Coding deficits in hidden hearing loss induced by noise: the nature and impacts.
Hidden hearing refers to the functional deficits in hearing without deterioration in hearing sensitivity. This concept is proposed based upon recent finding of massive noise-induced damage on ribbon synapse between inner hair cells (IHCs) and spiral ganglion neurons (SGNs) in the cochlea without significant permanent threshold shifts (PTS). Presumably, such damage may cause coding deficits in auditory nerve fibers (ANFs). However, such deficits had not been detailed except that a selective loss of ANFs with low spontaneous rate (SR) was reported. In the present study, we investigated the dynamic changes of ribbon synapses and the coding function of ANF single units in one month after a brief noise exposure that caused a massive damage of ribbon synapses but no PTS. The synapse count and functional response measures indicates a large portion of the disrupted synapses were re-connected. This is consistent with the fact that the change of SR distribution due to the initial loss of low SR units is recovered quickly. However, ANF coding deficits were developed later with the re-establishment of the synapses. The deficits were found in both intensity and temporal processing, revealing the nature of synaptopathy in hidden hearing loss.
Department of Otolaryngology, Affiliated Sixth People's Hospital, Shanghai Jiao Tong University, 600 Yishan Road, Shanghai 200233, China.
Qiang
Q
Song
Department of Physiology, Medical College of Southeast University, 87 Dingjiaoqiao Road, Nanjing 210009, China.
Pei
P
Shen
Department of Physiology, Medical College of Southeast University, 87 Dingjiaoqiao Road, Nanjing 210009, China.
Xiaowei
X
Li
Department of Physiology, Medical College of Southeast University, 87 Dingjiaoqiao Road, Nanjing 210009, China.
Lijuan
L
Shi
Department of Physiology, Medical College of Southeast University, 87 Dingjiaoqiao Road, Nanjing 210009, China.
Lijie
L
Liu
Department of Otolaryngology, Affiliated Sixth People's Hospital, Shanghai Jiao Tong University, 600 Yishan Road, Shanghai 200233, China.
Jiping
J
Wang
School of Human Communication Disorders, Dalhousie University, 1256 Barrington St. Dalhousie University, Halifax, NS B3J1Y6, Canada.
Zhiping
Z
Yu
School of Human Communication Disorders, Dalhousie University, 1256 Barrington St. Dalhousie University, Halifax, NS B3J1Y6, Canada.
Kegan
K
Stephen
School of Human Communication Disorders, Dalhousie University, 1256 Barrington St. Dalhousie University, Halifax, NS B3J1Y6, Canada.
Steve
S
Aiken
Department of Otolaryngology, Affiliated Sixth People's Hospital, Shanghai Jiao Tong University, 600 Yishan Road, Shanghai 200233, China.
Shankai
S
Yin
Department of Otolaryngology, Affiliated Sixth People's Hospital, Shanghai Jiao Tong University, 600 Yishan Road, Shanghai 200233, China.|School of Human Communication Disorders, Dalhousie University, 1256 Barrington St. Dalhousie University, Halifax, NS B3J1Y6, Canada.
Jian
J
Wang
D000818:Animals; D003056:Cochlear Nerve / Q000000981:diagnostic imaging / Q000503:physiopathology; D004195:Disease Models, Animal; D006168:Guinea Pigs; D006199:Hair Cells, Auditory, Inner / Q000473:pathology / Q000502:physiology; D006317:Hearing Loss, Noise-Induced / Q000000981:diagnostic imaging* / Q000503:physiopathology; D046529:Microscopy, Electron, Transmission; D013136:Spiral Ganglion / Q000000981:diagnostic imaging* / Q000503:physiopathology; D013569:Synapses / Q000473:pathology* / Q000502:physiology