Anatomy of the insula - functional and clinical correlates

Much information has been acquired on the anatomy and function of the insula over the past two decades. The insula has a dynamic cytoarchitectonic arrangement throughout its length. The anterior insula is comprised of an agranular-allocortical area which functionally is part of the paralimbic belt. Its cortical connections are predominantly with other allocortical areas. Subcortical, limbic, and brain stem connections underscore the anterior insula's role in processing and integrating autonomic and visceral information, The posterior insula is comprised of a granular-isocortical area which functionally is linked to somatomotor systems. Its cortical connections are predominantly with other neocortical areas. Insular-cortical and sub-cortical connections, especially with the thalamus and basal ganglia, underscore the posterior insula's role in somatosensory, vestibular, and motor integration. The dysgranular insula lying in between the anterior and posterior insula represents an anatomical and functional transition between these regions. The predominant flow of intra-insular projections from anterior to more posterior regions suggests that the posterior insula also serves as an integrative heteromodal association area for information received by all five senses. The insula plays a role in cardiovascular, gastrointestinal, vestibular, olfactory, gustatory, visual, auditory, somatosensory, and motor modulation. It is also felt to play a role in conditioned aversive learning, affective and motivational components of pain perception, stress induced immunosuppression, mood stability, sleep, and language. Clinical correlation of damage to the insula, and the resultant impairment of the above functions is discussed.