title: Silent damage of noise on cochlear afferent innervation in guinea pigs and the impact on temporal processing.
abstract: Noise-exposure at levels low enough to avoid a permanent threshold shift has been found to cause a massive, delayed degeneration of spiral ganglion neurons (SGNs) in mouse cochleae. Damage to the afferent innervation was initiated by a loss of synaptic ribbons, which is largely irreversible in mice. A similar delayed loss of SGNs has been found in guinea pig cochleae, but at a reduced level, suggesting a cross-species difference in SGN sensitivity to noise. Ribbon synapse damage occurs "silently" in that it does not affect hearing thresholds as conventionally measured, and the functional consequence of this damage is not clear. In the present study, we further explored the effect of noise on cochlear afferent innervation in guinea pigs by focusing on the dynamic changes in ribbon counts over time, and resultant changes in temporal processing. It was found that (1) contrary to reports in mice, the initial loss of ribbons largely recovered within a month after the noise exposure, although a significant amount of residual damage existed; (2) while the response threshold fully recovered in a month, the temporal processing continued to be deteriorated during this period.
authors.affiliation: Department of Physiology and Pharmacology, Medical College of Southeast University, Nanjing, China.
authors.forename: Lijie
authors.initials: L
authors.lastname: Liu
authors.forename: Hui
authors.initials: H
authors.lastname: Wang
authors.forename: Lijuan
authors.initials: L
authors.lastname: Shi
authors.forename: Awad
authors.initials: A
authors.lastname: Almuklass
authors.forename: Tingting
authors.initials: T
authors.lastname: He
authors.forename: Steve
authors.initials: S
authors.lastname: Aiken
authors.forename: Manohar
authors.initials: M
authors.lastname: Bance
authors.forename: Shankai
authors.initials: S
authors.lastname: Yin
authors.forename: Jian
authors.initials: J
authors.lastname: Wang
mesh_terms: D000200:Action Potentials; D000818:Animals; D001309:Auditory Threshold; D003051:Cochlea / Q000502:physiology; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology; D006168:Guinea Pigs; D006309:Hearing; D008297:Male; D051379:Mice; D018613:Microscopy, Confocal / Q000379:methods; D009474:Neurons / Q000187:drug effects; D009622:Noise; D013136:Spiral Ganglion / Q000294:innervation* / Q000503:physiopathology*; D013569:Synapses; D013997:Time Factors