Non-Invasive Electrical Brain Stimulation Montages for Modulation of Human Motor Function

Summary

Non-invasive electrical brain stimulation can modulate cortical function and behavior, both for research and clinical purposes. This protocol describes different brain stimulation approaches for modulation of the human motor system.

Abstract

Non-invasive electrical brain stimulation (NEBS) is used to modulate brain function and behavior, both for research and clinical purposes. In particular, NEBS can be applied transcranially either as direct current stimulation (tDCS) or alternating current stimulation (tACS). These stimulation types exert time-, dose- and in the case of tDCS polarity-specific effects on motor function and skill learning in healthy subjects. Lately, tDCS has been used to augment the therapy of motor disabilities in patients with stroke or movement disorders. This article provides a step-by-step protocol for targeting the primary motor cortex with tDCS and transcranial random noise stimulation (tRNS), a specific form of tACS using an electrical current applied randomly within a pre-defined frequency range. The setup of two different stimulation montages is explained. In both montages the emitting electrode (the anode for tDCS) is placed on the primary motor cortex of interest. For unilateral motor cortex stimulation the receiving electrode is placed on the contralateral forehead while for bilateral motor cortex stimulation the receiving electrode is placed on the opposite primary motor cortex. The advantages and disadvantages of each montage for the modulation of cortical excitability and motor function including learning are discussed, as well as safety, tolerability and blinding aspects.

Introduction

Non-invasive electrical brain stimulation (NEBS), the administration of electrical currents to the brain through the intact skull, can modify brain function and behavior^1-3. To optimize the therapeutic potential of NEBS strategies understanding the underlying mechanisms leading to neurophysiological and behavioral effects is still needed. Standardization of application across different laboratories and full transparency of stimulation procedures provides the basis for comparability of data which supports reliable interpretation of results and evaluation of the proposed mechanisms of action. Transcranial direct current stimulation (tDCS....

Protocol

Ethics statement: Human studies require written informed consent of participants before study entry. Obtain approval by the relevant ethics committee before recruitment of participants. Make sure studies are in accordance with the Declaration of Helsinki. The representative findings reported here (Figure 4) are based on a study performed in accordance with the Declaration of Helsinki amended by the 59^th WMA General Assembly, Seoul, October 2008 and approved by the local Ethics Committee of the University of Freiburg. All subjects gave written informed consent before study entry⁶.

1. Safety Screening

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Results

To investigate the effects of NEBS on the human motor system it is important to consider appropriate outcome measures. One advantage of the motor system is the accessibility of the cortical representations by electrophysiological tools. Motor evoked potentials are frequently used as an indicator of motor cortical excitability. After application of 9 or more minutes of anodal tDCS at a current density of 29 µA/cm², motor cortical excitability is increased for at least 30 min in .......

Discussion

This protocol describes typical materials and procedural steps for modulation of hand motor function and skill learning using NEBS, specifically unilateral and bilateral M1 stimulation for anodal tDCS, and unilateral tRNS. Before choosing a particular NEBS protocol for a human motor system study, e.g., in the context of motor learning, methodological aspects (safety, tolerability, blinding) as well as conceptual aspects (montage or current type specific effects on a particular brain region) need to be taken into.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
NEBS device (DC Stimulator plus)	Neuroconn
Electrode cables	Neuroconn
Conductive-rubber electrodes	Neuroconn		5x5 cm
Perforated sponge bags	Neuroconn		5x5 cm
Non-conductive rubber sponge cover	Amrex-Zetron	FG-02-A103	Rubber pad 3"*3"
NaCl isotonic solution	B. Braun Melsungen AG	A1151	Ecoflac, 0,9%
Cotton crepe bandage	Paul Hartmann AG	931004	8x5m, textile elasticity
Adhesive tape (Leukofix)	BSN medical	02122-00	2,5cm*5m
Skin preparation paste	Weaver	10-30
Magnetic stimulator	Magstim	3010-00	Magstim 200
EMG conductive paste	GE Medical Systems	217083
EMG bipolar electrodes	e.g., Natus Medical Inc. Viking 4
EMG amplifier	e.g., Natus Medical Inc. Viking 4
Cable for EMG signal transmission	e.g., Natus Medical Inc. Viking 4
Data acquisition unit	Cambridge Electronic Design (CED)	MK1401-3	AD converter
Computer for signal recording and offline analysis
Signal 4.0.9	Cambridge Electronic Design (CED)		Software
non-permanent skin marker	Edding	8020	1 mm, blue