Summary:
By recording directly from electrodes implanted in the human orbitofrontal cortex, neuroscientists discovered two neighboring circuits locked in a millisecond-by-millisecond “tug-of-war” between taking a risk and playing it safe. The distinct neural patterns predict whether a person will approach or avoid a hazard half a second before they take action, offering a precise target for therapies treating OCD, depression, and addiction.
Key Facts:
- Direct Millisecond Readout: Using intracranial electrodes in surgical epilepsy patients, researchers monitored human orbitofrontal cortex activity in real time, bypassing standard fMRI limitations.
- Opposing Neural Circuitry: A medial region (medial orbital sulcus) fires when opting into a risk, while a lateral patch located just two centimeters away fires when avoiding danger, oscillating rapidly like an electrical switch rather than a gradual dial.
- Clinical Potential: The neural activity signature accurately predicts choices 500 milliseconds before a person physically acts, offering biomarkers to calibrate targeted neuromodulation for conditions marked by pathological avoidance (such as OCD and depression) or compulsive risk-taking (such as addiction).
Source: UCSF
Every single day, the human brain performs thousands of rapid calculations weighing potential danger against tempting rewards. Should you dash through yellow traffic lights to avoid being late, or pump the brakes? Should you pull another dollar from your wallet at the casino, or walk away?
Now, an interdisciplinary team from UC San Francisco and UC Berkeley has pinpointed the anatomical hub where these high-stakes decisions take shape.
Published in Nature Neuroscience, their findings reveal that two adjacent brain patches in the orbitofrontal cortex engage in a rapid battle of signals, predicting a participant’s choice roughly half a second before they execute it.
“We’ve long suspected that this region was where the brain weighs reward against risk, but we’ve never been able to measure it while it is happening in the human brain in real time until now,” explained Edward Chang, MD, chair of Neurological Surgery at UCSF and co-senior author of the study.
Moving Beyond fMRI with Immersive Gaming
For years, investigations into human decision-making relied heavily on functional magnetic resonance imaging (fMRI). However, air-filled sinuses behind the eyes distort magnetic fields, blinding scanners to clean signals from the orbitofrontal cortex. Furthermore, static fMRI tasks often leave volunteers disengaged.
“They’d be falling asleep, and I thought there was no way they really cared about what they were doing,” said lead author Clara Starkweather, MD, PhD, a neurosurgery chief resident at UCSF. “But then I’d see patients sitting in their beds playing Candy Crush, getting really into it.”
To tap into that genuine intrinsic motivation, Starkweather developed an immersive video game. Participants navigate labyrinthine hallways lined with explosives to reach glowing treasure chests. In each trial, players face a single, critical crossroad: brave a bomb-lined corridor for a chance at precious rubies, or avoid the hallway to preserve their score.
Six patients who had temporary intracranial electrodes implanted for surgical evaluation of epilepsy volunteered to play the game while their neural activity was monitored on a millisecond timescale.
A Biological Tug-of-War
The direct intracranial recordings unveiled a clear anatomical divide:
- The Medial Orbital Sulcus: Located toward the midline of the brow, this region surges with activity when a player decides to confront a risk.
- The Lateral Orbitofrontal Patch: Positioned roughly two centimeters outward toward the temple, this area spikes in activity whenever a player opts to retreat or play it safe.
These neighboring clusters operated in exact, inverse synchronization. When one spiked, the other dropped.
Traditional neurocomputational models have assumed that decisions are made by accumulating sensory evidence over time until a threshold is crossed—analogous to a dial turning smoothly. But computational modeling developed by Starkweather and co-senior author Robert Knight, MD, of UC Berkeley showed a very different reality.
“What we saw instead was more like a switch flipping back and forth, oscillating between two extremes until one held,” said Knight. On obvious choices, such as a hallway filled with treasure and zero bombs, the “go” signal won out nearly instantaneously. On ambiguous, high-conflict choices, the two regions rapidly flickered back and forth before one side finally dominated.
By observing which circuit won the tug-of-war, scientists could accurately forecast whether the participant would advance or retreat 500 milliseconds before their hand hit the controls.
Personalizing Psychiatric Neuromodulation
These insights hold transformative implications for neuropsychiatry. Imbalances in the approach-avoidance calculus underlie multiple debilitating conditions. Major depressive disorder, severe anxiety, and obsessive-compulsive disorder (OCD) often manifest as hyperactive risk avoidance, whereas substance abuse and gambling disorders reflect runaway approach behavior.
While deep brain stimulation (DBS) and transcranial stimulation are increasingly used to treat severe psychiatric illness, targeting the orbitofrontal cortex has yielded mixed outcomes because the region was treated as a monolith. Differentiating the “stop” zone from the “go” zone just two centimeters away could allow clinicians to calibrate neuromodulation with millimeter precision.
“Right now, psychiatry mostly relies on asking people how they feel,” said Starkweather. “I want to give it something more objective: a real, measurable signature of how someone’s brain weighs risk, so treatment can target the specific circuit that’s off, in addition to a mood score.”
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by our staff.
About this Neuroscience Research:
- Media Contact: Laura Kurtzman
- Source: UCSF
- Image Credit: Image generated for Neuroscience News
- Original Research is Open Access: Nature Neuroscience (September 15, 2026). “Intracranial recordings in humans reveal differential contributions of medial and lateral orbitofrontal cortex to approach–avoidance decision-making” Authors: Clara Kwon Starkweather, Ethan H. Willbrand, Kristin Sellers, Patrick W. Hullett, Andrew D. Krystal, A. Moses Lee, Kevin S. Weiner, Jon T. Willie, Peter Brunner, Ming Hsu, Edward F. Chang & Robert T. Knight.
- DOI: 10.1038/s41593-026-02444-4
Abstract
Intracranial recordings in humans reveal differential contributions of medial and lateral orbitofrontal cortex to approach–avoidance decision-making
Approach–avoidance refers to the psychological conflict in which deciding to approach a reward also carries potential punishment. The orbitofrontal cortex (OFC) is proposed to arbitrate approach–avoidance decisions, yet little is known about the real-time computations within OFC during these decisions. We conducted intracranial recordings in humans implanted with stereotactic electroencephalography electrodes in the OFC while they played a gamified approach–avoidance task.
Here we identified two anatomically distinct signals within the OFC prior to approach: an increase in activity within the medial compartment and a decrease within the lateral compartment.
Prior to decisions, these signals rapidly alternated between discrete pro-approach and pro-avoidant states, thus introducing a new functional architecture within the human OFC during decision-making.
