Parietal Cortex Influences Risk-Taking Behaviour

Making decisions in situations involving risk and uncertainty is an inherent aspect of our daily lives. Should I obtain luggage insurance for my flight, cross the road when the light is red, or leave my current job for a new opportunity? Researchers at the HSE Institute for Cognitive Neuroscience conducted an experiment to clarify the role the parietal cortex plays in decision-making in the context of risk. They found that suppression of activity in the parietal cortex resulted in subjects being less inclined to take risks. A paper with the study findings has been published in Cerebral Cortex.

Scientists have long been trying to understand how our brains make decisions under uncertainty. Replicating real-life conditions in a laboratory setting can be difficult, adding complexity to research in this field. Simplified risk models are typically used in experiments; for example the study participants may be presented with a choice between receiving 200 roubles guaranteed or playing a lottery, where success could yield a higher reward but failure results in no winnings at all. Despite the apparent simplicity of these tasks, a comprehensive understanding of the brain processes underlying decision-making remains elusive.

Neuroimaging techniques such as functional MRI (fMRI) have revealed that the prefrontal and parietal cortical regions play active roles in the process of making decisions in situations involving risk. However, while much is understood about the role of the prefrontal cortex, that of the parietal cortex has been studied to a much lesser extent.

 

Scientists at the HSE Institute for Cognitive Neuroscience applied transcranial magnetic stimulation (TMS) to investigate the involvement of the posterior parietal cortex in decision-making under risk. This method enables temporary and safe suppression of activity in specific areas of the brain, thereby facilitating the study of changes in human behaviour before and after the stimulation of specific cortical regions and clarifying their respective roles in various cognitive processes.

The TMS method employs electromagnetic induction. A stimulator (coil) generating magnetic fields at specific frequencies and intensities is positioned near the subject's head. These currents readily penetrate through the skull and meninges, reaching nearby neurons at depths of up to 5 cm, where they can either activate or temporarily deactivate them.

Using TMS in research makes it possible to conduct multiple experiments under identical conditions with different individuals. This ensures a high level of control and reproducibility of the experimental setup.

Prior to this study, we had used a similar approach to investigate the role of the dorsolateral prefrontal cortex. Suppressing excitability in this region caused the subjects to act less rationally. For example, they paid less attention to the average winnings that could be obtained in a lottery. However, our findings in the new study are somewhat different.

Ksenia Panidi
Co-author of the study, Senior Research Fellow at the Centre for Cognition and Decision Making, Institute for Cognitive Neuroscience, HSE University

The experiment revealed that suppressing activity in the posterior parietal cortex decreased the subjects' risk appetite compared to the control group. However, the researchers emphasise that decision-making in a situation involving risk includes analysing a wide range of information, encompassing not only potential gains but also the likelihood of attaining them.

To further clarify the results, the authors employed economic models which help determine various parameters governing human behaviour. For instance, one of the parameters describes the subjective valuation of a monetary reward: the higher its perceived value, the greater the likelihood of risk-taking. Another parameter characterises one's perception of the likelihood of winning or losing in the lottery, essentially reflecting their relative optimism or pessimism.

According to the researchers, the reduced risk appetite observed when the posterior parietal cortex was suppressed was due to a decrease in the subjective valuation of money, rather than to participants becoming pessimistic about their chances of winning.

The study findings confirm those obtained by researchers in other laboratories. Often, the manner in which information is presented in experiments varies in detail, which can significantly impact the final results. In our case, we observe a relatively consistent effect that is no longer as dependent on factors such as the specific lotteries offered to participants. The study has raised new questions—specifically, it would be interesting to explore the interaction between the prefrontal and parietal cortices in the decision-making process of this type.

Ksenia Panidi
Co-author of the study, Senior Research Fellow at the Centre for Cognition and Decision Making, Institute for Cognitive Neuroscience, HSE University

IQ

May 06