Modulating uncertainty and risk-taking with tACS
Risk is an inevitable factor when making decisions. Most decisions we make freely we do with much certainty. However, in certain situations a more uncertain option may lead to more reward than a safe option. In these situations it might be good to take the risk. Our willingness to take risk in uncertain situations differs from person to person. Some prefer to stay with safe options even if other options may lead to more reward. This is called exploitation of known outcomes. Others prefer to take the risk and explore new option, even if it sometimes backfires. This is known as exploration of uncertain outcomes. Although such attitudes are somewhat stable, they can also differ over time within a single participant. One day you may feel more inclined to take risk than another day. In this study we explored if the willingness to take risk could be modulated with transcranial alternating current stimulation (tACS).
Risk-taking has been associated with frontal cortex theta oscillations. More specifically, the ratio of theta oscillations between left and right prefrontal cortex theta oscillations. With tACS brain oscillations can be modulated. We used two montages and explored if risk taking changes.
Participants performed a gambling task. In this task risk gradually increases. Subjects build up a points every round. If they bank the summed points they are safe. But there is a limited amount of trials. So, you can wait long to bank, which is risky as you may win a lot or lose everything. Banking early is a safe option, but will result in a low end score.
TACS was applied at 5 Hz and 1 mA peak-to-peak during this task in 18 healty volunteers. Participants participated in three sessions, in two they received actual tACS and in the third they received a placebo (sham tACS).
With the application of prefrontal tACS perceived uncertainty went significantly up, meaning that participants spent longer time to think about whether or not to take a risky option. Interestingly, this did have no effect on how much risk they actually took.
We did not find evidence that tACS can modulate risk-taking behavior. That does not mean that tACS is unaffective, as it did affect the perceived uncertainty of decisions. Others have shown that tACS can affect risk-taking (Sela et al., 2012; Dantas et al. 2021). Thus, the exact parameters needed to modulate risky behavior need to be further explored in the future.
Wischnewski & Compen (2022). Effects of theta transcranial alternating current stimulation (tACS) on exploration and exploitation during uncertain decision-making. Behav Brain Res, 426, 113840. https://doi.org/10.1016/j.bbr.2022.113840