Echteler S M, Arjmand E, Dallos P
Department of Neurobiology and Physiology, Northwestern University, Evanston, Illinois 60208.
Nature. 1989 Sep 14;341(6238):147-9. doi: 10.1038/341147a0.
The position of an auditory hair cell along the length of the cochlea determines the sound frequency to which it is most sensitive. Receptors located near the proximal end (base) of the cochlea are maximally stimulated by high-frequency sounds; those occupying successively more distal (apical) positions respond best to progressively lower frequencies. At present, it is unclear how this frequency place map emerges with respect to the development of the cochlea. It has been suggested, on the basis of acoustic trauma experiments with developing chicks and cochlear potential recordings from developing gerbils, that this map may arise through systematic changes in the spatial encoding of frequency along the cochlea. Others have inferred from frequency tuning curves derived from auditory-nerve recordings in developing mammals and chicks, that the cochlear frequency-place map remains stable throughout development. We analysed frequency tuning curves obtained from gerbil spiral ganglion cells at a constant location within the basal cochlea, and report here that these cells undergo significant increases (up to 1.5 octaves) in their best-response frequencies between the second and third weeks of postnatal life. These recordings provide direct evidence for developmental changes in the tonotopic organization of the mammalian cochlea.
听觉毛细胞在耳蜗长度上的位置决定了其最敏感的声音频率。位于耳蜗近端（底部）附近的感受器受到高频声音的最大刺激；那些依次占据更远端（顶部）位置的感受器对逐渐降低的频率反应最佳。目前，关于耳蜗发育过程中这种频率定位图是如何出现的尚不清楚。基于对发育中的小鸡进行的声学创伤实验以及对发育中的沙鼠进行的耳蜗电位记录，有人提出这种图谱可能是通过沿耳蜗的频率空间编码的系统性变化而产生的。其他人则从发育中的哺乳动物和小鸡的听神经记录得出的频率调谐曲线推断，耳蜗频率定位图在整个发育过程中保持稳定。我们分析了从沙鼠耳蜗基部恒定位置的螺旋神经节细胞获得的频率调谐曲线，并在此报告，这些细胞在出生后第二周和第三周之间其最佳反应频率有显著增加（高达1.5个八度）。这些记录为哺乳动物耳蜗音调组织的发育变化提供了直接证据。
