Journal of Neuroscience Methods 219 (2013) 297–311 Contents lists available at ScienceDirect Journal of Neuroscience Methods jou rnal homepage: www.elsevier.com/locate/jneumeth Clinical Neuroscience Classification of methods in transcranial Electrical Stimulation (tES) and evolving strategy from historical approaches to contemporary innovations a b d,e,f,g c,d Berkan Guleyupoglu , Pedro Schestatsky , Dylan Edwards , Felipe Fregni , a,∗ Marom Bikson a Neural Engineering Laboratory, Department of Biomedical Engineering, The City College of New York of CUNY, New York, NY 10031, USA b Department of Internal Medicine, Universida de Federal do Rio Grande do Sul, CAPES, Brazil c Laboratory of Neuromodulation, Spaulding Rehabilitation Hospital, Harvard Medical School, Boston, MA 02114, USA d Berenson-Allen Center for Noninvasive Brain Stimulation, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA e Burke Medical Research Institute, White Plains, NY, USA f Department of Neurology and Neuroscience, Weill Cornell Medical College, New York, NY, USA g Australian Neuromuscular Research Institute and the Centre for Neuromuscular and Neurological Disorders, University of Western Australia, Nedlands, Western Australia, Australia h i g h l i g h t s • Cranial Electrotherapy Stimulation is a descendant of Electrosleep. • Transcutaneous Cranial Electrical Stimulation is a descendant of Electroanesthesia. • There is a need for better reporting of dosages and devices used. • There is a shift to basic dosages in contemporary approaches. a r t i c l e i n f o a b s t r a c t Article history: Transcranial Electrical Stimulation (tES) encompasses all methods of non-invasive current application Received 20 February 2013 to the brain used in research and clinical practice. We present the first comprehensive and techni- Received in revised form 17 July 2013 cal review, explaining the evolution of tES in both terminology and dosage over the past 100 years of Accepted 25 July 2013 research to present day. Current transcranial Pulsed Current Stimulation (tPCS) approaches such as Cranial Electrotherapy Stimulation (CES) descended from Electrosleep (ES) through Cranial Electro-stimulation Keywords: Therapy (CET), Transcerebral Electrotherapy (TCET), and NeuroElectric Therapy (NET) while others like Electrosleep Transcutaneous Cranial Electrical Stimulation (TCES) descended from Electroanesthesia (EA) through Electroanesthesia Electronarcosis Limoge, and Interferential Stimulation. Prior to a contemporary resurgence in interest, variations of trans- TCES cranial Direct Current Stimulation were explored intermittently, including Polarizing current, Galvanic CET Vestibular Stimulation (GVS), and Transcranial Micropolarization. The development of these approaches CES alongside Electroconvulsive Therapy (ECT) and pharmacological developments are considered. Both the TCET roots and unique features of contemporary approaches such as transcranial Alternating Current Stimu- EA lation (tACS) and transcranial Random Noise Stimulation (tRNS) are discussed. Trends and incremental ES developments in electrode montage and waveform spanning decades are presented leading to the present EN day. Commercial devices, seminal conferences, and regulatory decisions are noted. We conclude with six tDCS rules on how increasing medical and technological sophistication may now be leveraged for broader HD-tDCS tES success and adoption of tES. ECT ∗ Corresponding author at: Department of Biomedical Engineering, The City College of New York, 160 Convent Avenue, T-403B Steinman Hall, New York, NY 10031, USA. Tel.: +1 212 650 6791; fax: +1 212 650 6727. E-mail address: [email protected] (M. Bikson). 0165-0270/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jneumeth.2013.07.016 298 B. Guleyupoglu et al. / Journal of Neuroscience Methods 219 (2013) 297–311 FEAST NET tPCS Electrostimulation tRNS Limoge Interferential Stimulation tACS Historical Dosage Contemporary Electrotherapy Cranial Transcerebral Transcutaneous History Direct Alternating Pulsed © 2013 Elsevier B.V. All rights reserved. Contents 1. Scope and approach . 298 2. Historical development . 302 2.1. Developments from Electrosleep to Cranial Electrotherapy Stimulation . 302 2.2. Developments from Electroanesthesia to Limoge current and other related methods . 302 2.3. DC stimulation . 304 2.4. ECT . 305 2.5. Contemporary approaches . 305 2.6. “TES” . 305 2.7. Non-cranial therapies . 305 3. Dosage . 306 3.1. Electrosleep and derivative techniques . 306 3.2. Electroanesthesia and derivative techniques . 306 3.3. Transcranial Direct Current Stimulation/transcranial Random Noise Stimulation/transcranial Alternating Current Stimulation. 307 3.4. “Transcranial Electrical Stimulation”. 307 3.5. Electroconvulsive therapy . 307 3.6. High-Definition transcranial Direct Current Stimulation . 307 4. Present outlook and summary – six rules for success of tES technology . 307 References . 309 (ES) through Cranial Electro-stimulation Therapy (CET), Transcere- 1. Scope and approach bral Electrotherapy (TCET), and NeuroElectric Therapy (NET); (2) Electroanestheisia went through several periods of waning inter- Transcranial Electrical Stimulation (tES) encompasses all forms est and resurgence when new waveform variations were proposed of research and clinical application of electrical currents to the brain including Transcutaneous Cranial Electrical Stimulation (TCES), non-invasively using (at least one) electrodes on the head. The Limoge, and Interferential Stimulation; (3) Polarizing or Direct Cur- dose of tES is defined by the electrode montage and the stimulation rent Stimulation includes recent transcranial Direct Current Stimu- waveform applied to the electrode (Peterchev et al., 2012). There lation, Transcranial Micropolarization, High-Definition transcranial has been a resurgence of interest since 2000, but “modern” tES Direct Current Stimulation (HD-tDCS) and Galvanic Vestibular developed incrementally over a century. This review provides the Stimulation (GVS); (4) Electroconvulsive Therapy (ECT), initially first comprehensive organization of approaches and dose used in called Electroshock Therapy, evolved in technique and dose, such modern tES since 1900. Though ‘dose’ is used historically in differ- as Focal Electrically Administered Seizure Therapy (FEAST); (5) ent context, throughout this review we follow the strict convention Finally, we categorize “contemporary” approaches that have been of Peterchev 2012 (Peterchev et al., 2012), where tES dosage is explored intensely over the last decade, such as transcranial Alter- defined by electrode parameters (including number, position, nating Current Stimulation (tACS), transcranial Sinusoidal Direct shape, and composition) and all details of stimulation waveform Current Stimulation (tSDCS), and transcranial Random Noise Stim- (including intensity and general waveform and when relevant ulation (tRNS). Though analogs to these contemporary approaches pulse shape, amplitude, width, polarity, repetition frequency; can be identified in earlier literature, contemporary methods con- duration of and interval between bursts or trains of pulses, interval tain dose features that motivate us to consider them novel as a between stimulation sessions and total number of sessions). category. Contemporary approaches to some extent reflect a “re- This process involves defining the litany of terminology that has boot” of tES approach, typically employing basic, well documented, developed and evolved around tES. We explain the terminology as and well-defined waveforms (e.g. one sinusoid; Paulus, 2011) in used contemporarily by researchers. Particular attention is paid to contrast to the increasingly complex waveforms developed (though historically linked categories of tES, “streams”, of which we identify not always justified) over decades in some streams. four that span decades plus “contemporary” approaches (Fig. 1): (1) As our technical focus is on dose clarification and classifica- Cranial Electrical Stimulation (CES) descended from Electrosleep tion, we minimize comments on the clinical efficacy or safety of B. Guleyupoglu et al. / Journal of Neuroscience Methods 219 (2013) 297–311 299 Fig. 1. A general timeline of ES/EA noting key points in the history from 1902 until 2011 as well as their relation to DC stimulation. A brief history of DC stimulation is also presented in this table. Other cranial therapies are mentioned for a complete cranial stimulation history and non-cranial therapies are mentioned for their connection to ES/EA. Arrows are used to connect historically related points while the horizontal purple lines are used to point out DC use in historically pulsed applications. any approaches except in special cases where findings resulted nomenclature. We did not attempt to perform an exhaustive cata- in historically notable and sudden changes in dose or terminol- loging of tES publications. ogy. We note specific conferences and regulatory agencies that Though we do not comment on efficacy, the nominal indications helped identify and shape the field of transcranial Electrical Stim- for tES use (intended clinical outcomes) are noted when contex- ulation including establishing terminology. Commercial (brand) tually relevant, especially for many historical streams (defined names of devices are noted ad hoc for context and linked to dose above). There are instances in which researchers used terminol- terms where appropriate. We do not comment