Integration of multi-frequency sounds into a unified perceptual object is critical for recognizing syllables in speech. This “feature binding” relies on the precise synchrony of each component’s onset timing, but little is known regarding its neural correlates. We find that multi-frequency sounds prevalent in vocalizations, specifically harmonics, preferentially activate the mouse secondary auditory cortex (A2), whose response deteriorates with shifts in component onset timings. The temporal window for harmonics integration in A2 was broadened by inactivation of somatostatin-expressing interneurons (SOM cells), but not parvalbumin-expressing interneurons (PV cells). Importantly, A2 has functionally connected subnetworks of neurons preferentially encoding harmonic over inharmonic sounds. These subnetworks are stable across days and exist prior to experimental harmonics exposure, suggesting their formation during development. Furthermore, A2 inactivation impairs performance in a discrimination task for coincident harmonics. Together, we propose A2 as a locus for multi-frequency integration, which may form the circuit basis for vocal processing.

将多频声音整合到一个统一的感知对象中对于识别语音中的音节至关重要。这种“特征绑定”依赖于每个组件开始时间的精确同步，但对其神经相关性知之甚少。我们发现发声中普遍存在的多频声音，特别是谐波，优先激活小鼠次级听觉皮层 (A2)，其响应随着成分开始时间的变化而恶化。A2 中谐波整合的时间窗口因表达生长抑素的中间神经元（SOM 细胞）而不是表达小清蛋白的中间神经元（PV 细胞）的失活而扩大。重要的是，A2 具有功能连接的神经元子网络，优先编码谐波而不是不和谐的声音。这些子网络在几天内是稳定的，并且在实验谐波暴露之前就存在，表明它们是在开发过程中形成的。此外，A2 失活会损害重合谐波识别任务的性能。我们一起建议将 A2 作为多频积分的轨迹，这可能构成人声处理的电路基础。