Optimal decision-making is a balance of experience and knowledge

In a constantly changing world, animals, including humans, must adapt quickly to their environment and make decisions that lead to the best possible outcomes. 

Typically, this type of learning occurs through direct experience, where animals rely on past experiences involving the same choices when faced with a decision between two specific options.

Balancing experience and knowledge

However, animals with more advanced brains, such as apes and monkeys, are capable of inferring the outcome of a decision based on their knowledge of similar past situations, even if they have not directly experienced those particular options before. 

This means that decision-making often involves a balance between experience-based strategies and knowledge-based strategies. In primates, the orbitofrontal cortex (OFC) is responsible for managing this balance. 

The brain’s role in decision-making 

The orbitofrontal cortex not only plays a direct role in decision-making but also helps to “update” the internal values primates use to evaluate the potential benefits of any given option. 

Moreover, the OFC is essential for assessing options that an individual has not directly experienced. 

Despite this understanding, the precise roles of the OFC in decision-making and whether these roles rely on separate neuronal pathways have remained unclear and difficult to study.

Fortunately, a research team from Japan has made significant progress in shedding light on this issue.

Selectively activating neuronal pathways 

The team was led by Kei Oyama and Takafumi Minamimoto from the National Institutes for Quantum Science and Technology. 

The researchers used a cutting-edge approach they previously developed to selectively activate and deactivate different neuronal pathways originating from the OFC in monkeys during specially designed behavioral tasks. This innovative method allowed the experts to uncover the independent functions of these pathways.

In these behavioral experiments, macaque monkeys were presented with two images to choose from, and depending on their choice, they received a predetermined amount of juice as a reward. The monkeys quickly learned to associate specific images with the amount of juice they would receive.

Capacity to learn from experience 

To further test the monkeys’ decision-making abilities, the researchers periodically changed the set of images presented and reversed the reward values, meaning the worst options became the best and vice versa. 

These tasks assessed the monkeys’ capacity to learn from experience (via trial and error) and to handle familiar situations (via knowledge-based inference).

As the monkeys performed these tasks, the researchers employed a genetically introduced chemical switch called a chemogenetic receptor, which could turn specific OFC neurons on or off upon the administration of a drug. 

Using computed tomography, positron emission tomography, and magnetic resonance imaging to guide their procedures, the team locally injected a drug to temporarily silence distinct neuronal pathways originating from the OFC.

Specific functions of the neuronal pathways 

By observing changes in the monkeys’ performance, the researchers determined the specific functions of these pathways. 

The experts discovered that the OFC pathway connecting to the caudate nucleus is critical for experience-based adaptation, while the pathway linking to the mediodorsal thalamus plays a key role in knowledge-based adaptation.

Understanding decision-making in humans

Given that monkey brains are remarkably similar to human brains in structure, the study’s findings hold important implications for understanding human behavior.

“One key implication of our work is that it could help explain why individuals approach the same situation in different ways. Some people may rely more on trial-and-error, while others prefer a more systematic approach based on prior knowledge,” Minamimoto explained.

“These differences in thinking styles, or ‘thought patterns,’ might be linked to how each person’s brain activates these specific circuits, and understanding these variations could help us develop personalized strategies for improving decision-making and problem-solving skills for those who might struggle with one particular type of thinking.”

Broader implications of the study 

Understanding the specific roles of brain structures also has significant implications for the study of neuropathologies and psychiatric disorders.

“Our findings could contribute to new treatments for mental and neurological disorders like obsessive-compulsive disorder, where patients have difficulty adapting to changing situations,” said Oyama.

“By targeting the specific brain circuits involved in these two strategies, we may be able to create more effective therapies that help restore balanced thinking.”

Furthermore, the research has potential applications in the fields of artificial intelligence and robotics, where insights into brain circuits could inspire the development of more adaptable systems capable of switching between different problem-solving methods depending on the situation.

Although the brain remains one of the most complex puzzles in the known universe, studies like this represent important progress toward a deeper understanding of how it operates, both in humans and other animals.

The study is published in the journal Nature Communications.

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