Anatomy of the insula - functional and clinical correlates

Much information has been acquired on the anatomy and function of the insul a over the past two decades. The insula has a dynamic cytoarchitectonic arr angement throughout its length. The anterior insula is comprised of an agra nular-allocortical area which functionally is part of the paralimbic belt. Its cortical connections are predominantly with other allocortical areas. S ubcortical, limbic, and brain stem connections underscore the anterior insu la's role in processing and integrating autonomic and visceral information, The posterior insula is comprised of a granular-isocortical area which fun ctionally is linked to somatomotor systems. Its cortical connections are pr edominantly with other neocortical areas. Insular-cortical and sub-cortical connections, especially with the thalamus and basal ganglia, underscore th e posterior insula's role in somatosensory, vestibular, and motor integrati on. The dysgranular insula lying in between the anterior and posterior insu la represents an anatomical and functional transition between these regions . The predominant flow of intra-insular projections from anterior to more p osterior regions suggests that the posterior insula also serves as an integ rative heteromodal association area for information received by all five se nses. The insula plays a role in cardiovascular, gastrointestinal, vestibul ar, olfactory, gustatory, visual, auditory, somatosensory, and motor modula tion. It is also felt to play a role in conditioned aversive learning, affe ctive and motivational components of pain perception, stress induced immuno suppression, mood stability, sleep, and language. Clinical correlation of d amage to the insula, and the resultant impairment of the above functions is discussed.