Dopamine neurons mull over your options

Date:
July 7, 2020
Source:
University of Tsukuba
Summary:
Researchers have found that dopamine neurons in the brain
can represent the decision-making process when making economic
choices. As monkeys contemplated whether or not to choose an item,
a subset of dopamine neurons transitioned from indicating the item's
value to indicating the monkey's ultimate decision. Encoding of
the decision into these dopamine neurons happened earlier than it
did in other parts of the brain related to economic decision-making.



FULL STORY ==========================================================================
In Indiana Jones and the Last Crusade, Indiana must choose his grail
"wisely," as a poor choice spells instant death. According to a new study
by Professor Masayuki Matsumoto at the University of Tsukuba, making these kinds of choices involves dopamine neurons in the brain. Specifically,
the study shows that dopamine neurons represent different parts of the decision-making process as it unfolds.


========================================================================== Although the choices we make are rarely as dramatic as Indiana's,
the ability to evaluate options and choose the one that leads to the
best outcome is critical -- even if the choice is simply from a lunch
menu. Researchers like Professor Matsumoto who study decision-making
in the brain often focus on what is called the "reward network." Two
important parts of this network are dopamine neurons deep in the midbrain
and a region called the orbito-frontal cortex in the front of the
brain. "We know that dopamine neurons encode reward prediction error,"
explains Professor Matsumoto. "They become very active after an animal
receives an unexpected reward and become less active as expectations
are learned." In their new study, the team wanted to find out what these neurons are doing as decisions are being made, rather than afterwards.

When making economic choices, typically, items are first evaluated,
then compared, a decision is made, and action is taken. This process
was replicated in a game for monkeys. The monkeys learned to associate
six pictures with different amounts of reward. They were shown one of
the images and could choose it and get the reward, or they could pass
and get the reward associated with a second image. With this setup, when
the first image gave a mid-level reward, the monkeys sometimes chose to
take the reward and sometimes risked passing to get a bigger reward. This allowed the researchers to separate the evaluation and decision processes.

The team found that dopamine neurons represented both parts of the
decision- making process. Some indicated the amount of reward represented
by the picture, and others indicated the final yes/no choice. Many
neurons displayed both types of information, transitioning from value
to choice over time. You can imagine Indiana's dopamine neurons firing
like crazy as he eyes a jewel-encrusted grail, but then dying down as he decides to choose the plain one. "These neurons especially reflect the
entire integrated decision-making process," says Professor Matsumoto,
"and we suspect that they send this decision out to other parts of the
brain such as the orbito-frontal cortex, and finally to the muscles for
an action to take place." The field of neuroeconomics is relatively new
and understanding the role of dopamine neurons in decision-making and risk-taking is critical. "The dopamine neurons we study are actually
the same dopamine neurons that die in Parkinson's disease and are over-sensitized in addition," says Professor Matsumoto. "Our research
may thus provide insight into decision-making deficits that might be
present in these illnesses."

========================================================================== Story Source: Materials provided by University_of_Tsukuba. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Mengxi Yun, Takashi Kawai, Masafumi Nejime, Hiroshi Yamada, Masayuki
Matsumoto. Signal dynamics of midbrain dopamine neurons during
economic decision-making in monkeys. Science Advances, 2020; 6
(27): eaba4962 DOI: 10.1126/sciadv.aba4962 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200707113327.htm

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