间隔标记信号带宽和强度对豚鼠下丘间隔反应的影响

目的探讨间隔检测中间隔标记信号的带宽和强度对豚鼠下丘间隔反应阈值的影响。方法经豚鼠下丘埋植金属电极，记录4种带宽间隔标记信号和3个强度下的间隔反应，得出间隔阈值。结果与以往行为实验结果类似，相同声音强度下，豚鼠下丘的间隔反应阈值随着间隔标记信号带宽的增加而下降。例如在85dBSPL时，0．5～8kHz，0．5～16kHz及0．5～32kHz带宽下的间隔反应阈值分别为1．35±0．32ms，1．33±0．33ms及1．17±0．44ms。但是在最高频段（16～32kHz）和线性等带宽低频段（0．5～16kHz），间隔反应阈值未见显著差异，提示高频段的时间分辨可能与低频段相当。相同间隔标记带宽下，声音强度愈低，间隔反应阈值愈大；但仅在最低频段（0．5～8kHz）声音强度效应具有显著性意义。结论豚鼠下丘的间隔反应阈值主要决定于间隔标记信号的总带宽而非频带位置；信号强度也对该阈值有一定影响。

The effect of gap marker bandwidth and level on gap responses from inferior colliculus of guinea pig

Objective To explore the effect of gap-marker bandwidth and signal level on gap responses recorded from inferior colliculus （IC） of guinea pigs. Methods Metal electrodes were implanted in the IC of guinea pigs. After one week of rest,we recorded the auditory evoked responses to gaps marked with noises of different bandwidths and presented under three levels to determine the gap response thresholds. Results The effect of gap marker bandwidth on gap response threshold was similar to that in previous behavioral test. At the same presentation level, the gap response thresholds from IC of guinea pigs were found to decrease with increasing gap-marker bandwidths. At 85 dB SPL, for example, the thresholds were found to be 1.35± 0.32 ms, 1.33 ± 0.33 ms and 1.17 ±0.44 ms for the bandwidths of 0.5 - 8 kHz, 0.5- 16 kHz and 0.5- 32 kHz respectively. However, the gap response threshold in response to the highest frequency band （16 ~ 32 kHz） was found not to be significantly different from that to the low-frequency band gap with equal bandwidth in linear scale （0.5- 16 kHz）. Within the same noise band, the gap response threshold decreased with increasing sound intensity （presentation level）. However, this effect was only significant in the lowest frequency band between the highest presentation level and the lowest presentation level. Conclusion The gap response threshold in IC of guinea pig may be determined by the total bandwidth of gap marker but not the position of the signal frequency. Gap marker level also has some effects on the gap response threshold.