CIRCUITRY AND FUNCTIONAL-ASPECTS OF THE INSULAR LOBE IN PRIMATES INCLUDING HUMANS

The progress made in understanding the insula in the decade following an earlier review (Augustine, Neurol. Res., 7 (1985) 2-10) is examined in this review. In these ten years, connections have been described b etween the insula and the orbital cortex, frontal operculum, lateral p remotor cortex, ventral granular cortex, and medial area 6 in the fron tal lobe. Insular connections between the second somatosensory area an d retroinsular area of the parietal lobe have been documented. The ins ula was found to connect with the temporal pole and the superior tempo ral sulcus of the temporal lobe. It has an abundance of local intrains ular connections and projections to subdivisions of the cingulate gyru s. The insula has connections with the lateral, lateral basal, central , cortical and medial amygdaloid nuclei. It also connects with nonamyg daloid areas such as the perirhinal cortex, entorhinal, and periamygda loid cortex. The thalamic taste area, the parvicellular part of the ve ntral posteromedial nucleus, projects fibers to the ipsilateral insula r-opercular cortex. In the past decade, confirmation has been given to the insula as a visceral sensory area, visceral motor area, motor ass ociation area, vestibular area, and language area. Recent studies have expanded the role of the insula as a somatosensory area, emphasizing its multifaceted, sensory role. The idea of the insula as limbic integ ration cortex has been affirmed and its role in Alzheimer's disease su ggested.