What the insula hears and does: Insights from human intracranial electrophysiology

The human insula is known to be involved in auditory processing, though its detailed response properties remain elusive. Intracranial recordings in human neurosurgical patients provide a unique opportunity to characterize the functional properties of the human insula with high spatiotemporal resolution. Local field potential recordings reveal that posterior insula (InsP) is characterized by larger broadband gamma (30-150 Hz) responses to monosyllabic words compared to anterior insula (InsA). Both subdivisions of the insula generate evoked responses to novel sounds. Single neurons within InsP and, to a lesser extent, InsA, respond to simple sounds in the absence of a behavioral context. InsP and InsA share similar resting state functional connectivity profiles with limbic structures. InsP is more closely linked to activity propagated from early auditory cortex, while InsA is more tightly coupled with prefrontal, anterior temporal regions and the amygdala. Clinical case studies identify language and music perception deficiencies associated with insula lesions. Finally, single unit recordings during emergence from general anesthesia reveal a temporal dissociation between reactivation of limbic structures and the insula, the latter marking the transition to connected consciousness and the capacity to act on commands. Together, these results begin to characterize the insula's place in the auditory hierarchy, with implications ranging from sensory processing to conscious awareness of our surroundings.

Kirill V. Nourski est invité par Julien Bastin.