Christensen-Dalsgaard J, Jørgensen M B, Kanneworff M
Center for Sound Communication, Institute of Biology, Odense University, Odense M, Denmark.
Hear Res. 1998 May;119(1-2):155-63. doi: 10.1016/s0378-5955(98)00047-1.
Responses to free-field sound of 401 fibers from the VIIIth nerve of the grassfrog, Rana temporaria, are described. The spontaneous activities of the fibers ranged from 0 to 75 spikes/s, showing only weak correlation with frequency or sensitivity of the fibers. The highest spontaneous activities were approximately twice as high as reported previously for frogs. Best frequencies ranged from 100 to 1600 Hz and thresholds ranged from 21 to 80 dB SPL. The median dynamic range was 20 dB and the slopes of the rate-level curves ranged from 5 to 20 spikes/(s-dB). Most of the units showed post-excitatory suppression (PS) of their spontaneous activity. The duration of PS increased with sound level, also in fibers showing a decrease in firing rate at high intensities. Most fibers showing one-tone suppression did not show PS at their best suppression frequencies. Strong suppression was observed also in very phasic cells giving one spike per stimulation. Therefore, the mechanism underlying PS is probably different from that underlying adaptation. The sharpening of the neural encoding of temporal parameters and the strong encoding of sound offset as well as onset caused by PS very likely is biologically important.
描述了对林蛙（Rana temporaria）第八神经401根纤维的自由场声音的反应。纤维的自发放电活动范围为0至75个脉冲/秒，与纤维的频率或灵敏度仅显示出微弱的相关性。最高自发放电活动约为先前报道的青蛙的两倍。最佳频率范围为100至1600赫兹，阈值范围为21至80分贝声压级。动态范围中位数为20分贝，速率-强度曲线的斜率范围为5至20个脉冲/（秒-分贝）。大多数单位显示出自发活动的兴奋后抑制（PS）。PS的持续时间随声级增加，在高强度下放电率降低的纤维中也是如此。大多数表现出单音抑制的纤维在其最佳抑制频率下未显示PS。在每个刺激产生一个脉冲的非常相位性的细胞中也观察到强烈抑制。因此，PS的潜在机制可能与适应的潜在机制不同。PS导致的时间参数神经编码的锐化以及声音起始和结束的强烈编码很可能具有生物学重要性。
