New research out of the Yale School of Medicine is the first to show that the size of a particular region of the brain can predict patterns in risky decision-making.
In a recent study which combined neuroanatomy with neuroeconomics, researchers working across three continents discovered that people with a larger volume in the posterior parietal cortex (PPC) are willing to take more risks, especially monetary ones. If these results are validated for other populations, it may be possible to make accurate estimations about the risk-taking distributions of people just from analyzing millions of existing brain scans, said Ifat Levy, study co-author and professor of comparative medicine and neurobiology at Yale School of Medicine. “In the past, people thought that function was the best window into the person’s mind,” said study first author Sharon Gilaie-Dotan of the Institute of Cognitive Science at the University College London. “But lately, it has been shown that on top of functional studies, neuroanatomy has a growing role in explaining people’s perception and behavioral traits.”
Until now, researchers studied the neural basis of risk preference by scanning individuals while they performed a test or reported their own behavior. While many of these functional imaging studies have linked certain neuronal activity to individuals’ risky attitudes, the researchers wanted to test if brain structure could also be an indication of how a person would behave, said Gilaie-Dotan.
A large amount of brain imaging data was collected from a functional study on risk-taking in 2010, but Levy, Gilaie-Dotan, and their colleagues recently decided to analyze the anatomical images. Before beginning this study, the researchers hypothesized that the lateral parietal cortex and medial prefrontal cortex were the areas most likely to predict these differences, since hundreds of functional MRI and electrophysiological studies have implicated those regions in decision-making and evaluation processes.
In the 2010 study, subjects made a series of 180 choices between two monetary lotteries varying in the degree of risk while their brains were scanned. The reference lottery, which was a 50 percent chance of winning $5, was present in every round, while the other lottery varied in risk and reward, but was always a higher risk than the reference lottery. All subjects were found to be risk-averse, but to varying degrees.
With this data, Levy and colleagues correlated the volume of each point in the brain with the individual’s risk attitude and looked for areas that showed a significant correlation. They discovered that the volume of the right PPC was highly predictive of individual risk preferences. Subjects with larger gray matter volume in this area demonstrated less risk aversion.
To confirm this finding, the researchers performed a similar study on a new group of subjects. Instead of scanning while subjects made monetary decisions, the participants first completed the task and then received an anatomical scan. Levy said the team found the same pattern as before.
Since the size of the PPC and an individual’s risk preferences are known to remain relatively stable over time, cortical volume could be a reliable biomarker in predicting a behavioral trait without requiring a person to undergo any behavioral tests at all, Gilaie-Dotan said. If the results of this study are validated, researchers and policymakers can extract PPC volume information from these scans and make estimations about the risk-taking behaviors of large populations from the millions of simple clinical scans that already exist.
Researchers said they recognized several caveats to their study. First, it is not clear why certain individuals have larger brain regions than others, and both genetics and the environment may play an important role in determining cortical volume. The causal direction of neuroanatomy and risk behavior has not been established either: The results do not determine whether a larger PPC volume causes individuals to make more risky decisions, or whether a history of such decisions influences brain anatomy.
Finally, all participants in this study were young university students from the northeastern United States, so further research needs to be conducted on other geographical, age and socioeconomic populations to confirm that the findings are universal, Gilaie-Dotan said. The researchers plan to answer this question in the near future. Indeed, Levy has already discovered some differences in risk-taking attitudes across ages which show that people become more risk-averse and lose cortical volume in the PPC as they grow older.
The finding appeared in the Journal of Neuroscience on Sept. 10.