M. F. Villamar, P. Wivatvongvana, J.Patumanond, M. Bikson, D.Q. Truong, A. Datta, F. Fregni. Focal modulation of primary motor cortex in Fibromyalgia using 4×1-Ring High-Definition Transcranial Direct Current Stimulation (HD-tDCS): Immediate and delayed analgesic effects of cathodal and anodal stimulation. J Pain, 2013; 14(4): 371-83 – Can be downloaded here: Villamar_Bikson_Focal_Modulation_HDtDCS_Pain_2013

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H.I. Kuo, A. Datta, M. Bikson, P. Minhas. W. Paulus, M.F. Kuo, M.A. Nitsche Comparing cortical plasticity induced by conventional and high-definition 4×1 ring tDCS: a neurophysiological study. Brain Stimulation. 2013 6(4):644-8  Can be downloaded here: Kuo_Bikson_HDtDCS_Cortical_Plasticity_BrainStimulation_2013

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__________

and

Watch the new HD-tDCS methods video

HERE: JOVE

M.F. Villamar, M.S. Volz, A. Datta, M. Bikson, A.F. DaSilva, F. Fregni. Technique and Considerations in the Use of 4×1 Ring High-definition Transcranial Direct Current Stimulation (HD-tDCS) JOVE 2013 (77) doi: 10.3791/50309.

Jacek P. Dmochowski, Abhishek Datta, Yu Huang, Jessica D. Richardson, Marom Bikson, Julius Fridriksson, Lucas C. Parra

City College of New York, New York, NY, USA, Soterix Medical, New York, NY, USA, University of South Carolina, Columbia, SC, USA

Abstract: Transcranial direct current stimulation (tDCS) is being investigated as an adjunctive technique to behavioral rehabilitation treatment after stroke. The conventional “dosage”, consisting of a large (25 cm2) anode over the target with the cathode over the contralateral hemisphere, has been previously shown to yield broadly distributed electric fields whose intensities at the target region are less than maximal. Here, we report the results of a systematic targeting procedure with small “high-definition” electrodes that was used in preparation for a pilot study on 8 stroke patients with chronic aphasia. We employ functional and anatomical magnetic resonance imagery (fMRI/MRI) to define a target and optimize (with respect to the electric field magnitude at the target) the electrode configuration, respectively, and demonstrate that electric field strengths in targeted cortex can be substantially increased (63%) over the conventional approach. The optimal montage exhibits significant variation across subjects as well as when perturbing the target location within a subject. However, for each displacement of the target co-ordinates, the algorithm is able to determine a montage which delivers a consistent amount of current to that location. These results demonstrate that MRI-based models of current flow yield maximal stimulation of target structures, and as such, may aid in reliably assessing the efficacy of tDCS in neuro-rehabilitation.

Read the full paper here: Dmochowski_Bikson_tDCS_targeted_for_stroke_2013_Neuroimage

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Brain Stimulation 6(3) 433-439

J. Medina, J. Beauvais, A. Datta, M. Bikson, H.B. Coslett, R.H. Hamilton.

Background

Previous research on hemispatial neglect has provided evidence for dissociable mechanisms for egocentric and allocentric processing. Although a few studies have examined whether tDCS to posterior parietal cortex can be beneficial for attentional processing in neurologically intact individuals, none have examined the potential effect of tDCS on allocentric and/or egocentric processing.

Objective/hypothesis

Our objective was to examine whether transcranial direct current stimulation (tDCS), a noninvasive brain stimulation technique that can increase (anodal) or decrease (cathodal) cortical activity, can affect visuospatial processing in an allocentric and/or egocentric frame of reference.

Methods

We tested healthy individuals on a target detection task in which the target – a circle with a gap – was either to the right or left of the viewer (egocentric), or contained a gap on the right or left side of the circle (allocentric). Individuals performed the task before, during, and after tDCS to the posterior parietal cortex in one of three stimulation conditions – right anodal/left cathodal, right cathodal/left anodal, and sham.

Results

We found an allocentric hemispatial effect both during and after tDCS, such that right anodal/left cathodal tDCS resulted in faster reaction times for detecting stimuli with left-sided gaps compared to right-sided gaps.

Conclusions

Our study suggests that right anodal/left cathodal tDCS has a facilitatory effect on allocentric visuospatial processing, and might be useful as a therapeutic technique for individuals suffering from allocentric neglect.

Read the Full Paper here:  Medina_tDCS_BrainStimulation_2012

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 Keywords:
  • Transcranial direct current stimulation;
  • Neglect;
  • Egocentric;
  • Allocentric;
  • Current density modeling

Brain Stimulation 6 (2013): 704-705

Marom Bikson, Jacek Dmochowski, Asif Rahman

From the articles ” Computational models of transcranial stimulation predict brain current flow patterns for dose optimization. Translational animal models aim at elucidating the cellular mechanisms of neuromodu- lation. Here we identify and define a ubiquitous assumption under- lying both computational and animal models, referred to herein as the “quasi-uniform assumption”. Though we attempt to rationalize the biophysical plausibility for the quasi-uniform assumption based on the limited electric field gradients generated during stimulation, our goal is neither to justify nor repudiate it, but rather emphasize its implicit use in a majority of modeling and animal studies. ”

Read the whole thing here

QuasiUniform_BrainStimulation_2013_Bikson

Cranial electrotherapy stimulation and transcranial pulsed current stimulation: A computer based high-resolution modeling study

Abhishek Datta, Jacek P. DmochowskiBerkan GuleyupogluMarom BiksonFelipe Fregni

Neuroimage. 2013 Jan 15;65:280-7. doi: 10.1016/j.neuroimage.2012.09.062. Epub 2012 Oct 5

Highlights:

► CES-induced current passes the skull and reaches cortical and subcortical areas.

► CES induced brain electric fields ranges from 0.2 to 0.6 V/m depending on the model.

► CES induced electrical current varies according to the electrode montage.

► Peak electric fields in some subcortical areas were similar to cortical regions.

► CES induced currents in the mid-brain exceed cortical values in some montages.

Download PDF CES_tPCS_model_Bikson_Neuroimage_2013

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Computational modeling of transcranial direct current stimulation (tDCS) in obesity: Impact of head fat and dose guidelines

NeuroImage: Clinical 2 (2013) 759–766

Dennis Q. Truong, Greta Magerowski, George L. Blackburn, Marom Bikson,Miguel Alonso-Alonso

Full PDF: Bikson_Obestity_Neuroimage_2013a

Abstract

Recent studies show that acute neuromodulation of the prefrontal cortex with transcranial direct current stim- ulation (tDCS) can decrease food craving, attentional bias to food, and actual food intake. These data suggest po- tential clinical applications for tDCS in the field of obesity. However, optimal stimulation parameters in obese individuals are uncertain. One fundamental concern is whether a thick, low-conductivity layer of subcutaneous fat around the head can affect current density distribution and require dose adjustments during tDCS adminis- tration. The aim of this study was to investigate the role of head fat on the distribution of current during tDCS and evaluate whether dosing standards for tDCS developed for adult individuals in general are adequate for the obese population. We used MRI-derived high-resolution computational models that delineated fat layers in five human heads from subjects with body mass index (BMI) ranging from “normal-lean” to “super-obese” (20.9 to 53.5 kg/m2). Data derived from these simulations suggest that head fat influences tDCS current density across the brain, but its relative contribution is small when other components of head anatomy are added. Cur- rent density variability between subjects does not appear to have a direct and/or simple link to BMI. These results indicate that guidelines for the use of tDCS can be extrapolated to obese subjects without sacrificing efficacy and/ or treatment safety; the recommended standard parameters can lead to the delivery of adequate current flow to induce neuromodulation of brain activity in the obese population.

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