Information Processing Laboratory, Department of Electronics and Electrical Communication Engineering, IIT Kharagpur, Kharagpur 721302, India.
Advanced Technology Development Centre, IIT Kharagpur, Kharagpur 721302, India.
J Neurosci. 2024 Oct 30;44(44):e0364242024. doi: 10.1523/JNEUROSCI.0364-24.2024.
Harmonics are an integral part of music, speech, and vocalizations of animals. Since the rest of the auditory environment is primarily made up of nonharmonic sounds, the auditory system needs to perceptually separate the above two kinds of sounds. In mice, harmonics, generally with two-tone components (two-tone harmonic complexes, TTHCs), form an important component of vocal communication. Communication by pups during isolation from the mother and by adult males during courtship elicits typical behaviors in female mice-dams and adult courting females, respectively. Our study shows that the processing of TTHC is specialized in mice providing neural basis for perceptual differences between tones and TTHCs and also nonharmonic sounds. Investigation of responses in the primary auditory cortex (Au1) from in vivo extracellular recordings and two-photon Ca imaging of excitatory and inhibitory neurons to TTHCs exhibit enhancement, suppression, or no-effect with respect to tones. Irrespective of neuron type, harmonic enhancement is maximized, and suppression is minimized when the fundamental frequencies ( ) match the neuron's best fundamental frequency (BF). Sex-specific processing of TTHC is evident from differences in the distributions of neurons' best frequency (BF) and best fundamental frequency (BF) in single units, differences in harmonic suppressed cases re-BF, independent of neuron types, and from pairwise noise correlations among excitatory and parvalbumin inhibitory interneurons. Furthermore, TTHCs elicit a higher response compared with two-tone nonharmonics in females, but not in males. Thus, our study shows specialized neural processing of TTHCs over tones and nonharmonics, highlighting local network specialization among different neuronal types.
谐波是音乐、言语和动物发声的一个组成部分。由于听觉环境的其余部分主要由非谐波声音组成，因此听觉系统需要在感知上分离上述两种声音。在小鼠中，谐波通常由两个音组成（两音谐波复合体，TTHC），是发声通讯的一个重要组成部分。幼鼠与母亲隔离时以及成年雄鼠求偶时的叫声会引起雌鼠的典型行为——母鼠和成年求偶雌鼠。我们的研究表明，TTHC 的处理在小鼠中是专门化的，为音调与 TTHC 以及非谐波声音之间的感知差异提供了神经基础。通过在体细胞外记录和对 TTHC 的兴奋性和抑制性神经元进行双光子 Ca2+成像，研究了初级听觉皮层（Au1）中的反应，结果显示，相对于音调，TTHC 会产生增强、抑制或无效应。无论神经元类型如何，当基频（）与神经元的最佳基频（BF）匹配时，谐波增强达到最大值，抑制达到最小值。TTHC 的性别特异性处理从单神经元的最佳频率（BF）和最佳基频（BF）分布、谐波抑制情况下的再 BF 分布、兴奋性和 Parvalbumin 抑制性中间神经元之间的成对噪声相关性的差异中可以明显看出，这些差异与神经元类型无关。此外，与两音非谐波相比，TTHC 在雌性中会引起更高的反应，但在雄性中则不然。因此，我们的研究表明，TTHC 对音调的专门神经处理，强调了不同神经元类型之间局部网络的专业化。
