摘要
目的探讨在加入弱噪声前掩蔽的条件下,下丘神经元对声信号的频率调谐(frequency-tuning)的改变。方法12只小鼠在自由声场条件下,选用相当于纯音听阈上5dB强度不同时程(40、60、80、100ms)的弱包络白噪声作为前掩蔽声,观察其对神经元频率调谐的影响。结果弱噪声前掩蔽使大部分神经元的频率调谐曲线(frequencytuningcurve,FTC)锐化(P<0.01),并有随掩蔽声时程的延长而锐化程度增加的趋势(P<0.05)。通过计算FTC的反转斜率(inverse-slope,IS),发现弱噪声前掩蔽对高频边的抑制率明显高于低频边,大部分神经元的高频边反转斜率(IShigh)减小,且有随掩蔽声时程延长而减小程度增加的趋势(P<0.01);而低频边反转斜率(ISlow)的变化无规律。掩蔽声还使神经元对探测声的反应阈值升高(P<0.0001,n=31),且随着掩蔽声时程的延长而升高幅度增大。结论弱噪声前掩蔽使神经元FTC发生锐化、阈值升高,此效应随掩蔽声时程的延长而加强。
Objective To study the change of frequency tuning in inferior collicular neurons when added weak noise forward masking. Methods We examined the changes in neuronal frequency tuning resulted from a weak white noise as forward masking relative to 5dB beyond minimum threshold （reMT＋ 5） and different duration （40,60,80,100 ms） under free field stimulation conditions. Results Weak noise forward masking sharpens frequency tuning curves （FTCs） of most neurons （ P 〈 0.01, n = 25）. The effect increased with masker duration increasing （ P 〈 0.05）. By accounting the inverse - slope （IS）, we discovered the inhibitory rate to high frequency was clearly higher than low frequency. Most ISnigh decreased, this effect increased with masker duration increasing （ P 〈 0.01 ） ; however, there was random changes in ISlow. Masker sound also increased the minimum threshold of neurons to probe sound （ P 〈 0. 0001, n = 31 ）, and the effect also increased with masker duration increasing. Conclusion The weak noise forward masking could sharpen frequency tuning and increased threshold, this effect increased with the masker duration lengthening.
出处
《听力学及言语疾病杂志》
CAS
CSCD
2005年第5期333-336,共4页
Journal of Audiology and Speech Pathology
基金
国家自然科学基金资助项目(编号90208012
30470564)
关键词
弱白噪声
前掩蔽
时程
频率调谐
Weak white noise
Forward masking
Duration
Frequency tuning
