Table 1.

Summary of this study’s hypotheses, predictions or questions, and results.

Embodied Predictive Interoception Coding (EPIC) Hypothesis	Experimental Prediction	Result in the Current Study
Interoception and visceromotor control are part of a unified brain system that supports allostasis (Fig 1)	Primary interoceptive cortex (e.g., dorsal mid/posterior insula) is anatomically and functionally connected to agranular and dysgranular visceromotor hubs of the cortex (e.g., sgACC, pACC, aMCC)	The interoceptive and visceromotor hubs are anatomically connected in monkeys (Table 2) The interoception and visceromotor hubs are functionally connected in humans (Fig. 2, Supplementary Table 1) Coordinates for human hubs are show in Table 3
	The allostatic/interoceptive system also includes subcortical and brainstem visceromotor regions.	Previously established subcortical and brainstem visceromotor regions (e.g., hypothalamus, periaqueductal gray) are part of the unified system for allostasis/interoception (Fig. 4, Supplementary Figure 6)
	The allostatic/interoceptive brain system contains limbic cortices.	The allostatic/interoceptive system comprises two established large scale brain networks that contain the majority of limbic cortices: the salience network and the default mode networks (Fig. 3, Supplementary Figure 3)
	Connectivity in the allostatic/interoceptive system is related to an implicit performance measure of interoception in humans	The correspondence between sympathetic arousal (electrodermal activity) and experienced arousal during an allostatically challenging task is related to functional connectivity within the allostatic/interoceptive system in humans (Supplementary Figure 8)
The allostatic/interoceptive system is domain-general.	The allostatic/interoceptive system sits at the core of the brain’s computational architecture.	Many hubs of the allostatic/interoceptive system have been previously identified as members of the “rich club,” which are the most densely connected within the brain and therefore help constitute the brain’s “neural backbone” for coordinating neural synchrony (Fig. 3, Supplementary Table 4)
	Brain activity and connectivity in the allostatic/interoceptive system is associated with a variety of psychological functions	Both the default mode network and the salience network support a variety of mental phenomena across major psychological domains (e.g., cognition, emotion, perception, and action; Fig. 5)

Other hypotheses, such as the computational dynamics of the proposed allostatic/interoceptive network are beyond the scope of this study. ACC = anterior cingulate cortex; aMCC = anterior midcingulate cortex; dmIns = dorsal mid insula; dpIns = dorsal posterior insula; pACC = pregenual anterior cingulate cortex; sgACC = subgenual anterior cingulate cortex.