Name: stimulation location determination using a 3d digitizer with high-definition transcranial direct current stimulation
Uploaded: 2019-12-20T13:00:00.000+00:00
Duration: 7 min 20 s
Description: Watch this Scientific Journal Video about Stimulation Location Determination using a 3D Digitizer with High-Definition Transcranial Direct Current Stimulation at JoVE.com

This study was supported by the National Natural Science Foundation of China (31972906), Entrepreneurship and Innovation Program for Chongqing Overseas Returned Scholars (cx2017049), Fundamental Research Funds for Central Universities (SWU1809003), Open Research Fund of the Key Laboratory of Mental Health, Institute of Psychology, Chinese Academy of Sciences (KLMH2019K05), Research Innovation Projects of Graduate Student in Chongqing (CYS19117), and the Research Program Funds of the Collaborative Innovation Center of Assessment toward Basic Education Quality at Beijing Normal University (2016-06-014-BZK01, SCSM-2016A2-15003, and JCXQ-C-LA-1). We would like to thank Prof. Ofir Turel for his suggestions on the early draft of this manuscript.

The protocol meets the guidelines of the Institutional Review Board of Southwest University.
1. Determination of Stimulation Location
<ol>
	<li>Review the literature and confirm the stimulation location (here, the rTPJ)19,20,21.</li>
</ol>
2. Preparation of Electrode Holding Cap
NOTE: The following steps are shown in Figure 1.
<ol>
	<li>Ensure that all necessary materials are readily available: the 3D digitizer (Figure 2), standard measurement tape, a marking pen, the headform, and a swimming cap.</li>
	<li>Put the cap on the headform and mark the points on the cap.
	<ol>
		<li>Localize the Vertex (Cz). To do so, first mark the midpoint of the distance between the nasion and inion using a skin marker13,14,22. Then, measure the distance between the pre-auricular points and mark the midpoint. The point at which both points intersect is the Cz.</li>
		<li>Check the location of the center electrode and the return electrodes. Here, the stimulation was applied on rTPJ. The rTPJ roughly corresponds to the midpoint between CP6 and P6 in the 10-10 EEG system19,20,21.</li>
		<li>Find CP6 and P622,23,24,25. According to the proportional requirements of the 10-10 system, locate the approximate location of the rTPJ on the scalp and mark it on the cap.</li>
		<li>Adjust the radius of the four return electrodes based on the objectives11,14,26. After this decision, mark the center electrode and return electrode locations on the cap.</li>
	</ol>
	</li>
</ol>
3. 3D Digitizer Measurement
<ol>
	<li>Scan with the metal scanner to ensure that the environment for 3D digitizer is metal-free.</li>
	<li>Placement of the cap on the subject&#39;s head
	<ol>
		<li>Make sure that the references (Cz, Fpz, Oz, left preauricular point, and right preauricular point) on the cap align with the international 10-10 system for scalp location22. For example, localize the Vertex (Cz) on the scalp and place the cap onto the subject&#39;s head, aligning the cap&#39;s Cz to the subjects.</li>
	</ol>
	</li>
	<li>Arranging the 3D digitizer equipment
	<ol>
		<li>Connect the 3D digitizer to the computer using the Universal Serial Bus (USB) interface and make sure that the digitizer software is available and ready27.</li>
		<li>Put the source in front of the subject and fasten the elastic rope of the sensor around the head. Importantly, make sure that neither the source nor sensor moves during 3D digitizer measurement. 
		NOTE: The source is a magnetic transmitter that emits an electromagnetic dipole field. The sensor is a receiver that detects the field.</li>
		<li>Open the digitizer software on the computer and make sure that the 3D digitizer system communicates with the software.</li>
		<li>Test the accuracy of the stylus. Find a length of 10 cm on the ruler and record the zero graduation and ten graduation, respectively, using the stylus. 
		NOTE: The measurement distance between the two recording points of the 3D digitizer should be captured. Compare the error with the reading from the 3D tracker.</li>
		<li>Select the New icon and create a new subject file. Select the Sessions box, then Reference. 
		NOTE: Using the 3D digitizer stylus, the reference position data (Cz, inion, nasion, left ear, right ear) of the subject are collected according to the software prompts.</li>
		<li>To cater to the requirement of fNIRS experiments, use the Transmitter, Detector, and Channel options. Collect the position data of the center electrode and four return electrodes 3x for the transmitter, detector, and channel, in order to reduce error. Ensure that five electrodes are numbered and localize in turn.</li>
		<li>Save the three files that are generated.</li>
	</ol>
	</li>
</ol>
4. Data Conversion and Spatial Registration
<ol>
	<li>Select the three files into the NIRS-SPM to achieve the real coordinates registration into MNI space28. Affine transform the reference points and five electrode points in participants to the corresponding points in each entry according to the MRI database in MNI space.</li>
	<li>Register the data to anatomical automatic labels and Brodmann areas and register the spatial information of the five electrode points to both of these.</li>
	<li>Compare the coordinates of stimulation in previous research with the obtained coordinates20,29.</li>
	<li>Make a small cut aligned to the five points marked on the cap, such that the plastic casing is embedded snugly into the cap.</li>
</ol>
5. Stimulation
<ol>
	<li>Make sure that participant have no contraindications (i.e., history of neurological or psychiatric disorders) for HD-tDCS1,3 and that they provided written informed consent prior to the study (including HD-tDCS stimulation).</li>
	<li>For device installation, ensure that all the necessary materials are available (Figure 3). Install the device as detailed in published literature14. A brief description is provided below.
	<ol>
		<li>Install the batteries and check that they are charged.</li>
		<li>Connect the conventional tDCS and 4x1 Stimulation Adapter.</li>
		<li>Connect the cables of five Ag/AgCI sintered ring electrodes to the matching receivers on the 4x1 adapter output cable.</li>
		<li>Check that all materials are connected correctly.</li>
	</ol>
	</li>
	<li>Measure the head of the participant and place the cap on the head.
	<ol>
		<li>Embed the five plastic HD casings in the swimming cap.</li>
		<li>Localize the Cz, Fpz, and Oz of the subject13,14. Adjust the reference on the cap to align with the international 10-10 system for scalp locations22. Once the cap is in position, ensure that it does not move.</li>
		<li>Collect the position data of the stimulated brain areas using the 3D digitizer. Make the corresponding adjustments according to the generated data.</li>
	</ol>
	</li>
	<li>Cover the scalp surface with electrically conductive gel. First, carefully separate the hair through the opening of the plastic casing using the end of a plastic syringe, until the scalp is exposed. Then, cover the exposed scalp with the electrically conductive gel through the plastic casing opening on the scalp surface.</li>
	<li>Set the parameters of the tDCS device: quality value, stimulus duration, intensity, and condition setting.
	<ol>
		<li>Turn on the 4x1 Multichannel Stimulation Adapter.</li>
		<li>Ensure that the default setting is SCAN, which shows the impedance of one electrode at a time in the display window by scanning the electrodes14,30,31. Here, the impedance is described as &#34;quality value&#34;. Values below 1.5 indicate sufficient quality14,30,31. In this case, the values were lower than 1. 
		NOTE: If the impedance value exceeds these required limits, open the cap of the plastic casing with high impedance and adjust the hair and electrode to obtain the desired impedance value.</li>
		<li>Press the &#34;MODE SELECT&#34; button and switch from &#34;SCAN&#34; to &#34;PASS&#34;, after the impedance values are acceptable.</li>
		<li>Select the center-anode or center-cathode by pressing the &#34;POLARITY&#34; button. &#34;CENTRAL ANODE&#34; is the default setting.</li>
		<li>Adjust the settings on the conventional tDCS device to include stimulus duration (min), intensity (mA) and sham condition setting. In this case, anodal active stimulation was 1.5 mA, and the stimulus lasted 20 min. Next, push the &#34;RELAX&#34; lever to switch to full current.</li>
		<li>Once everything is set, initiate the stimulation. Press the &#34;START&#34; button, and the DC intensity will ramp up until the target current is reached. The timer will then show the remaining time. 
		NOTE: Some participants may feel uncomfortable during periods of increased DC intensity. In such cases, the current may be moderately decreased slightly for a few seconds by pulling down the &#34;RELAX&#34; lever. Then, push the dolly bar to full current, gradually, when participants feel comfortable again.</li>
	</ol>
	</li>
</ol>
6. Post-stimulation
<ol>
	<li>When the stimulation is over, turn the lever slowly to adjust the current to zero before turning off the power. Otherwise, participants may perceive stinging sensation or dizziness when turning off the power directly.</li>
	<li>After the stimulation, open the plastic cap and remove the Ag/AgCI sintered ring electrodes from the casing.</li>
	<li>Remove the swimming cap and clean the materials. Provide participants with tools to clean their hair.</li>
	<li>Ask participants to fill out a questionnaire after each stimulation session, if necessary (e.g., to measure adverse effects of screening following HD-tDCS, participant tolerance to brain stimulation, etc.; see Supplementary File).</li>
</ol>

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The authors have nothing to disclose.

Compared to traditional tDCS, HD-tDCS increases the focality of stimulation. Typical sites of stimulation are often based on the 10-20 EEG system. However, determining the precise stimulation points beyond this system can be difficult. This paper combines a 3D digitizer with HD-tDCS to determine stimulation points beyond the 10-20 system. It is important to clearly define the steps and precautions for making and using the electrode cap in such cases.
In general, the position of target stimulat...

Transcranial direct current stimulation (tDCS) is a noninvasive technique that modulates cortical excitability with weak direct currents over the scalp. It aims to establish causality between neural excitability and behavior in healthy humans1,2,3. In addition, as a motor neurorehabilitation tool, tDCS is widely used in the treatment of Parkinson's disease, stroke, and cerebral palsy4. Existing evidence suggests that traditional pad-based tDCS produces current flow through a relatively larger brain region5,6,7. High-definition transcranial direct current stimulation (HD-tDCS), with the center ring electrode sitting over a target cortical region surrounded by four return electrodes8,9, increases focality by circumscribing four ring areas5,10. In addition, changes in excitability of the brain induced by HD-tDCS have significantly larger magnitudes and longer durations than those generated by traditional tDCS7,11. Therefore, HD-tDCS is widely used in research7,11.
Noninvasive brain stimulation (NIBS) requires specialized methods to ensure that a stimulation site is present in the standard MNI and Talairach systems12. Neuronavigation is a technique that allows for mapping interactions between transcranial stimuli and the human brain. Its visualization and 3D image data are used for precise stimulation. In both tDCS and HD-tDCS, a common assessment of stimulation sites on the scalp is typically the EEG 10-20 system13,14. This measurement is widely used for placing the tDCS pads and optode holders for functional near infrared spectroscopy (fNIRS) in the initial stage13,14,15.
Determining the precise stimulation points when using the 10-20 system can be difficult (e.g., in the temporo-parietal junction [TPJ]). The best way to solve this is to obtain structural images from participants using magnetic resonance imaging (MRI), then obtain the exact probe position by matching target points to their structural images using digitizing products15. MRI provides good spatial resolution but is expensive to use15,16,17. Moreover, some participants (e.g., those with metal implants, claustrophobic people, pregnant women, etc.) cannot be subjected to MRI scanners. Therefore, there is a strong need for a convenient and efficient way to overcome the abovementioned limitations and increase accuracy in determining stimulation points.
This protocol uses a 3D digitizer to overcome these limitations. Compared to MRI, key advantages of a 3D digitizer are low costs, simple application, and portability. It combines five reference points (i.e., Cz, Fpz, Oz, left preauricular point, and right preauricular point) of individuals with location information of the target stimulation points. Then, it produces a 3D position of electrodes on the subject's head and estimates their cortical positions by fitting with the vast data from the structural image12,15. This probabilistic registration method enables the presentation of transcranial mapping data in the MNI coordinate system without recording a subject's magnetic resonance images. The approach generates anatomical automatic labels and Brodmann areas11.
The 3D digitizer, used to mark space coordinates based on the data from structural images, was first used to determine the position of optodes in fNIRS research18. For those who use HD-tDCS, a 3D digitizer breaks the finite stimulation points of the EEG 10-20 system. The distance of the four return electrodes and center electrode is flexible and can be adjusted as needed. When using the 3D digitizer with this protocol, the coordinates of the rTPJ were obtained, which is beyond the 10-20 system. Also shown are the procedures for targeting and stimulating the right temporo-parietal junction (rTPJ) of the human brain.

<table><tbody><tr><td>1X1 Low Intensity transcranial DC Stimulator</td><td>Soterix Medical</td><td>1300A</td><td></td></tr><tr><td>3-dimensional Polhemus-Patriot Digitizer</td><td>POLHEMUS</td><td>1A0453-001</td><td>PATRIOT system component</td></tr><tr><td>4X1 Multi-Channel Stimulation Interface</td><td>Soterix Medical</td><td>4X1-C3</td><td></td></tr><tr><td>Dell desktop computer</td><td>Dell</td><td>CRFC4J2</td><td>Master computer to run 3D digitizer application</td></tr></tbody></table>

stimulation location determination using a 3d digitizer with high-definition transcranial direct current stimulation

The abundance of neuroimaging data and rapid development of machine learning has made it possible to investigate brain activation patterns. However, causal evidence of brain area activation leading to a behavior is often left missing. Transcranial direct current stimulation (tDCS), which can temporarily alter brain cortical excitability and activity, is a noninvasive neurophysiological tool used to study causal relationships in the human brain. High-definition transcranial direct current stimulation (HD-tDCS) is a noninvasive brain stimulation (NIBS) technique that produces a more focal current compared to conventional tDCS. Traditionally, the stimulation location has been roughly determined through the 10-20 EEG system, because determining precise stimulation points can be difficult. This protocol uses a 3D digitizer with HD-tDCS to increase accuracy in determination of stimulation points. The method is demonstrated using a 3D digitizer for more accurate localization of stimulation points in the right temporo-parietal junction (rTPJ).

Using the methods presented, coordinates of the rTPJ were determined, which requires stimulation points beyond the 10-20 system. First, the circumference of the headform should be similar to the actual head. Here, the length of the nasion to inion of the headform was ~36 cm, and the length between the bilateral preauricular was ~37 cm.
The steps for producing the electrode cap guide the measuring positions of the 10-20 system. Here, Nz, Iz, Cz, Fpz, Oz, Pz, T8, T7, C4, P8, O2, P4, C6, P6, and ...

Watch this Scientific Journal Video about Stimulation Location Determination using a 3D Digitizer with High-Definition Transcranial Direct Current Stimulation at JoVE.com

Stimulation Location Determination using a 3D Digitizer with High-Definition Transcranial Direct Current Stimulation

Presented here is a protocol to achieve higher accuracy in determination of stimulation location combining a 3D digitizer with high-definition transcranial direct current stimulation.

The abundance of neuroimaging data and rapid development of machine learning has made it possible to investigate brain activation patterns. However, ...

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Research

JoVE Journal

Neuroscience

6.8K Views.  Southwest University. Deze methode maakt gebruik van een 10-10-systeem om de beperkingen van transcraniële direct stroom stimulatie elektrode plaatsing te overwinnen, het verbeteren van de nauwkeurigheid en reproduceerbaarheid van de methode. De belangrijkste voordelen van deze techniek zijn de lage kosten, eenvoudige toepassing en draagbaarheid. Deze methode is geschikt voor gebruik met andere technieken, bijvoorbeeld functionele nabij-infrarood spectroscopie, om de locatie van specifieke hersengebieden van bela...

Video: Stimulation Location Determination using a 3D Digitizer with High-Definition Transcranial Direct Current Stimulation

Simultaneous EEG Monitoring During Transcranial Direct Current Stimulation

Transcranial direct current stimulation (tDCS) is a technique that delivers weak electric currents through the scalp. This constant electric current induces shifts in neuronal membrane excitability, resulting in secondary changes in cortical activity. Although tDCS has most of its neuromodulatory effects on the underlying cortex, tDCS effects can also be observed in distant neural networks. Therefore, concomitant EEG monitoring of the effects of tDCS can provide valuable information on the mechanisms of tDCS. In addition, EEG findings can be an important surrogate marker for the effects of tDCS and thus can be used to optimize its parameters. This combined EEG-tDCS system can also be used for preventive treatment of neurological conditions characterized by abnormal peaks of cortical excitability, such as seizures. Such a system would be the basis of a non-invasive closed-loop device. In this article, we present a novel device that is capable of utilizing tDCS and EEG simultaneously. For that, we describe in a step-by-step fashion the main procedures of the application of this device using schematic figures, tables and video demonstrations. Additionally, we provide a literature review on clinical uses of tDCS and its cortical effects measured by EEG techniques.

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique that has shown initial therapeutic effects in several neurological conditions. The main mechanism underlying these therapeutic effects is the modulation of cortical excitability. Therefore, online monitoring of cortical excitability would help guide stimulation parameters and optimize its therapeutic effects. In the present article we review the use of a novel device that combines simultaneous tDCS and EEG monitoring in real time.

Transcranial  direct current stimulation (tDCS) is a technique that delivers weak electric  currents through the scalp. This constant electric current ...

Behavior

Transcranial Direct Current Stimulation and Simultaneous  Functional Magnetic Resonance Imaging

Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that uses weak electrical currents administered to the scalp to manipulate cortical excitability and, consequently, behavior and brain function. In the last decade, numerous studies have addressed short-term and long-term effects of tDCS on different measures of behavioral performance during motor and cognitive tasks, both in healthy individuals and in a number of different patient populations. So far, however, little is known about the neural underpinnings of tDCS-action in humans with regard to large-scale brain networks. This issue can be addressed by combining tDCS with functional brain imaging techniques like functional magnetic resonance imaging (fMRI) or electroencephalography (EEG).
In particular, fMRI is the most widely used brain imaging technique to investigate the neural mechanisms underlying cognition and motor functions. Application of tDCS during fMRI allows analysis of the neural mechanisms underlying behavioral tDCS effects with high spatial resolution across the entire brain. Recent studies using this technique identified stimulation induced changes in task-related functional brain activity at the stimulation site&#160;and also in more distant brain regions, which were associated with behavioral improvement. In addition, tDCS administered during resting-state fMRI allowed identification of widespread changes in whole brain functional connectivity.
Future studies using this combined protocol should yield new insights into the mechanisms of tDCS action in health and disease and new options for more targeted application of tDCS in research and clinical settings. The present manuscript describes this novel technique in a step-by-step fashion, with a focus on technical aspects of tDCS administered during fMRI.

Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique. It has successfully been used in basic research and clinical settings to modulate brain function in humans. This article describes the implementation of tDCS and simultaneous functional magnetic resonance imaging (fMRI), to investigate the neural basis of tDCS effects.

Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that uses weak electrical currents administered to the scalp ...

Electrode Positioning and Montage in Transcranial Direct Current Stimulation

Transcranial direct current stimulation (tDCS) is a technique that has been intensively investigated in the past decade as this method offers a non-invasive and safe alternative to change cortical excitability2. The effects of one session of tDCS can last for several minutes, and its effects depend on polarity of stimulation, such as that cathodal stimulation induces a decrease in cortical excitability, and anodal stimulation induces an increase in cortical excitability that may last beyond the duration of stimulation6. These effects have been explored in cognitive neuroscience and also clinically in a variety of neuropsychiatric disorders &#x2013; especially when applied over several consecutive sessions4. One area that has been attracting attention of neuroscientists and clinicians is the use of tDCS for modulation of pain-related neural networks3,5. Modulation of two main cortical areas in pain research has been explored: primary motor cortex and dorsolateral prefrontal cortex7. Due to the critical role of electrode montage, in this article, we show different alternatives for electrode placement for tDCS clinical trials on pain; discussing advantages and disadvantages of each method of stimulation.

Transcranial direct current stimulation (tDCS) is an established technique to modulate cortical excitability1,2. It has been used as an investigative tool in neuroscience due to its effects on cortical plasticity, easy operation, and safe profile. One area that tDCS has been showing encouraging results is pain alleviation 3-5.

Transcranial direct current stimulation (tDCS) is a technique that has been intensively investigated in the past decade as this method offers a ...

Technique and Considerations in the Use of 4x1 Ring High-definition Transcranial Direct Current Stimulation (HD-tDCS)

High-definition transcranial direct current stimulation (HD-tDCS) has recently been developed as a noninvasive brain stimulation approach that increases the accuracy of current delivery to the brain by using arrays of smaller "high-definition" electrodes, instead of the larger pad-electrodes of conventional tDCS. Targeting is achieved by energizing electrodes placed in predetermined configurations. One of these is the 4x1-ring configuration. In this approach, a center ring electrode (anode or cathode) overlying the target cortical region is surrounded by four return electrodes, which help circumscribe the area of stimulation. Delivery of 4x1-ring HD-tDCS is capable of inducing significant neurophysiological and clinical effects in both healthy subjects and patients. Furthermore, its tolerability is supported by studies using intensities as high as 2.0 milliamperes for up to twenty minutes.
Even though 4x1 HD-tDCS is simple to perform, correct electrode positioning is important in order to accurately stimulate target cortical regions and exert its neuromodulatory effects. The use of electrodes and hardware that have specifically been tested for HD-tDCS is critical for safety and tolerability. Given that most published studies on 4x1 HD-tDCS have targeted the primary motor cortex (M1), particularly for pain-related outcomes, the purpose of this article is to systematically describe its use for M1 stimulation, as well as the considerations to be taken for safe and effective stimulation. However, the methods outlined here can be adapted for other HD-tDCS configurations and cortical targets.

Technique and Considerations in the Use of 4x1 Ring High-definition Transcranial Direct Current Stimulation HD-tDCS

High-definition transcranial direct current stimulation (HD-tDCS), with its 4x1-ring montage, is a noninvasive brain stimulation technique that combines both the neuromodulatory effects of conventional tDCS with increased focality. This article provides a systematic demonstration of the use of 4x1 HD-tDCS, and the considerations needed for safe and effective stimulation.

High-definition transcranial direct current stimulation (HD-tDCS) has recently been developed as a noninvasive brain stimulation approach that increases ...

Medicine

The Combined Use of Transcranial Direct Current Stimulation and Robotic Therapy for the Upper Limb

Neurologic disorders such as stroke and cerebral palsy are leading causes of long-term disability and can lead to severe incapacity and restriction of daily activities due to lower and upper limb impairments. Intensive physical and occupational therapy are still considered main treatments, but new adjunct therapies to standard rehabilitation that may optimize functional outcomes are being studied.
Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that polarizes underlying brain regions through the application of weak direct currents through electrodes on the scalp, modulating cortical excitability. Increased interest in this technique can be attributed to its low cost, ease of use, and effects on human neural plasticity. Recent research has been performed to determine the clinical potential of tDCS in diverse conditions such as depression, Parkinson&#39;s disease, and motor rehabilitation after stroke. tDCS helps enhance brain plasticity and seems to be a promising technique in rehabilitation programs.
A number of robotic devices have been developed to assist in the rehabilitation of upper limb function after stroke. The rehabilitation of motor deficits is often a long process requiring multidisciplinary approaches for a patient to achieve maximum independence. These devices do not intend to replace manual rehabilitation therapy; instead, they were designed as an additional tool to rehabilitation programs, allowing immediate perception of results and tracking of improvements, thus helping patients to stay motivated.
Both tDSC and robot-assisted therapy are promising add-ons to stroke rehabilitation and target the modulation of brain plasticity, with several reports describing their use to be associated with conventional therapy and the improvement of therapeutic outcomes. However, more recently, some small clinical trials have been developed that describe the associated use of tDCS and robot-assisted therapy in stroke rehabilitation. In this article, we describe the combined methods used in our institute for improving motor performance after stroke.

The combined use of transcranial direct current stimulation and robotic therapy as an add-on for conventional rehabilitation therapy may result in improved therapeutic outcomes due to modulation of brain plasticity. In this article, we describe the combined methods used in our institute for improving motor performance after stroke.

Neurologic disorders such as stroke and cerebral palsy are leading causes of long-term disability and can lead to severe incapacity and restriction of ...

Non-Invasive Modulation and Robotic Mapping of Motor Cortex in the Developing Brain

Mapping the motor cortex with transcranial magnetic stimulation (TMS) has potential to interrogate motor cortex physiology and plasticity but carries unique challenges in children. Similarly, transcranial direct current stimulation (tDCS) can improve motor learning in adults but has only recently been applied to children. The use of tDCS and emerging techniques like high&#8211;definition tDCS (HD-tDCS) require special methodological considerations in the developing brain. Robotic TMS motor mapping may confer unique advantages for mapping, particularly in the developing brain. Here, we aim to provide a practical, standardized approach for two integrated methods capable of simultaneously exploring motor cortex modulation and motor maps in children. First, we describe a protocol for robotic TMS motor mapping. Individualized, MRI-navigated 12x12 grids centered on the motor cortex guide a robot to administer single-pulse TMS. Mean motor evoked potential (MEP) amplitudes per grid point are used to generate 3D motor maps of individual hand muscles with outcomes including map area, volume, and center of gravity. Tools to measure safety and tolerability of both methods are also included. Second, we describe the application of both tDCS and HD-tDCS to modulate the motor cortex and motor learning. An experimental training paradigm and sample results are described. These methods will advance the application of non-invasive brain stimulation in children.

We demonstrate protocols for the modulation (tDCS, HD-tDCS) and mapping (robotic TMS) of the motor cortex in children.

Mapping the motor cortex with transcranial magnetic stimulation (TMS) has potential to interrogate motor cortex physiology and plasticity but carries ...

Simultaneous Application of Transcranial Direct Current Stimulation during Virtual Reality Exposure

Transcranial direct current stimulation (tDCS) is a form of non-invasive brain stimulation that changes the likelihood of neuronal firing through modulation of neural resting membranes. Compared to other techniques, tDCS is relatively safe, cost-effective, and can be administered while individuals are engaged in controlled, specific cognitive processes. This latter point is important as tDCS may predominantly affect intrinsically active neural regions. In an effort to test tDCS as a potential treatment for psychiatric illness, the protocol described here outlines a novel procedure that allows the simultaneous application of tDCS during exposure to trauma-related cues using virtual reality (tDCS+VR) for veterans with posttraumatic stress disorder (NCT03372460). In this double-blind protocol, participants are assigned to either receive 2 mA tDCS, or sham stimulation, for 25 minutes while passively watching three 8-minute standardized virtual reality drives through Iraq or Afghanistan, with virtual reality events increasing in intensity during each drive. Participants undergo six sessions of tDCS+VR over the course of 2-3 weeks, and psychophysiology (skin conductance reactivity) is measured throughout each session. This allows testing for within and between session changes in hyperarousal to virtual reality events and adjunctive effects of tDCS. Stimulation is delivered through a built-in rechargeable battery-driven tDCS device using a 1 (anode) x 1 (cathode) unilateral electrode set-up. Each electrode is placed in a 3 x 3 cm (current density 2.22 A/m2) reusable sponge pocket saturated with 0.9% normal saline. Sponges with electrodes are attached to the participant&#8217;s skull using a rubber headband with the electrodes placed such that they target regions within the ventromedial prefrontal cortex. The virtual reality headset is placed over the tDCS montage in such a way as to avoid electrode interference.

This manuscript outlines a novel protocol to allow the simultaneous application of transcranial direct current stimulation during exposure to warzone trauma-related cues using virtual reality for veterans with posttraumatic stress disorder.

Transcranial direct current stimulation (tDCS) is a form of non-invasive brain stimulation that changes the likelihood of neuronal firing through ...

Transcranial Direct Current Stimulation (tDCS) for Memory Enhancement

Memory enhancement is one of the great challenges in cognitive neuroscience and neurorehabilitation. Among various techniques used for memory enhancement, transcranial direct current stimulation (tDCS) is emerging as an especially promising tool for improvement of memory functions in a non-invasive manner. Here, we present a tDCS protocol that can be applied for memory enhancement in healthy-participant studies as well as in aging and dementia research. The protocol uses weak constant anodal current to stimulate cortical targets within cortico-hippocampal functional network engaged in memory processes. The target electrode is placed either on the posterior parietal cortex (PPC) or the dorsolateral prefrontal cortex (DLPFC), while the return electrode is placed extracranially (i.e., on the contralateral cheek). In addition, we outline a more advanced method of oscillatory tDCS, mimicking a natural brain rhythm to promote hippocampus-dependent memory functions, which can be applied in a personalized and non-personalized manner. We present illustrative results of associative and working memory improvement following single tDCS sessions (20 minutes) in which the described electrode montages were used with current intensities between 1.5 mA and 1.8 mA. Finally, we discuss crucial steps in the protocol and methodological decisions that must be made when designing a tDCS study on memory.

Transcranial Direct Current Stimulation tDCS for Memory Enhancement

A protocol for memory enhancement by using transcranial direct current stimulation (tDCS) targeting dorsolateral prefrontal and posterior parietal cortices, as core cortical nodes within hippocampo-cortical network, is presented. The protocol has been well evaluated in healthy-participant studies and is applicable to aging and dementia research as well.

Memory enhancement is one of the great challenges in cognitive neuroscience and neurorehabilitation. Among various techniques used for memory enhancement, ...

Mapping Cerebral Blood Flow and Electrical Fields: Electrode Placement in Mice

Placement of Extracranial Stimulating Electrodes and Measurement of Cerebral Blood Flow and Intracranial Electrical Fields in Anesthetized Mice

The detection of cerebral blood flow (CBF) responses to various forms of neuronal activation is critical for understanding dynamic brain function and variations in the substrate supply to the brain. This paper describes a protocol for measuring CBF responses to transcranial alternating current stimulation (tACS). Dose-response curves are estimated both from the CBF change occurring with tACS (mA) and from the intracranial electric field (mV/mm). We estimate the intracranial electrical field based on the different amplitudes measured by glass microelectrodes within each side of the brain. In this paper, we describe the experimental setup, which involves using either bilateral laser Doppler (LD) probes or laser speckle imaging (LSI) to measure the CBF; as a result, this setup requires anesthesia for the electrode placement and stability. We present a correlation between the CBF response and the current as a function of age, showing a significantly larger response at higher currents (1.5 mA and 2.0 mA) in young control animals (12-14 weeks) compared to older animals (28-32 weeks) (p &lt; 0.005 difference). We also demonstrate a significant CBF response at electrical field strengths &lt;5 mV/mm, which is an important consideration for eventual human studies. These CBF responses are also strongly influenced by the use of anesthesia compared to awake animals, the respiration control (i.e., intubated vs. spontaneous breathing), systemic factors (i.e., CO2), and local conduction within the blood vessels, which is mediated by pericytes and endothelial cells. Likewise, more detailed imaging/recording techniques may limit the field size from the entire brain to only a small region. We describe the use of extracranial electrodes for applying tACS stimulation, including both homemade and commercial electrode designs for rodents, the concurrent measurement of the CBF and intracranial electrical field using bilateral glass DC recording electrodes, and the imaging approaches. We are currently applying these techniques to implement a closed-loop format for augmenting the CBF in animal models of Alzheimer's disease and stroke.

Author Spotlight: Stimulation-Based Approach to Improve Cerebral Blood Flow in Alzheimer's Model 

We describe a protocol for assessing dose-response curves for extracranial stimulation in terms of brain electrical field measurements and a relevant biomarker-cerebral blood flow. Since this protocol involves invasive electrode placement into the brain, general anesthesia is needed, with spontaneous breathing preferred rather than controlled respirations.

The detection of cerebral blood flow (CBF) responses to various forms of neuronal activation is critical for understanding dynamic brain function and ...

Neuronavigated tDCS for Enhanced Electrode Placement Accuracy in fMRI Studies

Neuronavigated Focalized Transcranial Direct Current Stimulation Administered During Functional Magnetic Resonance Imaging

Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that allows the modulation of the excitability and plasticity of the human brain. Focalized tDCS setups use specific electrode arrangements to constrain the current flow to circumscribed brain regions. However, the effectiveness of focalized tDCS can be compromised by electrode positioning errors on the scalp, resulting in significant reductions of the current dose reaching the target brain regions for tDCS. Electrode placement guided by neuronavigation based on the individual&#39;s head and brain anatomy derived from structural magnetic resonance imaging (MRI) data may be suited to improve positioning accuracy.
This protocol describes the method of neuronavigated electrode placement for a focalized tDCS setup, which is suitable for concurrent administration during functional MRI (fMRI). We also quantify the accuracy of electrode placement and investigate electrode drift in a concurrent tDCS-fMRI experiment. Critical steps involve the optimization of electrode positions based on current modeling that considers the individual&#39;s head and brain anatomy, the implementation of neuronavigated electrode placement on the scalp, and the administration of optimized and focal tDCS during fMRI.
The regional precision of electrode placement is quantified using the Euclidean norm (L2&#160;Norm) to determine deviations of the actual from the intended electrode positions during a concurrent tDCS-fMRI study. Any potential displacement of electrodes (drift) during the experiment is investigated by comparing actual electrode positions before and after the fMRI acquisition. In addition, we directly compare the placement accuracy of neuronavigated tDCS to that achieved by a scalp-based targeting approach (a 10-20 Electroencephalography (EEG) system). These analyses demonstrate superior placement accuracy for neuronavigation compared to scalp-based electrode placement and negligible electrode drift across a 20 min scanning period.

This protocol describes the method of neuronavigated electrode placement for focal, transcranial direct current stimulation (tDCS) administered during functional magnetic resonance imaging (fMRI).

Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that allows the modulation of the excitability and plasticity ...

Stimulation Location Determination using a 3D Digitizer with High-Definition Transcranial Direct Current Stimulation

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