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Researchers at the RIKEN Brain Science Institute (BSI)
in Japan have uncovered two brain signals in the
human prefrontal cortex involved in how humans
predict the decisions of other people. Their results
suggest that the two signals, each located in
distinct prefrontal circuits, strike a balance
between expected and observed rewards and choices,
enabling humans to predict the actions of people
with different values than their own.
Neural activity for the simulation of another person:
Reward Signal (red) and Action Signal (green).
Every day, humans are faced with situations in which
they must predict what decisions other people will
make. These predictions are essential to the social
interactions that make up our personal and
professional lives. The neural mechanism underlying
these predictions, however, by which humans learn to
understand the values of others and use this
information to predict their decision-making
behavior, has long remained a mystery.
Researchers at the RIKEN Brain Science Institute (BSI)
in Japan have now shed light on this mystery with a
paper to appear in the June 21st issue of Neuron.
The researchers describe for the first time the
process governing how humans learn to predict the
decisions of another person using mental simulation
of their mind.
Learning another person's values and mental
processes is often assumed to require simulation of
the other's mind: using one's own familiar mental
processes to simulate unfamiliar processes in the
mind of the other. While simple and intuitive, this
explanation is hard to prove due to the difficulty
in disentangling one's own brain signals from those
of the simulated other.
Research scientists Shinsuke Suzuki and Hiroyuki
Nakahara, a Principal Investigator of the Laboratory
for Integrated Theoretical Neuroscience at RIKEN BSI,
together with their collaborators, set out to
disentangle these signals using functional Magnetic
Resonance Imaging (fMRI) on humans.
First, they studied the behavior of subjects as they
played a game by making predictions about the
other's behavior based on the knowledge of others
and their decisions. Then they generated a computer
model of the simulation process to examine the brain
signals underlying the prediction of the other's
behavior.
The authors found that humans simulate the decisions
of other people using two brain signals encoded in
the prefrontal cortex, an area responsible for
higher cognition (Figure 1).
One signal involves the estimated value of the
reward to the other person, and is called the reward
signal, referring to the difference between the
other's values, simulated in one's mind, and the
reward benefit that the other actually received.
The other signal is called the action signal,
relating to the other's expected action predicted by
the simulation process in one's mind, and what the
other person actually did, which may or may not be
different.
They found that the reward signal is processed in a
part of the brain called the ventromedial prefrontal
cortex. The action signal, on the other hand, was
found in a separate brain area called the
dorsomedial prefrontal cortex.
"Every day, we interact with a variety of other
individuals," Suzuki said. "Some may share similar
values with us and for those interactions simulation
using the reward signal alone may suffice. However,
other people with different values may be quite
different and then the action signal may become
quite important."
For more information
http://www.riken.go.jp/
(MDN)
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