This project seeks to identify causal neural mechanisms underlying unwanted, repetitive behaviors (compulsions). Using non-invasive brain stimulation coupled with practice in a computer task, we will modulate activity in a target brain region in two directions (up or down) and measure effects on compulsive behaviors and related measures. This work could ultimately lead to the ability to treat compulsions more effectively by targeting the regions of the brain that can help or hinder attempts to overcome compulsions.

Inclusion Criteria:

Participants will:

1. Be between the ages of 18 and 55 years
2. Endorse problematic compulsive behaviors, per self-report and clinician-administered measures.
3. Agree to video taping of structured clinical interview
4. Report that they will reside in the Pittsburgh area for at least 5 weeks

Exclusion Criteria:

1. Failure to meet standard MRI inclusion criteria: those who endorse claustrophobia, those who have cardiac pacemakers, neural pacemakers, surgical clips in the brain or blood vessels, surgically implanted metal plates, screws or pins, cochlear implants, implanted uterine devices, metal braces, or other metal objects in their body, especially in the eye. Dental fillings do not present a problem. Plastic or removable dental appliances do not require exclusion. History of significant injury or surgery to the brain or spinal cord that would impair interpretation of results. Pregnancy, determined by pregnancy tests on females.

2. Medical contraindications for Transcranial Magnetic Stimulation (TMS):

   1. Presence of a neurologic disorder or medication therapy known to alter seizure threshold (e.g., stroke, aneurysm, brain surgery, structural brain lesion, brain injury, frequent/severe headaches)
   2. Recurrent seizures or epilepsy in participant or family history of hereditary epilepsy
   3. Pregnancy
   4. Metallic implants in body or other devices that may be affected by magnetic field
   5. Significant heart disease or cerebrovascular disease
   6. Medications with seizure threshold lowering potential, e.g., clomipramine, Monoamine Oxidase inhibitors (MAOi's), imipramine, clozapine

3. Acute suicidality or other psychiatric crises requiring treatment escalation

4. Changes made to treatment regimen within 4 weeks of baseline assessment

5. Reading level <6th grade

6. Presence of bipolar, psychotic, autism spectrum, or substance use disorder (i.e. current use of mood altering drugs such as cocaine, cannabis or marijuana, opiates, amphetamines, and barbiturates)

7. Presence of movement disorder or tics affecting manual responses

8. Inability to read text from 2 feet away (corrective lenses allowed)

We will comply with all National Institute of Mental Health (NIMH) guidelines regarding data sharing and make use of NIMH databases.