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

The overall goal of this video is to demonstrate the use of four by one ring, high definition transcranial direct current stimulation, using primary motor cortex stimulation as an example, and to describe the considerations needed for safe and effective stimulation. This is accomplished by first inspecting the equipment and preparing the materials needed for delivery of HD TDCS. Next, the subject's head is measured and based on the study protocol, the areas to be stimulated are localized.

Then the electrodes are positioned on the subject's head and adequate contact quality is confirmed. Finally, the stimulation parameters are verified, including current polarity intensity and duration, and the intervention is delivered. Ultimately, this technique is capable of modifying cortical excitability with an increased vocality as compared to conventional TDCS resulting in different neurophysiological and clinical effects.

The near advantage of H-E-D-T-D-C-S over conventional transcranial direct current stimulation is that in addition to being portable simple to perform inexpensive and well tolerated among subjects, it also allows for stimulation of AL targets with an increased vocalocity. Brain modeling Studies show that the vocalocity of high definition TVCS is restricted to the perimeter of the electrode ring, and different trials have reported its ability to induce neurophysiological and clinical effects in humans. The method described here can be adapted for other montages and cortical targets.

Ultimately, this will translate into more rational research and clinical neuromodulatory applications. Since there are currently no strict guidelines regarding the setup of this montage and device operation, visual demonstration of this method is critical. No, no, prior to device setup.

Confirm that the participant does not have any contraindications for H-D-T-D-C-S as indicated here. Ensure that all the necessary materials are readily available as shown here, and as noted in table two of the text protocol. Next, embed the plastic HD casings in the modular electroencephalogram recording cap.

The center electrode should correspond to the target area in this demonstration, the primary motor cortex or M1 and the radius of the four return electrodes should be adjusted based on the protocol that is being studied. Turn on the conventional TDCS device and the multi-channel stimulation adapter and check that the batteries are charged prior to each session. Visually inspect the electrodes for signs of unusual wear or damage.

Connect the cables of five silver, silver chloride centered ring electrodes to the matching receivers on the four by one adapter output cable. The center electrode will be the one defining the polarity of the stimulation as either ANODAL or C oal. Make sure to connect the center electrode.

Lead to the center receiver plug. Then connect the remaining electrodes into the surrounding plugs. Have the participant sit comfortably in a chair.

Inspect the participants'scalp thoroughly for cutaneous lesions, such as cuts or inflammatory signs. To begin localize the vertex or CZ by first measuring the distance from the nations to the Indian and divide the distance by half. Mark the spot as a line, then measure the distance between the left and right preauricular points.

Divide this distance in half and mark the spot with a line. Now, connect both lines to create a cross. In order to stimulate the M1, calculate 20%of the distance from CZ to the left or right preauricular point, beginning the measurement at cz.

Next, keeping the M1 mark in sight, place the modular EEG recording cap on the subject's head while holding the center plastic casing over the mark to keep the M1 cross mark on the scalp in sight, one can move the hair around before placing the HD casing over it. Ensure that the cap fits snugly but comfortably, and adjust the position of the four return plastic casings. Then adjust the straps of the cap using a measuring tape.

Confirm that the interelectrode distance is adequate based upon the study protocol. Then using the end of a wooden cotton swab, separate the hair through the opening in the plastic casing until the scalp is exposed. Repeat this under each casing using a plastic syringe or applying directly from the bottle.

Introduce about 1.5 milliliters of electrically conductive gel through the opening of each plastic casing beginning at the scalp surface. Carefully avoid spreading gel beyond the circumference of the plastic casing as this may lead to shunting of electrical current. Next, with its rough surface facing down and the smooth rounded surface facing up, lower the ring electrode until it rests on the base of the plastic casing using the syringe or the plunger as a guide.

If necessary, add some more gel to cover the electrode, and then use the caps provided with the HD plastic casings to lock the electrodes in place. To reduce tension on the electrode cables. Loop them around each plastic casing and tape them to the chair or to the subject's clothes.

Then connect the rounded end of the output cable to the four by one adapter output port. Connect the cone plug end of the input cable to the four by one adapter input port, and connect the other end of the input cable to the output port of the conventional TDCS device. Importantly, the cable that is labeled as center is the one that will define DC polarity delivered from the center electrode as either anodal or cath oal.

When the connections are ready, turn on the device. Ensure that the impedance values are within an adequate range by turning the mode select knob in the four by one multi-channel stimulation adapter to scan. The device will then scan the electrodes showing the impedance of one electrode at a time in the display window.

Use the lead toggle button to toggle the automatic switching of electrodes in the display. Then press the button to lock the display on the selected electrode and examine the impedance. The four by one multi-channel stimulation adapter device will measure impedance in quality units values lower than or equal to 1.5 to 2.0.

Quality units have been used as a cutoff in previous studies. If impedance values are beyond these desired limits, open the cap of the plastic casing containing the electrode showing high impedance and remove the silver, silver chloride centered ring electrode. Follow the procedures just described to adjust the hair and electrode to obtain optimal impedance.

Once the target quality value is achieved, replace the cap on the casing. After the impedance quality for all electrodes is confirmed to be within the desired range, turn the mode select knob in the four by one multi-channel stimulation adapter from scan to pass. Ensure that the participant is seated comfortably in the chair and remains awake during the stimulation.

Adjust the setting to either the sham or the active mode in the conventional TDCS device and confirm the duration and intensity of stimulation. To initiate the HD TDCS session, press the start button on the conventional TDCS device. The start light will flash as DC intensity is ramped up and then light continuously when target current is reached.

The timer will then show the remaining time and the true current indicator will show the current intensity delivered to the center electrode and the four return electrodes combined. If the subject experiences discomfort due to itching or tingling, use the relax feature to manually ramp down the intensity by 0.2 to 0.5 milliamps for a few seconds until the subject feels comfortable. Immediately thereafter, gradually increase the intensity back to the original dose.

After the session is complete, resistances across all channels can be measured again, if desired, open the plastic caps and gently remove the silver, silver chloride centered ring electrodes from the casings. If necessary, use the blunt end of a cotton swab. To avoid tugging on the electrode wires, remove the EEG cap with the embedded plastic casings.

Then using a paper towel and water if necessary, remove the remaining gel from the subject's head. Have the subject fill out a questionnaire to monitor for any adverse events events. If the electrodes are positioned appropriately and the impedance values are within an adequate range, current will flow from anode to cathode.

The target current intensity will be delivered by the device and shown in its true current indicator in the sham mode. The device will automatically stop delivering current approximately 30 seconds after its initiation, and the indicator will show its cessation. In addition to the four by one ring configuration demonstrated in this video, high definition, TDCS can be customized for different other electrode deployments based on the protocol being studied.

Computational models show that four by one ring HD TDCS results in more focal brain stimulation as compared with conventional TDCS. The area of cortical excitability modulation is restricted within the ring perimeter and the peak of electrical field is under the center electrode. In contrast, conventional TDCS causes stimulation of different regions such as the ipsilateral, temporal, and bilateral frontal lobes, and the electrical field peaks midway between the two electrodes instead of underneath.

One of them studies using four by one ring H-D-T-D-C-S show that in healthy volunteers, it can significantly decrease heat and cold sensory thresholds as well as lead to marginal analgesic effect for cold pain thresholds. In addition, it can cause significant changes in cortical excitability as measured using motor evoked potentials. In fact, a single 10 minute session of Anodal H-D-T-D-C-S at 2.0 milliamps has been reported to exert more prominent and longer lasting excitatory after effects than conventional TDCS.

Moreover, in fibromyalgia patients active four by one ring, H-D-T-D-C-S induced a significant reduction in overall perceived pain and significantly increased mechanical detection thresholds as compared to sham stimulation. After watching this video, it should have a good understanding of how a session of high definition TDCS is performing in a safe and Effective manner. While attempting this procedure, it's important to remember to carefully verify the polarity of the cables when connecting the four x one multi-channel stimulation adapter to the conventional TDCS device.

Although high definition TVCS offers many options for customization, the methods for positioning and preparing electrodes as described here should be followed for safety reasons only. Hardware and accessories that have specifically been tested for high definition TVCS should be used. This noggle technique can pave the way for researchers in the field of brain stimulation to study the effects of noninvasive more focal delivery of direct current to discrete AL targets.

Potential applications may include neurophysiological studies, cognitive and behavioral assessments, and therapeutic interventions focused on disorders such as chronic pain, stroke, Parkinson's disease, and migraine, and with others. It's true to be explored.