Behavior
Using Virtual Environments to Study Gut Microbiome-Linked Decision Making During Road Crossing in Older Adults Kshitij Sachdev* Kshitij Sachdev Sachdev Sachdev Sachdev Sachdev Sachdev Sachdev The University of Iowa
Background: Older adults experience disproportionately high rates of pedestrian injury and mortality, in part due to age-related declines in Executive Function (EF) that impair safe road-crossing decisions. The Gut Microbiome (GM) regulates brain function via the gut-brain axis, including through microbial metabolites such as Short-Chain Fatty Acids (SCFAs). However, the role of the GM in decision making remains largely unexplored.
Methods: Participants (n = 102), aged 60-87, completed cognitive testing, a virtual reality (VR) road-crossing task, and provided stool samples. GM composition was characterized using 16s sequencing to derive alpha and beta diversity metrics. Stool SCFAs (acetate, butyrate, propionate) were quantified using mass spectrometry. EF was assessed using the NIH Cognitive Toolbox and Trail Making Test, a behavioral measure of EF. In the VR task, participants crossed two lanes of opposing traffic 20 times, with repeated crossing opportunities defined by temporal overlap between near- and far- lane traffic gaps. VR Crossings were modeled using logistic mixed-effects regression with participant random intercepts, including traffic structure, microbiome features, and their interaction as predictors, adjusting for age, gender, and education. Associations between GM, SCFAs, and EF were evaluated using linear regression and PERMANOVA.
Results: Higher butyrate levels were associated with faster performance on Trail Making Test Part A (β = −0.0259, p = 0.048). Beta diversity (Bray-Curtis) was associated with NIH Toolbox measures of EF (R2 = 6.12%, p = 0.048), Inhibitory Control (R2 = 6.13%, p = 0.053), and Processing Speed (R2 = 6.11%, p = 0.057). In the VR task, gap acceptance was strongly driven by near-far lane overlap. Alpha diversity modestly modified this relationship (p = 0.084), such that individuals with lower microbial diversity showed a steeper increase in crossing probability as overlap increased, indicating reliance on larger gaps.
Conclusion: These findings suggest lower microbial diversity amplifies conservative gap-selection strategies during road crossing. Together, these results support the gut microbiome as a modifiable target for improving cognitive mechanisms underlying pedestrian safety and decision making in aging populations.
