Neurotransmitters and Receptors Changes in Medial Nucleus of the Trapezoid Body (MNTB) of Early-Developmental Rats with Single-Side Deafness

Single-sided deafness and unilateral auditory deprivation in children: current challenge of improving sound localization ability

Interaural time difference and interaural level difference signals are insufficient in patients with single-sided deafness (SSD). This insufficiency leads to an absence of sound localization abilities and a decrease in speech intelligibility in noisy environments. SSD occurring in children further affects their language learning and cognitive abilities and their academic performance because they lack spatial abilities and binaural hearing. The early stages of central auditory system development are critical for auditory function development and morphological refinement. SSD occurring in the critical period can cause significant lateralization in the bilateral auditory pathway. This may increase the risk that affected individuals cannot re-establish binaural benefits after rehabilitation of hearing loss in the post-sensitive period. For otorhinolaryngologists, there is the concern that children with congenital SSD cannot benefit from cochlear implantation. Only a few studies have investigated auditory rehabilitation in children with congenital SSD with cochlear implantation and their results were inconsistent. The present review aims to clarify the main problems and challenges of clinical rehabilitation of congenital SSD, particularly focusing on the effect of CI on sound localization ability in children with congenital SSD.

Intrinsic and Miniature Postsynaptic Current Changes in Rat Principal Neurons of the Lateral Superior Olive after Unilateral Auditory Deprivation at an Early Age

Unilateral auditory deprivation results in lateralization changes in the central auditory system, interfering with the integration of binaural information and thereby leading to a decrease in binaural auditory functions such as sound localization. Principal neurons of the lateral superior olive (LSO) are responsible for computing the interaural intensity differences that are critical for sound localization in the horizontal plane. To investigate changes caused by unilateral auditory deprivation, electrophysiological activity was recorded from LSO principal neurons in control rats and rats with unilateral cochlear ablation. At one week after unilateral cochlear ablation, the excitability of LSO principal neurons on the side ipsilateral to the ablation (the ablated side) was greater than that on the side contralateral to the ablation (the intact side); however, the input resistance increased on both sides. Furthermore, by analysing the miniature inhibitory postsynaptic currents and miniature excitatory postsynaptic currents, we found that unilateral auditory deprivation weakened the inhibitory driving force on the intact side, whereas it strengthened the excitatory driving force on the ablated side. In summary, asymmetric changes in the electrophysiological activity of LSO principal neurons were found on both sides at postnatal day 19, one week after unilateral cochlear ablation.