Norton S J, Bargones J Y, Rubel E W
Hearing Development Laboratories, University of Washington, Seattle.
Hear Res. 1991 Jan;51(1):73-91. doi: 10.1016/0378-5955(91)90008-w.
The development of the acoustic distortion product (ADP) 2f1-f2 was studied in gerbils, beginning 12 days after birth (P12). ADPs were measured as a function of stimulus frequency region (1.0 to 13.0 kHz) and level (10 to 80 dB SPL). There was an orderly progression in the appearance and maturation of the emissions, with responses to high-frequency stimuli (f2 = 13.0 kHz) appearing first, at P13-14. Responses to mid and high frequencies (f2 = 3.9 to 13.0 kHz) matured earlier than responses to lower frequencies. Responses to low-frequency stimuli (f2 = 1.3 KHz) did not appear until P18-19 and were not mature until after one month of age. The first emissions to develop in a given frequency region had elevated thresholds, were reduced in amplitude, and displayed monotonic input-output functions. As the auditory system matured, emission growth functions became non-monotonic displaying saturation, but initially retained a reduced dynamic range. Data from the developing gerbil suggest that initially its cochlear mechanics are passive and that active elements associated with normal outer hair cell function mature first in the basal turn and last near the apex. Furthermore, the development of active nonlinear elements underlying ADP generation is consistent with the development of frequency selectivity and developmental shifts in the place code which have been demonstrated in the gerbil.
在沙土鼠出生后12天（P12）开始研究畸变产物耳声发射（ADP）2f1 - f2的发育情况。测量了ADP随刺激频率范围（1.0至13.0 kHz）和强度（10至80 dB SPL）的变化。耳声发射的出现和成熟有一个有序的过程，对高频刺激（f2 = 13.0 kHz）的反应最早在P13 - 14出现。对中高频（f2 = 3.9至13.0 kHz）的反应比低频反应成熟得更早。对低频刺激（f2 = 1.3 kHz）的反应直到P18 - 19才出现，且在一个月龄后才成熟。在给定频率范围内最早出现的耳声发射阈值较高、幅度较小，并表现出单调的输入 - 输出函数。随着听觉系统的成熟，耳声发射增长函数变得非单调，显示出饱和现象，但最初动态范围仍较小。发育中的沙土鼠的数据表明，最初其耳蜗力学是被动的，与正常外毛细胞功能相关的主动元件首先在基底转成熟，最后在靠近蜗顶处成熟。此外，ADP产生背后的主动非线性元件的发育与沙土鼠已证明的频率选择性发育和部位编码的发育变化一致。
