Encoding of conspecific signals during development can reinforce species barriers as well as set the stage for learning and production of species‐typical vocalizations. In altricial songbirds, the development of the auditory system is not complete at hatching, so it is unknown the degree to which recently hatched young can process auditory signals like birdsong. We measured in vivo extracellular responses to song stimuli in a zebra finch (Taeniopygia guttata) secondary auditory forebrain region, the caudomedial nidopallium (NCM). We recorded from three age groups between 13 days post‐hatch and adult to identify possible shifts in stimulus encoding that occur before the opening of the sensitive period of song motor learning. We did not find differences in putative cell type composition, firing rate, response strength, and selectivity across ages. Across ages narrow‐spiking units had higher firing rates, response strength, accuracy, and trial‐by‐trial reliability along with lower selectivity than broad‐spiking units. In addition, we showed that stimulus‐specific adaptation, a characteristic of adult NCM, was also present in nestlings and fledglings. These results indicate that most features of secondary auditory processing are already adult‐like shortly after hatching. Furthermore, we showed that selectivity for species‐specific stimuli is similar across all ages, with the greatest fidelity in temporal coding in response to conspecific song and domesticated Bengalese finch song, and reduced fidelity in response to owl finch song, a more ecologically relevant heterospecific, and white noise. Our study provides the first evidence that the electrophysiological properties of higher‐order auditory neurons are already mature in nestling songbirds.

中文翻译：

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斑胸草雀雏鸟听觉前脑中物种特异性歌曲的类似成人的神经表征

在发育过程中对同种信号进行编码可以强化物种障碍，并为学习和产生物种典型发声奠定基础。在晚成鸣禽中，听觉系统的发育在孵化时尚未完成，因此尚不清楚刚孵化的幼鸟能在多大程度上处理鸟鸣等听觉信号。我们在体内测量了斑胸草雀（Taeniopygia guttata）次级听觉前脑区域尾内侧巢状皮质（NCM）对鸣叫刺激的细胞外反应。我们对孵化后 13 天到成年之间的三个年龄组进行记录，以确定在鸣叫运动学习敏感期开始之前发生的刺激编码可能发生的变化。我们没有发现不同年龄的推定细胞类型组成、放电率、反应强度和选择性存在差异。在各个年龄段，窄尖峰单元比宽尖峰单元具有更高的发射率、响应强度、准确性和逐项试验的可靠性，但选择性较低。此外，我们发现，刺激特异性适应（成年 NCM 的一个特征）也存在于雏鸟和雏鸟中。这些结果表明，次级听觉处理的大多数特征在孵化后不久就已经像成人一样了。此外，我们发现，所有年龄段对物种特异性刺激的选择性都是相似的，对同种鸣叫和驯化孟加拉雀鸣叫的时间编码的保真度最高，而对鸮雀鸣叫的响应保真度降低，这是一种与生态更相关的异种异种鸣叫。和白噪声。我们的研究提供了第一个证据，表明高阶听觉神经元的电生理特性在雏鸟中已经成熟。