Essentials: Compulsive Behaviors & Deep Brain Stimulation | Dr. Casey Halpern
Dr. Casey Halpern, a neurosurgeon specializing in deep brain stimulation at Penn Medicine, discusses OCD, compulsive behaviors, and the brain circuits underlying urges and cravings. He explains current surgical and non-invasive treatments, the role of the nucleus accumbens in reward and compulsion, and the future of AI and machine learning in detecting and treating psychiatric disorders.
Summary
Dr. Casey Halpern, chief of stereotactic functional neurosurgery at Penn Medicine, begins by explaining the broad scope of neurosurgery and his specialized focus on deep brain stimulation (DBS) and transcranial focused ultrasound. DBS involves implanting a thin insulated wire deep into brain structures and delivering precise electrical stimulation, which has proven transformative for movement disorders like Parkinson's disease and is being explored for psychiatric conditions.
Halpern describes OCD as a spectrum disorder, noting that obsessive and compulsive tendencies can be adaptive at low levels but become debilitating when uncontrolled. First-line treatments include SSRIs, tricyclic antidepressants, and exposure and response prevention therapy (ERP), a form of cognitive behavioral therapy. However, roughly 30% of patients remain refractory to these treatments, and it is this severe population that Halpern targets with surgical interventions such as DBS and capsulotomy (ablation).
Halpern identifies a core neurological circuit involved in OCD, binge eating, addiction, and other compulsive disorders: the prefrontal and orbitofrontal cortex projecting to the basal ganglia and ventral striatum, particularly the nucleus accumbens. This region gates reward-seeking behavior, and when dysregulated, it drives compulsive pursuit of rewards despite negative consequences — a hallmark shared across OCD, eating disorders, and addiction. His research has focused on identifying 'craving cells' or 'obsession cells' in the nucleus accumbens that fire before a compulsive episode, with the goal of using DBS to intervene at that moment.
On non-invasive approaches, Halpern discusses TMS (FDA-approved for depression, OCD, and nicotine addiction) and MRI-guided focused ultrasound (FDA-approved for tremor). He acknowledges their promise but notes limitations in spatial precision and mechanistic understanding. He advocates for using invasive recordings — similar to stereoelectroencephalography used in epilepsy — to map disease-specific brain signals, which could eventually inform precise non-invasive targets for psychiatric conditions.
Halpern also addresses the role of AI and machine learning, expressing optimism about using physiological signals to anticipate compulsive or impulsive episodes before the patient is consciously aware of them. He draws a distinction between compulsion (urge-driven pursuit of a reward despite risk) and impulsivity (inability to delay gratification), noting that suicidality represents the most dangerous form of impulsivity. He emphasizes that while surgical solutions can only reach the most severe patients, the mechanistic insights they generate could inspire scalable, non-invasive therapies for the broader population affected by obesity, addiction, depression, and suicidality.
Key Insights
- Halpern argues that when DBS electrodes are placed to treat Parkinson's tremor, patients sometimes report unexpected improvements in gambling urges or mood, revealing that motor and limbic circuits overlap — and that therapeutic side effects can become the basis for new psychiatric indications.
- Halpern identifies a common neurological denominator across OCD, addiction, eating disorders, and other compulsive conditions: the nucleus accumbens gating 'urge despite the risk' behavior, and argues this single circuit may underlie some of the most prevalent public health crises in modern society.
- Halpern describes a laboratory paradigm where patients with binge eating disorder — even under full video surveillance and knowing they are being studied — still binge eat when a mood provocation is applied, which he interprets as evidence that awareness alone is insufficient for the most severe patients and that loss of behavioral control is the core pathology.
- Halpern contends that before non-invasive targets for psychiatric conditions like depression or OCD can be established with ultrasound or TMS, invasive recordings inside the human brain are necessary to identify disease-specific neural signals — and that the stereoEEG technique used in epilepsy surgery is being adapted for this purpose.
- Halpern argues that while only about 200,000 DBS surgeries have ever been performed — making it impossible for surgeons to address psychiatric epidemics affecting tens of millions — the mechanistic insights from invasive brain studies could inform rigorous, scalable non-invasive therapies and machine-learning tools to anticipate impulsive episodes before they occur.
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