Dynamic spike thresholds during synaptic integration preserve and enhance temporal response properties in the avian cochlear nucleus.
Dynamic spike thresholds during synaptic integration preserve and enhance temporal response properties in the avian cochlear nucleus.
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DOI：
10.1523/jneurosci.1840-10.2010
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发表时间：
2010-09-08
期刊：
影响因子：
--
通讯作者：
Rubel EW
中科院分区：
文献类型：
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作者：
Howard MA;Rubel EW
耳蜗核的神经元在解剖学和生理学上专门用于对关于声音刺激的时间和频谱信息进行最佳编码，部分用于双耳听觉处理。鸟类耳蜗大细胞核（NM）整合兴奋性第八神经输入和去极化GABA能抑制，使得跨突触的时间保真度增强。这种去极化抑制的生物物理机制及其在时间处理中的作用尚未完全了解。我们使用全细胞电生理学和计算建模来研究阈下兴奋性输入是如何整合的，以及去极化IPSP如何影响鸡NM神经元的尖峰阈值和突触整合。我们发现，去极化抑制和阈下兴奋性输入引起电压阈值调节，非线性时间总和，分流。抑制引起如此大的变化阈值，阈下兴奋性输入后，由一个不应期。我们假设，这些大的变化阈值消除尖峰异步输入，提供了一种机制，增强的时间保真度看到整个第八神经/耳蜗核突触。因此，去极化抑制和阈值漂移磨练这个系统的时间响应特性，以提高时间的保真度是必不可少的听觉感知。
Neurons of the cochlear nuclei are anatomically and physiologically specialized to optimally encode temporal and spectral information about sound stimuli, in part for binaural auditory processing. The avian cochlear nucleus magnocellularis (NM) integrates excitatory eighth nerve inputs and depolarizing GABAergic inhibition such that temporal fidelity is enhanced across the synapse. The biophysical mechanisms of this depolarizing inhibition, and its role in temporal processing, are not fully understood. We used whole-cell electro-physiology and computational modeling to examine how subthreshold excitatory inputs are integrated and how depolarizing IPSPs affect spike thresholds and synaptic integration by chick NM neurons. We found that both depolarizing inhibition and subthreshold excitatory inputs cause voltage threshold accommodation, nonlinear temporal summation, and shunting. Inhibition caused such large changes in threshold that subthreshold excitatory inputs were followed by a refractory period. We hypothesize that these large shifts in threshold eliminate spikes to asynchronous inputs, providing a mechanism for the enhanced temporal fidelity seen across the eighth nerve/cochlear nucleus synapse. Thus, depolarizing inhibition and threshold shifting hone the temporal response properties of this system so as to enhance the temporal fidelity that is essential for auditory perception.