Wu Chung Hsin, Jen Philip H-S
Department of Life Science, National Taiwan Normal University, Taipei, China.
Neurosci Lett. 2008 Jun 27;438(3):362-7. doi: 10.1016/j.neulet.2008.04.069. Epub 2008 Apr 25.
During hunting, insectivorous bats such as Eptesicus fuscus progressively increase the pulse repetition rate, shorten the pulse duration, and lower the frequency and amplitude of emitted pulses as they search, approach and finally intercept insects or negotiate obstacles. As such, analysis of an echo parameter by the bat is inevitably affected by other co-varying echo parameters. The present study examined the effect of pulse duration on frequency selectivity of neurons in the central nucleus of the inferior colliculus (IC) of the big brown bat. A family of iso-level frequency tuning curves of each IC neuron was first measured with tone bursts of different durations. The bandwidth of iso-level frequency tuning curves within each family was then compared. Our data show that most IC neurons discharge maximally to a particular pulse duration which is defined as the best duration (BDu). The iso-level frequency tuning curves of these duration-selective neurons have the narrowest bandwidth when measured with the BDu pulse than with non-BDu pulses. They also have the narrowest bandwidth when measured with a short than with a long BDu pulse. These data suggest that frequency selectivity of duration-selective IC neurons becomes sharper when short echo duration at the final phase of hunting is encoded by IC neurons that have short BDu.
在狩猎过程中，诸如棕蝠（Eptesicus fuscus）这样的食虫蝙蝠在搜索、接近并最终捕获昆虫或避开障碍物时，会逐渐提高脉冲重复率，缩短脉冲持续时间，并降低所发射脉冲的频率和幅度。因此，蝙蝠对回声参数的分析不可避免地会受到其他共同变化的回声参数的影响。本研究考察了脉冲持续时间对大棕蝠下丘中央核（IC）神经元频率选择性的影响。首先用不同持续时间的纯音脉冲串测量每个IC神经元的一组等响度频率调谐曲线。然后比较每组中等响度频率调谐曲线的带宽。我们的数据表明，大多数IC神经元对特定的脉冲持续时间放电最多，该持续时间被定义为最佳持续时间（BDu）。与非BDu脉冲相比，用BDu脉冲测量时，这些持续时间选择性神经元的等响度频率调谐曲线带宽最窄。与长BDu脉冲相比，用短BDu脉冲测量时，它们的带宽也最窄。这些数据表明，当狩猎最后阶段的短回声持续时间由具有短BDu的IC神经元编码时，持续时间选择性IC神经元的频率选择性会变得更敏锐。
