This study explores the potential of transcranial ultrasound stimulation (TUS) as an innovative therapeutic approach for individuals with obsessive-compulsive disorder (OCD). By targeting specific brain regions associated with compulsive behaviors and anxiety, the researchers aim to assess the safety and efficacy of TUS in reducing symptoms and enhancing cognitive flexibility.

Obsessive Compulsive Disorder (OCD) is a common and highly debilitating disorder with the manifestation of obsessions/compulsions and is associated with a significant impairment in social functioning and quality of life. Estimates show that the effects of OCD create an economic burden of £5 billion/year in the UK alone (Kochar et al. 2023). Novel interventions with greater efficacy in addressing the symptoms of OCD in patients, aiming to surpass the current standards of effectiveness and comprehensiveness in treatment outcomes are needed. Low-intensity transcranial focused ultrasound stimulation (TUS) is a promising emerging non-invasive brain stimulation technique which can neuromodulate any brain region with high spatial resolution.

The neural underpinning of OCD is thought to involve many prefrontal regions including the anterior cingulate cortex (ACC) but also deeper brain regions like the striatum (habit formation: Ahmari et al. 2017, Denys et al. 2013), the thalamus (Subirà et al. 2016) and the amygdala (overactivity: Fullana et al. 2020, Milad et al. 2013). TUS can focally induce changes in neuronal activity in both cortical and subcortical brain regions with incredibly high spatial resolution (Darmani et al. 2022). The current study will focus on targeting multiple regions playing a significant role in regulating various cognitive and repeated actions in OCD. We will assess safety and efficiency of TUS to different parts of the brain in alleviating OCD symptoms.

Inclusion Criteria will be:

• Male or female, aged 21-55 years, and fluent English speaking.
• Participants score ≥ 17 on the Obsessive-Compulsive Inventory-Revised (OCI-R).
• Participant is willing and able to give informed consent for participation in the trial.
• Participant is willing to comply with all trial requirements and committed to participating in all six testing sessions.

Exclusion Criteria will be:

The participant may not enter the trial if ANY of the following apply.

History:

• serious head trauma or brain surgery
• (first-degree relatives with) epilepsy, convulsion, or seizure
• diagnosis of a neurological or psychiatric disorder (other than OCD)
• adverse reactions to non-invasive brain stimulation
• participation in another short-term non-invasive brain stimulation study in the past 3 days
• participation in another long-term non-invasive brain stimulation study in the past 28 days
• recent head trauma that was diagnosed as a concussion or associated with loss of consciousness

Current:

• pregnancy or planning a pregnancy during the course of the trial
• use of psychoactive drugs or any drugs listed in the Neurostimulation Safety Report
• heart pacemaker, mechanical heart valve, mechanical implant such as an aneurysm clip, hip replacement
• metal in the head or body
• claustrophobia
• extreme mood fluctuations
• predisposition to fainting spells (syncope)
• medication that will interfere with the study or constitutes an increased risk of adverse effects (e.g., affects brain excitability)
• hearing problems or ringing in the ears
• skin diseases or sensitivity at intended TUS stimulation site
• Any significant disease or disorder which, in the opinion of the Investigator, may either put the participants at risk because of participation in the trial, or may influence the result of the trial, or the participant's ability to participate in the trial.

Last 24 hours:

• more than four alcoholic units
• recreational psychoactive drugs
• antibiotics

Anonymous behavioral data upon publication

data will be available after analysis of primary and secondary outcomes are completed

anyone with access to the link to the data (OSF)