An Improved Model for the Rate-Level Functions of Auditory-Nerve Fibers
An Improved Model for the Rate-Level Functions of Auditory-Nerve Fibers
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DOI：
10.1523/jneurosci.1638-11.2011
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发表时间：
2011-10-26
影响因子：
5.3
通讯作者：
Irvine, Dexter R. F.
中科院分区：
文献类型：
--
作者：
Heil, Peter;Neubauer, Heinrich;Irvine, Dexter R. F.
声音信息通过听觉神经纤维（ANF）中的尖峰模式传递到大脑。在哺乳动物中，每个 ANF 通过单个内毛细胞 (IHC) 中的单个带状突触受到激发，因此尖峰模式也提供了有关这些有趣突触的有价值的信息。在这里，我们重新检查并建模 ANF 的一个关键属性，即它们的尖峰速率对声刺激声压级的依赖性（速率级函数）。我们建立在 Sachs 和 Abbas (1974) 的开创性模型的基础上，该模型与实验数据非常吻合，但对于定义生理机制的实用性有限。我们提出了一种改进的、生理上合理的模型，根据该模型，峰值速率遵循 Hill 方程，自发活动及其实验观察到的与 ANF 敏感性的紧密相关性是新兴特性。我们将其应用于使用力学线性频率的 156 个猫 ANF 速率级函数，并发现单个 Hill 系数 3 可以解释函数的总体。我们还证明了 ANF 速率水平函数与 IHC 胞吐作用的 Ca2+ 依赖性之间的紧密对应关系，并得出了 IHC 各个活性区的有效细胞内 Ca2+ 浓度的估计值。 Wergue 认为 Hill 系数可能反映了参与 IHC 胞吐作用的 Ca2+ 传感器的内在生化 Ca2+ 协同性。该模型还将 ANF 属性与心理物理学绝对阈值属性联系起来。
Acoustic information is conveyed to the brain by the spike patterns in auditory-nerve fibers (ANFs). In mammals, each ANF is excited via a single ribbon synapse in a single inner hair cell (IHC), and the spike patterns therefore also provide valuable information about those intriguing synapses. Here we reexamine and model a key property of ANFs, the dependence of their spike rates on the sound pressure level of acoustic stimuli (rate-level functions). We build upon the seminal model of Sachs and Abbas (1974), which provides good fits to experimental data but has limited utility for defining physiological mechanisms. We present an improved, physiologically plausible model according to which the spike rate follows a Hill equation and spontaneous activity and its experimentally observed tight correlation with ANF sensitivity are emergent properties. We apply it to 156 cat ANF rate-level functions using frequencies where the mechanics are linear and find that a single Hill coefficient of 3 can account for the population of functions. We also demonstrate a tight correspondence between ANF rate-level functions and the Ca2+ dependence of exocytosis from IHCs, and derive estimates of the effective intracellular Ca2+ concentrations at the individual active zones of IHCs. Weargue that the Hill coefficient might reflect the intrinsic, biochemical Ca2+ cooperativity of the Ca2+ sensor involved in exocytosis from the IHC. The model also links ANF properties with properties of psychophysical absolute thresholds.