Animals navigate unpredictable environments not just by reacting to new situations, but by making inferences about their surroundings. For example, squirrels learn that certain bird calls do not indicate a predator, allowing them to remain calm when these sounds are heard again. However, the neurological basis for these inferences has remained largely elusive—until now.
In a groundbreaking study published in the journal Neuron, researchers from New York University have pinpointed a specific brain region responsible for this cognitive process. The study identifies the orbitofrontal cortex (OFC) as the brain’s “inference engine,” enabling animals to adapt their understanding of the world based on evolving circumstances.
The Role of the Orbitofrontal Cortex
“To survive, animals cannot simply react to their surroundings,” explains Christine Constantinople, a professor at NYU’s Center for Neural Science and the study’s senior author. “They must generalize and make inferences—a cognitive process that is among the most vital and complicated operations that nervous systems perform. These findings advance our knowledge of how the brain works in applying what we’ve learned.”
The implications of this discovery extend beyond understanding animal behavior. The researchers suggest that these insights could illuminate the workings of neuropsychiatric disorders such as bipolar disorder and schizophrenia, where the ability to make inferences is often impaired.
Experimenting with Inference
The study, which included contributions from NYU’s Center for Data Science, involved a series of experiments with laboratory rats. The rodents were trained to obtain water rewards by recognizing audio and light cues indicating the presence and volume of water in designated ports. The total water amounts varied, presenting “low,” “high,” and “mixed” states, with some water quantities appearing across multiple states.
This experimental design aimed to assess whether the rats could make inferences during trials. The hypothesis was that rats would wait longer for a 20 microliter water block in a “low” state, anticipating no further rewards, compared to the same amount in a “high” state, where more water was available.
“In a low state, if they were making inferences, they would wait longer for water to come because they were not going to get more water on the next trial—so it’s worth the wait,” explains Constantinople. “However, 20 microliters is the worst option in a high state, meaning it’s worth less, so they would spend less time waiting for it.”
The experiment mirrored a “willingness-to-pay” task in economics, where humans determine the value of different items. In this study, the rats “paid” with their time, indicating their understanding of the reward system.
Unveiling the Inference Engine
The results were telling. Rats trained in the experiment waited longer for water in low states and less time in high states, demonstrating their ability to infer the reward state. Untrained rats, however, did not exhibit this behavior.
Crucially, when the OFC was disrupted, trained rats lost their ability to update their understanding of available rewards, indicating that the OFC plays a direct role in making inferences in changing situations. These conclusions were drawn from recordings of more than 10,000 neurons.
The study was supported by grants from the National Institutes of Health (DP2MH126376), the National Science Foundation (R01MH125571, K01MH132043, 5T32MH019524, 5T90DA043219, and F31MH130121), and the Department of Energy. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
Implications for Future Research
This discovery not only enhances our understanding of animal cognition but also opens avenues for exploring human neurological disorders. By understanding how the OFC contributes to inference-making, researchers may develop new strategies for addressing cognitive impairments associated with mental health conditions.
As science continues to unravel the complexities of the brain, studies like this underscore the intricate connections between cognitive processes and neurological structures. The findings from New York University’s research offer a promising step forward in comprehending the sophisticated operations of the mind.
