Reversible conductive hearing loss: restored activity in the central auditory system

The effect of a reversible, unilateral hearing loss on 2-deoxyglucose (2-DG) uptake in the central auditory system was studied using young gerbils. All animals had a unilateral conductive hearing loss (CHL), induced by atresia, on postnatal day 21 (P21). One week later, on P28, animals had their atresia repaired (CHL/R), or not repaired (CHL/NR), and CHL/NR animals entered the 2-DG experiments. CHL/R animals were allowed a 1-week period of restored binaural hearing experience prior to entering 2-DG experiments on P35. Animals in each group were injected with 2-DG and exposed to ambient sounds for 45 min prior to sacrifice. Uptake of 2-DG was measured in the anteroventral cochlear nucleus (AVCN), the medial superior olive (MSO), and the inferior colliculus (IC) on both sides of the brain. In CHL/NR animals, there were significant differences in uptake between the AVCN, MSO, and IC ipsilateral versus contralateral to the manipulated ear, indicating an imbalance in ascending afferent activity. In CHL/R animals, there were no significant differences, suggesting that 1 week after CHL repair, the appearance of balanced afferent activity had been restored.