The CogLinks model shows how the brain adapts to changing rules

Every day, your brain makes thousands of decisions under conditions of uncertainty. In most cases you are right. When you don’t do that, you learn. But when the brain’s ability to assess context or assign meaning weakens, thoughts and behavior can go astray. In mental disorders ranging from attention deficit hyperactivity disorder to schizophrenia, the brain may misjudge how much evidence to gather before taking action, or fail to adapt when the rules of the world change based on new information.

Uncertainty is built into the brain’s wiring. Imagine groups of neurons casting votes – some optimistic, some pessimistic. Your decisions reflect the average.” When this balance is disturbed, the brain can misread the world: giving too much importance to random events, as in schizophrenia, or getting stuck in rigid patterns, as in obsessive-compulsive disorder.

Understanding these duds has long been a challenge for scientists. The brain speaks the language of individual neurons. However, fMRI – the tool we use to study brain activity in humans – tracks blood flow, not the electrical oscillations of individual brain cells.”

Michael Halassa, professor of neurology, Tufts University School of Medicine

Filling this gap means combining insights from single-cell studies in animals, imaging of the human brain and behavior. Now a new type of computer model, based on real biology, allows scientists to simulate how brain circuits make decisions and adapt to changing rules.

Called Gear cablesthe model incorporates biological realism into its design, reflecting how real brain cells are wired and encoding how they assign value to often ambiguous and incomplete observations about the external environment. Unlike many artificial intelligence systems that act as “black boxes”, Gear cables shows researchers exactly how virtual neurons connect structure to function. As a result, scientists can map how this virtual brain learns from experience and changes based on new information.

In study published on October 16 in used by senior author Halassa and colleagues at the Massachusetts Institute of Technology (MIT). Gear cables to investigate how brain circuits coordinate flexible thinking. Like a flight simulator for the brain, Gear cables allow researchers are examining what happens when key decision-making circuits lose course. When they weakened the virtual connection between two simulated brain regions – the prefrontal cortex and medial thalamus – the system defaulted to slower, habit-based learning. This result suggests this pathway is essential for adaptive capacity.

To test whether these predictions held true in humans, the team then conducted a companion fMRI study research they both supervised Burkhard Pleger from the Ruhr University of Bochum and Halassa. Volunteers played a game in which the rules unexpectedly changed. As expected, the prefrontal cortex handled planning and a deep, central area of ​​the brain called the striatum guided habits, but the medial-frontal thalamus lit up as players realized the rules had changed and adjusted their strategy.

Imaging confirmed the model’s predictions: The medial thalamus acts as a switchboard connecting the brain’s two main learning systems – flexible and habitual – helping the brain infer changes in context and change strategies accordingly.

Halassa hopes the research will help lay the groundwork for a new type of “algorithmics.” psychiatry”, in which computer models help discover how mental illnesses arise from changes in brain circuits, identifying biological markers to precisely target treatments.

“One of the most important questions in psychiatry is how to relate our knowledge of genetics to cognitive symptoms,” he says. Face Brabeeb Wang, main author Gear cables research, co-author of the book fMRI research and MIT graduate student in Halassa’s lab.

“Many of the mutations associated with schizophrenia affect chemical receptors found throughout the brain,” Wang says. “Future applications Gear cables may help us see how these widespread molecular changes may make it harder for the brain to organize information for flexible thinking.”