# A gut feeling: Exploring the effects of probiotics on risk-taking behavior using TMS

## TL;DR

This study finds that probiotics can increase risk-taking behavior in a gambling task, independent of brain stimulation effects.

## Contribution

The study is among the first to link probiotics to risk-taking behavior via the gut-brain axis using TMS.

## Key findings

- Probiotics increased risky choices and response times in the Maastricht Gambling Task.
- Probiotics' effects on risk-taking were independent of TMS stimulation to the VMPFC or SPL.
- VMPFC inhibition led to increased risk-taking, but this was not linked to probiotics.

## Abstract

This study explores the impact of the gut-brain axis (GBA) on risk-taking through a 4-week, double-blinded, placebo-controlled probiotics protocol and the Maastricht Gambling Task (MGT). We used transcranial magnetic stimulation (TMS) on the ventromedial prefrontal cortex (VMPFC), a region thought to mediate GBA signals in risk-related decisions. Continuous theta burst stimulation (cTBS) targeted the VMPFC, with the superior parietal lobule (SPL) and sham as control conditions, applied before and after the probiotics/placebo intervention. Results show that probiotics significantly increased risky choices and response times in the MGT compared to placebo, without reducing choice optimality. VMPFC stimulation, independent of probiotics intake, also led to riskier choices when controlling for task repetition. The nonsignificant interaction between probiotics and VMPFC stimulation suggests that the VMPFC does not play a key functional role in the effects of probiotics on risk-taking behavior. These findings offer insights into GBA influences on human decision-making through probiotics.

•Probiotics increased risk-taking vs. placebo in the Maastricht Gambling Task•Response time increased, and choice optimality was not compromised•Probiotics' effects were independent of TMS stimulation (VMPFC or SPL)•VMPFC inhibition led to order-dependent (task repetition) increases in risk-taking

Probiotics increased risk-taking vs. placebo in the Maastricht Gambling Task

Response time increased, and choice optimality was not compromised

Probiotics' effects were independent of TMS stimulation (VMPFC or SPL)

VMPFC inhibition led to order-dependent (task repetition) increases in risk-taking

Neuroscience; Behavioral neuroscience; Microbiology