A Review on the Functional Connectivity of the Human Opercular Cortex

SUMMARY: The opercular cortex is the part of the brain that overlies the insula and is the prolongation of the frontal, parietal, and temporal lobes in the lateral fissure. Over the years, this region has undergone multiple parcellations, and updated, multimodal, large-scale brain atlases highlight up to 16 subregions organized within the frontal, parietal, and temporal opercula. Using complementary methods for brain mapping-such as functional neuroimaging, source connectivity on scalp EEG or magnetoencephalography signals, and effective connectivity measures based on intracranial EEG recordings and cortico-cortical evoked potentials-several connectivity patterns have been identified. The main bidirectional opercular connections are with the insular cortex. The anterior insula is preferentially connected with the temporal and frontal operculum (OpF), whereas the posterior insula is connected to all opercular subdivisions. All three opercular subdivisions are interconnected. The OpF is functionally connected to the cingulate cortex consistent with a role in salience processing and to the temporal basal, temporal neocortex, premotor, and primary sensorimotor regions implicated in language processing. The parietal operculum is functionally connected with the premotor-motor and parietal regions for sensorimotor and vestibular processing. Finally, the temporal operculum is functionally connected with the temporal basal, temporal pole, mesial temporal structures, and parietal cortex supporting auditory, vestibular, and language processing.