Effects of theta transcranial alternating current stimulation (tACS) on exploration and exploitation during uncertain decision-making

Abstract

Exploring ones surroundings may yield unexpected rewards, but is associated with uncertainty and risk. Alternatively, exploitation of certain outcomes is related to low risk, yet potentially better outcomes remain unexamined. As such, risk-taking behavior depends on perceived uncertainty and a trade-off between exploration-exploitation. Previously, it has been suggested that risk-taking may relate to theta activity in the prefrontal cortex. Furthermore, previous studies hinted at a relationship between a right-hemispheric bias in frontal theta asymmetry and risky behavior. In the present double-blind sham-controlled within-subject study, we applied bifrontal transcranial alternating current stimulation (tACS) at the theta frequency (5 Hz) on eighteen healthy volunteers during a gambling task. Two tACS montages with either left-right or posterior-anterior current flow were employed at an intensity of 1 mA. Results showed that, compared to sham, theta tACS increased perceived uncertainty irrespective of current flow direction. Despite this observation, no direct effect of tACS on exploration behavior and general risk-taking was observed. Furthermore, frontal theta asymmetry was more right-hemispherically biased after posterior-anterior tACS, compared to sham. Finally, we used electric field simulation to identify which regions were targeted by the tACS montages as an overlap in regions may explain why the two montages resulted in comparable outcomes. Our findings provide a first step towards understanding the relationship between frontal theta oscillations and different features of risk-taking.

Modulating hierarchical learning by high-definition transcranial alternating current stimulation at theta frequency

“…In line with previous NIBS studies about adaptive learning (medium effect size, Cohen's d = 0.5) (Soutschek et al 2018;Wischnewski and Compen 2022), a priori power analysis conducted via G*Power 3.1.9 (Faul et al 2007) showed that 34 participants would ensure 95% statistical power. This calculation was performed on a paired t-test, with a power of 0.8 and an α = 0.05.…”

“…Previous studies established links between theta frequency and uncertainty (Cavanagh et al 2012; Wischnewski and Compen 2022). For example, the increase in reaction time during a decision-making task when theta tACS was applied, has been suggested to reflect an increase in perceived uncertainty (Wischnewski and Compen 2022). Consistently, our findings further provide insight into how theta tACS may influence subjective uncertainty from a computational perspective.…”

Modulating hierarchical learning by high-definition transcranial alternating current stimulation at theta frequency

“…Previous studies established links between theta frequency and uncertainty (Cavanagh et al 2012;Wischnewski and Compen 2022). For example, the increase in reaction time during a decision-making task when theta tACS was applied, has been suggested to reflect an increase in perceived uncertainty (Wischnewski and Compen 2022).…”

“…The copyright holder for this preprint this version posted August 13, 2022. ; https://doi.org/10.1101/2022.06.28.497899 doi: bioRxiv preprint Cohen's d = 0.5) (Soutschek et al 2018;Wischnewski and Compen 2022), a priori power analysis conducted via G*Power 3.1.9 (Faul et al 2007) showed that 34 participants would ensure 95% statistical power. This calculation was performed on a paired t-test, with a power of 0.8 and an α = 0.05.…”