We thank Mr. Rodrigo de Souza for assistance in maintaining mouse colonies. L.A.V.M is a CAPES postdoctoral fellow. This work was supported by the grant PRONEX (FAPEMIG: APQ-00476-14).

Individually-housed male adult (8-12 weeks) C57BL/6 mice were used in this experiment. Animals received proper care before, during and after experimental procedures with food and water ad libitum. All procedures were approved by the animal ethics committee from Federal University of Minas Gerais (protocol number 59/2014).
1. Electrode Placement
<ol>
	<li>Sedating and fixating the animal onto the stereotaxic apparatus
	<ol>
		<li>Sterilize all the necessary surgical instruments. 
		Note. Surgical instruments were sterilized for 3 minutes at 440 &#176;C. Cotton swabs were autoclaved at 20 psi (pounds per square inch) at 121 &#176;C for 20 min.</li>
		<li>Adjust the thermal platform controller to 37 &#176;C.</li>
		<li>Weigh the animal and calculate the appropriate dose for anesthesia induction. Use a mixture of ketamine and xylazine at a dose of 100 mg/kg ketamine and 8 mg/kg xylazine, given intraperitoneally (needle size, 31 G). The animal should fall asleep within 2 to 3 min.</li>
		<li>Use an electric shaver or razor to shave down the surgical site.</li>
		<li>Place the animal onto the stereotaxic apparatus over the pre-warmed heating plate.</li>
		<li>Hold the animal&#39;s head and insert the tip ear bars into each of the animal&#39;s ears to fix it to the stereotaxic platform.</li>
		<li>Verify there is no lateral head shifting and little vertical movement after by slowly shifting the animal&#39;s head positioning.</li>
		<li>Gently slide the anesthesia mask over the mouse&#39;s nose and fix it in place by tightening the screw.</li>
		<li>Set the isoflurane to 1% with 1.0 L/min of O2.</li>
		<li>Apply eye ointment to the animal&#39;s eyes to prevent corneal drying during the surgery.</li>
	</ol>
	</li>
	<li>Attaching the implant to the animal&#39;s head
	<ol>
		<li>Use the cotton swabs to prepare the surgical site with three alternating scrubs of povidone-iodine (or 2% chlorhexidine) and 70% ethanol.</li>
		<li>Use a pair of tweezers to verify anesthesia depth by lightly squeezing the animal&#39;s toes and verifying the loss of animal&#39;s pedal withdrawal (toe pinch) reflex.</li>
		<li>Make an incision about 3 mm posterior to the animal&#39;s ear line and stop at the eye line. The incision site must have approximately 1 cm in length to be large enough to receive the implant.</li>
		<li>Gently scrape the cranium with a bone scraper to improve glue and cement adherence. Do this light handedly with the intention of creating micro scratches.</li>
		<li>Carefully position surgical hooks to the loose skin to maintain an open surgical field and free of obstructions such as skin and fur.</li>
		<li>Use a sterile cotton swab to dry the animal&#39;s scalp.</li>
		<li>Use a dissecting microscope to visualize the top of the animal&#39;s cranium.</li>
		<li>Attach a needle to the stereotaxic holder and locate the bregma. Position the needle directly above the animal&#39;s head slightly touching the bregma.</li>
		<li>Zero out all coordinates on the digital tracer and then raise the needle.</li>
		<li>Fix the tDCS implant on the stereotaxic holder. Position the implant over the animal&#39;s head and lower it slowly onto the region of interest using the proper stereotaxic coordinates.</li>
		<li>Use a needle to spread 1 drop (approximately 35 &#956;L) of super glue onto the implant&#39;s base.</li>
		<li>Slowly move the holder downwards until it touches the skull. Be sure that the implant base is entirely in contact with the surface.</li>
		<li>Prepare the surgical cement according to the manufacturer&#39;s instructions.</li>
		<li>After precise positioning, apply 3 thin, even layer of cement across the cranium and onto the lower portion of the implant. Apply drop per drop using an application brush. Layers must form a hill-shaped structure for further structural support of the implant.</li>
		<li>Leave the implant&#39;s screw thread clean of cement to allow a smooth, unobstructed connection.</li>
		<li>Allow each layer to dry for approximately 4 minutes.</li>
		<li>When dry, carefully remove the holder until it is completely detached from the implant. Always use extreme caution when handling the implant, since it may be accidentally extracted from the animal&#39;s skull.</li>
	</ol>
	</li>
	<li>Finishing surgery and post-surgical care
	<ol>
		<li>Hydrate the animal&#39;s skin in the incision site with a saline-soaked cotton swab.</li>
		<li>Coat the skin over the base of the tDCS implant.</li>
		<li>Use a pair of tweezers to bring the tissue together and close the incision with a drop of surgical tissue glue per 0.2 cm of tissue.</li>
		<li>Infiltrate 1-2% lidocaine in the incision site and underlying tissues.</li>
		<li>Hydrate the mouse with 500 &#181;L of lactate Ringer&#39;s solution subcutaneously.</li>
		<li>Place the mouse into a pre-warmed (37 &#176;C) clean, single-housed cage.</li>
		<li>Put a small dish with wet food pellets in the cage for easy access to food in the following hours.</li>
		<li>Register the animal&#39;s post-surgical weight.</li>
		<li>Give the animal ketoprofen (5 mg/kg) subcutaneously after the surgery and on the next 2 days.</li>
		<li>Monitor the recovery of the animal closely for at least 1 week. Assess any sign of distress, such as piloerection, lack of grooming, reduced locomotion, wound scratching and inflammation of the surgical site.</li>
	</ol>
	</li>
</ol>
2. tDCS Setup and Stimulation
<ol>
	<li>tDCS Setup (see Figure 2) 
	&#8203;Note. Make sure that the tDCS stimulator is fully charged.
	<ol>
		<li>Attach the anode and cathode cables to the tDCS stimulator and make them available near the stimulation site. Attach the pin-type electrode to the stereotaxic holder.</li>
		<li>Set the thermal platform to 37 &#176;C.</li>
		<li>Turn on the oxygen flowmeter on the inhalation anesthesia system to 1 L/min.</li>
		<li>Place the mouse into the anesthesia induction chamber.</li>
		<li>Turn on the isoflurane vaporizer to 3%. Allow the animal to undergo isoflurane effects for 4 min.</li>
		<li>While the animal is in the induction chamber, use a sterile syringe to fill the body electrode with 0.9% saline solution.</li>
		<li>Remove the animal from the induction chamber and position its chest over the body electrode.</li>
		<li>Gently slide the anesthesia mask over the mouse&#39;s nose and fix it in place. Lower the isoflurane output to 1.5%.</li>
		<li>Fill the implant and the pin-type electrode with saline and carefully attach them.</li>
		<li>Adjust stimulation time and current intensity.</li>
		<li>Verify the contact quality on the tDCS stimulator.Optimal contact goes from 7 to 10 on a 1 to 10 scale.</li>
	</ol>
	</li>
	<li>Stimulation
	<ol>
		<li>Start the stimulation.</li>
		<li>Observe the current ramping up for 30 s to the selected value and maintaining itself steady for the established time, then, at the end of the session ramping down again.</li>
		<li>Activate the sham button for control mice.</li>
		<li>Observe the current ramping up for 30 s to the selected value and then down to 1 for the rest of the stimulation period with a final ramp to the selected value at the end with a consecutive ramp down.</li>
		<li>Once the stimulation session is complete, carefully transfer the animal to a pre-warmed (37 &#176;C) cage for 10 min. 
		Note. Animals start to awaken after 3 min.</li>
		<li>Turn the inhalation anesthesia system off.</li>
	</ol>
	</li>
</ol>

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</ol>

In recent years, neurostimulation techniques have been entering clinical practice as a promising procedure to treat neuropsychiatric disorders23. To reduce the constraint imposed by the lack of knowledge of the mechanisms of neurostimulation, we presented here a tDCS mouse model carrying an electrode that can target brain regions. Since the electrode is chronically implantable, this animal model enables the investigation of long-lasting biological effects evoked by tDCS (for at least 1 month) in c...

Transcranial Direct Current Stimulation (tDCS) is a non-invasive, low-cost, therapeutic technique, which focuses on neuronal modulation through the use of low-intensity continuous currents1. There are currently two setups (anodal and cathodal) for tDCS. While the anodal stimulation exerts a current electric field too weak to trigger action potentials, electrophysiology studies have shown that this method produces changes in synaptic plasticity2. For example, evidence shows that tDCS induces long-term potentiation (LTP) effects such as increased peak amplitude of the excitatory postsynaptic potentials3,4 and modulation of cortical excitability5.
Conversely, cathodal stimulation induces inhibition, resulting in membrane hyperpolarization6. A hypothesis for this mechanism is based on the physiological findings where tDCS is described to modulate action potential frequency and duration in the neuronal body3. Notably, this effect does not directly evoke action potentials, though it can shift the depolarization threshold and facilitate or hamper neuronal firing7. These contrasting effects have been previously demonstrated. For example, anodal and cathodal stimulation produced opposing effects in conditioned responses registered via electromyography activity in rabbits8. However, studies have also shown that prolonged anodal stimulation sessions may decrease excitability while increasing cathodal currents may lead to excitability, presenting self-contrasting effects3.
Both anodal and cathodal stimuli aggregate the use of electrode pairs. For example, in anodal stimulation, the &#34;active&#34; or &#34;anode&#34; electrode is placed over the brain region to be modulated whereas the &#34;reference&#34; or &#34;cathode&#34; electrode is situated over a region where the effect of current is assumed to be insignificant9. In the cathodal stimulation, electrode disposition is inverted. The stimulation intensity for effective tDCS depends on the current intensity and electrode dimensions, which affect the electric field differently10. In most published studies, the average current intensity is between 0.10 to 2.0 mA and 0.1 mA to 0.8 mA for human and mice, respectively6,11. Although the electrode size of 35 cm2 is typically used in humans, there is no proper understanding regarding electrode dimensions for rodents and a more thorough investigation is needed6.
tDCS has been proposed in clinical studies with the attempt of offering an alternative or complementary treatment for several neurological and neuropsychiatric disorders11 such as epilepsy12, bipolar disorder13, stroke5, major depression14, Alzheimer&#39;s disease15, multiple sclerosis16 and Parkinson&#39;s disease17. Despite growing interest in tDCS and its use in clinical trials, detailed cellular and molecular evoked alterations in brain tissue, short and long-lasting effects, as well as behavioral outcomes, are yet to be more deeply investigated18,19. Since a direct human approach to thoroughly study tDCS is not viable, the use of a tDCS animal model may offer valuable insights into the cellular and molecular events underlying the therapeutic mechanisms of tDCS due to the accessibility to the animal&#39;s brain tissue.
Available evidence is limited regarding tDCS models in mice. Most of the reported models used different implanting layouts, electrode dimensions, and materials. For example, Winkler et al. (2017) implanted the head electrode (Ag/AgCl, 4 mm in diameter) filled with saline and fixed it to the cranium with acrylic cement and screws20. Different from our approach, their chest electrode was implanted (platinum, 20 x 1.5 mm). Nasehi et al. (2017) used a procedure very similar to ours, although the thoracic electrode was made from a saline-soaked sponge (carbon filled, 9.5 cm2)21. Another study implanted both electrodes into the animal&#39;s head, which was achieved by using fixed plates and covering the animal&#39;s head with a hydrogel conductor22. Here, we describe a tDCS mouse model that uses a chronically implanted electrode through simple surgical procedures and tDCS setup (Figure 1).

<table><tbody><tr><td>BD Ultra-Fine 50U Syringe</td><td>BD</td><td>10033430026</td><td>For intraperitonially injection.</td></tr><tr><td>Shaver (Philips Multigroom)</td><td>Philips (Brazil)</td><td>QG3340/16</td><td>For surgical site trimming.</td></tr><tr><td>&lt;strong&gt;Surgical Equipment&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Model 940 Small Animal Stereotaxic Instrument with Digital Display Console</td><td>KOPF</td><td>940</td><td>For animal surgical restriction and positioning.</td></tr><tr><td>Model 922 Non-Rupture 60 Degree Tip Ear Bars</td><td>KOPF</td><td>922</td><td>For animal surgical restriction and positioning.</td></tr><tr><td>Cannula Holder</td><td>KOPF</td><td>1766-AP</td><td>For implant positioning.</td></tr><tr><td>Precision Stereo Zoom Binocular Microscope (III) on Boom Stand</td><td>WPI</td><td>PZMIII-BS</td><td>For bregma localization and implant positioning.</td></tr><tr><td>Temperature Control System Model&amp;nbsp;</td><td>KOPF</td><td>TCAT-2LV</td><td>For animal thermal control.</td></tr><tr><td>Cold Light Source&amp;nbsp;</td><td>WPI</td><td>WA-12633</td><td>For focal brightness</td></tr><tr><td>Tabletop Laboratory Animal Anesthesia System with Scavenging</td><td>VetEquip</td><td>901820</td><td>For isoflurane delivery and safety.</td></tr><tr><td>VaporGuard Activated Charcoal Adsorption Filter</td><td>VetEquip</td><td>931401</td><td>Delivery system safety measures.&amp;nbsp;</td></tr><tr><td>Model 923-B Mouse Gas Anesthesia Head Holder</td><td>KOPF</td><td>923-B</td><td>For animal restriction and O&lt;sub&gt;2&lt;/sub&gt; and isoflurane delivery.</td></tr><tr><td>Oxygen regulator, E-cylinder&amp;nbsp;</td><td>VetEquip</td><td>901305</td><td>For O&lt;sub&gt;2&lt;/sub&gt; regulation and delivery.</td></tr><tr><td>Oxygen hose &amp;ndash; green&amp;nbsp;</td><td>VetEquip</td><td>931503</td><td>For O&lt;sub&gt;2&lt;/sub&gt; and isoflurane delivery.</td></tr><tr><td>Infrared Sterilizer 800 &amp;ordm;C</td><td>Marconi</td><td>MA1201</td><td>For instrument sterilization.</td></tr><tr><td>&lt;strong&gt;Surgical Instruments&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Fine Scissors - ToughCut</td><td>Fine Science Tools</td><td>14058-11</td><td>For incision.</td></tr><tr><td>Surgical Hooks</td><td>INJEX</td><td>1636</td><td>In House Fabricated - Used to clear the surgical site from skin and fur.</td></tr><tr><td>Standard Tweezers or Forceps</td><td>-</td><td>-</td><td>For skin grasping.</td></tr><tr><td>&lt;strong&gt;Surgical Consumables&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Vetbond</td><td>3M</td><td>SC-361931</td><td>For incision closing.</td></tr><tr><td>Cement and Catalyzer KIT (Duralay)</td><td>Reliance</td><td>2OZ</td><td>For implant fixation.</td></tr><tr><td>Sterile Cotton Swabs (Autoclaved)</td><td>JnJ</td><td>75U</td><td>For surgical site antisepsis.&amp;nbsp;</td></tr><tr><td>24 Well Plate (Tissue Culture Plate)</td><td>SARSTEDT</td><td>831,836</td><td>For cement preparation.</td></tr><tr><td>Application Brush</td><td>parkell</td><td>S286</td><td>For cement mixing and application.</td></tr><tr><td>&lt;strong&gt;Pharmaceutics&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Xylazin (ANASEDAN 2%)</td><td>Ceva Pharmaceutical (Brazil)</td><td>P10160</td><td>For anesthesia induction.</td></tr><tr><td>Ketamine (DOPALEN 10%)</td><td>Ceva Pharmaceutical (Brazil)</td><td>P30101</td><td>For anesthesia induction.</td></tr><tr><td>Isoflurane (100%)</td><td>Crist&amp;aacute;lia (Brazil)</td><td>100ML</td><td>For anesthesia maintenance.</td></tr><tr><td>Lidocaine (XYLESTESIN 5%)</td><td>Cristal Pharma</td><td>-</td><td>For post-surgical care.</td></tr><tr><td>Ketoprofen (PROFENID 100 mg)</td><td>Sanofi Aventis</td><td>20ML</td><td>For post-surgical care.</td></tr><tr><td>Ringer&#039;s Lactate Solution</td><td>SANOBIOL LAB</td><td>7898153652145</td><td>For post-surgical care.</td></tr><tr><td>TobraDex (Dexamethasone 1 mg/g)</td><td>Alcon</td><td>631</td><td>For eye lubrification and protection.&amp;nbsp;</td></tr><tr><td>&lt;strong&gt;Stimulation&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Animal Transcranial Stimulator</td><td>Soterix Medical</td><td>2100</td><td>For current generation.</td></tr><tr><td>Pin-type electrode Holder (Cylindrical Holder Base)</td><td>Soterix Medical</td><td>2100</td><td>Electrode support (Implant).</td></tr><tr><td>Pin-type electrode (Ag/AgCl)</td><td>Soterix Medical</td><td>2100</td><td>For current delivery (electrode).&amp;nbsp;</td></tr><tr><td>Pin-type electrode cap</td><td>Soterix Medical</td><td>2100</td><td>For implant protection.</td></tr><tr><td>Body Electrode (Ag/AgCl Coated)</td><td>Soterix Medical</td><td>2100</td><td>For current delivery (electrode).&amp;nbsp;</td></tr><tr><td>Saline Solution (0.9%)</td><td>FarmaX</td><td>7896902206441</td><td>Conducting medium for current delivery.</td></tr><tr><td>Standard Tweezers or Forceps</td><td>-</td><td>-</td><td>For tDCS setup.</td></tr><tr><td>&lt;strong&gt;Real Time Polymerase Chain Reaction&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>BioRad CFX96 Real Time System</td><td>BioRad</td><td>C1000</td><td>For qPCR</td></tr><tr><td>SsoAdvancedTM Universal SYBR Green Supermix (5 X 1mL)</td><td>BioRad</td><td>1725271</td><td>For qPCR</td></tr><tr><td>Hard Shell PCR Plates PCT COM 50 p/ CFX96</td><td>BioRad</td><td>HSP9601</td><td>For qPCR</td></tr><tr><td>Microseal &quot;B&quot; seal pct c/ 100</td><td>BioRad</td><td>MSB1001</td><td>For qPCR</td></tr></tbody></table>

transcranial direct current stimulation (tdcs) in mice

Transcranial direct current stimulation (tDCS) is a non-invasive neuromodulation technique proposed as an alternative or complementary treatment for several neuropsychiatric diseases. The biological effects of tDCS are not fully understood, which is in part explained due to the difficulty in obtaining human brain tissue. This protocol describes a tDCS mouse model that uses a chronically implanted electrode allowing the study of the long-lasting biological effects of tDCS. In this experimental model, tDCS changes the cortical gene expression and offers a prominent contribution to the understanding of the rationale for its therapeutic use.

The surgical protocol presented long-term implant stability for at least one month, with no inflammatory signals at the stimulated site nor any other undesired effect. All the animals survived the surgical procedure and tDCS sessions (n = 8). In this experiment, tDCS implants were positioned over the M1 and M2 cortices (+1.0 mm anterior-posterior and 0.0 mm lateral to bregma). One week later, tDCS (n = 3-4) and sham (n = 3) mice were stimulated for five consecutive days during 10 min at 0...

Watch this Scientific Journal Video about Transcranial Direct Current Stimulation tDCS in Mice at JoVE.com

Transcranial Direct Current Stimulation tDCS in Mice

Transcranial direct current stimulation (tDCS) is a therapeutic technique proposed to treat psychiatric diseases. An animal model is essential for understanding the specific biological alterations evoked by tDCS. This protocol describes a tDCS mouse model that uses a chronically implanted electrode.

Transcranial Direct Current Stimulation (tDCS) in Mice

Transcranial direct current stimulation (tDCS) is a non-invasive neuromodulation technique proposed as an alternative or complementary treatment for ...

transcranial-direct-current-stimulation-tdcs-in-mice

Research

JoVE Journal

Neuroscience

14.1K Views.  Universidade Federal de Minas Gerais. De Alvar Gaaud Procedure is het toepassen van transcraniële directe stroom stimulatie bij muizen. Dit werd bereikt door het genereren van lage intense stromingen van een gelijkstroom generator, en het verzenden van het naar beneden rechtstreeks naar het dier door middel van elektroden. tDCS is onderzocht als een niet-medicamenteuze therapeutische alternatief voor de belangrijkste psychiatrische stoornissen bij de mens, zoals depressie, schizofrenie, de ziekte van Alzheimer, AHDH, en autisme....

Video: Transcranial Direct Current Stimulation tDCS in Mice

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 ...

Direct-current Stimulation and Multi-electrode Array Recording of Seizure-like Activity in Mice Brain Slice Preparation

Cathodal transcranial direct-current stimulation (tDCS) induces suppressive effects on drug-resistant seizures. To perform effective actions, the stimulation parameters (e.g., orientation, field strength, and stimulation duration) need to be examined in mice brain slice preparations. Testing and arranging the orientation of the electrode relative to the position of the mice brain slice are feasible. The present method preserves the thalamocingulate pathway to evaluate the effect of DCS on anterior cingulate cortex seizure-like activities. The results of the multichannel array recordings indicated that cathodal DCS significantly decreased the amplitude of the stimulation-evoked responses and duration of 4-aminopyridine and bicuculline-induced seizure-like activity. This study also found that cathodal DCS applications at 15 min caused long-term depression in the thalamocingulate pathway. The present study investigates the effects of DCS on thalamocingulate synaptic plasticity and acute seizure-like activities. The current procedure can test the optimal stimulation parameters including orientation, field strength, and stimulation duration in an in vitro mouse model. Also, the method can evaluate the effects of DCS on cortical seizure-like activities at both the cellular and network levels.

Studies have shown that cathodal transcranial direct-current stimulation can produce suppressive effects on drug-resistant seizures. In this study, an in vitro experimental setup was devised in which the direct-current stimulation and multielectrode array recording of seizure-like activity were evaluated in mice brain slice preparation. The direct-current stimulation parameters were evaluated.

Cathodal transcranial direct-current stimulation (tDCS) induces suppressive effects on drug-resistant seizures. To perform effective actions, the ...

Transcranial Electrical Brain Stimulation in Alert Rodents

Transcranial electrical brain stimulation can modulate cortical excitability and plasticity in humans and rodents. The most common form of stimulation in humans is transcranial direct current stimulation (tDCS). Less frequently, transcranial alternating current stimulation (tACS) or transcranial random noise stimulation (tRNS), a specific form of tACS using an electrical current applied randomly within a pre-defined frequency range, is used. The increase of noninvasive electrical brain stimulation research in humans, both for experimental and clinical purposes, has yielded an increased need for basic, mechanistic, safety studies in animals. This article describes a model for transcranial electrical brain stimulation (tES) through the intact skull targeting the motor system in alert rodents. The protocol provides step-by-step instructions for the surgical set-up of a permanent epicranial electrode socket combined with an implanted counter electrode on the chest. By placing a stimulation electrode into the epicranial socket, different electrical stimulation types, comparable to tDCS, tACS, and tRNS in humans, can be delivered. Moreover, the practical steps for tES in alert rodents are introduced. The applied current density, stimulation duration, and stimulation type may be chosen depending on the experimental needs. The caveats, advantages, and disadvantages of this set-up are discussed, as well as safety and tolerability aspects.

This protocol describes a surgical set-up for a permanent epicranial electrode socket and an implanted chest electrode in rodents. By placing a second electrode into the socket, different types of transcranial electrical brain stimulation can be delivered to the motor system in alert animals through the intact skull.

Transcranial electrical brain stimulation can modulate cortical excitability and plasticity in humans and rodents. The most common form of stimulation in ...

Home-Based Transcranial Direct Current Stimulation Device Development: An Updated Protocol Used at Home in Healthy Subjects and Fibromyalgia Patients

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation (NIBS) method, which modulates the membrane potential of neurons in the cerebral cortex by a low-intensity direct current. tDCS is a low-cost technique with minimal adverse effects and easy application. This neurostimulation method has a promising future to improve pain therapy, treatment of neuropsychiatric disorders, and physical rehabilitation.
Current studies demonstrate the benefits of using tDCS over consecutive multiple sessions. However, the daily displacement to the specialized centers, travel costs, and disruptions to daily activities are some of the difficulties faced by patients. Thus, to be more comfortable, easy-to-use, and not disrupt daily commitments, a home-based tDCS was designed. Therefore, the objective of this study was to evaluate the feasibility of a portable tDCS device for home use in healthy subjects and fibromyalgia patients.
Despite increased tDCS use and a reasonably large body of research on the effects across a range of clinical conditions, there is a limited amount of research on developing secure devices that guarantee the dose and contain a block system to avoid excessive use. Therefore, we used a tDCS device with a security system to permit daily use for 20 minutes with a minimal interval of 12 hours between sessions. A programmer preconfigures the equipment, which has a neoprene cap that allows the electrode positions in any assembly, according to individualized protocols for treatments or research. After, researchers can assess the effectiveness of treatment, and its adherence using information kept in the device software.
Results suggest that the device is feasible for home use, with proper monitoring of adherence and contact impedance. There were reports of a few adverse effects, which do not differ from those reported in the literature in studies with the treatment under direct supervision.

This study provides an updated home-based tDCS protocol that enables subjects to receive the beneficial effects of tDCS at home with an easy to use device with settings to control the use and dosage, enhancing the feasibility for long-term use at home.

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation (NIBS) method, which modulates the membrane potential of neurons in the ...

Medicine

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).

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, ...

Stimulating Mouse Brain with a Low-Cost EEG and Millimeter-Sized Coil

Low-Cost Electroencephalographic Recording System Combined with a Millimeter-Sized Coil to Transcranially Stimulate the Mouse Brain In Vivo

A low-cost electroencephalographic (EEG) recording system is proposed here to drive transcranial magnetic stimulation (TMS) of the mouse brain in vivo, utilizing a millimeter-sized coil. Using conventional screw electrodes combined with a custom-made, flexible, multielectrode array substrate, multi-site recording can be carried out from the mouse brain. In addition, we explain how a millimeter-sized coil is produced using low-cost equipment usually found in laboratories. Practical procedures for fabricating the flexible multielectrode array substrate and the surgical implantation technique for screw electrodes are also presented, which are necessary to produce low-noise EEG signals. Although the methodology is useful for recording from the brain of any small animal, the present report focuses on electrode implementation in an anesthetized mouse skull. Furthermore, this method can be easily extended to an awake small animal that is connected with tethered cables via a common adapter and fixed with a TMS device to the head during recording.The present version of the EEG-TMS system, which can include a maximum of 32 EEG channels (a device with 16 channels is presented as an example with fewer channels) and one TMS channel device, is described. Additionally, typical results obtained by the application of the EEG-TMS system to anesthetized mice are briefly reported.

Author Spotlight: Low-Cost Electroencephalographic Recording System Combined with a Millimeter-Sized Coil to Transcranially Stimulate the Mouse Brain In Vivo  

A low-cost electroencephalographic recording system combined with a millimeter-sized coil is proposed to drive transcranial magnetic stimulation of the mouse brain in vivo. Using conventional screw electrodes with a custom-made, flexible, multielectrode array substrate, multi-site recording can be carried out from the mouse brain in response to transcranial magnetic stimulation.

A low-cost electroencephalographic (EEG) recording system is proposed here to drive transcranial magnetic stimulation (TMS) of the mouse brain in vivo, ...

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 ...

Transcranial Direct Current Stimulation (tDCS) in Mice

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