FIGURE 4.

Associations between the driving genera and threat‐related brain processes. Principal components analysis (PCA) was used to reduce the dimensionality of brain variables, which resulted in seven PCs representing connectivity strengths during threat learning (task acquisition phase), threat reversal (task reversal phase), and percent BOLD signal change responses at the AIC and dACC. Results from four independent multiple regressions showed that brain responses predicted the relative abundance of Ruminococcus (a). While there were individual regression weights that were significant for (b) Bacteroides and (c) Oscillospira, the overall regression model was not significant. Variance in (d) Prevotella was not related to any specific set of brain measures. 95% confidence intervals are represented by the dashed red lines. (e) Multivariate analysis (sparse CCA, sCCA) showed a single significant mode of population covariation linking threat processing measures of brain activity and effective connectivity with Ruminococcus abundance. (f) Bold text shows microbiome and brain weights (coefficients) contributing to the sCCA. Features in grey text represent zero‐contributing features to the sCCA, as imposed by the $l_1$‐norm penalty term. Brain variables prefixed with an ‘A' refer to those occurring in the task acquisition phase, ‘R' refers to brain variables in the task reversal phase, and ‘SC’ refers to modulatory self‐connections