聴覚、前庭感覚、および嗅覚システム Auditory, Vestibular and Olfactory Systems
O2-7-2-1 ほ乳類蝸牛基底板上進行波における有毛細胞感覚毛自動能の貢献 Contribution of active hair-bundle motility to nonlinear amplification in the mammalian cochlea ○任書晃1,2 ○Fumiaki Nin1,2, Tobias Reichenbach2, Jonathan Fisher2, James Hudspeth2 新潟大学大学院 医歯学総合研究科 分子生理学1, ロックフェラー大学　感覚器神経科学2 Dept Molecular Physiology, Faculty of Medicine, Niigata Univ, Niigata1, Lab of Sensory Neuroscience, Rockefeller University, New York, US2 The cochlea's high sensitivity stems from the active process ofouter hair cells, which possess two force-generating mechanisms:active hair-bundle motility elicited by Ca2+ influx and somatic motilitymediated by the voltage-sensitive protein prestin. Althoughinterference with prestin has demonstrated a role for somatic motilityin the active process, it remains unclear whether hair-bundlemotility contributes in vivo. We selectively perturbed the twomechanisms by infusing substances into the endolymph or perilymphof the chinchilla's cochlea and then used scanning laser interferometryto measure vibrations of the basilar membrane.Blocking somatic motility, damaging the tip links of hair bundles,or depolarizing hair cells eliminated amplification. While reducingamplification to a lesser degree, pharmacological perturbation ofactive hair-bundle motility diminished or eliminated the nonlinearcompression underlying the broad dynamic range associated withnormal hearing. The results suggest that active hair-bundle motilityplays a significant role in the amplification and compressivenonlinearity of the cochlea.	O2-7-2-2 時間規則性が聴覚誘発脳磁場に与える影響―脳磁図を用いて Effects of temporal regularity on the auditory evoked fields: a magnetoencephalography study ○岡本秀彦1, , 柿木隆介1 ○Hidehiko Okamoto1, Sumru Keceli1, Ryusuke Kakigi1 生理学研究所統合生理研究系感覚運動調節研究部門1 Dept Integrative Physiology, National Institute for Physiological Sciences, Aichi1 In a daily life, we are continuously exposed to many sound signals simultaneously. There are some evidences that the neural responses under noisy environments are different from those under a silent condition. Many previous studies have demonstrated that the repeated presentation of identical tones can decrease neural activity due to stimulus specific adaptation. However, recently some studies reported that the repetition of the same frequency sounds could increase the auditory evoked neural responses in noisy environments. In the present study, we investigated the effects of temporal regularity of sound sequencing in silent and noisy environments. We designed two temporal regularity conditions: "Constant" and "Random". In the constant condition the inter-stimulus interval between two successive test sounds was fixed to 1.5 sec, whereas the inter-stimulus interval was either 0.5, 1.0, 1.5, 2.0, or 2.5 sec in the random condition. The obtained results demonstrated that high temporal regularity (constant sequencing) differentially affected the auditory evoked response depending on the acoustic environment: the response amplitude decreased in silence, but increased in noise. Our results indicate that humans can involuntary detect the temporal regularity of sound signals and can modulate their neural activity according to the timing of sound inputs.
O2-7-2-3 加齢性難聴と関連するc-Retの解析 Partial impairment of c-Ret accelerates age-related hearing loss ○大神信孝1,2, 飯田真智子1,2,3, 加藤昌志3 ○Nobutaka Ohgami1,2, Machiko Iida1,2,3, Kato Masashi3 中部大・生命医科・環境衛生学1, 中部大・次世代食育センター2, 名大院・医・環境労働衛生学3 Environ Health Sci, Dept Biomed Sci, Chubu Univ, Aichi1, Nutritional Health Science Research Center, Chubu Univ, Aichi2, Occupational Environ Health, Nagoya Univ Graduate School of Medicine, Nagoya3 c-Ret has been shown to play an important role for neural development and survival. We have shown that impairment of c-Ret causes congenital hearing loss with neurodegeneration of spiral ganglion neurons (SGNs) in homozygous c-Ret knock-in mice. However, it remains unclear if impairment of c-Ret has relevance to age-related hearing loss. In this study, we show that partial impairment of c-Ret accelerates age-related hearing loss in heterozygous c-Ret Y1062F knock-in mice (c-Ret-KIYF/+-mice). The hearing loss showed late-onset degeneration of SGNs in c-Ret-KIYF/+-mice. Morphological impairments in inner- and outer-hair cells and the stria vascularis in c-Ret-KIYF/+-mice were undetectable. The acceleration of age-related hearing loss in c-Ret-KIYF/+-mice was significantly restored by introducing constitutively activated RET. Thus, our results suggest that c-Ret is an age-related hearing loss-related molecule in mice.	O2-7-2-4 食後睡眠時に増加する嗅球顆粒細胞の除去における嗅皮質からのトップダウン入力の役割 Participation of top-down inputs from the olfactory cortex to the olfactory bulb in the enhanced elimination of granule cells during postprandial sleep period ○駒野-井上清香1, 眞部寛之1, 太田瑞穂1, 楠本-吉田郁恵1, 横山健1, 森憲作1, 山口正洋1 ○Sayaka Komano-Inoue1, Hiroyuki Manabe1, Mizuho Ota1, Ikue Kusumoto-Yoshida1, Takeshi Yokoyama1, Kensaku Mori1, Masahiro Yamaguchi1 東京大学大学院 医学系研究科 細胞分子生理学1 Dept Physiol, Univ of Tokyo, Tokyo1 Among adult-born granule cells (GCs) in the mouse olfactory bulb (OB), nearly half are incorporated into the OB while the other half are eliminated, and the fate choice of adult-born GCs between survival and death is influenced by olfactory sensory experience. Our group previously showed that sensory experience-dependent GC elimination is enhanced during postprandial (after-meal) period, in particular in association with postprandial sleep. However, it remained unknown what mechanisms promote GC elimination during postprandial period. During slow-wave sleep, the olfactory cortex (OC) generates highly synchronized top-down inputs to GCs in the OB. Here we examined whether the synchronized top-down synaptic inputs during postprandial period play a role in the enhanced elimination of GCs. Driving synchronized top-down inputs by electrical stimulation of the OC significantly increased the number of apoptotic GCs in the OB of anesthetized mice. Further, suppression of the synchronized top-down inputs during postprandial period by injecting GABAA receptor agonist or acetylcholine receptor agonist locally in the OC in freely-behaving mice suppressed the GC elimination during the period. Large enhancement of GC elimination during postprandial period of the sensory deprived mice was also attenuated by inhibiting the top-down inputs. These results showed that the synchronized top-down inputs from the OC is crucial in promoting GC elimination during postprandial period, suggesting that activities of the OC during sleep states promote structural changes in the neuronal circuits of the OB.

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