Abstract: We investigated the responses of neuron groups in the inferior colliculus of Pratt’s leaf-nosed bat (Hipposideros pratti),during 500 -4 000 μm recording depth,to constant frequency components of three harmonics (CF1 - CF3 ),using auditory evoked potential combined with the computer averaging technique. The results showed that evoked potential waves included 2 -4 peaks under the given stimuli,and all exhibited on-off responses below the 1 000 μm recording depth. With increasing recording depth,the amplitudes of on-responses all reached maximum at 3 000 μm and then decreased(P <0.001),while the latencies decreased linearly (P < 0. 001);the off-responses triggered by CF2 had the largest amplitudes, while the amplitudes of off-responses evoked by CF1 and CF3 were smaller. The off-responses of CF2 (P <0.001)had linearly decreasing latencies,but the CF1 (P > 0. 05)and CF3 (P >0. 05)had no such linear change with the increased recording depth. The results reveal there were unanimous tendency of neuron groups’processing on-responses, indicating that the processing of the acoustic signals related to behavior may have complex interactions among frequency layers;and off-responses were sensitive to the frequency near the dominant frequency, suggesting that they may play a role in Doppler shift,capturing the fluttering of insects or communication of constant frequency-frequency modulation bats.

Key words: Auditory evoked potentials, Hipposideros pratti, Inferior colliculus, On-off response

摘要： 利用听觉诱发电位和计算机叠加平均技术研究了普氏蹄蝠下丘(Inferior colliculus,IC)500-4 000 μm 记录深度间,神经元群对3 个谐波恒频(Constant frequency,CF) 声刺激(CF1 -CF3 )的反应。结果显示,在蝙蝠回声定位信号CF 成分刺激下,其IC 的诱发电位包括2 -4 个波,在1 000 μm 以下的记录区域,3 种刺激均能诱发on-off 反应,on-反应的幅度均在3 000 μm 达最大之后减小(P < 0.001),而潜伏期则逐渐缩短(P < 0.001);CF2 能诱发大幅度的off-反应,而CF1 、CF3 诱发的off-反应幅度较小,随着记录深度的增加,CF2 (P <0. 001)的off-反应潜伏期逐渐缩短,而CF1 (P > 0. 05)和CF3 (P >0. 05)的潜伏期则无此单调性。结果表明神经元群体加工CF1 - CF3 的on-反应存在一致性变化,提示其对行为相关的声信号加工可能存在频率层间复杂的相互作用;对CF 信号加工的off-反应对主频附近声较敏感,提示其可能在恒频-调频蝙蝠的多普勒频移、捕获振翅昆虫信息或种间交流中起着某种作用。

关键词: 普氏蹄蝠, 下丘, 听觉诱发电位, on-off 反应