[Emotional functions of the insula].

This paper reviews theories and research pertaining to emotional functions of the insula--a cortical area that is located deep in the lateral sulcus and has been included in the limbic lobe because of its intimate connections with the cingulate, amygdala, and orbitofrontal cortex. The insula is known to contain the primary gustatory cortex across mammalian species, and thus, earlier studies have focused on its special role in disgust, which is an emotion closely associated with the sensation of bad taste. In recent years, more emphasis has been placed on the insular contribution to conscious experience of emotion in general. Emotional experience has been known to depend on both the perception of bodily reactions to emotion-provoking objects and the cognitive appraisal of contexts. The insula is theoretically suited for representing such emotional experience because it receives interoceptive inputs from the whole body, and its connections with the prefrontal regions can provide contextual information. In fact, many studies have shown that the activation of the insula, particularly its anterior part, covaries with subjective feelings, which reflect not only physical stimulus intensity but also cognitive factors such as prediction. Such insular activation seems to work as a so-called "as if" somatic marker that inclines us to approach or avoid the stimulus; in addictive disorders, insular activation is proposed to be the neural basis for intense urges. In addition, the insula also represents "simulated" emotional experience, including empathy with others, which may play an important role in social learning. Thus, further investigations into the emotional functions of the insula would help elucidate the still unknown role of conscious experience in regulating cognitive processes and behavior.