Level-tuned neurons in primary auditory cortex adapt differently to loud versus soft sounds.
Level-tuned neurons in primary auditory cortex adapt differently to loud versus soft sounds.
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DOI：
10.1093/cercor/bhq079
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发表时间：
2011
期刊：
影响因子：
3.7
通讯作者：
P. V. Watkins;D. Barbour
中科院分区：
文献类型：
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作者：
P. V. Watkins;D. Barbour
通常使用消除神经元对最近刺激统计数据的适应的刺激范式来分析对刺激强度（即非单调速率水平响应者）的听觉神经元的反应。这个过程通常是通过呈现各个声音以及它们之间的长静默期来完成的。使用此类范式的研究得出了这样的假设：非单调神经元可能在振幅谱编码或复杂谱形状的电平不变表示中发挥作用。我们之前提出了另一种假设，即电平调谐神经元可能代表低声级的专门编码器，因为即使平均声级相对较高，它们也能保持对低声级的敏感性。在这里，我们证明了清醒狨猴初级听觉皮层中的非单调神经元通过调整其较高动态范围来编码具有高平均水平的声音，从而使较低动态范围可用于编码相对罕见的低水平声音来实现这一壮举。相对于单调神经元，这种自适应行为在非单调中表现为：1）速率水平响应阈值的整体移动量较小，以及（2）随着平均刺激水平的增加而进行非单调增益调整。
The responses of auditory neurons tuned to stimulus intensity (i.e., nonmonotonic rate-level responders) have typically been analyzed with stimulus paradigms that eliminate neuronal adaptation to recent stimulus statistics. This procedure is usually accomplished by presenting individual sounds with long silent periods between them. Studies using such paradigms have led to hypotheses that nonmonotonic neurons may play a role in amplitude spectrum coding or level-invariant representations of complex spectral shapes. We have previously proposed an alternate hypothesis that level-tuned neurons may represent specialized coders of low sound levels because they preserve their sensitivity to low levels even when average sound level is relatively high. Here we demonstrate that nonmonotonic neurons in awake marmoset primary auditory cortex accomplish this feat by adapting their upper dynamic range to encode sounds with high mean level, leaving the lower dynamic range available for encoding relatively rare low-level sounds. This adaptive behavior manifests in nonmonotonic relative to monotonic neurons as 1) a lesser amount of overall shifting of rate-level response thresholds and (2) a nonmonotonic gain adjustment with increasing mean stimulus level.