Model 4 was identified by BMS as the best fitting model in both hemispheres. This model suggests that descending connectivity from the dACC and dlPFC are modulated during the PA condition. Arrow and glow widths are weighted to represent parameter strengths: green arrows represent positive endogenous couplings and experimental inputs; red arrows indicate negative endogenous couplings; yellow glow indicates positive PA-related modulatory effects; blue glow indicates negative PA-related modulatory effects. Abbreviates: P, baseline stimuli; PAG, periaqueductal gray; THAL, thalamus; pINS, posterior insula; dACC, dorsal anterior cingulate cortex; dlPFC dorsolateral prefrontal cortex.