Rübsamen R, Schäfer M
Zoological Department, University of Kelaniya, Sri Lanka.
J Comp Physiol A. 1990 Dec;167(6):757-69. doi: 10.1007/BF00189766.
This report describes the ontogenesis of tonotopy in the inferior colliculus (IC) of the rufous horseshoe bat (Rhinolophus rouxi). Horseshoe bats are deaf at birth, but consistent tonotopy with a low-to-high frequency gradient from dorsolateral to ventromedial develops from the 2nd up to the 5th week. The representation of the auditory fovea is established in ventro-medio-caudal parts of the IC during the 3rd postnatal week (Fig. 3). Then, a narrow frequency band 5 kHz in width, comprising 16% of the bat's auditory range, captures 50-60 vol% of the IC (Fig. 3c). However, foveal tuning is 10-12 kHz (1/3 octave) lower than in adults; foveal tuning in females (65-68 kHz) is 2-3 kHz higher than in males (62-65 Khz). Thereafter, foveal tuning increases by 1-1.5 kHz per day up to the 5th postnatal week, when the adult hearing range is established (Figs. 4, 5). The increase of sensitivity and of tuning sharpness of single units also follows a low-to-high frequency gradient (Fig. 6). Throughout this development the foveal tuning matches the second harmonic of the echolocation pulses vocalised by these young bats. The results confirm the hypothesis of developmental shifts in the frequency-place code for the foveal high frequency representation in the IC.
本报告描述了棕果菊头蝠（Rhinolophus rouxi）下丘（IC）中音调拓扑学的个体发生。菊头蝠出生时耳聋，但从第2周到第5周，从背外侧到腹内侧会形成从低频到高频的一致音调拓扑。出生后第3周，听觉中央凹的表征在IC的腹内侧尾侧部分建立（图3）。然后，一个宽度为5 kHz的窄频带，占蝙蝠听觉范围的16%，占据了IC的50 - 60体积%（图3c）。然而，中央凹调谐比成年蝙蝠低10 - 12 kHz（1/3倍频程）；雌性的中央凹调谐（65 - 68 kHz）比雄性（62 - 65 kHz）高2 - 3 kHz。此后，直到出生后第5周成年听觉范围建立时，中央凹调谐每天增加1 - 1.5 kHz（图4、5）。单个单元的灵敏度和调谐锐度的增加也遵循从低频到高频的梯度（图6）。在整个发育过程中，中央凹调谐与这些幼蝠发出的回声定位脉冲的二次谐波相匹配。结果证实了关于IC中中央凹高频表征的频率-位置编码发育变化的假设。
