Cortical, thalamic, and amygdaloid connections of the anterior and posterior insular cortices

Abstract

Cortical, thalamic, and amygdaloid projections of the rat anterior and posterior insular cortices were examined using the anterograde transport of biocytin. Granular and dysgranular posterior insular areas between bregma and 2 mm anterior to bregma projected to the gustatory thalamic nucleus. Granular cortex projected to the subjacent dysgranular cortex which in turn projected to the agranular (all layers) and granular cortices (layers I and VI). Both granular and dysgranular posterior areas projected heavily to the dysgranular anterior insular cortex. Agranular posterior insular cortex projected to medial mediodorsal nucleus, agranular anterior insular and infralimbic cortices as well as granular and dysgranular posterior insula. No projections to the amygdala were observed from posterior granular cortex, although dysgranular cortex projected to the lateral central nucleus, dorsolateral lateral nucleus, and posterior basolateral nucleus. Agranular projections were similar, although they included medial and lateral central nucleus and the ventral lateral nucleus. Dysgranular anterior insular cortex projected to lateral agranular frontal cortex and granular and dysgranular posterior insular regions. Agranular anterior insular cortex projected to the dysgranular anterior and prelimbic cortices. Anterior insuloamygdaloid projections targeted the rostral lateral and anterior basolateral nuclei with sparse projections to the rostral central nucleus. The data suggest that the anterior insula is an interface between the posterior insular cortex and motor cortex and is connected with motor-related amygdala regions. Amygdaloid projections from the posterior insular cortex appear to be organized in a feedforward parallel fashion targeting all levels of the intraamygdaloid connections linking the lateral, basolateral, and central nuclei.

The effect of pain on cognitive function: A review of clinical and preclinical research

“…The IC is interconnected with the entorhinal cortex and the amygdala (Insausti et al, 1997;Shi and Cassell, 1998) and is therefore presumed to play a role in affective processing of pain and pain control. Activation of the IC caused by experimental thermal pain was reduced when subjects were distracted by a visual stimulus (Brooks et al, 2002).…”

The Insular Cortex and the Amygdala: Shared Functions and Interactions

“…Although a clear map of the viscerosensory area of the IC is still missing, areas within both the dysgranular and granular cortices have been identified as viscerosensory responsive [3,10,19,[92][93][94]. In Cechetto and Saper (1987) [3], a viscerosensory area within the Insular cortex was reported while exploring from 2.0 mm anterior to 0.5 mm posterior to the crossing of the anterior commissure (around the bregma) in rats.…”

“…Zhang and Oppenheimer [94] found responsive cells throughout the rat insular cortex, as far rostral as +2.0 mm and as posterior as -1.5 mm from the bregma, with rightward predominance. In contrast, Shi and Casell (1998) found responsive cells throughout the rat insular cortex, but with leftward predominance [10,23]. Unlike the visceromotor infralimbic cortex, the IC is usually considered viscerosensory [42,95,96].…”

“…The Insular Cortex and the Amygdala: Shared Functions and Interactions 239 between the insular cortex and the amygdala [10,23,29,177,178] to all amygdalar subdivisions [179]. The ventral agranular insular area projects preferentially to the medial extended amygdala, while the viscerosensory and somatosensory portions of the insular cortex project preferentially to the central extended amygdala [180].…”

“…The ventral agranular insular area projects preferentially to the medial extended amygdala, while the viscerosensory and somatosensory portions of the insular cortex project preferentially to the central extended amygdala [180]. Furthermore, the amygdaloid projections from the posterior insular cortex appear to be organized in a feedforward parallel fashion targeting all levels of the intra-amygdaloid connections linking the lateral, basolateral and central nuclei [10,23]. It must be noted that the PBN-insular cortex projections pass across the central nucleus of the amygdala [21].…”