This study will investigate the test-retest reliability of transcranial magnetic stimulation (TMS) -evoked potentials (TEPs) as measured by electroencephalography (EEG), using three different TMS protocols over five different brain regions in healthy volunteers. The goal is to compare the test-retest reliability of single pulse, inhibitory and excitatory TMS protocols as well as two distinct targeting approaches. The main questions to answer are:

1. This study will investigate whether the test-retest reliability of TEPs differ across TMS protocols.
2. This study will investigate whether the test-retest reliability of TEPs differ between individualized and non-individualized targeting approaches.

Participants will first undergo functional magnetic resonance imaging (fMRI) scanning where structural and resting-state functional images will be obtained. In two separate sessions, participants will attend two concurrent TMS/EEG session with one week in between.

During the TMS/EEG sessions, an EEG cap will be placed on the participant's head and the resting motor threshold will be obtained to calibrate the TMS intensity required for the stimulation of target regions. Once setup procedures are complete, eleven total blocks of TMS with simultaneous EEG recording will take place. Among eleven blocks, five of will use single-pulse stimulation (to stimulate cortical excitation), three will use paired-pulse stimulation with 3ms between pulses (to stimulate cortical inhibition), and three will use paired-pulse stimulation with 11ms between pulses (to stimulate greater cortical excitation). Five different brain regions will be targeted: three individualized targets either derived anatomically (motor cortex) or based on the individual's resting-state functional connectivity (dorsolateral prefrontal cortex and angular gryus) and two regions that are based on the literature (dorsolateral prefrontal cortex and angular gryus).

Inclusion Criteria:

• Medically and psychiatrically healthy
• Between the ages of 18 and 65 years old
• Fluent in English and capable of providing informed consent
• Willing to remove any jewelry, hair clips, bobby pins, or any other potentially conducting or magnetic objects worn on or near the head

Exclusion Criteria:

• Weight greater than 350 lbs (the weight limit of the specialized TMS/EEG chair)
• Current serious medical or psychiatric illness, or recent heart disease
• Acute intoxication with any drug of abuse, including alcohol or cannabis
• Pregnancy
• History of neurological problems, including epilepsy, seizures, syncope, tinnitus, migraine, or frequent non-migraine (e.g. tension) headaches
• History of head trauma associated with loss of consciousness
• Language or hearing impairment that would undermine communication regarding consent, study procedures, and overall volunteer safety.
• Irritable skin
• For those undergoing MRI procedures in the current study: Any standard MRI contraindication (including implanted medical devices, metal in the body, or claustrophobia incompatible with MRI procedures)
• TMS-contraindicated medical devices, including cochlear implants, pacemaker, neurosensory stimulator, implantable defibrillator, insulin pump, clips, stents, or shunts that may be disrupted by or interact with TMS coil operation
• Taking medications that lower seizure threshold (see Appendix A: List of Contraindicated Medications)