Health Adult Subjects
Conditions
Keywords
tDCS, tACS, RNS, QST, CPM-test
Brief summary
Transcranial modulation of the corticospinal sensorimotor pathway is a promising approach in neuroscientic functions. Among the techniques used, transcranial direct current stimulation (tDCS), transcranial alternating current stimulation (tACS) and the application of random noise current stand out. Objective: To compare the e stimulus, in the EEG frequency bands, on Motor Evoked Potentials (MEP) and on the functional activation of the motor cortex, assessed by Functional Near Infrared Spectroscopy (fNIRS) and pain measurements in healthy subjects subjected to a standardized algogenic stimulus. Subjects and Method: This is a randomized, double-blind, controlled and crossover clinical trial, involving the inclusion of 14 healthy male subjects, with complete secondary education, aged between 18 and 40. years. Participants will be randomized to receive Transcranial Direct Current Stimulation (tDCS), (2) Transcranial Alternating Current Stimulation (tACs), (3) Random Noise Current, (4) Simulated Stimulation Session and (5) Rest Session. Experimental conditions will take place in a standard, quiet and bright room. Assessments will include Motor Evoked Potential, Heat Pain Threshold, Motor Area Activation through metabolic activation measured by fNIRS and analysis of EEG frequency waves. After the baseline assessment, participants will undergo a session of transcranial stimulation, followed by an algogenic stimulus with water at zero degrees, immersion of the dominant hand for 1 minute, with rest intervals of 3 minutes between each of the four serial stimuli. After this stimulus session, outcome measurements will be carried out. Expected results: This clinical trial is expected to provide insights into how tDCS, tACs and random stimulation in to an algogenic stimulus. The results may contribute to the development of therapeutic or neuromodulation strategies in clinical conditions where the regulation of the cortico-spinal sensorimotor pathway is relevant.
Interventions
DEVICETranscranial Alternating Current Stimulation
Single session of active gamma transcranial alternating current stimulation delivered for 30 minutes using a battery-powered external stimulator. Stimulation is applied through two sponge electrodes (5 × 7 cm) mounted on a neoprene cap. The stimulation frequency is 40 Hz, based on previous gamma-band transcranial alternating current stimulation (tACS) studies. The anode is positioned at C3 (left primary motor cortex, M1), and the cathode over the ipsilateral clavicular region.
DEVICETranscranial Direct Current Stimulation
Stimulation is delivered using two sponge electrodes (5 × 7 cm) mounted on a neoprene cap. The electrodes are positioned on the scalp according to the international 10-20 system. The anode is placed at position C3 (left primary motor cortex, M1) and the cathode over the ipsilateral clavicular region. The sinusoidal current intensity per channel ranges from ±2 mA. The session duration is 20 minutes.
Stimulation is delivered using two sponge electrodes mounted on a neoprene cap. The anode is positioned at C3 (left primary motor cortex, M1), and the cathode over the ipsilateral clavicular region. A random current level is generated for each sample at a sampling rate of 1280 samples per second. The random values are normally distributed, following a bell-shaped probability density function. The noise signal contains all frequencies up to half the sampling rate (maximum 640 Hz) and has no DC offset.
DEVICESham Stimulation
During the sham stimulation session, the tDCS device ramps up the current to 2 mA over 30 seconds and then is immediately turned off. This procedure mimics the sensations of active stimulation without delivering therapeutic current for the remainder of the session.
Sponsors
Hospital de Clinicas de Porto Alegre
Study design
Allocation
RANDOMIZED
Intervention model
CROSSOVER
Primary purpose
OTHER
Masking
TRIPLE (Subject, Investigator, Outcomes Assessor)
Eligibility
Sex/Gender
MALE
Age
18 Years to 45 Years
Healthy volunteers
Yes
Inclusion criteria
* Healthy male subjects aged 18-45 years, with at least a high school diploma, and not engaged in night-shift work.
Exclusion criteria
* Contraindications to transcranial stimulation include implanted medical devices in the brain, cardiac pacemakers, and cochlear implants. * Current use of psychotropic medications. * History of alcohol or substance abuse within the past 6 months. * Neurological disorders, history of traumatic brain injury, or prior neurosurgery. * Beck Depression Inventory-II (BDI-II) score \>13. * Self-Reporting Questionnaire (SRQ) score \>7.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Resting-State EEG Power Spectra Across Frequency Bands (Delta, Theta, Alpha, Beta 1, Beta 2, and Gamma) | Immediately before and immediately after the intervention. | Electroencephalography (EEG) will be used to quantify neuronal activity through quantitative EEG (qEEG) analysis. Resting-state EEG power spectra will be analyzed across delta, theta, alpha, beta, and gamma frequency bands, reflecting synchronized neuronal oscillations. EEG data will be recorded using a 20-electrode montage according to the international 10-20 system during an 8-minute resting-state paradigm with alternating eyes-open and eyes-closed conditions. Cortical source localization will be performed using standardized Low-Resolution Brain Electromagnetic Tomography (sLORETA). |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Corticospinal Excitability | Immediately before and immediately after the intervention. | Corticospinal excitability will be assessed using single-pulse transcranial magnetic stimulation (TMS) applied over the left primary motor cortex. Motor evoked potentials (MEPs) will be recorded from the right first dorsal interosseous muscle, and measures will include resting motor threshold (RMT) and MEP amplitude, with MEPs obtained at 130% of the motor threshold. |
| Motor Cortex Functional Connectivity | Immediately before and immediately after the intervention. | Functional connectivity of the motor cortex will be assessed using functional near-infrared spectroscopy (fNIRS) with a continuous-wave NirScout® system. Optodes will be positioned according to the international 10-10 system to cover the bilateral motor cortex. Data will be acquired during resting-state conditions and during the cold pressor task. Functional connectivity will be analyzed within predefined motor cortex regions of interest. |
| Heat Pain Threshold | Immediately before and immediately after the intervention. | Heat pain threshold will be assessed via quantitative sensory testing (QST) on the left forearm using a thermode that increases temperature from 30°C to 52°C at a rate of 1°C per second. The pain threshold is calculated as the average temperature at which pain is first reported across three trials. Higher values indicate greater pain threshold. |
| Function of the Descending Pain Inhibitory System | Immediately before and immediately after the intervention. | The function of the descending pain inhibitory system will be assessed using the Conditioned Pain Modulation Test (CPM-test). Pain intensity is rated using a verbal numerical rating scale (0 = no pain to 10 = worst possible pain) before (T0) and during (T1) cold-water immersion. The CPM effect is calculated as the difference between pain ratings at T0 and T1, with greater reductions indicating more effective pain inhibition. |
| Cold Pressor Test Pain Tolerance | Immediately before and immediately after the intervention. | Pain intensity and tolerance will be assessed using the Cold Pressor Test, in which participants immerse the non-dominant hand in ice-saturated water (\~1°C) for up to 2 minutes. Pain intensity will be continuously rated using an electronic visual analog scale, allowing calculation of peak pain, mean pain, and area under the curve (AUC) over the test duration. |
Countries
Brazil
Outcome results
None listed