Neuroscientists achieve "foreground theory" at the level of individual neurons

The mechanisms behind decision-making have been a long-standing focus of
neuroscience research.
But now, researchers from Japan have discovered new information
about how reward systems in the brain process risky decisions.

In a recent study published in the journal Nature Communications, researchers at the University of Tsukuba revealed that individual neurons in neural circuits that process reward information are consistent
with well-established theories used to describe the decision-making process 。 Prospect theory, first proposed in the 70s of the 2002 Nobel Prize winner in economics and professor at Princeton University in the United States, is a very influential concept used to describe how people and animals make choices
.
The main contents of prospect theory include: most people are risk-averse when faced with profit; Between a defined benefit and a "gamble", most people will choose a defined benefit
.
When you can definitely make 3,000 yuan and you have an 80% chance of making 4,000 yuan and a 20% chance of getting nothing, most people choose the
former.

Although this theory has been supported by thousands of studies, the limitations of human neuroimaging techniques in temporal and spatial resolution make it impossible for researchers to determine whether the activity of individual neurons follows this pattern, which is exactly the problem
that researchers at the University of Tsukuba want to solve.

Author Professor Hiroshi Yamada and Professor of Economics Agnieszka Tymula said: "Although the field of neuroeconomics has made great strides in understanding how the brain makes economic decisions, we still don't know how the reward circuit handles subjective value judgments
in this context.
This has important implications
for understanding the relationship between subjective value judgments and perceptions of the probability of a given outcome.
”

To test this, the researchers trained rhesus monkeys to perform two lottery tasks, one in which they chose between two options with different reward probabilities and one in which they did not make a choice but received a reward
at the end of the trial.
Neural activity of monkeys as they performed tasks was recorded, and the correspondence between behavioral task performance and neural activity was
assessed.
"The results are surprising," explains author Professor Yasuhiro Tsubo
.
"We found that individual neuronal activity in the four core regions of the reward circuit reflected the subjective value judgments made by the monkeys when completing economic decision-making tasks, suggesting that the activity fits within the framework
of prospect theory.
"

In addition, patterns of neural activity corresponding to foreground theory are distributed in many regions
of the reward system.

Professor Agnieszka Tymula said: "Our study shows for the first time that prospect theory can be used to describe the activity of
individual neurons in reward systems.
"

The activity of individual neurons in monkeys corresponded to their risk appetite and probability-weighted behavior, validating the findings
of human neuroimaging studies.
In addition, this new evidence supports the idea of a neuronal foreground theoretical model in which computation is distributed in
neural structures that process rewards.
These results open up exciting new avenues
for future work.