Kang HiJee, Dos Santos Ednei B, Kojima Satoshi
Sensory and Motor Systems Research Group, Korea Brain Research Institute, Daegu, South Korea.
Department of Biomedical Engineering, Johns Hopkins University, Baltimore, USA.
Brain Struct Funct. 2024 Dec 18;230(1):11. doi: 10.1007/s00429-024-02877-2.
Vocal learners, including humans and songbirds, acquire their complex vocalizations by accurately memorizing and imitating the vocal patterns of other individuals. In songbirds, the caudomedial nidopallium (NCM), considered the secondary auditory region, has been suggested to play a critical role in memorizing and recognizing the songs of tutors. However, the mechanisms by which NCM neurons encode the acoustic information of tutor song are not yet fully understood. Here, we investigate the neural representation of tutor song information in NCM neurons by examining their sensitivity to spectral changes in song structure, using electrophysiological recordings in anesthetized male zebra finches. We manipulated the acoustic structures of both tutor songs and unfamiliar conspecific songs by shifting the fundamental frequency (FF) of harmonic syllables by various frequency steps and recorded neural responses to those FF-shifted and original songs. Our results demonstrate that NCM neurons are highly sensitive to FF shifts in tutor song but much less in unfamiliar conspecific song, providing novel evidence for neural encoding of tutor song information in NCM neurons. Moreover, we find that the effects of FF shifts on neural responses depend on the direction of FF shifts. These findings suggest that NCM neurons encode detailed information of tutor song, which can serve as a tutor song template required for song learning.
包括人类和鸣禽在内的声乐学习者，通过准确记忆和模仿其他个体的发声模式来习得复杂的发声。在鸣禽中，被认为是次级听觉区域的内侧巢皮质尾侧部（NCM），被认为在记忆和识别导师的歌声中起关键作用。然而，NCM神经元编码导师歌声声学信息的机制尚未完全了解。在这里，我们通过在麻醉的雄性斑胸草雀身上进行电生理记录，研究NCM神经元对歌声结构频谱变化的敏感性，以此来探究NCM神经元中导师歌声信息的神经表征。我们通过以不同的频率步长改变和声音节的基频（FF）来操纵导师歌声和不熟悉的同种歌声的声学结构，并记录对那些FF偏移和原始歌声的神经反应。我们的结果表明，NCM神经元对导师歌声中的FF偏移高度敏感，但对不熟悉的同种歌声的敏感性要低得多，这为NCM神经元中导师歌声信息的神经编码提供了新的证据。此外，我们发现FF偏移对神经反应的影响取决于FF偏移的方向。这些发现表明，NCM神经元编码导师歌声的详细信息，这可以作为歌声学习所需的导师歌声模板。
