Human cochlear hydrodynamics: A high-resolution μCT-based finite element study

Annalisa De Paolis, Hirobumi Watanabe, Jeremy T. Nelson, Marom Bikson, Mark Packer, Luis Cardoso

Journal of Biomechanics 50 (2017) 209–216

PDF: Human cochlear hydrodynamics   Journal Link

Abstract: Measurements of perilymph hydrodynamics in the human cochlea are scarce, being mostly limited to the fluid pressure at the basal or apical turn of the scalae vestibuli and tympani. Indeed, measurements of fluid pressure or volumetric flow rate have only been reported in animal models. In this study we imaged the human ear at 6.7 and 3-mm resolution using mCT scanning to produce highly accurate 3D models of the entire ear and particularly the cochlea scalae. We used a contrast agent to better distinguish soft from hard tissues, including the auditory canal, tympanic membrane, malleus, incus, stapes, ligaments, oval and round window, scalae vestibule and tympani. Using a Computational Fluid Dynamics (CFD) approach and this anatomically correct 3D model of the human cochlea, we examined the pressure and perilymph flow velocity as a function of location, time and frequency within the auditory range. Perimeter, surface, hydraulic diameter, Womersley and Reynolds numbers were computed every 45° of rotation around the central axis of the cochlear spiral. CFD results showed both spatial and temporal pressure gradients along the cochlea. Small Reynolds number and large Womersley values indicate that the perilymph fluid flow at auditory frequencies is laminar and its velocity profile is plug-like. The pressure was found 102–106° out of phase with the fluid flow velocity at the scalae vestibule and tympani, respectively. The average flow velocity was found in the sub-mm/s to nm/s range at 20–100 Hz, and below the nm/s range at 1–20 kHz.

Khadka N, Zannou AL, Zunura F,  Truong DQ,  Dmochowski J, Bikson M
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Download PDF Published in Neuromodulation  DOI

Abstract

Objective: To assess if transcranial direct current stimulation (tDCS) produces a temperature change at the skin surface, if any change is stimulation polarity (anode or cathode) specific, and the contribution of passive heating (joule heat) or blood flow on such change.

Material and Methods: Temperature differences (ΔTs) in an agar phantom study and an in vivo study (forearm stimulation) including 20 volunteers with both experimental measures and finite element method (FEM) multiphysics prediction (current flow and bioheat) models of skin comprising three tissue layers (epidermis, dermis, and subcutaneous layer with blood perfusion) or of the phantom for active stimulation and control cases were compared. Temperature was measured during pre, post, and stimulation phases for both phantom and subject’s forearms using thermocouples.

Results: In the phantom, ΔT under both anode and cathode, compared to control, was not significantly different and less than 0.1°C. Stimulation of subjects resulted in a gradual increase in temperature under both anode and cathode electrodes, compared to control (at t = 20 min: ΔTanode = 0.9°C, ΔTcathode = 1.1°C, ΔTcontrol = 0.05°C). The FEM phantom model predicted comparable maximum ΔT of 0.27°C and 0.28°C (at t = 20 min) for the control and anode/cathode cases, respectively. The FEM skin model predicted a maximum ΔT at t = 20 min of 0.98°C for control and 1.36°C under anode/cathode electrodes.

Conclusions: Taken together, our results indicate a moderate and nonhazardous increase in temperature at the skin surface during 2 mA tDCS that is independent of polarity, and results from stimulation induced blood flow rather than joule heat.

Published in the same issue of Brain Stimulation.

—- Direct Current Stimulation Alters Neuronal Input/Output Function.

Lafon B, Rahman A, Bikson M, Parra LC. Brain Stimul. 2016 Sep 1. pii: S1935-861X(16)30248-0. doi: 10.1016/j.brs.2016.08.014.

PDF: IO_tDCS_2017

— Direct Current Stimulation Modulates LTP and LTD: Activity Dependence and Dendritic Effects

Kronberg G, Bridi M, Abel T, Bikson M, Parra LC Brain Stimul. 2016 10 (2017) 51–58

PDF: Dendrites_tDCS_2017

Front. Hum. Neurosci., 12 January 2017 | https://doi.org/10.3389/fnhum.2016.00695

Cerebellar tDCS: A Novel Approach to Augment Language Treatment Post-stroke

People with post-stroke aphasia may have some degree of chronic deficit for which current rehabilitative treatments are variably effective. Accumulating evidence suggests that transcranial direct current stimulation (tDCS) may be useful for enhancing the effects of behavioral aphasia treatment. However, it remains unclear which brain regions should be stimulated to optimize effects on language recovery. Here, we report on the therapeutic potential of right cerebellar tDCS in augmenting language recovery in SMY, who sustained bilateral MCA infarct resulting in aphasia and anarthria. We investigated the effects of 15 sessions of anodal cerebellar tDCS coupled with spelling therapy using a randomized, double-blind, sham controlled within-subject crossover trial. We also investigated changes in functional connectivity using resting state functional magnetic resonance imaging before and 2 months post-treatment. Both anodal and sham treatments resulted in improved spelling to dictation for trained and untrained words immediately after and 2 months post-treatment. However, there was greater improvement with tDCS than with sham, especially for untrained words. Further, generalization to written picture naming was only noted during tDCS but not with sham. The resting state functional connectivity data indicate that improvement in spelling was accompanied by an increase in cerebro-cerebellar network connectivity. These results highlight the therapeutic potential of right cerebellar tDCS to augment spelling therapy in an individual with large bilateral chronic strokes.

Full paper: fnhum-10-00695   Journal link: Link

Conference information

NYC Neuromodulation 2017 will focus on technologies and mechanism for advanced brain stimulation in areas that include transcranial direct current stimulation (tDCS), transcranial alternating current stimulation (tACS), transcranial magnetic stimulation (TMS), high-definition transcranial direct current stimulation (HD-tDCS), electroconvulsive therapy (ECT), deep brain stimulation (DBS), and other emerging areas. Applications span treatment of neuropsychiatric disorders, neurorehabilitation, and performance enhancement. Interactive lectures from key opinion leaders and emerging young scientists, poster sessions with abstracts published in Brain Stimulation and extensive opportunities to network with colleagues, along with an exhibit showcase featuring the latest neuromodulation technologies are all part of the main conference agenda.

This conference is among the most forward-looking neuromodulation meetings with the goal of advancing innovation from bench-top to bedside and home. Given the increased media, public, and commercial interest in personal non-invasive brain stimulation, the 2017 meeting will emphasize emerging “consumer” technologies, and their scientific and regulatory barriers. The off-label use of new clinical protocols will be addressed from scientific, medical, and regulatory perspectives. The conference will also focus on timely and novel targets of neuromodulation including glia, as well as new waveforms including high-rate (10 kHz) stimulation. Representatives from funding agencies and journal editors will be available to discuss priorities. NYC Neuromodulation is the largest meeting focused on non-invasive neuromodulation in North America, but this year it considers the role of invasive and non-invasive techniques in the continuum of care.

Chair: Marom Bikson

Front. Hum. Neurosci., 12 January 2017 | https://doi.org/10.3389/fnhum.2016.00695

Cerebellar tDCS: A Novel Approach to Augment Language Treatment Post-stroke

People with post-stroke aphasia may have some degree of chronic deficit for which current rehabilitative treatments are variably effective. Accumulating evidence suggests that transcranial direct current stimulation (tDCS) may be useful for enhancing the effects of behavioral aphasia treatment. However, it remains unclear which brain regions should be stimulated to optimize effects on language recovery. Here, we report on the therapeutic potential of right cerebellar tDCS in augmenting language recovery in SMY, who sustained bilateral MCA infarct resulting in aphasia and anarthria. We investigated the effects of 15 sessions of anodal cerebellar tDCS coupled with spelling therapy using a randomized, double-blind, sham controlled within-subject crossover trial. We also investigated changes in functional connectivity using resting state functional magnetic resonance imaging before and 2 months post-treatment. Both anodal and sham treatments resulted in improved spelling to dictation for trained and untrained words immediately after and 2 months post-treatment. However, there was greater improvement with tDCS than with sham, especially for untrained words. Further, generalization to written picture naming was only noted during tDCS but not with sham. The resting state functional connectivity data indicate that improvement in spelling was accompanied by an increase in cerebro-cerebellar network connectivity. These results highlight the therapeutic potential of right cerebellar tDCS to augment spelling therapy in an individual with large bilateral chronic strokes.

Full paper

Journal Link

Marom Bikson is quoted in two scientific magazines on his work on devices for non-invasive neuromodulation

“Do DIY Brain-Booster Devices Work?” Scientific American. Jan 10, 2017 LINK

“Zapping the brain really does seem to improve depression”, New Scientist. Jan 9, 2017 LINK

image courtesy of Caputron.

Use of Computational Modeling to Inform tDCS Electrode Montages for the Promotion of Language Recovery in Post-stroke Aphasia.

Galletta EE, Cancelli A, Cottone C, Simonelli I, Tecchio F, Bikson M, Marangolo P.
Brain Stimul. 2015 Nov-Dec;8(6):1108-15. doi: 10.1016/j.brs.2015.06.018.

Download PDF

Shin D, Khadka N, Fan J, Bikson M, Fu B. 2016
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Download: PDF published in  SPIE Medical Imaging– DOI

Abstract
Transcranial Direct Current Stimulation (tDCS) is a non-invasive electrical stimulation technique investigated for a broad range of medical and performance indications. Whereas prior studies have focused exclusively on direct neuron polarization, our hypothesis is that tDCS directly modulates endothelial cells leading to transient changes in blood-brain-barrier (BBB) permeability (P) that are highly meaningful for neuronal activity. For this, we developed state-of-the-art imaging and animal models to quantify P to various sized solutes after tDCS treatment. tDCS was administered using a constant current stimulator to deliver a 1mA current to the right frontal cortex of rat (approximately 2 mm posterior to bregma and 2 mm right to sagittal suture) to obtain similar physiological outcome as that in the human tDCS application studies. Sodium fluorescein (MW=376), or FITC-dextrans (20K and 70K), in 1% BSA mammalian Ringer was injected into the rat (SD, 250-300g) cerebral circulation via the ipsilateral carotid artery by a syringe pump at a constant rate of ~3 ml/min. To determine P, multiphoton microscopy with 800-850 nm wavelength laser was applied to take the images from the region of interest (ROI) with proper microvessels, which are 100-200 micron below the pia mater. It shows that the relative increase in P is about 8-fold for small solute, sodium fluorescein, ~35-fold for both intermediate sized (Dex-20k) and large (Dex-70k) solutes, 10 min after 20 min tDCS pretreatment. All of the increased permeability returns to the control after 20 min post treatment. The results confirmed our hypothesis.

Fall 2016 Seminar Series Fall 2016 Seminar Series Department of Biomedical Engineering Wednesday, Nov. 30 @ 3PM in Steinman Hall Rm 402

Patient-centric innovation intersection

Dr. Hugo Caicedo

Janssen-Johnson & Johnson Pharmaceutical R&D

Abstract: The current FDA-based roadmap to drug and product development as well as regulatory decision- making and labeling, is based on four Clinical outcome assessments (COAs): Patient-reported outcome (PRO) measures, Clinician-reported outcome (ClinRO) measures, Observer-reported outcome (ObsRO) measures, and Performance outcome (PerfO) measures. In general, COAs are used to determine whether or not a therapy has demonstrated a net clinical benefit in a disease or health condition, in other words COAs assess safety and efficacy of a therapy. Under these conditions, individuals are subjected to “adequate and well-controlled studies”. The gap, however, is that in real life patients, in their natural environments, are under neither adequate nor well-controlled conditions, which limits both our capacity to understand the patient experience and our ability to develop innovated & targeted healthcare solutions. Additionally, current highly homogeneous and randomized clinical trials (RCTs) do not shed light on patient adherence to those therapies; about 50% of the patients with chronic diseases do not comply with medication therapy. During my presentation, I will talk about how three paradigms (Real World Evidence (RWE), Digital Analytics and Design Thinking) can converge and form a model that I created, the “Patient-centric innovation intersection”, to enable actionable insights for the development of targeted healthcare solutions, with particular focus in Diabetes therapy adherence.

Biosketch: Dr. Hugo Caicedo is a scientist subject matter expert in microfluidics, biomedical engineering and consumer healthcare at Janssen-Johnson & Johnson Pharmaceutical R&D in the Philadelphia area. There, he conducts preclinical research on drug discovery as well as strategic design on healthcare innovation to translate relevant science and technology into high-value partnerships that enable differentiated healthcare solutions. Currently, he is also a scholar trainee at the Corporate Sustainability and Innovation program at Harvard University. Dr. Caicedo holds a B.S in Electronics Engineering from the Universidad del Valle (Cali-Colombia) and a Ph.D. in Biomedical Engineering from the University of Illinois at Chicago (UIC). He was the recipient of MIT, Bogazicy University, Antalya University (Turkey) and UniversitéPierre and Marie Curie (France) pre-doctoral fellowships as well as one Harvard-MIT/HST post-doctoral fellowship. Dr. Caicedo has multiple publications including several peer-reviewed papers, two book chapters and a provisional patent application. Additionally, he has been awarded more than 20 recognition awards including: 2011, Ph.D student, African Colombian of the year in academia; 2012, Mayor’s Civic Merit Medal of Cali given directly by the President of Colombia; 2012, Distinguished PhD Student speaker at the 3rd US-Turkey Advanced Study Institute on Global Healthcare Challenges; 2015, BMES4SUCCESS, highlighted by the US Biomedical Engineering Society, as one of three —and the only member from industry— successful earlier career members in biomedical engineering; and 2016 Honorable Speaker invitation at the Biotechnology World Convention in Sao Paulo, Brazil.

Textbook of Neuromodulation
Principles, Methods and Clinical Applications

Springer. ISBN: 978-1-4939-1407-4 

Methods and Technologies for Low-Intensity Transcranial Electrical Stimulation: Waveforms, Terminology, and Historical Notes
Page 7-16. Berkan Guleyupoglu, Pedro Schestatsky, Felipe Fregni, Marom Bikson

PDF: 10-1007978-1-4939-1408-12

A Role of Computational Modeling in Customization of Transcranial Direct Current Stimulation for Susceptible Populations
Dennis Truong, Preet Minhas, Albert Mokrejs, Marom Bikson

PDF: 10-1007978-1-4939-1408-110

Direct current stimulation over the anterior temporal areas boosts semantic processing in primary progressive aphasia.

Teichmann M, Lesoil C, Godard J, Vernet M, Bertrand A, Levy R, Dubois B, Lemoine L, Truong DQ, Bikson M, Kas A, Valero-Cabré A. Ann Neurol. 2016 Nov;80(5):693-707. doi: 10.1002/ana.24766.

Download PDF

Abstract: Objective: Noninvasive brain stimulation in primary progressive aphasia (PPA) is a promising approach. Yet, applied to single cases or insufficiently controlled small-cohort studies, it has not clarified its therapeutic value. We here address the effectiveness of transcranial direct current stimulation (tDCS) on the semantic PPA variant (sv-PPA), applying a rigorous study design to a large, homogeneous sv-PPA cohort. Methods: Using a double-blind, sham-controlled counterbalanced cross-over design, we applied three tDCS condi- tions targeting the temporal poles of 12 sv-PPA patients. Efficiency was assessed by a semantic matching task orthogonally manipulating “living”/”nonliving” categories and verbal/visual modalities. Conforming to predominantly left-lateralized damage in sv-PPA and accounts of interhemispheric inhibition, we applied left hemisphere anodal- excitatory and right hemisphere cathodal-inhibitory tDCS, compared to sham stimulation. Results: Prestimulation data, compared to 15 healthy controls, showed that patients had semantic disorders predomi- nating with living categories in the verbal modality. Stimulation selectively impacted these most impaired domains: Left- excitatory and right-inhibitory tDCS improved semantic accuracy in verbal modality, and right-inhibitory tDCS improved processing speed with living categories and accuracy and processing speed in the combined verbal 3 living condition. Interpretation: Our findings demonstrate the efficiency of tDCS in sv-PPA by generating highly specific intrasemantic effects. They provide “proof of concept” for future applications of tDCS in therapeutic multiday regimes, potentially driv- ing sustained improvement of semantic processing. Our data also support the hotly debated existence of a left temporal- pole network for verbal semantics selectively modulated through both left-excitatory and right-inhibitory brain stimulation.

Contemp Clin Trials. 2016 Nov;51:65-71. doi: 10.1016/j.cct.2016.10.002. Epub 2016 Oct 15.

Study design and methodology for a multicentre, randomised controlled trial of transcranial direct current stimulation as a treatment for unipolar and bipolar depression.

Alonzo A, Aaronson S, Bikson M, Husain M, Lisanby S, Martin D, McClintock SM, McDonald WM, O’Reardon J, Esmailpoor Z, Loo C.

Download PDF: 10-1016j-cct-2016-10-002

Abstract: Transcranial Direct Current Stimulation (tDCS) is a new, non-invasive neuromodulation approach for treating depression that has shown promising efficacy. The aim of this trial was to conduct the first international, multicentre randomised controlled trial of tDCS as a treatment for unipolar and bipolar depression. The study recruited 120 participants across 6 sites in the USA and Australia. Participants received active or sham tDCS (2.5mA, 20 sessions of 30min duration over 4weeks), followed by a 4-week open label active treatment phase and a 4-week taper phase. Mood and neuropsychological outcomes were assessed with the primary antidepressant outcome measure being the Montgomery-Asberg Depression Rating Scale (MADRS). A neuropsychological battery was administered to assess safety and examine cognitive effects. The study also investigated the possible influence of genetic polymorphisms on outcomes. The trial was triple-blinded. Participants, tDCS treaters and study raters were blinded to each participant’s tDCS group allocation in the sham-controlled phase. Specific aspects of tDCS administration, device operation and group allocation were designed to optimise the integrity of blinding. Outcome measures will be tested using a mixed effects repeated measures analysis with the primary factors being Time as a repeated measure, tDCS condition (sham or active) and Diagnosis (unipolar or bipolar). A restricted number of random and fixed factors will be included as required to account for extraneous differences. As a promising treatment, tDCS has excellent potential for translation into widespread clinical use, being cost effective, portable, easy to operate and well tolerated.

Using Soterix Medical 1×1 CT platform: link

New Paper: Tolerability of Repeated Application of Transcranial Electrical Stimulation with Limited Outputs to Healthy Subjects

tolerability_limited_output_paper

Brain Stimulation 2016 May 24. pii: S1935-861X(16)30104-8. doi: 10.1016/j.brs.2016.05.008. [Epub ahead of print]

Abstract: The safety and tolerability of limited output tES in clinical populations support a non-significant risk designation. The tolerability of long-term use in a healthy population had remained untested. We tested the tolerability and compliance of two tES waveforms, tDCS and modulated high frequency transcranial pulsed current stimulation (MHF-tPCS) compared to sham-tDCS, applied to healthy subjects for three to five days (17–20 minutes per day) per week for up to six weeks in a communal setting. MHF-tPCS consisted of asymmetric high-frequency pulses (7–11 kHz) having a peak amplitude of 10–20 mA peak, adjusted by subject, resulting in an average current of 5–7 mA. A total of 100 treatment blind healthy subjects were randomly assigned to one of three treatment groups: tDCS (n = 33), MHF-tPCS (n = 30), or sham-tDCS (n = 37). In order to test the role of waveform, electrode type and montage were fixed across tES and sham-tDCS arms: high-capacity self-adhering electrodes on the right lateral forehead and back of the neck. We conducted 1905 sessions (636 sham-tDCS, 623 tDCS, and 646 MHF-tPCS sessions) on study volunteers over a period of six weeks. Common adverse events were primarily restricted to influences upon the skin and included skin tingling, itching, and mild burning sensations. The incidence of these events in the active tES treatment arms (MHF-tPCS, tDCS) was equivalent or significantly lower than their incidence in the sham-tDCS treatment arm. Other adverse events had a rarity (<5% incidence) that could not be significantly distinguished across the treatment groups. Some subjects were withdrawn from the study due to atypical headache (sham-tDCS n = 2, tDCS n = 2, and MHF-tPCS n = 3), atypical discomfort (sham-tDCS n = 0, tDCS n = 1, and MHF-tPCS n = 1), or atypical skin irritation (sham-tDCS n = 2, tDCS n = 8, and MHF-tPCS n = 1). The rate of compliance, elected sessions completed, for the MHF-tPCS group was significantly greater than the sham-tDCS group’s compliance (p = 0.007). There were no serious adverse events in any treatment condition. We conclude that repeated application of limited output tES across extended periods, limited to the hardware, electrodes, and protocols tested here, is well tolerated in healthy subjects, as previously observed in clinical populations.

Special CCNY BME Seminar Oct 26, 2016 featuring two Neural Engineering Lab researchers.

3 PM in the CCNY BME conference room. Steinman Hall Room 402

Modulating synaptic plasticity with tDCS

Mr. Greg Kronberg

Department of Biomedical Engineering, The City College of New York

Abstract: Synapses allow communication between neurons and guide the flow of information throughout the brain. Modification of synapses in response to experience, or synaptic plasticity, is thought to be a cellular mechanism for learning and memory. Noninvasive tools to alter synaptic plasticity are therefore highly desirable. Recently, transcranial direct current stimulation (tDCS), has received much attention as a such a tool. tDCS is the noninvasive application of weak DC electric current to the brain through electrodes on the scalp. In this talk I will discuss mechanisms by which tDCS may influence synaptic plasticity, and how this can inform tDCS protocols to improve learning and memory

Bio-sketch: Greg Kronberg is currently a PhD student in the Biomedical Engineering department at The City College of New York (CCNY), where he works under Lucas Parra. He received his BS in Biology from the University of Maryland and his MS in Biomedical Engineering from CCNY. His research focuses on the use of electrical brain stimulation to improve learning and memory.

Measurements and models of electric fields in the in vivo human brain during transcranial electric stimulation

Yu (Andy) Huang, Ph.D.

Department of Biomedical Engineering, The City College of New York

Abstract: Transcranial electric stimulation aims to stimulate the brain by applying weak electrical currents at the scalp. However, the magnitude and spatial distribution of electric fields in the human brain are unknown. Here we measure electric potentials intracranially in ten patients and estimate electric fields across the entire brain by leveraging calibrated current-flow models. Electric field magnitudes at the cortical surface reach values of 0.4 V/m, which is at the lower limit of effectiveness in animal studies. When individual anatomy is taken into account, the predicted electric field magnitudes match the recorded values with r=0.77. Modeling white matter anisotropy and different skull compartments does not improve accuracy, but correct magnitude estimates require an adjustment of conductivity values used in the literature. This is the first study to validate and calibrate current-flow models with in vivo intracranial recordings in humans, providing a solid foundation for targeting and interpretation of clinical trials.

Biosketch: Yu (Andy) Huang received his Ph.D. from Department of Biomedical Engineering, City College of New York. His research focuses on neuroimaging, image segmentation and computational modeling of image data. He received his B.S. and M.S. from University of Electronic Science and Technology of China, both in Biomedical Engineering.

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

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.

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

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

Bikson M,Paneri B, Giordano J. The off-label use, utility and potential value of tDCS in the clinical care of particular neuropsychiatric conditions. Journal of Law and the Biosciences, 1–5 doi:10.1093/jlb/lsw044

PDF

Olympic Athletes Are Electrifying Their Brains, and You Can Too

If a brain-stimulation gadget catches on, expect controversy over “brain doping”

IEEE Spectrum, August 21, 2916 Link