The anterior insula and the anterior cingulate cortex form a “salience network” that functions to segregate the most relevant among internal and extrapersonal stimuli in order to guide behavior. Within the framework of our network model, the disparate functions ascribed to the insula can be conceptualized by a few basic mechanisms: (1) bottom–up detection of salient events, (2) switching between other large-scale networks to facilitate access to attention and working memory resources when a salient event is detected, (3) interaction of the anterior and posterior insula to modulate autonomic reactivity to salient stimuli, and (4) strong functional coupling with the anterior cingulate cortex that facilitates rapid access to the motor system. In this manner, with the insula as its integral hub, the salience network assists target brain regions in the generation of appropriate behavioral responses to salient stimuli. We suggest that this framework provides a parsimonious account of insula function in neurotypical adults, and may provide novel insights into the neural basis of disorders of affective and social cognition.

https://link.springer.com/article/10.1007/s00429-010-0262-0

An examination of the differential pattern of input–output connectivity of the AI and the ACC provides further insights into the functions of the AI and SN. While the AI receives multimodal sensory input, the ACC and associated dorsomedial prefrontal cortex receive very little sensory input (Averbeck and Seo 2008). Conversely, while the ACC and associated dorsomedial prefrontal cortex send strong motor output, there is very little direct motor input to or output from the AI. Furthermore, the ACC and dorsomedial prefrontal cortex have direct connections to the spinal cord and sub-cortical oculomotor areas (Fries 1984) giving them direct control over action. With these differential anatomical pathways and von Economo neurons that facilitate rapid signaling between the AI and the ACC, the SN is well positioned to influence not only attention but also motor responses to salient sensory stimuli. In this manner, the AI plays both a direct and indirect role in attention, cognitive, and behavioral control.