1,721,101 research outputs found
On the Use of Metaanalysis in Neuromodulatory Non-invasive Brain Stimulation
No full textWellcome Trust [091593
Use of Computational Modeling to Inform tDCS Electrode Montages for the Promotion of Language Recovery in Post-stroke Aphasia
No full textBackground: Although pilot trials of transcranial direct current stimulation (tDCS) in aphasia are encouraging, protocol optimization is needed. Notably, it has not yet been clarified which of the varied electrode montages investigated is the most effective in enhancing language recovery.
Objective: To consider and contrast the predicted brain current flow patterns (electric field distribution) produced by varied 11 tDCS (1 anode, 1 cathode, 5 7 cm pad electrodes) montages used in aphasia clinical trials.
Methods: A finite element model of the head of a single left frontal stroke patient was developed in order to study the pattern of the cortical EF magnitude and inward/outward radial EF under five different electrode montages: Anodal-tDCS (A-tDCS) over the left Wernicke’s area (Montage A) and over the left Broca’s area (Montage B); Cathodal tDCS (C-tDCS) over the right homologue of Wernicke’s area (Montage C), and of Broca’s area (Montage D), where for all montages A-D the “return” electrode was placed over the supraorbital contralateral forehead; bilateral stimulation with A-tDCS over the left Broca’s and CtDCS over the right Broca’s homologue (Montage E).
Results: In all cases, the “return” electrode over the contralesional supraorbital forehead was not inert and influenced the current path through the entire brain. Montage B, although similar to montage D in focusing the current in the perilesional area, exerted the greatest effect over the left perilesional cortex, which was even stronger in montage E.
Conclusions: The position and influence of both electrodes must be considered in the design and inter- pretation of tDCS clinical trials for aphasia
Comparing Cortical Plasticity Induced by Conventional and High-Definition 4 x 1 Ring tDCS: A Neurophysiological Study
No full textBackground: Transcranial direct current stimulation (tDCS) induces long-lasting NMDA receptor-dependent cortical plasticity via persistent subthreshold polarization of neuronal membranes. Conventional bipolar tDCS is applied with two large (35 cm(2)) rectangular electrodes, resulting in directional modulation of neuronal excitability. Recently a newly designed 4 x 1 high-definition (HD) tDCS protocol was proposed for more focal stimulation according to the results of computational modeling. HD tDCS utilizes small disc electrodes deployed in 4 x 1 ring configuration whereby the physiological effects of the induced electric field are thought to be grossly constrained to the cortical area circumscribed by the ring. Objective: We aim to compare the physiological effects of both tDCS electrode arrangements on motor cortex excitability. Methods: tDCS was applied with 2 mA for 10 min. Fourteen healthy subjects participated, and motor cortex excitability was monitored by transcranial magnetic stimulation (TMS) before and after tDCS. Results: Excitability enhancement following anodal and a respective reduction after cathodal stimulation occurred in both, conventional and HD tDCS. However, the plastic changes showed a more delayed peak at 30 min and longer lasting after-effects for more than 2 h after HD tDCS for both polarities, as compared to conventional tDCS. Conclusion: The results show that this new electrode arrangement is efficient for the induction of neuroplasticity in the primary motor cortex. The pattern of aftereffects might be compatible with the concept of GABA-mediated surround inhibition, which should be explored in future studies directly. (C) 2013 Elsevier Inc. All rights reserved
Imaging artifacts induced by electrical stimulation during conventional fMRI of the brain
No full textFunctional magnetic resonance imaging (fMRI) of brain activation during transcranial electrical stimulation is used to provide insight into the mechanisms of neuromodulation and targeting of particular brain structures. However, the passage of current through the body may interfere with the concurrent detection of blood oxygen level-dependent (BOLD) signal, which is sensitive to local magnetic fields. To test whether these currents can affect concurrent fMRI recordings we performed conventional gradient echo-planar imaging (EPI) during transcranial direct current (tDCS) and alternating current stimulation (tACS) on two post-mortem subjects. tDCS induced signals in both superficial and deep structures. The signal was specific to the electrode montage, with the strongest signal near cerebrospinal fluid (CSF) and scalp. The direction of change relative to non-stimulation reversed with tDCS stimulation polarity. For tACS there was no net effect of the MRI signal. High-resolution individualized modeling of current flow and induced static magnetic fields suggested a strong coincidence of the change EPI signal with regions of large current density and magnetic fields. These initial results indicate that (1) fMRI studies of tDCS must consider this potentially confounding interference from current flow and (2) conventional MRI imaging protocols can be potentially used to measure current flow during transcranial electrical stimulation. The optimization of current measurement and artifact correction techniques, including consideration of the underlying physics, remains to be addressed. (C) 2012 Elsevier Inc. All rights reserved.NIMH NIH HHS [R01 MH092926
Assessing the Effect of Automated Thermo-Mechanical Therapy on Abdominal Blood Flow With Magnetic Resonance Imaging
No full textThermal and mechanical tissue stimulation is widely utilized in various medical contexts, particularly to enhance local circulation, alleviate pain, and restore movement. Techniques to objectively quantify the physiological effects of these interventions support therapeutic efficacy and explain clinical benefits. Here we conducted a pilot trial to evaluate the feasibility of magnetic resonance imaging (MRI) technology to provide an objective assessment of acute treatment effects in enhancing blood flow. Subjects (n=10) received an MRI flow quantification scan of the abdominal aorta before and immediately after undergoing a 20-min thermo-mechanical massage delivered to the lumbar spine by a commercial automated device. We report a significant increase of 27% in the peak velocity of blood flow following treatment. There were no significant changes in the volume of the imaged vessel, in mean heart rate, or heart rate variability (HRV), which is consistent with direct local effects of therapy on circulation. These findings are consistent with the potential utility of MRI in detecting and quantifying regional increases in blood flow following thermo-mechanical stimulation.
A checklist for assessing the methodological quality of concurrent tES-fMRI studies (ContES checklist): a consensus study and statement
No full textOklahoma Center for the Advancement of Science and Technolog
Digitalized transcranial electrical stimulation: A consensus statement
No full textObjective
Although relatively costly and non-scalable, non-invasive neuromodulation interventions are treatment alternatives for neuropsychiatric disorders. The recent developments of highly-deployable transcranial electric stimulation (tES) systems, combined with mobile-Health technologies, could be incorporated in digital trials to overcome methodological barriers and increase equity of access. The study aims are to discuss the implementation of tES digital trials by performing a systematic scoping review and strategic process mapping, evaluate methodological aspects of tES digital trial designs, and provide Delphi-based recommendations for implementing digital trials using tES.
Methods
We convened 61 highly-productive specialists and contacted 8 tES companies to assess 71 issues related to tES digitalization readiness, and processes, barriers, advantages, and opportunities for implementing tES digital trials. Delphi-based recommendations (>60% agreement) were provided.
Results
The main strengths/opportunities of tES were: (i) non-pharmacological nature (92% of agreement), safety of these techniques (80%), affordability (88%), and potential scalability (78%). As for weaknesses/threats, we listed insufficient supervision (76%) and unclear regulatory status (69%). Many issues related to methodological biases did not reach consensus. Device appraisal showed moderate digitalization readiness, with high safety and potential for trial implementation, but low connectivity.
Conclusions
Panelists recognized the potential of tES for scalability, generalizability, and leverage of digital trials processes; with no consensus about aspects regarding methodological biases.
Significance
We further propose and discuss a conceptual framework for exploiting shared aspects between mobile-Health tES technologies with digital trials methodology to drive future efforts for digitizing tES trials
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