Nature Scientific Reports

In-vivo Imaging of Magnetic Fields Induced by Transcranial Direct Current Stimulation (tDCS) in Human Brain using MRI

Mayank V. Jog, Robert X. Smith, Kay Jann, Walter Dunn, Belen Lafon, Dennis Truong, Allan Wu, Lucas Parra, Marom Bikson & Danny J. J. Wang

Transcranial direct current stimulation (tDCS) is an emerging non-invasive neuromodulation technique that applies mA currents at the scalp to modulate cortical excitability. Here, we present a novel magnetic resonance imaging (MRI) technique, which detects magnetic elds induced by tDCS currents. This technique is based on Ampere’s law and exploits the linear relationship between direct current and induced magnetic elds. Following validation on a phantom with a known path of electric current and induced magnetic eld, the proposed MRI technique was applied to a human limb (to demonstrate in- vivo feasibility using simple biological tissue) and human heads (to demonstrate feasibility in standard tDCS applications). The results show that the proposed technique detects tDCS induced magnetic elds as small as a nanotesla at millimeter spatial resolution. Through measurements of magnetic elds linearly proportional to the applied tDCS current, our approach opens a new avenue for direct in-vivo visualization of tDCS target engagement.

Full PDF: srep34385

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Our new review is published:

Jackson MP, Rahman A, Lafon B, Kronberg G, Ling D, Parra LC, Bikson M, Animal Models of transcranial Direct Current Stimulation: Methods and Mechanisms, Clinical Neurophysiology, doi:10.1016/j.clinph.2016.08.016

Full PDF here: animalmodelstdcs_2016

Abstract:  The objective of this review is to summarize the contribution of animal research using direct current stimulation (DCS) to our understanding of the physiological effects of transcranial direct current stimulation (tDCS). We comprehensively address experimental methodology in animal studies, broadly classified as: 1) transcranial stimulation; 2) direct cortical stimulation in vivo and 3) in vitro models. In each case advantages and disadvantages for translational research are discussed including dose translation and the overarching “quasi-uniform” assumption, which underpins translational relevance in all animal models of tDCS. Terminology such as anode, cathode, inward current, outward current, current density, electric field, and uniform are defined. Though we put key animal experiments spanning decades in perspective, our goal is not simply an exhaustive cataloging of relevant animal studies, but rather to put them in context of ongoing efforts to improve tDCS. Cellular targets, including excitatory neuronal somas, dendrites, axons, interneurons, glial cells, and endothelial cells are considered. We emphasize neurons are always depolarized and hyperpolarized such that effects of DCS on neuronal excitability can only be evaluated within subcellular regions of the neuron. Findings from animal studies on the effects of DCS on plasticity (LTP/LTD) and network oscillations are reviewed extensively. Any endogenous phenomena dependent on membrane potential changes are, in theory, susceptible to modulation by DCS. The relevance of morphological changes (galvanotropy) to tDCS is also considered, as we suggest microscopic migration of axon terminals or dendritic spines may be relevant during tDCS. A majority of clinical studies using tDCS employ a simplistic dose strategy where excitability is singularly increased or decreased under the anode and cathode, respectively. We discuss how this strategy, itself based on classic animal studies, cannot account for the complexity of normal and pathological brain function, and how recent studies have already indicated more sophisticated approaches are necessary. One tDCS theory regarding “functional targeting” suggests the specificity of tDCS effects are possible by modulating ongoing function (plasticity). Use of animal models of disease are summarized including pain, movement disorders, stroke, and epilepsy

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Dr. Lucas Parra, Dr. Jacek Dmochowski, and Dr. Marom Bikson are speakers at the National Institute of Health (NIH) workshop on Transcranial Electrical Stimulation. Sept 29-30, 2016. Dr. Bikson is also a co-organizer of the event.

Full event details here  (watch it on WebX)

Synaptic Plasticity Mechanism Explains the Specificity of tDCS- Lucas Parra, PhD– Download Parra talk slides: talk-plasticity-september-2016

Computational Modeling-assisted Design of tDCS Protocols- Marom Bikson, PhD. — Download Bikson talk slides: nih_2016_bikson

Targeted Stimulation of Active Brain Sources Using Electromagnetic Reciprocity- Jacek Dmochowski, PhD

 

D.Q. Truong. D. Adair, M. Bikson. Computer-based models of tDCS of tACS in Transcranial Direct Current Stimulation in Neuropsychiatric Disorders: Clinical Principles ed. M.Nitsche, C. Loo and A. Brunoni 2016 10.1007/978-3-319-33967-2_5 p.47-66 . PDF:computermodels_chapter

D. Ling, A. Rahman, M. Jackson M. Bikson Animal studies in the field of transcranial electric stimulation in Transcranial Direct Current Stimulation in Neuropsychiatric Disorders: Clinical Principles M.Nitsche, C. Loo and A. Brunoni 2016 10.1007/978-3-319-33967-2_5 p.67-83 PDF: animalstudies_chapter

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Safety of Transcranial Direct Current Stimulation: Evidence Based Update 2016
Marom Bikson, Pnina Grossman, Chris Thomas, Adantchede Louis Zannou, Jimmy Jiang, Tatheer Adnan, Antonios P. Mourdoukoutas, Greg Kronberg, Dennis Truong, Paulo Boggio, André R. Brunoni, Leigh Charvet, Felipe Fregni, Brita Fritsch, Bernadette Gillick, Roy H. Hamilton, Benjamin M. Hampstead, Ryan Jankord, Adam Kirton, Helena Knotkova, David Liebetanz, Anli Liu, Colleen Loo, Michael A. Nitsche, Janine Reis, Jessica D. Richardson, Alexander Rotenberg, Peter E. Turkeltaub, Adam J. Woods
Brain Stimulation 2016, Vol. 9, Issue 5

Full PDF: Bikson_Safety_tDCS_2016

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