Functional neuroimaging studies using auditory stimuli consistently show activation of the insular cortex. However, due to the limited temporal resolution of non-invasive neuroimaging techniques, the role(s) of the insula in auditory processing remains unclear. As the anterior insula (aI) and the posterior insula (pI) have different connections and are thought to be functionally distinct, it is likely that these two areas contribute differently to auditory processing. Our study examines the spatiotemporal dynamics of auditory processing in the insula using intracranial electroencephalography (EEG). Eight epileptic patients completed two passive listening tasks and one three-stimulus auditory oddball detection task during the intracranial EEG monitoring of their drug-resistant seizures. Recordings were obtained from depth electrodes implanted in 11 insulae. Event-related potentials (ERPs) were analyzed using permutation analyses during the N100 and the P300 intervals, and modulations of alpha, theta, and gamma band responses were compared using Wilcoxon/Mann-Whitney analyses. N100 responses to auditory stimuli were mostly observed in the pI and were little affected by task conditions. Auditory target detection was associated with P300 ERPs, and alpha, theta, high- and low-gamma responses, preferentially at aI contacts. Results suggest that the aI is involved in voluntary attentional processing of task-relevant information, whereas the pI is involved in automatic auditory processing.
Keywords: Attention; Epilepsy; Insula; Intracranial EEG; Salience network.