Risky Behavior Tied to Two Key Brain Regions

A person’s tolerance for taking risks may have a foothold in two distinct regions of the brain, shows a new animal study.

The study, assessing risk-and-reward behavior among rats, may provide clues as to why some people prefer to live a steady, predictable life while others are more prone to taking chances.

The researchers monitored two brain regions — the orbitofrontal cortex and basolateral amygdala regions — during weeks of experimentation with rats, during which time they assessed how likely the animals were to work for a reward.

The researchers presented the animals with the option of choosing from two images on an iPad-like device, which, when selected, would lead to the reward of a sugar pellet. However, the researchers varied the amount of time that lapsed before rewarding the rats with a sugar pellet depending on the image they selected. Choosing one image led to a reward after 10 seconds, while selecting the other one led to a reward at an uncertain time.

The latter option is considered the riskier choice because the animals might receive a sugar pellet after five seconds or have to wait as long as 15 seconds.

After training the rats to play the game for about a month, the researchers discovered that the animals could detect changes in the amount of time they had to wait when selecting the riskier option — and that led to variations in their brain activity.

“When the rats experienced more variation in those wait times for their reward, the amount of the brain protein gephyrin in the basolateral amygdala region doubled,” report the study authors.

Gephyrin is known as a critical element of neural functioning, according to research.

The researchers also discovered that switching up the wait times had an effect on the animals’ behavior. For one portion of the trial, they made one screen selection better than the other. That is, selecting one screen led to a much shorter wait time for the sugar pellet than choosing the other screen.

While all of the animals eventually learned the trick and opted for the screen with the shorter wait time, some rats that had an impaired basolateral amygdala took longer to figure it out — they were about two days behind the normal rats.

The researchers also found that animals with an impaired orbitofrontal cortex never learned the trick at all. Those animals simply never learned that one option was more rewarding than the other.

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In addition to rising levels of gephyrin, the researchers found that levels of a brain protein called GluN1 also increased when the animals were faced with a risk-reward situation.

“I think the experience of uncertainty is making these changes occur in these brain regions,” said Alicia Izquierdo, UCLA associate professor of Psychology and a member of UCLA’s Brain Research Institute.

Previous research has found that the orbitofrontal cortex and basolateral amygdala are key elements of decision-making, and the new study makes the case that those brain regions are even more critical during times of change or uncertainty.

The study appeared in the journal eLife.