AUDITORY CORTICAL FUNCTIONS STUDIED BY IN-VIVO OPTICAL RECORDING METHOD

采用12 * 12通道光电二极管阵列和电压敏感染料（RH795）的光学记录方法，在麻醉条件下（Nembutal 30 mg/kg）测量豚鼠听觉皮层前（a：初级）和背尾（DC）神经活动的时空模式。本研究进行了两个项目：(1)双耳交互和(2)调频（FM）声音和动物叫声的信息处理。为了测量双耳相互作用，我们使用了自由场刺激和闭耳刺激。对自由场刺激的光学记录的响应表明，当说话人被放置在与记录侧30度左右时，响应最大，当它被放置在同侧时，响应较小。方位角选择性在高频下更明显，在低频下更宽。这些反应模式被认为是耳廓特征的反映。没有观察到对特定方位角有更多响应的皮质位置，这表明在a和DC区域中没有方位角的地形表征。封闭耳刺激结果显示，刺激主要是对侧引起的，抑制主要是同侧引起的。这种兴奋和抑制发生在两个脑区的同一皮质区域。对调频声音和动物叫声的反应与对纯音的反应不同。对纯音的反应沿着同频带反向移动，而对调频的反应则在不同的同频带中斜向移动。上下扫频时，响应运动方向相反。对动物叫声的反应非常复杂：它们在叫声中表现出多次重复的兴奋和抑制。大脑皮层中没有发现专门对调频声音和叫声做出反应的区域。这些结果表明，对调频声音和鸣叫声的时空响应模式与这些声音的频谱成分的时间结构有关。少

Using an optical recording method with a 12 * 12-channel photodiode array and a voltage-sensitive dye (RH795), spatiotemporal patterns of neural activities in anterior (A : primary) and dorsocaudal (DC) fields of the guinea pig auditory cortex were measured under anesthetized condition (Nembutal 30 mg/kg). In this research, two projects were conducted : (1) binaural interaction and (2) information processing of frequency-modulated (FM) sounds and animal calls.To measure binaural interaction, we used both free-field stimulation and closed-ear stimulation. The optically-recorded responses to free-field stimulation showed that the responses were maximal when the speaker was placed at around 30 degrees contralateral to the recoding side and small when it was placed on the ipsilateral side. The azimuth selectivity was sharper for higher frequencies and broader for lower frequencies. These response patterns were suggested to be a reflection of pinna characteristics. Cortical locations specif … More ically responding to a certain azimuth were not observed, indicating that there is no topographic representation of azimuth in fields A and DC.Closed-ear stimulation revealed that the excitation was evoked mainly contralaterally and the inhibition was evoked mainly ipsilaterally. This excitation and inhibition occurred at the same cortical places in both fields.The responses to FM sounds and animal calls were different from those to pure-tones. The response to a pure-tone moved dorsally along an isofrequency band, but those to FM sounds moved obliquenly crossing different isofrequency bands. The direction of the response movement was opposite between upward and downward frequency sweeps. The responses to animal calls were very complicated : they showed several times repetition of excitation and inhibition during the calls. No cortical place which specifically responds to FM sounds and the calls was found. These results indicate that spatiotemporal patterns in response to the FM sounds and the calls are related to the temporal structures of spectral components of these sounds. Less