The investigators will conduct a pilot study to evaluate the safety and feasibility of low-intensity focused ultrasound on obsessive-compulsive disorder (OCD) symptoms when delivered to subcortical brain targets. The investigators will use the ATTN201 device to deliver single sessions of unfocused and focused ultrasound to up to three brain targets over 4 study visits and assess the intervention through self-rated scales of OCD symptoms.

Inclusion Criteria:

1. Participants must be enrolled in the IRB #853085 study

The inclusion criteria for the IRB #853085 study, which are also included in this trial are:

In order to be eligible to participate in this study, an individual must meet all of the following criteria:

1. Adults aged 18-60 years old
2. Chronic OCD (5 years preceding date of enrollment), diagnosed as per the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition guidelines (DSM-5)
3. Presence of obsessions, compulsions, or both time-consuming obsessions and compulsions that take more than one hour a day or cause significant distress or impairment in social, occupation, or other important areas of functioning Obsessive-compulsive symptoms that are not attributable to the physiological effects of a substance (e.g., a drug of abuse, a medication) or another medical condition
4. Disturbance not better explained by the symptoms of another mental disorder listed in the DSM-5 Severe OCD symptoms, as defined by Y-BOCS I score of 28 or higher, within two weeks prior to enrollment
5. Compulsions need to involve movement of the hands and/or arms so that the sleeve is able to detect participant's actions (cannot be solely mental or verbal compulsions)
6. Ability to understand procedure-related instructions and to complete study assessments in English, and ability to comply with protocol requirements (e.g., procedure visits, treatment schedule, follow-up visit schedule, evaluations, etc.), in the opinion of the Principal Investigator
7. Willingness and ability to provide written agreement to allow any and all forms of communication between the research team and treating clinician(s) 8 Willingness and ability to provide informed consent, in the opinion of the Principal Investigator

Exclusion Criteria:

An individual who meets any of the following criteria will be excluded from participation in this study:

1. Unable to undergo MRI scan

   • Presence of metallic implants or devices or tattoos
   • Claustrophobia or severe anxiety
   • Inability to remain still for duration of scan

2. Inability to fit and wear the ATTN201 device for the entire

Exclusion criteria for IRB study #853085 include:

1. Hearing loss that, in the opinion of the Principal Investigator, an audiologist, or a treating physician, is likely to affect the subject's ability to comply with all of the requirements of the study, or may affect the integrity of the study data
2. Pregnancy - this is an exclusion criterion because we will be intentionally increasing anxiety in participants to evaluate optimal strategies to provoke distress and then promote relaxation
3. Any past or present medical condition, disease, disorder, or injury that, in the opinion of the Principal Investigator, may reduce or hinder the subject's ability to fully comply with all study requirements for the duration of the study or may impact, compromise, or affect the integrity of the data or results of the study.
4. Have a previous injury or surgery which could affect the nerve distribution
5. Have nerve damage (neuropathy)
6. Have a diagnosed neuromuscular disorder
7. Have a pacemaker
8. Have a history of skin allergies, psoriasis eczema, dermatitis, or other skin inflammation conditions
9. Compulsions cannot be completely mental or verbal actions, such as repeating words, counting objects, or performing mental rituals, and cannot involve only facial muscles/actions such as blinking or staring

Individual participant data (IPD) will not be shared with outside researchers at this time to ensure the protection of participant privacy and to maintain strict compliance with the University of Pennsylvania Institutional Review Board (IRB) approved protocol.