The overall goal of this procedure is to demonstrate the technique of simultaneous EEG monitoring during transcranial direct current stimulation. For that, we will describe in a step-by-step fashion all the procedures of application of this device using schematic figures, tables, and video demonstrations. The procedure begins by assembling the necessary materials and measuring the head.
Next, the transcranial direct current stimulation or TDCS and EEG recording electrodes are positioned in the cap. Then the electrical stimulation over the head is activated. The final step is to interpret the EEG signals obtained during TDCS.Quaia.
Direct current stimulation is a technique that delivers weak electric currents through the scalp. This constant electric current induces shifts in neuronal membrane acceptability that results in secondary changes in cortical plasticity. Although D Cs has most of its neuromodulatory effects on the underlying cortex, TDCS effects can also be observed in distant neural networks before the use of simultaneous EEG with TDCS can provide valuable information on the mechanisms of TDCS.
In addition, ELECTROENCEPHALOGRAPHIC findings can be an important surrogate marker for the effects of TDCS and those be used to optimize its parameters and to warrant T the safety of the procedure. For instance, in children Compared to functional MRI, EEG has the disadvantage of special resolution assessment. However, it has superior temporal resolution reflecting timing of neuronal activity more accurately.
In addition, as compared with TMS cortico parameters, EEG might provide a more accurate understanding of ongoing cortical activity during and after the TCS. To begin the procedure, prepare all the required materials, then connect all the electrodes to the control box device. This device has to be charged periodically using the control box battery charger.
Next, connect the control box to the computer with A USB for Bluetooth connection. For head measurement, measure the distance between the nasion and Indian. Then mark the halfway point as the vertex or CZ using a skin marker.
Inspect the skin for any preexisting lesions and avoid electrical stimulation. EEG recording over any damaged skin or over skull lesions. Clean the surface of the skin to remove any signs of lotion, dirt, and grease, and allow it to dry.
Now soak the TDCS sponge electrodes with the saline solution for a 25 to 35 centimeter squared sponge, approximately six milliliters of solution per side may suffice. Next, insert the TDCS sponge electrodes and the EEG electrodes in the cap. Make sure the subject is seated comfortably.
Put the cap on the subject's head so that the vertex measured on the head matches the CZ point of the cap. Use a curved syringe to fill the EEG electrodes with gel. Attach the control box to the posterior part of the cap.
Use channel one and two for stimulation and channel three to eight for EEG recording. Their position in the cap depends on the desired experimental approach for both recording and stimulation. In this demonstration, the classical left anodal TDCS setup will be displayed.
Connect the anode indicated by the red sponge electrode to the C3 and the cathode indicated by the black sponge electrode to FP two. Connect the wires to the control box and fix it to the occipital region of the cap. The control box connects to the computer through a wireless interface.
To start the stimulation procedure first, click stimulation in the horizontal bar on the upper screen, select edit in the upper screen and choose TDCS or sham out of other electrical stimulation techniques such as transcranial, alternating current stimulation, and transcranial random noise stimulation. Then click launch in the lower part of the screen. Check if the vertical gray bar is moving.
During TDCS electrode impedance values should be constantly monitored and click aboard to suspend the stimulation at any moment if needed. The EEG time domain allows us to check the baseline ongoing EEG activity and select EEG band frequencies if needed. The EEG power spectrum allows us to check the predominant EEG frequency band after automatic fast four year transform analysis over the raw ongoing EEG activity in the EEG spectrogram.
We can transform the EEG signals into images using a technique called time frequency analysis. These figures show the differences in frontal alpha amplitude in response to active TDCS when compared to sham TDCS over the left do lateral prefrontal cortex. Using the automatic fast forward air transformation analysis, the investigator is able to determine and measure the amplitude of the predominant EEG frequency activity during and after the TDCS.
Depending on the region of the stimulation and other experimental conditions, the amplitude of the specific EEG frequency bands is expected to change after TDCS. Indeed, this analysis offers a unique opportunity to understand the neuromodulatory effects in real time. The closed loop system application might not be restricted to patients with epilepsy only.
A number of recent studies have suggested that the EG alterations may be markers of various neuropsychiatric diseases. Therefore, a combination of TDCS and EEG could be an option for rapid detection of TDCS neurophysiological effects in order to optimize stimulation protocols In comparison with transcranial magnetic stimulation, that's another technique of non-invasive brain stimulation. CDCS is considered much more suitable for therapeutic goals, mainly because of its low costs and portability.
However, even being portable, having a system that uses a head cap with predetermined electro locations can standardize location of simulation and improve results. Another advantage of its device is the possibility to stimulate more than one site at the same time, which has been found to be clinically superior to conventional stimulation according to some authors.
