Table 2.

Summary of tract-tracing study results in non-human animals, demonstrating anatomical connections between cortical visceromotor and primary interoceptive sensory regions, as well as between cortical and non-cortical visceromotor regions.

	Primary Interoceptive Cortex	Visceromotor Regions				Subcortical and Brainstem Visceromotor Structures
	To dpIns/dmIns	To vaIns	To sgACC (BA 25)	To pACC (BA 24, 32)	To aMCC (BA 24)	To Amygdala	To other subcortical and brainstem regionsa
From dpIns/dmIns	-	Case A, Fig 1155	Not evidentb	Case 1, Fig 5157	Case B, Fig 3158	Case 2, Fig 3154 Case BB-B, Fig 160	Hypothalamus (rat)159 PAG: not observed160 PBN (rat)161,162 V. Striatum 163 NTS (rat)162
From vaInsc	Case C, Fig 4155 Case A, Fig 1158	-	Case OM20, Fig 8164	Case 1, Fig 5157	Case 2, Fig 6157 Case A, Fig 1158	Case A, Fig 1158 Case 103, Fig 3165 Fig 2, Table 2166	Hypothalamus43 PAG160 PBN (rat)161 V. striatum167 NTS (rat)162
From sgACC (BA 25)	Not evidentd	Case M707168	-	Case 1, Fig 5157 Fig 2A169	Case 3, Fig 7157 Fig 3A169	Case 103, Fig 3165 Fig 5156	Hypothalamus154,170,171 PAG160,171 PBN 171 Striatum 171 NTS (rat)172,173
From pACC (BA 24, 32)	Not evidentd	Case M776168	Fig 1169	-	Case 3, Fig 7157 Fig 3A169	Case 103, Fig 3165 Fig 5156	Hypothalamus43, PAG160 PBN (cat)174 V. striatum (cat)174 NTS (rat)173
From aMCC (BA 24)	Case C, Fig 4155	Case A, Fig 1155	Case 3, Fig 4175	Case 1, Fig 5157 Fig 2A169	-	Case 103, Fig 3165 Fig 5156	Hypothalamus43 PAG160 PBN: not present176 V. striatum177 NTS (rat)172
From Amygdala	Case C, Fig 4155 Lateral basal nucleus; Case 5, Fig 6154	Case A, Fig 1155 Case 4, Fig 5154	Fig 6156	Fig 13169	Fig 6156	-	Hypothalamus43, PAG160 PBN178 V. striatum179 NTS178

Note. Connectivity evidence is in monkeys unless otherwise indicated (e.g., rats, cats). Some connections from dpIns/dmIns to the NTS are unclear due to ambiguity in how Saper (1982)¹⁶² reported subregions of the insula.

^aWe did not assess for projections from subcortical and brainstem regions to cortical regions because we only wanted to determine if the cortical regions support visceromotor control.

^bConnection from dpIns/dmIns to sgACC not evident in several monkey studies that have the potential to show them (e.g., ^{158,169,180–182}).

^cThe medial portion of the vaIns exhibits connectivity with subcortical and brainstem regions, but not the lateral portion of the vaIns^43,183.

^dConnection from sgACC to dpIns/dmIns and from pACC to dpIns/dmIns not evident in several monkey studies that have the potential to show them (e.g., ^{155,168,180,181}), although weak, direct connectivity is evident in a recent tractography study in humans (Ghaziri, et al., 2015¹⁸⁴, Figure 5). Moreover, connections between sgACC, pACC, and dpIns have been observed in intrinsic functional connectivity analyses in humans (e.g., Fig. 6 of ¹⁸⁵). The discrepancy between human findings and the tract tracing studies in monkeys failing to show connectivity might reflect an expansion of Brodmann area (BA) 24 anterior and ventral to the corpus callosum in humans relative to monkeys and/or the presence of connections between BAs 25/32 and the posterior insula in humans that do not exist in monkeys (Evrard, H. personal communication, December 27, 2015).

BA = Brodmann area; aMCC = anterior midcingulate cortex; dmIns = dorsal mid insula; dpIns = dorsal posterior insula; NTS = nucleus of the solitary tract; PAG = periaqueductal gray; PBN = parabrachial nucleus; pACC = pregenual anterior cingulate cortex; sgACC = subgenual anterior cingulate cortex; V. striatum = ventral striatum.