Altered regional activity and connectivity of functional brain networks in congenital unilateral conductive hearing loss

Neuroimaging studies have shown marked alterations in brain function after auditory deprivation, with these alterations mainly caused by sensorineural hearing loss. To date, however, little is known about the patterns of functional brain reorganization in conductive hearing loss (CHL). The effects of congenital unilateral CHL on human brain were assessed by resting-state functional magnetic resonance imaging in 24 patients with unilateral microtia (UM) and 25 healthy controls. Focal brain function and seed-based functional connectivity were analyzed to characterize spontaneous activity and network changes in UM. Patients with UM showed common alterations in focal brain activities in the left inferior temporal gyrus across different measurements, with these alterations significantly associated with the duration of hearing loss. Additionally, focal brain activities were decreased in the auditory system and increased in the visual system, with a disassociated pattern shown in the default-mode system. Using the left inferior temporal gyrus as the seed region, patients with UM showed lower connectivity with the default-mode system and right visual regions but higher connectivity with the left frontoparietal regions when compared with controls. These results indicate that congenital partial hearing deprivation, despite normal bone conduction hearing, can induce widespread reorganizations that continue into adolescence and adulthood.