effetti di plasticità corticale indotti dalla stimolazione catodica in soggetti sani, sia a riposo che durante l’esecuzione di un compito, utilizzando il sistema integrato di Stimolazione Magnetica Transcranica ed Elettroencefalografia (TMS-EEG). Il TMS-EEG è una tecnica molto efficace in quando permette di misurare direttamente la modulazione dell’eccitabilità corticale su tutta la corteccia. In questa tesi sono riportati tre studi. Nel primo, partendo dai risultati sulla tDCS anodica già precedentemente pubblicati, sono stati esplorati gli effetti della tDCS catodica sulla Corteccia Parietale Posteriore (PPC) destra a riposo. Nel secondo studio, abbiamo indagato gli effetti comportamentali indotti dalla tDCS catodica sulla PPC destra, durante l’esecuzione di due compiti: uno di memoria di lavoro visuospaziale e uno di orientamento dell’attenzione visuospaziale. Nel terso studio, infine, abbiamo utilizzato nuovamente il TMS-EEG per tracciare gli effetti neurofisiologici della tDCS catodica sulla PPC di destra mentre i partecipanti erano impegnati nell’esecuzione dei compiti individuati nello studio precedente. I risultati per la tDCS catodica a riposo non hanno mostrato effetti di modulazione dell’eccitabilità corticale, sia a livello dei sensori che a livello delle sorgenti, sia a livello locale che globale. I risultati precedentemente ottenuti con la tDCS anodica, hanno invece mostrato un aumento diffuso dell’eccitabilità corticale lungo un network bilaterale frontoparietale, che rispecchia le connessioni strutturali tra le aree d’interesse. Durante l’esecuzione di un compito, invece, la stimolazione catodica, così come quella anodica, ha mostrato una modulazione nell’eccitabilità corticale solo in quelle aree che sono coinvolte nell’esecuzione del compito. In conclusione, in questo lavoro di tesi emergono diversi interessanti risultati. Innanzitutto, questi dati mostrano un effetto non lineare della tDCS sull’eccitabilità corticale a riposo, che non possono essere completamente spiegati dal semplice dualismo anodico-eccitatorio catodico-inibitorio. Un altro risultato rilevante è dato dal ruolo cruciale giocato dai differenti stati ti attivazione corticale (a riposo Vs attivo). Questi risultati sembrano mostrare che il livello di attivazione corticale di base contribuisca a modulare gli effetti della stimolazione, in accordo con l’ipotesi “attività-selettività”. Lo stato di attivazione di base deve quindi essere preso in considerazione, in particolare se si vogliono osservare degli effetti di neuromodulazione con tDCS catodica. In generale, tutte queste osservazioni contribuiscono a costruire quel corpus di conoscenze necessario soprattutto per la definizione dei parametri tDCS sia per esperimenti di neuroscienze cognitive che per protocolli riabilitativi.<br>Transcranial direct current stimulation (tDCS) is a non-invasive neuromodulatory technique able to induce plasticity-related alterations in neuronal excitability. There is a growing interest in the use of tDCS in both experimental and clinical settings; in particular, the chance to induce long-term effects fostered the used of the technique to treat cognitive impairments associated with different neuropsychological and psychiatric disorders. Although tDCS is increasingly used, presently little is still known about its neurophysiological underpinnings, particularly concerning the activity on the brain regions that underlie high cognitive brain functions. In these cases, optimal tDCS stimulation parameters also have yet to be clearly defined. A deeper understanding of the mechanisms underpinning this technique would be crucial to achieving a better refinement of stimulation protocols for clinical and research purposes. For this reason, a systematic and comprehensive study of its cortical effects acquires a critical relevance. In the last years, there has been indeed a keen interest in understanding the working mechanisms of this technique. To address this issue, in this project we explored the cortical plasticity modulation induced by cathodal stimulation on healthy subjects while resting or during task execution, using an integrated system of Transcranial Magnetic Stimulation and Electroencephalography (TMS-EEG), which allows to directly measure cortical excitability modulation all over the cortex and effective connectivity. In the first study, starting from the previous results with anodal tDCS, the effects of cathodal stimulation over the right Posterior Parietal Cortex (PPC) were explored during resting state. The contralateral homologue brain area, namely the left posterior parietal cortex (PPC), was targeted with TMS before, during, and after cathodal stimulation. In the second study, we explored the behavioural effects induced by the application of cathodal tDCS over right PPC during the execution of two tasks, one of visuospatial working memory and a second tapping visual attention reorienting, which are known to involve this brain area. The aim was to find tasks sensitive to the effect of cathodal tDCS over the right PCC, to be used in the third study. A disruption of the performance was found for the Posner Cueing Task. In the third study, we employed again TMS-EEG to track the neurophysiological effects of cathodal tDCS on right PPC at an active state, i.e. while the participants were performing the task tested on the second study. The results at resting state for cathodal tDCS, both at sensors and cortical sources levels, converge in showing no differences during and after tDCS compared to pre-stimulation sessions, both at a global and local level. The previous results with anodal tDCS, instead, reported a widespread rise of cortical excitability along with a bilateral frontoparietal network, following structural connections. On the other hand, at an active state, cathodal, as well as anodal, tDCS induced modulation of cortical excitability only in the task-relevant brain regions. Several significant findings emerged from this empirical work. First of all, these data highlight a non-linear impact of anodal and cathodal stimulation on cortical excitability at rest that is not depicted by the simplistic view of anodal-excitatory and cathodal-inhibitory effects. Another relevant point is the crucial role played by the different cortical states (resting vs active). These results seem to point out that the level of cortical state can contribute to modulate the tDCS effects, in line with “activity-selectivity” hypothesis. The level of cortical state needs to be taken into account, especially to observe neuromodulatory effects also with cathodal tDCS. All these findings hold relevant implications for tDCS setup in both cognitive neuroscience experiments and rehabilitation protocols.

Background: There is limited information about effects of transcranial Direct Current Stimulation(tDCS), delivered within the first weeks post-stroke, on performance of the paretic upper limb and on connectivity between motor areas in the affected and unaffected hemispheres. Objectives: We compared changes in Fugl-Meyer Assessment of Motor Recovery(FMA) scores, connectivity between the primary motor cortex of the unaffected(M1UH) and the affected hemisphere(M1AH), as well as between M1UH and the premotor cortex of the unaffected hemisphere(PMUH) before and after 6 sessions of cathodal tDCS targeting the primary motor cortex of the unaffected hemisphere(M1UH) early after stroke in 13 patients. Methods: This hypothesis-generating substudy was a randomized parallel, two-arm, double-blind, sham-controlled clinical trial performed at the Albert Einstein Hospital. Subjects were randomized active(N=6) or sham(N=7) groups. Results: Clinically relevant differences in FMA scores(≥ 9 points) were observed more often in the sham than in the active group. Between-group differences in changes in FMA scores were not statistically significant(Mann-Whitney test, p=0.133) but the effect size was -0.619(rank biserial correlation). Connectivity measures(Fisher’s z- transform of ROI-to-ROI correlations) between M1AH-M1UH increased in 5/6 participants in the active, and in 2/7 in the sham group after treatment. Between-group differences in changes in connectivity(M1UH-M1AH or PMUH-M1AH) were not statistically significant. In contrast with M1AH-M1UH connectivity, improvements in motor performance were more frequent in the active than in the sham group. Conclusions: Effects of cathodal tDCS on motor performance and on Resting-state Functional Magnetic Resonance Imaging may have distinct underpinnings in subjects at an early stage after stroke.

Background: Among the diseases that encompass chronic pain is fibromyalgia (FM), a syndrome characterized by changes in the functional, chemical and structural networks of the brain. Objectives: To analyze the effects of anodic Transcranial Direct Current Stimulation (tDCS) on the Primary Motor Cortex (M1) for 26 minutes for 10 sessions in the treatment of pain in patients with FM. Design and setting: Randomized double-blind clinical trial to be carried out at the Municipal Physiotherapy Clinic of Fátima do Sul - MS, Brazil. Methods: This is a Research protocol that is in progress. Forty women aged between 18 and 60 years with a medical diagnosis of FM will be selected. Participants will be randomly assigned to two groups (active tDCS and tDCS sham). There will be 10 consecutive sessions. The anode will be positioned at M1 and the cathode in the right sub-orbital region. The intensity will be 2mA applied for 13 minutes, a break of 20 minutes followed by another 13 minutes of stimulation. In the tDCS sham group, the device stays on for 30 seconds and turns off automatically. Participants will be evaluated at the beginning, after 10 sessions and after 30 and 90 days with the visual analogue scale, inventory of attitudes towards pain (primary outcome). Results: this will be the first clinical trial to use this prochotole. Potential limitations include patient compliance. Conclusions: we hope to demonstrate the effects of tDCS on FM and direct further studies.