In a groundbreaking study published in the journal Neuron, researchers from New York University have identified the orbitofrontal cortex (OFC) as a critical brain region that functions as an “inference engine” in animals. This discovery provides significant insights into how animals, much like humans, navigate and adapt to changing environments by making inferences about their surroundings.
Christine Constantinople, a professor at NYU’s Center for Neural Science and the senior author of the study, emphasized the importance of this cognitive process. “To survive, animals cannot simply react to their surroundings,” she explained. “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.”
Understanding the Brain’s Inference Mechanism
The study’s revelations come at a time when understanding the brain’s ability to make inferences could have broader implications, particularly in addressing neuropsychiatric disorders such as bipolar disorder and schizophrenia. These conditions often impair the ability to make inferences, and the research offers a promising avenue for further exploration.
The study involved a series of experiments with laboratory rats, conducted by a team that included researchers from NYU’s Center for Data Science. The experiments were designed to observe how rats inferred the availability of rewards—in this case, water—based on audio and light cues.
Experimental Design and Findings
In the experiments, rats were trained to recognize the presence and volume of water rewards, which varied in discrete amounts from 5 to 80 microliters. The water was offered in different states—”low,” “high,” and “mixed”—with some water amounts present in multiple states. This setup created a scenario where the underlying reward state was “hidden” to the animals, challenging them to make inferences.
The experiment was akin to a “willingness-to-pay” task in economics, where humans decide how much they would pay for different items. Here, the rats “paid” with their time, waiting for the water rewards. The trained rats demonstrated the ability to infer the reward state, waiting longer for water in low states and less time in high states, indicating their understanding of the value of the reward in different contexts.
“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,” explained 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 Role of the Orbitofrontal Cortex
The study’s most significant finding was the role of the OFC in this cognitive process. When the OFC was disrupted, the trained rats lost their ability to update their understanding of available rewards, unable to distinguish among hidden states. This suggests that the OFC is directly involved in helping the brain make inferences in changing situations.
These results were based on recordings of more than 10,000 neurons, providing robust evidence of the OFC’s involvement in inference-making. The implications of this research extend beyond animal cognition, offering potential insights into human brain function and disorders.
Implications for Human Health
The findings could pave the way for new approaches in understanding and treating neuropsychiatric disorders. By understanding how the brain makes inferences, researchers hope to develop better interventions for conditions where this ability is compromised.
The study was supported by grants from the National Institutes of Health and the National Science Foundation, among others, highlighting the collaborative effort and significance of this research.
The discovery of the brain’s “inference engine” marks a significant advancement in neuroscience, offering a deeper understanding of cognitive processes that are essential for survival in both animals and humans. As research continues, the potential applications of these findings in medicine and psychology could be profound, providing new pathways for addressing complex mental health challenges.
