Auditory Cortex Basal Activity Modulates Cochlear Responses in Chinchillas
Auditory Cortex Basal Activity Modulates Cochlear Responses in Chinchillas
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DOI：
10.1371/journal.pone.0036203
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发表时间：
2012-04-30
期刊：
影响因子：
3.7
通讯作者：
Delano, Paul H.
中科院分区：
文献类型：
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作者：
Leon, Alex;Elgueda, Diego;Delano, Paul H.
背景：听觉传出系统具有独特的神经解剖学通路，连接大脑皮层和感觉感受细胞。位于初级听觉皮层第V层和第VI层的锥体神经元构成了向丘脑、下丘甚至直接向上级橄榄复合体和耳蜗核的下行投射。传出通路通过橄榄耳蜗系统连接到耳蜗受体，橄榄耳蜗系统支配外毛细胞和听神经纤维。皮质橄榄耳蜗传出系统的功能作用仍有争议。我们假设，听觉皮层的基础活动调制耳蜗和神经传入反应通过传出system.Methodology/主要调查结果：耳蜗微音（CM），神经复合动作电位（CAP）和听觉皮层诱发电位（ACEP）记录在二十麻醉龙猫，听觉皮层失活前，期间和之后两种方法：利多卡因微量注射或皮质冷却与冷冻环。听觉皮层失活引起的ACEP振幅在15只动物（失活实验）和永久性减少5龙猫（病变实验）的短暂减少。我们发现，在这两种类型的实验中，CM的振幅发生了显着变化，这是在15只动物中发现的CM降低的最常见效应。伴随着CM幅度的变化，我们发现CAP增加在7龙猫和CAP减少在13只动物。虽然ACEP振幅完全恢复90分钟后，在失活实验中，只有部分恢复观察到耳蜗responses.Conclusions/Significance的幅度：这些结果表明，正在进行的听觉皮层活动的阻断调制CM和CAP响应，表明皮质橄榄耳蜗电路调节听觉神经和耳蜗反应，通过一个基础传出音。所获得的效果的多样性表明，至少有两个功能通路从听觉皮层到耳蜗。
Background: The auditory efferent system has unique neuroanatomical pathways that connect the cerebral cortex with sensory receptor cells. Pyramidal neurons located in layers V and VI of the primary auditory cortex constitute descending projections to the thalamus, inferior colliculus, and even directly to the superior olivary complex and to the cochlear nucleus. Efferent pathways are connected to the cochlear receptor by the olivocochlear system, which innervates outer hair cells and auditory nerve fibers. The functional role of the cortico-olivocochlear efferent system remains debated. We hypothesized that auditory cortex basal activity modulates cochlear and auditory-nerve afferent responses through the efferent system.Methodology/Principal Findings: Cochlear microphonics (CM), auditory-nerve compound action potentials (CAP) and auditory cortex evoked potentials (ACEP) were recorded in twenty anesthetized chinchillas, before, during and after auditory cortex deactivation by two methods: lidocaine microinjections or cortical cooling with cryoloops. Auditory cortex deactivation induced a transient reduction in ACEP amplitudes in fifteen animals (deactivation experiments) and a permanent reduction in five chinchillas (lesion experiments). We found significant changes in the amplitude of CM in both types of experiments, being the most common effect a CM decrease found in fifteen animals. Concomitantly to CM amplitude changes, we found CAP increases in seven chinchillas and CAP reductions in thirteen animals. Although ACEP amplitudes were completely recovered after ninety minutes in deactivation experiments, only partial recovery was observed in the magnitudes of cochlear responses.Conclusions/Significance: These results show that blocking ongoing auditory cortex activity modulates CM and CAP responses, demonstrating that cortico-olivocochlear circuits regulate auditory nerve and cochlear responses through a basal efferent tone. The diversity of the obtained effects suggests that there are at least two functional pathways from the auditory cortex to the cochlea.