Healthy Volunteers (HV)Phase 1NCT07707284
Frequency-Dependent Effects of Transcranial Photobiomodulation on Cortical Excitability
A Phase 1 study testing Transcranial Photobiomodulation in people with Healthy Volunteers (HV) and Transcranial Photobiomodulation, run by Hospital de Clinicas de Porto Alegre at 1 site in Brazil.
Trial summary
This study aims to investigate the frequency-dependent effects of near-infrared (NIR) transcranial photobiomodulation (tPBM) on human cortical excitability and fine motor performance. Read more about this study
- Who is it for?
- Ages 18 to 35 yearsHealthy volunteers can take part
- Conditions the study is for
- Healthy Volunteers (HV), Transcranial Photobiomodulation, Cortical Excitability
- What is being tested?
- Transcranial Photobiomodulation
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 20 participants
- Where
- 1 siteBrazil
- Study dates
- May 2027to Jul 2028
- Phase
- Phase 1
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 35 years
- All sexes
- Healthy volunteers accepted
- Adult
Who may be able to join
- Voluntary Participation: Participants who are clear of their cognitive faculties, capable of understanding all experimental procedures, and who provide written informed consent prior to enrollment.
- Neurologically and Psychiatrically Healthy Status: Individuals with no current or prior history of neurological, neurodevelopmental, or psychiatric conditions;
- Age Range: Young adult volunteers aged between 18 and 35 years.
Who cannot join
- Use of any continuous psychotropic medication within the past 12 months.
- Any current psychiatric diagnosis based on the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5).
- Diagnosis of any neurological disorder capable of altering cortical excitability (e.g., seizures/epilepsy, cerebrovascular accidents/stroke, brain tumors).
- Any clinical, psychological, or social condition that, in the investigator's opinion, places the participant at an increased risk, compromises participant safety, or precludes full compliance and successful completion of the study protocol.
- Presence of any intracranial devices or implants, including cochlear implants and aneurysm clips.
- Severe or uncompensated systemic medical illness that could interfere with study participation or confound physiological outcomes.
- Participation in any other interventional neuromodulation study within the preceding 6 months.
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
Brazil1 site
Hospital de Clínicas de Porto Alegre
Porto Alegre, Rio Grande do Sul
Marco A Caldieraro, MD PhD, +5551991095177, mcaldieraro@hcpa.edu.br
Victor CS Araújo, MD Msc, +5551997360799, vcaraujo@hcpa.edu.br
About this study
Official title: Frequency-Dependent Effects of Transcranial Photobiomodulation on Cortical Excitability and Fine Motor Performance: A Randomized, Double-Blind, Sham-Controlled, Crossover Trial
This study aims to investigate the frequency-dependent effects of near-infrared (NIR) transcranial photobiomodulation (tPBM) on human cortical excitability and fine motor performance. A cohort of 20 healthy adult volunteers (aged 18-35 years) will participate in a randomized, double-blind, sham-controlled, single-center study utilizing a within-subject, five-arm crossover design. Each participant will undergo five distinct experimental conditions separated by a strict washout period: active Continuous Wave (CW) tPBM, active pulsed tPBM at three neural oscillation frequencies (10 Hz, 40 Hz, and 100 Hz), and an inactive Sham comparator. All interventions will be delivered using a clinical-grade near-infrared device.
To isolate the specific effects of pulse frequency from overall energy delivery, the total energy dose (cumulative Joules) and total exposure time will be held perfectly constant across all active arms. The pulsed conditions will keeps the average irradiance and cumulative fluence identical to the continuous wave mode. Cortical excitability will be assessed via single- and paired-pulse Transcranial Magnetic Stimulation (TMS) protocols over the primary motor cortex (M1). Fine motor performance will be quantified using a smartphone-based Finger Tapping Test (FTT). Safety and systemic parameters will be tracked using the Systematic Assessment for Treatment Emergent Events - Systematic Inquiry (SAFTEE-SI) and vital signs. The central hypothesis is that distinct modulation frequencies will differentially influence corticospinal excitability and motor execution, independent of the total energy delivered.
Read the detailed description
Transcranial photobiomodulation (tPBM) has emerged as a promising non-invasive tool to modulate neural activity through the absorption of near-infrared (NIR) photons by mitochondrial cytochrome c oxidase (CCO). However, whether the biological effects on the human cortex are driven solely by cumulative energy delivery or are significantly modulated by pulse frequency remains a critical question in neurophysiology. This study implements a rigorous within-subject crossover design to systematically isolate the effects of pulse frequency from total dosimetric parameters. Participants and Screening: A sample of 20 healthy volunteers (aged 18-35) will be recruited. Potential candidates will undergo a strict screening protocol to ensure safety and baseline homogeneity. Exclusion criteria include any contraindications to magnetic fields assessed by the Transcranial Magnetic Stimulation Adult Safety Screen (TASS; Rossi et al., 2021), psychiatric conditions according to DSM-5, a history of neurological disorders, the use of psychotropic medications within the last 12 months, or prior participation in an interventional neuromodulation study within the preceding 6 months. Experimental Design \& Intervention: Enrolled participants will complete five experimental sessions in a randomized, counterbalanced order to eliminate carryover or sequence effects, separated by a mandatory washout period to ensure the return of cortical excitability to baseline. In each session, a clinical-grade near-infrared system will be applied over the primary motor cortex (M1) hot spot. The five experimental arms consist of:
Continuous Wave (CW) active tPBM at baseline irradiance. 10 Hz near-infrared active tPBM. 40 Hz near-infrared active tPBM. 100 Hz near-infrared active tPBM. Sham Comparator (inactive control). Physical Calibration and Blinding: To ensure flawless dosimetric matching, total energy dose (Joules) and application duration will be kept constant across all active arms. The active pulsed interventions (10 Hz, 40 Hz, and 100 Hz) will utilize a 50% duty cycle with a peak irradiance exactly twice that of the Continuous Wave (CW) mode, thereby ensuring that the average irradiance (mW/cm2) and cumulative fluence (J/cm2) remain strictly identical to the CW. For the Sham condition, the device will emit a minimal, sub-therapeutic visual output of visible red light. This serves as a visual guide mimic to maintain complete participant blinding without transferring active near-infrared photons to the cortex (0 J active NIR dose). Double-blinding will be enforced for the participant and investigator. Alphanumeric codes will mask the active protocols on the user interface, and participants will wear opaque safety goggles. Outcome Measures: Multiple neurophysiological, behavioral, and safety endpoints will be collected immediately pre-intervention (baseline) and post-intervention. Neurophysiology (TMS): Motor Evoked Potential (MEP) amplitude (primary excitability index); Intracortical Facilitation (ICF); Short-Interval Intracortical Inhibition (SICI); and Cortical Silent Period (CSP). Behavioral Performance (FTT): Evaluated via a dedicated Android application tracking total number of taps, variability of the inter-tap interval (vITI), spatial resultant sum (Σ||Δr||), and the 95% confidence ellipse area (X,Y).
Safety and Hemodynamics: Systemic tolerability will be recorded via the Systematic Assessment for Treatment Emergent Events - Systematic Inquiry (SAFTEE-SI). Hemodynamic variations will be closely monitored through independent analyses of Systolic Blood Pressure (SBP), Diastolic Blood Pressure (DBP), and Heart Rate (HR). Data will be processed using Linear Mixed-Effects Models to account for the repeated-measures structure of the crossover design.
- Being tested
- Transcranial Photobiomodulation
- Keywords
- Transcranial photobiomodulation, Cortical excitability, Healthy volunteers, Finger Tapping Test
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Transcranial PhotobiomodulationCombination product
Transcranial photobiomodulation (tPBM) is a non-invasive, non-thermal neuromodulatory modality that utilizes low-power coherent (laser) or non-coherent (light-emitting diodes, LEDs) light sources within the red (lambda = 600-700 nm) and near-infrared (NIR; lambda = 700-1100 nm) spectral windows to modulate cortical function. Structurally tailored to penetrate superficial anatomical barriers-including the scalp, skull, and meninges-tPBM delivers photons directly to the cerebral cortex.
| Study group | Role | What they receive |
|---|---|---|
| Continuous Wave (CW) tPBM | Experimental | Active near-infrared (NIR) transcranial photobiomodulation delivered in Continuous Wave (CW) mode using the NIR device, providing a constant baseline irradiance to achieve the target total energy dose (J). Receives: Combination Product: Transcranial Photobiomodulation |
| 10 Hz Pulsed tPBM | Experimental | Active NIR light delivered in pulsed mode at a frequency of 10 Hz. It matched across frequencies to ensure that the average irradiance (mW/cm2) and total energy dose (J) remain identical to the CW baseline within the same exposure time. Receives: Combination Product: Transcranial Photobiomodulation |
| 40 Hz Pulsed tPBM | Experimental | Active NIR light delivered in pulsed mode at a frequency of 40 Hz. It matched across frequencies to ensure that the average irradiance (mW/cm2) and total energy dose (J) remain identical to the CW baseline within the same exposure time. Receives: Combination Product: Transcranial Photobiomodulation |
| 100 Hz Pulsed tPBM | Experimental | Active NIR light delivered in pulsed mode at a frequency of 100 Hz. It matched across frequencies to ensure that the average irradiance (mW/cm2) and total energy dose (J) remain identical to the CW baseline within the same exposure time. Receives: Combination Product: Transcranial Photobiomodulation |
| Sham Comparator (Sham tPBM) | Sham comparator | Inactive transcranial photobiomodulation (tPBM) delivered near-infrared device. To ensure successful participant blinding, the device will be programmed to deliver a minimal, non-therapeutic power output of visible red light (660 nm), which serves as a visual guide mimic but delivers negligible energy to the cortical tissue (0 J of active near-infrared light). Total exposure time, acoustic signals, and equipment interface will be identical to the active arms. Receives: Combination Product: Transcranial Photobiomodulation |
What is being measured
The primary outcome is the main question the study is designed to answer.
Motor Evoked Potential (MEP) Amplitude - TMS
Single-pulse TMS will be applied over the primary motor cortex (M1) hotspot to elicit Motor Evoked Potentials (MEPs) recorded via electromyography (EMG) from the target muscle (e.g., first dorsal interosseous, FDI). Peak-to-peak MEP amplitude (mV) will be measured at a stimulation intensity adjusted to evoke a baseline response of approximately 1 mV. This outcome reflects overall baseline corticospinal excitability and its modulation following the tPBM protocol.
Measured: Immediately before the intervention (pre-intervention) and 20 minutes after the intervention (post-intervention)
Intracortical Facilitation (ICF) - TMS
Evaluated using a paired-pulse TMS protocol consisting of a subthreshold conditioning stimulus (80% of resting motor threshold, RMT) followed by a suprathreshold test stimulus (120% RMT) at a long interstimulus interval (ISI) of 10 ms. The outcome is expressed as the ratio of the conditioned MEP amplitude to the unconditioned test MEP amplitude. ICF is primarily mediated by cortical glutamatergic circuits and NMDA receptor activity.
Measured: Immediately before the intervention (pre-intervention) and 20 minutes after the intervention (post-intervention)
Short-Interval Intracortical Inhibition (SICI) - TMS
Assessed via a paired-pulse TMS paradigm using a subthreshold conditioning stimulus (80% RMT) followed by a suprathreshold test stimulus (120% RMT) at a short interstimulus interval (ISI) of 3 ms. The resulting SICI value is quantified as the percentage of inhibition of the conditioned MEP relative to the unconditioned test MEP. This parameter indexes local intracortical inhibitory interneuron activity mediated by GABA_A receptors.
Measured: Immediately before the intervention (pre-intervention) and 20 minutes after the intervention (post-intervention)
Cortical Silent Period (CSP) - TMS
Induced by applying a single suprathreshold TMS pulse (120% RMT) over the M1 hotspot while the participant maintains a stable, isometric voluntary contraction of the target muscle (e.g., 20% of maximum voluntary contraction). The CSP duration (ms) is measured from the onset of the MEP to the return of rectified background EMG activity. CSP duration provides a precise marker of interhemispheric and intracortical inhibition mediated by GABA_B receptors.
Measured: Immediately before the intervention (pre-intervention) and 20 minutes after the intervention (post-intervention)
Secondary outcomes (5)
Total Number of Taps - FTT
The cumulative count of valid screen contacts executed by the participant's index finger within a fixed, standardized testing interval (e.g., 30 seconds). This metric serves as a behavioral index of maximal motor execution speed and tapping frequency.
Measured: Immediately before the intervention (pre-intervention) and immediately after the intervention (post-intervention)
Variability of the Inter-Tap Interval (vITI) - FTT
Calculated as the standard deviation (or coefficient of variation) of the temporal intervals between consecutive screen contacts (in milliseconds). This outcome quantifies the temporal rhythmic precision and stability of the central motor program.
Measured: Immediately before the intervention (pre-intervention) and immediately after the intervention (post-intervention)
Spatial Resultant Sum (Σ||Δr||) - FTT
The cumulative Euclidean distance calculated across all sequential tap coordinates on the 2D Android screen interface. This parameter reflects spatial dispersion and motor drift, tracking the continuous precision of the targeted finger-pointing trajectory.
Measured: Immediately before the intervention (pre-intervention) and immediately after the intervention (post-intervention)
95% Confidence Ellipse Area (X,Y) - FTT
Computed as the total geometric surface area (in squared millimeters, mm2) of the bivariate error ellipse that encompasses 95% of the coordinates of all performed taps on the horizontal (X) and vertical (Y) axes. This spatial metric quantifies overall motor accuracy and targeting consistency.
Measured: Immediately before the intervention (pre-intervention) and immediately after the intervention (post-intervention)
Adverse Events and Tolerability (SAFTEE-SI)
The safety and tolerability profile of the combined neuromodulation protocol will be systematically evaluated using the Systematic Assessment for Treatment Emergent Events - Systematic Inquiry (SAFTEE-SI). This structured instrument will track the incidence, severity, and potential causal relationship of any somatic, neurological, or behavioral symptoms (e.g., headache, scalp discomfort, fatigue, dizziness, or localized thermal sensations) emerging during or after stimulation.
Measured: Baseline, before all interventions and one week after the intervention
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted16 Jul 2026
- Study startMay 2027 (estimated)
- Primary completionMay 2028 (estimated)
- Study completionJul 2028 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Healthy Volunteers (HV)Studies of the same condition, open and under way.
- More trials run by Hospital de Clinicas de Porto AlegreThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 1
- Primary purpose
- Device feasibility
- Allocation
- Randomised
- Intervention model
- Crossover
- Model description
- This study is a randomized, double-blind, sham-controlled, single-center clinical trial utilizing a five-arm crossover assignment design to evaluate the frequency-dependent effects of near-infrared (NIR) transcranial photobiomodulation (tPBM) on human cortical excitability. By implementing a within-subject crossover design with a sample of 20 healthy participants, each volunteer will serve as their own control, drastically reducing inter-individual neuroanatomical and neurophysiological variance. All 20 participants will undergo all five experimental conditions in a randomized and counterbalanced order to mitigate any potential order or carryover effects. To ensure complete elimination of residual neuromodulatory effects, a minimum washout period of 7 days will be strictly enforced between consecutive experimental sessions.
- Masking
- Double blind
- Who is masked
- Participant, Investigator
- Enrolment
- 20 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Hospital de Clinicas de Porto Alegre
- Sponsor type
- University, hospital or other
- Collaborators
- Federal University of Rio Grande do Sul, Coordenação de Aperfeiçoamento de Pessoal de Nível Superior.
- Responsible party
- Sponsor
- Investigators
- Marco A Caldieraro, Doctor, Principal investigator, Federal University of Health Science of Porto Alegre
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07707284
- Sponsor's protocol ID
- 2025-0082
- Status last verified
- Jul 2026
- First submitted
- 8 Jul 2026
- Last updated
- 28 Jul 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 28 Jul 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Frequency-Dependent Effects of Transcranial Photobiomodulation on Cortical Excitability and Fine Motor Performance: A Randomized, Double-Blind, Sham-Controlled, Crossover Trial
- ClinicalTrials.gov ID
- NCT07707284
- Acronym / sponsor ID
- 2025-0082
- Keywords
- Transcranial photobiomodulation, Cortical excitability, Healthy volunteers, Finger Tapping Test
- Phase
- Phase 1
- Study type
- Interventional
- Recruitment status
- Not yet recruiting
- Enrolment
- 20 participants (estimated)
- Lead sponsor
- Hospital de Clinicas de Porto AlegreUniversity, hospital or other
- Collaborators
- Federal University of Rio Grande do Sul, Coordenação de Aperfeiçoamento de Pessoal de Nível Superior.
- Study start
- May 2027 (estimated)
- Primary completion
- May 2028 (estimated)
- Study completion
- Jul 2028 (estimated)
- First posted
- 16 Jul 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
This study aims to investigate the frequency-dependent effects of near-infrared (NIR) transcranial photobiomodulation (tPBM) on human cortical excitability and fine motor performance. A cohort of 20 healthy adult volunteers (aged 18-35 years) will participate in a randomized, double-blind, sham-controlled, single-center study utilizing a within-subject, five-arm crossover design. Each participant will undergo five distinct experimental conditions separated by a strict washout period: active Continuous Wave (CW) tPBM, active pulsed tPBM at three neural oscillation frequencies (10 Hz, 40 Hz, and 100 Hz), and an inactive Sham comparator. All interventions will be delivered using a clinical-grade near-infrared device.
To isolate the specific effects of pulse frequency from overall energy delivery, the total energy dose (cumulative Joules) and total exposure time will be held perfectly constant across all active arms. The pulsed conditions will keeps the average irradiance and cumulative fluence identical to the continuous wave mode. Cortical excitability will be assessed via single- and paired-pulse Transcranial Magnetic Stimulation (TMS) protocols over the primary motor cortex (M1). Fine motor performance will be quantified using a smartphone-based Finger Tapping Test (FTT). Safety and systemic parameters will be tracked using the Systematic Assessment for Treatment Emergent Events - Systematic Inquiry (SAFTEE-SI) and vital signs. The central hypothesis is that distinct modulation frequencies will differentially influence corticospinal excitability and motor execution, independent of the total energy delivered.
Detailed description
Transcranial photobiomodulation (tPBM) has emerged as a promising non-invasive tool to modulate neural activity through the absorption of near-infrared (NIR) photons by mitochondrial cytochrome c oxidase (CCO). However, whether the biological effects on the human cortex are driven solely by cumulative energy delivery or are significantly modulated by pulse frequency remains a critical question in neurophysiology. This study implements a rigorous within-subject crossover design to systematically isolate the effects of pulse frequency from total dosimetric parameters. Participants and Screening: A sample of 20 healthy volunteers (aged 18-35) will be recruited. Potential candidates will undergo a strict screening protocol to ensure safety and baseline homogeneity. Exclusion criteria include any contraindications to magnetic fields assessed by the Transcranial Magnetic Stimulation Adult Safety Screen (TASS; Rossi et al., 2021), psychiatric conditions according to DSM-5, a history of neurological disorders, the use of psychotropic medications within the last 12 months, or prior participation in an interventional neuromodulation study within the preceding 6 months. Experimental Design \& Intervention: Enrolled participants will complete five experimental sessions in a randomized, counterbalanced order to eliminate carryover or sequence effects, separated by a mandatory washout period to ensure the return of cortical excitability to baseline. In each session, a clinical-grade near-infrared system will be applied over the primary motor cortex (M1) hot spot. The five experimental arms consist of:
Continuous Wave (CW) active tPBM at baseline irradiance. 10 Hz near-infrared active tPBM. 40 Hz near-infrared active tPBM. 100 Hz near-infrared active tPBM. Sham Comparator (inactive control). Physical Calibration and Blinding: To ensure flawless dosimetric matching, total energy dose (Joules) and application duration will be kept constant across all active arms. The active pulsed interventions (10 Hz, 40 Hz, and 100 Hz) will utilize a 50% duty cycle with a peak irradiance exactly twice that of the Continuous Wave (CW) mode, thereby ensuring that the average irradiance (mW/cm2) and cumulative fluence (J/cm2) remain strictly identical to the CW. For the Sham condition, the device will emit a minimal, sub-therapeutic visual output of visible red light. This serves as a visual guide mimic to maintain complete participant blinding without transferring active near-infrared photons to the cortex (0 J active NIR dose). Double-blinding will be enforced for the participant and investigator. Alphanumeric codes will mask the active protocols on the user interface, and participants will wear opaque safety goggles. Outcome Measures: Multiple neurophysiological, behavioral, and safety endpoints will be collected immediately pre-intervention (baseline) and post-intervention. Neurophysiology (TMS): Motor Evoked Potential (MEP) amplitude (primary excitability index); Intracortical Facilitation (ICF); Short-Interval Intracortical Inhibition (SICI); and Cortical Silent Period (CSP). Behavioral Performance (FTT): Evaluated via a dedicated Android application tracking total number of taps, variability of the inter-tap interval (vITI), spatial resultant sum (Σ||Δr||), and the 95% confidence ellipse area (X,Y).
Safety and Hemodynamics: Systemic tolerability will be recorded via the Systematic Assessment for Treatment Emergent Events - Systematic Inquiry (SAFTEE-SI). Hemodynamic variations will be closely monitored through independent analyses of Systolic Blood Pressure (SBP), Diastolic Blood Pressure (DBP), and Heart Rate (HR). Data will be processed using Linear Mixed-Effects Models to account for the repeated-measures structure of the crossover design.
Study design
- Primary purpose
- Device feasibility
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- Double blind (participant, investigator)
- Number of arms
- 5
- Model description
- This study is a randomized, double-blind, sham-controlled, single-center clinical trial utilizing a five-arm crossover assignment design to evaluate the frequency-dependent effects of near-infrared (NIR) transcranial photobiomodulation (tPBM) on human cortical excitability. By implementing a within-subject crossover design with a sample of 20 healthy participants, each volunteer will serve as their own control, drastically reducing inter-individual neuroanatomical and neurophysiological variance. All 20 participants will undergo all five experimental conditions in a randomized and counterbalanced order to mitigate any potential order or carryover effects. To ensure complete elimination of residual neuromodulatory effects, a minimum washout period of 7 days will be strictly enforced between consecutive experimental sessions.
| Arm | Type | Receives |
|---|---|---|
| Continuous Wave (CW) tPBM | Experimental | Combination Product: Transcranial PhotobiomodulationActive near-infrared (NIR) transcranial photobiomodulation delivered in Continuous Wave (CW) mode using the NIR device, providing a constant baseline irradiance to achieve the target total energy dose (J). |
| 10 Hz Pulsed tPBM | Experimental | Combination Product: Transcranial PhotobiomodulationActive NIR light delivered in pulsed mode at a frequency of 10 Hz. It matched across frequencies to ensure that the average irradiance (mW/cm2) and total energy dose (J) remain identical to the CW baseline within the same exposure time. |
| 40 Hz Pulsed tPBM | Experimental | Combination Product: Transcranial PhotobiomodulationActive NIR light delivered in pulsed mode at a frequency of 40 Hz. It matched across frequencies to ensure that the average irradiance (mW/cm2) and total energy dose (J) remain identical to the CW baseline within the same exposure time. |
| 100 Hz Pulsed tPBM | Experimental | Combination Product: Transcranial PhotobiomodulationActive NIR light delivered in pulsed mode at a frequency of 100 Hz. It matched across frequencies to ensure that the average irradiance (mW/cm2) and total energy dose (J) remain identical to the CW baseline within the same exposure time. |
| Sham Comparator (Sham tPBM) | Sham comparator | Combination Product: Transcranial PhotobiomodulationInactive transcranial photobiomodulation (tPBM) delivered near-infrared device. To ensure successful participant blinding, the device will be programmed to deliver a minimal, non-therapeutic power output of visible red light (660 nm), which serves as a visual guide mimic but delivers negligible energy to the cortical tissue (0 J of active near-infrared light). Total exposure time, acoustic signals, and equipment interface will be identical to the active arms. |
Who may qualify
- Ages
- 18 to 35 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (3 listed)
- Voluntary Participation: Participants who are clear of their cognitive faculties, capable of understanding all experimental procedures, and who provide written informed consent prior to enrollment.
- Neurologically and Psychiatrically Healthy Status: Individuals with no current or prior history of neurological, neurodevelopmental, or psychiatric conditions;
- Age Range: Young adult volunteers aged between 18 and 35 years.
Key exclusion criteria (7 listed)
- Use of any continuous psychotropic medication within the past 12 months.
- Any current psychiatric diagnosis based on the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5).
- Diagnosis of any neurological disorder capable of altering cortical excitability (e.g., seizures/epilepsy, cerebrovascular accidents/stroke, brain tumors).
- Any clinical, psychological, or social condition that, in the investigator's opinion, places the participant at an increased risk, compromises participant safety, or precludes full compliance and successful completion of the study protocol.
- Presence of any intracranial devices or implants, including cochlear implants and aneurysm clips.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Transcranial PhotobiomodulationTranscranial photobiomodulation (tPBM) is a non-invasive, non-thermal neuromodulatory modality that utilizes low-power coherent (laser) or non-coherent (light-emitting diodes, LEDs) light sources within the red (lambda = 600-700 nm) and near-infrared (NIR; lambda = 700-1100 nm) spectral windows to modulate cortical function. Structurally tailored to penetrate superficial anatomical barriers-including the scalp, skull, and meninges-tPBM delivers photons directly to the cerebral cortex. | Combination product | 10 Hz Pulsed tPBM, 100 Hz Pulsed tPBM, 40 Hz Pulsed tPBM, Continuous Wave (CW) tPBM, Sham Comparator (Sham tPBM) |
Primary outcome
Motor Evoked Potential (MEP) Amplitude - TMS
Time frame: Immediately before the intervention (pre-intervention) and 20 minutes after the intervention (post-intervention)
Single-pulse TMS will be applied over the primary motor cortex (M1) hotspot to elicit Motor Evoked Potentials (MEPs) recorded via electromyography (EMG) from the target muscle (e.g., first dorsal interosseous, FDI). Peak-to-peak MEP amplitude (mV) will be measured at a stimulation intensity adjusted to evoke a baseline response of approximately 1 mV. This outcome reflects overall baseline corticospinal excitability and its modulation following the tPBM protocol.
Intracortical Facilitation (ICF) - TMS
Time frame: Immediately before the intervention (pre-intervention) and 20 minutes after the intervention (post-intervention)
Evaluated using a paired-pulse TMS protocol consisting of a subthreshold conditioning stimulus (80% of resting motor threshold, RMT) followed by a suprathreshold test stimulus (120% RMT) at a long interstimulus interval (ISI) of 10 ms. The outcome is expressed as the ratio of the conditioned MEP amplitude to the unconditioned test MEP amplitude. ICF is primarily mediated by cortical glutamatergic circuits and NMDA receptor activity.
Short-Interval Intracortical Inhibition (SICI) - TMS
Time frame: Immediately before the intervention (pre-intervention) and 20 minutes after the intervention (post-intervention)
Assessed via a paired-pulse TMS paradigm using a subthreshold conditioning stimulus (80% RMT) followed by a suprathreshold test stimulus (120% RMT) at a short interstimulus interval (ISI) of 3 ms. The resulting SICI value is quantified as the percentage of inhibition of the conditioned MEP relative to the unconditioned test MEP. This parameter indexes local intracortical inhibitory interneuron activity mediated by GABA_A receptors.
Cortical Silent Period (CSP) - TMS
Time frame: Immediately before the intervention (pre-intervention) and 20 minutes after the intervention (post-intervention)
Induced by applying a single suprathreshold TMS pulse (120% RMT) over the M1 hotspot while the participant maintains a stable, isometric voluntary contraction of the target muscle (e.g., 20% of maximum voluntary contraction). The CSP duration (ms) is measured from the onset of the MEP to the return of rectified background EMG activity. CSP duration provides a precise marker of interhemispheric and intracortical inhibition mediated by GABA_B receptors.
5 secondary outcomes
Total Number of Taps - FTT
Time frame: Immediately before the intervention (pre-intervention) and immediately after the intervention (post-intervention)
Variability of the Inter-Tap Interval (vITI) - FTT
Time frame: Immediately before the intervention (pre-intervention) and immediately after the intervention (post-intervention)
Spatial Resultant Sum (Σ||Δr||) - FTT
Time frame: Immediately before the intervention (pre-intervention) and immediately after the intervention (post-intervention)
95% Confidence Ellipse Area (X,Y) - FTT
Time frame: Immediately before the intervention (pre-intervention) and immediately after the intervention (post-intervention)
Adverse Events and Tolerability (SAFTEE-SI)
Time frame: Baseline, before all interventions and one week after the intervention
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 28 Jul 2026.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Marco A Caldieraro, Doctor principal investigator
Federal University of Health Science of Porto Alegre
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 1 study testing Transcranial Photobiomodulation in people with Healthy Volunteers (HV) and Transcranial Photobiomodulation, run by Hospital de Clinicas de Porto Alegre at 1 site in Brazil.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 3 inclusion and 7 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: opening soon, as of the sponsor's last update on 28 Jul 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Brazil. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. Some participants in this study may receive a placebo. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Phase 1 studies test a treatment in a small group of people for the first time or in a new way, mainly to check safety and find the right dose.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Marco A Caldieraro, MD PhD (+555199109-5177, mcaldieraro@hcpa.edu.br), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Motor Evoked Potential (MEP) Amplitude - TMS (time frame: Immediately before the intervention (pre-intervention) and 20 minutes after the intervention (post-intervention)). The study lists 4 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 28 Jul 2026.