Study Reveals the Brain Areas Responsible for Economic Decisions Under Risk in Rats

Sunday - October 29 2023, 06:20 UTC - 1 year ago

Neuroscientists have uncovered a key brain area in rats that encodes the value of economic choices when faced with the uncertainty of a lottery.The research team used pharmacological and optogenetic silencing to confirm the results. The findings provide a foundation for understanding the neurobiology of risky decisions, and could be beneficial in understanding and treating disorders where decision-making is impaired.

Neuroscientists have uncovered a key brain area in rats that encodes the value of economic choices when faced with the uncertainty of a lottery. This is the first time the causal role of frontal and parietal cortex has been tested in economic decision-making. The findings are critically important for our understanding of the neurobiology of risky decisions and could be beneficial in understanding and treating disorders where decision-making is impaired, such as Addiction.

"We live in a world where financial decisions have a huge impact, and our economic choices are typically associated with uncertainty. For example, right now the cost of living is rising and savers may be choosing whether or not to invest in the stock market to try to avoid their savings being diminished by high inflation. We wanted to develop a rodent model of economic decision-making that is similar to the kinds of problems humans encounter, so that we can understand how the brain makes choices when faced with uncertainty," said Jeffrey Erlich, Group Leader at the Sainsbury Wellcome Centre and corresponding author on the paper.

The researchers at the Sainsbury Wellcome Centre at UCL and NYU Shanghai presented rats with the choice of a ‘surebet’ (a small but guaranteed reward), or a lottery with a fixed probability. In each trial, a sound was played to the rats to indicate the magnitude of the potential lottery reward.

"We presented six sounds which each mapped to a different lottery offer. The worst offer was zero, so in that case the rats should never choose to play the lottery. This gave us a baseline, as there’s no reward-maximizing strategy that would ever choose zero. We were therefore able to quantify the offer-independent biases, which helped us get a better estimate of the true risk tolerance of the rats," explained Erlich.

To test the causal role of the frontal and parietal cortex in the rats’ decisions of whether to play the lottery, the researchers temporarily silenced two specific brain areas: the frontal orienting field (FOF) and the posterior parietal cortex (PPC). The team used pharmacological and optogenetic silencing to confirm the results.

The researchers found that the animals were less willing to take risks when FOF was silenced (with either pharmacological or optogenetic silencing), whereas there was a smaller, short-lived, effect when PPC was silenced. Using a Bayesian hierarchical model, the team found that FOF was affecting risk tolerance rather than a choice bias, as the rats were still willing to play the lottery when the potential reward was very high, but they became less likely to play when the lottery had an intermediate potential value. As expected, their behavior was unchanged when the potential lottery value was low.

To understand this behavior, the researchers developed a dynamical model of FOF silencing. The model suggests that the FOF is coding the value of the lottery and comparing it with the remembered value of the surebet, which did not change from trial to trial. And so, when FOF is silenced, the value of the lottery (which is dynamic as it is encoded on a trial-by-trial basis) shrinks, but the surebet value remains stable.

This study provides a crucial understanding of the way rats make economic decisions in uncertain situations. This could pave the way for our understanding of how humans make decisions where large financial implications are at stake. In addition, the results illuminate the neural mechanisms of decision-making in individuals with Yonathan cognitive deficits. It is hoped that this research could inform the development of therapies targeting the frontal and parietal cortex areas of the brain to help treat decision-making deficits in various pathologies.