Issa John B, Haeffele Benjamin D, Young Eric D, Yue David T
Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Ross Building, Room 713, 720 Rutland Avenue, Baltimore, MD 21205, USA.
Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Ross Building, Room 713, 720 Rutland Avenue, Baltimore, MD 21205, USA.
Hear Res. 2017 Feb;344:207-222. doi: 10.1016/j.heares.2016.11.018. Epub 2016 Dec 21.
Functional organization is a key feature of the neocortex that often guides studies of sensory processing, development, and plasticity. Tonotopy, which arises from the transduction properties of the cochlea, is the most widely studied organizational feature in auditory cortex; however, in order to process complex sounds, cortical regions are likely specialized for higher order features. Here, motivated by the prevalence of frequency modulations in mouse ultrasonic vocalizations and aided by the use of a multiscale imaging approach, we uncover a functional organization across the extent of auditory cortex for the rate of frequency modulated (FM) sweeps. In particular, using two-photon Ca imaging of layer 2/3 neurons, we identify a tone-insensitive region at the border of AI and AAF. This central sweep region behaves fundamentally differently from nearby neurons in AI and AII, responding preferentially to fast FM sweeps but not to tones or bandlimited noise. Together these findings define a second dimension of organization in the mouse auditory cortex for sweep rate complementary to that of tone frequency.
功能组织是新皮层的一个关键特征，它常常指导着对感觉处理、发育和可塑性的研究。由耳蜗的转导特性产生的音频拓扑是听觉皮层中研究最广泛的组织特征；然而，为了处理复杂声音，皮层区域可能专门负责更高阶的特征。在这里，受小鼠超声发声中频率调制普遍存在的启发，并借助多尺度成像方法，我们揭示了听觉皮层范围内针对调频（FM）扫描速率的功能组织。具体而言，通过对第2/3层神经元进行双光子钙成像，我们在初级听觉皮层（AI）和前听皮层（AAF）的边界处识别出一个音调不敏感区域。这个中央扫描区域的行为与AI和AII中附近的神经元有根本不同，它优先对快速FM扫描做出反应，而对纯音或带限噪声不做反应。这些发现共同定义了小鼠听觉皮层中与音调频率互补的扫描速率组织的第二个维度。
