Cui Zhongdan, Yu Chao, Wang Xindong, Yin Kuiying, Luo Jinhong
Hubei Key Laboratory of Genetic Regulation & Integrative Biology, School of Life Sciences, Central China Normal University, Wuhan 430079, China.
Nanjing Research Institute of Electronics Technology, Nanjing 210039, China.
J Neurosci. 2024 Dec 4;44(49):e0916242024. doi: 10.1523/JNEUROSCI.0916-24.2024.
Animal vocalizations and human speech are typically characterized by a complex spectrotemporal structure, composed of multiple harmonics, and patterned as temporally organized sequences. However, auditory research often employed simple artificial acoustic stimuli or their combinations. Here we addressed the question of whether the neuronal responses to natural echolocation call sequences can be predicted by manipulated sequences of incomplete constituents at the midbrain inferior colliculus (IC). We characterized the extracellular single-unit activity of IC neurons in the great roundleaf bat, (both sexes), using natural call sequences, various manipulated sequences of incomplete vocalizations, and pure tones. We report that approximately two-thirds of IC neurons exhibited a harmonic interaction. Neurons with high harmonic interactions exhibited greater selectivity to natural call sequences, and the degree of harmonic interaction was robust to the natural amplitude variations between call harmonics. For 81% of the IC neurons, the responses to the natural echolocation call sequence could not be predicted by altered sequences of missing call components. Surprisingly, nearly 70% of the neurons that showed a harmonic interaction were characterized by a single excitatory response peak as revealed by pure tones. Our results suggest that prevalent harmonic processing has already emerged in the auditory midbrain IC in the echolocating bat.
动物发声和人类言语通常具有复杂的频谱时间结构，由多个谐波组成，并被组织成时间上有规律的序列。然而，听觉研究常常采用简单的人工声学刺激或其组合。在此，我们探讨了中脑下丘（IC）对自然回声定位叫声序列的神经元反应是否能通过对不完整成分的操纵序列来预测这一问题。我们使用自然叫声序列、各种不完整发声的操纵序列以及纯音，对大蹄蝠（两性）IC神经元的细胞外单单位活动进行了表征。我们报告称，约三分之二的IC神经元表现出谐波相互作用。具有高谐波相互作用的神经元对自然叫声序列表现出更高的选择性，并且谐波相互作用的程度对叫声谐波之间的自然幅度变化具有鲁棒性。对于81%的IC神经元，缺失叫声成分的改变序列无法预测其对自然回声定位叫声序列的反应。令人惊讶的是，近70%表现出谐波相互作用的神经元，如纯音所揭示的那样，具有单个兴奋性反应峰值。我们的结果表明，在回声定位蝙蝠的听觉中脑IC中已经出现了普遍的谐波处理。
