iScienceFeb 18, 2026

Probiotics may influence risk-taking behavior measured by brain stimulation

Gut-Brain Axis Weekly Brief ↗PubMed ↗DOI ↗

Updated Jun 27, 2026

Abstract

Essence

Probiotics were linked to more risk-taking in a gambling task, while VMPFC stimulation did not explain that effect.

Evidence

In a 4-week double-blinded placebo-controlled human probiotics study using the Maastricht Gambling Task and TMS to VMPFC, SPL, or sham, probiotics increased risky choices and response times versus placebo without reducing choice optimality.

Caveat

The probiotics-by-VMPFC stimulation interaction was nonsignificant, so the proposed VMPFC mechanism was not supported.

Simplified

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.

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Probiotics may influence risk-taking behavior measured by brain stimulation

Abstract

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