Christensen-Dalsgaard Jakob, Kanneworff Morten
Center for Sound Communication, Institute of Biology, University of Southern Denmark, Odense M.
Brain Res Bull. 2005 Sep 15;66(4-6):522-5. doi: 10.1016/j.brainresbull.2005.03.005. Epub 2005 Apr 2.
We have studied binaural and directional processing in cells in the frog dorsal medullary nucleus (DMN) stimulated with dichotic sound (couplers) and free-field sound. We present evidence that already at this stage of central processing the neural directionality is sharpened, probably by binaural interaction. Binaural interaction in the DMN was usually interpreted as inhibition, mostly driven from the contralateral side and dependent on a certain combination of interaural time differences (ITD) and interaural level differences (ILD). In free-field measurements, the strength and timing of the binaural inputs will depend on sound direction as processed by the auditory fibers. Thus, the directionality of DMN cells is caused by both monaural directional cues generated by acoustical coupling of the eardrums and non-tympanic pathways as well as binaural interaction. Most DMN cells show ovoidal directional characteristics and the directionality is sharpened compared to that of auditory nerve fibers. We suggest that the sharpening is due to the inhibitory interactions.
我们研究了用双耳声音（耦合器）和自由场声音刺激青蛙背髓核（DMN）中的细胞时的双耳和定向处理。我们提供的证据表明，在中枢处理的这个阶段，神经方向性已经得到增强，这可能是通过双耳相互作用实现的。DMN中的双耳相互作用通常被解释为抑制作用，主要由对侧驱动，并依赖于耳间时间差（ITD）和耳间声级差（ILD）的特定组合。在自由场测量中，双耳输入的强度和时间将取决于听觉纤维处理的声音方向。因此，DMN细胞的方向性是由鼓膜的声学耦合和非鼓膜途径产生的单耳定向线索以及双耳相互作用共同引起的。大多数DMN细胞呈现卵形定向特征，并且与听觉神经纤维相比，方向性得到了增强。我们认为这种增强是由于抑制性相互作用。
