Healthy
Conditions
Brief summary
Transcranial Alternating Current Stimulation (tACS) is one method that has been demonstrated to enhance alpha oscillations in healthy participants by applying weak electrical currents to the scalp to modulate rhythmic brain activity patterns. This study will involve tACS-induced frontal alpha oscillations, EEG recordings, and other physiological and biological measures.
Interventions
Transcranial alternating current stimulation (tACS) is a method of noninvasive brain stimulation in which weak electrical current are applied to the scalp in a sine wave pattern to induce cortical oscillations at the frequency at which they are applied.
The participant will receive up to one minute of tACS stimulation until the stimulation fades. Sham stimulation mimics the skin sensations a participant would experience during a tACS session.
Sponsors
National Institutes of Health (NIH)
National Institute of Mental Health (NIMH)
University of North Carolina, Chapel Hill
Study design
Allocation
RANDOMIZED
Intervention model
CROSSOVER
Primary purpose
BASIC_SCIENCE
Masking
DOUBLE (Subject, Investigator)
Masking description
This study will follow a double-blind experimental design, so neither the participant nor the experimenter will know what kind of stimulation the participant is receiving at what session. A separate unblinded monitor, who will not interact with the participants, will be responsible for creating the stimulation codes for each session.
Intervention model description
Each participant will receive sham stimulation or 10 Hz tACS stimulation at two separate sessions. The order will be randomized (ie, half the participants will receive sham stimulation at the first session and 10 Hz tACS stimulation at the second session, and the other half will receive 10 Hz tACS stimulation at the first session and sham stimulation at the second session).
Eligibility
Sex/Gender
ALL
Age
18 Years to 65 Years
Healthy volunteers
Yes
Inclusion criteria
* Ages 18-65 * Capacity to understand all relevant risks and potential benefits of the study (informed consent) * Negative pregnancy test for female participants
Exclusion criteria
* History of major neurological or psychiatric illness, including epilepsy * Medication use associated with neurological or psychiatric illnesses * Currently undergoing counseling or psychotherapy treatment for depression, anxiety, eating disorders, PTSD or other behavioral conditions * First degree relative (parent, sibling, child) with major neurological or psychiatric illness * Prior brain surgery * Major head injury * Any brain devices/implants (including cochlear implants and aneurysm clips) * Braids or other hair styling that prevents direct access to the scalp (if removal not possible) * Skin allergies or very sensitive skin * Pregnant or nursing females * Failure to pass a urinary drug test at the first session * Use of hormonal birth control or supplements in the past two weeks * Non English speakers * Cardiovascular disease
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Salivary Alpha Amylase | Before and after 40-minute stimulation at each session. | Change after stimulation |
| Salivary Cortisol | Before and after 40 minutes of stimulation | Change before and after stimulation |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Heart Rate Variability | Before and after 40-minute stimulation at each session. | Change in the ratio between the power in low frequency band and the power in high frequency band. As this outcome variable is a ratio between two items that are measured in microvolt\^2, the ratio does not have a unit of measure. |
| Percent Change in Respiration | Before and after 40-minute stimulation at each session. | Respiration rate, measured via a belt placed around the participant's abdomen as breaths per second. |
| Electroencephalogram (EEG) | Before and after 40-minute stimulation at each session. | The investigators will compare alpha oscillation power from resting-state EEG recordings before and after stimulation/sham at each session. |
Countries
United States
Participant flow
Participants by arm
| Arm | Count |
|---|---|
| Overall Group (Both Sham and Alpha Stimulation) Participants received sham stimulation at one session and alpha stimulation at the other in a randomized order. Sessions were separated by 5-9 days. | 20 |
| Total | 20 |
Baseline characteristics
| Characteristic | Overall Group (Both Sham and Alpha Stimulation) |
|---|---|
| Age, Categorical <=18 years | 0 Participants |
| Age, Categorical >=65 years | 0 Participants |
| Age, Categorical Between 18 and 65 years | 20 Participants |
| Race (NIH/OMB) American Indian or Alaska Native | 0 Participants |
| Race (NIH/OMB) Asian | 4 Participants |
| Race (NIH/OMB) Black or African American | 4 Participants |
| Race (NIH/OMB) More than one race | 1 Participants |
| Race (NIH/OMB) Native Hawaiian or Other Pacific Islander | 0 Participants |
| Race (NIH/OMB) Unknown or Not Reported | 0 Participants |
| Race (NIH/OMB) White | 11 Participants |
| Sex: Female, Male Female | 5 Participants |
| Sex: Female, Male Male | 15 Participants |
Adverse events
| Event type | EG000 affected / at risk | EG001 affected / at risk |
|---|---|---|
| deaths Total, all-cause mortality | 0 / 20 | 0 / 20 |
| other Total, other adverse events | 0 / 20 | 0 / 20 |
| serious Total, serious adverse events | 0 / 20 | 0 / 20 |
Outcome results
Primary
Salivary Alpha Amylase
Change after stimulation
Time frame: Before and after 40-minute stimulation at each session.
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Sham Stimulation | Salivary Alpha Amylase | 0.00695 log-normalized percent change of U/mL | Standard Deviation 0.196 |
| Alpha Stimulation | Salivary Alpha Amylase | 0.03055 log-normalized percent change of U/mL | Standard Deviation 0.188 |
p-value: 0.7ANOVA
Primary
Salivary Cortisol
Change before and after stimulation
Time frame: Before and after 40 minutes of stimulation
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Sham Stimulation | Salivary Cortisol | -0.0551 log-normalized percent change µg/dL | Standard Deviation 0.168 |
| Alpha Stimulation | Salivary Cortisol | -0.0702 log-normalized percent change µg/dL | Standard Deviation 0.164 |
p-value: 0.71ANOVA
Secondary
Electroencephalogram (EEG)
The investigators will compare alpha oscillation power from resting-state EEG recordings before and after stimulation/sham at each session.
Time frame: Before and after 40-minute stimulation at each session.
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Sham Stimulation | Electroencephalogram (EEG) | -0.0087 percent change of uV^2/Hz | Standard Deviation 0.036 |
| Alpha Stimulation | Electroencephalogram (EEG) | 0.0114 percent change of uV^2/Hz | Standard Deviation 0.0752 |
Secondary
Heart Rate Variability
Change in the ratio between the power in low frequency band and the power in high frequency band. As this outcome variable is a ratio between two items that are measured in microvolt\^2, the ratio does not have a unit of measure.
Time frame: Before and after 40-minute stimulation at each session.
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Sham Stimulation | Heart Rate Variability | 1.599 log-normalized percent change | Standard Deviation 3.33 |
| Alpha Stimulation | Heart Rate Variability | 0.308 log-normalized percent change | Standard Deviation 3.7 |
Secondary
Percent Change in Respiration
Respiration rate, measured via a belt placed around the participant's abdomen as breaths per second.
Time frame: Before and after 40-minute stimulation at each session.
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Sham Stimulation | Percent Change in Respiration | -0.0075 Percent change in breaths per second | Standard Deviation 0.076 |
| Alpha Stimulation | Percent Change in Respiration | 0.0325 Percent change in breaths per second | Standard Deviation 0.093 |