Dr. Casey Halpern — A functional neurosurgeon and chief of stereotactic functional neurosurgery at Penn Medicine. He specializes in deep brain stimulation and focused ultrasound, and researches the brain circuits behind compulsive behaviors like OCD, addiction, and eating disorders.
The gist
Andrew Huberman revisits a conversation with neurosurgeon Dr. Casey Halpern about the brain basis of compulsive and impulsive behaviors. Halpern explains what neurosurgeons do, how deep brain stimulation (DBS) treats Parkinson's tremor, and how the same approach is being adapted for psychiatric conditions like OCD, depression, and binge eating disorder. The discussion centers on the nucleus accumbens and reward circuits, and the shared theme of pursuing a reward despite risk. They also cover non-invasive tools (TMS, MRI-guided focused ultrasound), the limits of current treatments like CBT and SSRIs, and the potential role of machine learning in predicting impulsive episodes before they happen.
Big reveals
- Stimulating motor circuits in Parkinson's patients sometimes unexpectedly improved their mood, gambling problems, and OCD symptoms.
- Even with the best therapies, about 30% of OCD patients continue to suffer, and surgical responder rates are only around 50%.
- Halpern's team identified 'craving cells' and obsession-related cells in the operating room, analogous to tremor cells in Parkinson's.
- Patients knowingly under video surveillance still binge during lab mood-provocation studies because they simply cannot control it.
- Halpern's guiding principle: 'we have to get in the brain before we get out of it' to define non-invasive treatment targets.
- Compulsive disorders affect roughly 50 million Americans, but only about 200,000 DBS surgeries have ever been performed worldwide.
Things worth remembering
- 90% of what neurosurgeons do nationally is spine work like herniated discs and lumbar fusions, not brain surgery.
- In DBS the implanted wire isn't the therapy; the therapy is electricity delivered through its tip 'like a medication.'
- A capsulotomy can intentionally destroy 3-4mm of brain tissue with no obvious side effects, likened to removing an appendix.
- The nucleus accumbens gates reward-seeking; when perturbed, a rat will chase a reward despite repeated foot shocks.
- OCD, addiction, and eating disorders share a common denominator: 'urge despite the risk.'
- TMS is FDA-approved for depression, OCD, and nicotine addiction, but lacks spatial precision.
- MRI-guided focused ultrasound can ablate brain tissue with no incision and is FDA-approved for tremor.
- Operating-room electrodes are about a tenth of a millimeter wide; home-implant devices are ten times larger and detect thousands of cells.
- Researchers use a validated 'mood provocation' with a psychiatrist plus eye-tracking to capture the brain signal right before a binge bite.