弱噪声对小鼠下丘神经元频率调谐的影响

为探讨弱噪声对小鼠 (MusmusculusKm)中脑下丘 (inferiorcolliculus ,IC)神经元声信号提取的影响 ,采用单位胞外记录方法 ,研究了加入弱白噪声 (强度相当于纯音阈强度下 5dB)前后神经元频率调谐曲线的变化。实验共记录到 10 4个下丘神经元 ,测量了 32个神经元的频率调谐曲线。结果显示 :①弱噪声条件下神经元的频率调谐曲线表现出 3种类型 ,即锐化 (34 4 % ,11/ 32 )、拓宽 (18 8% ,6 / 32 )和不受影响 (4 6 9% ,15 / 32 ) ,其中锐化呈现有意义的变化 ;②频率调谐受弱噪声锐化的神经元 ,其Q10 、Q3 0 平均分别增大 (34 4 2±17 0 4 ) % (P =0 0 2 6 ,n =11)和 (4 6 34± 2 2 88) % (P =0 0 0 9,n =7) ,且Q3 0 变化率大于Q10 ;③弱噪声对调谐曲线的高、低频边锐化度不一 ,神经元低频边的反转斜率基本不变 由 0 16± 0 0 8变为 0 16± 0 0 7kHz/dB (P =0 94 7,n =7) ],而高频边明显下降 由 0 5 2± 0 2 5下降为 0 2 6± 0 13kHz/dB ,平均减小 (4 3 81±2 4 0 6 ) % ,(P =0 0 4 6 ,n =7) ]。上述结果表明 ,弱噪声可锐化小鼠IC神经元频率调谐 ,并强化神经元的声信号高频分析能力

Effect of Weak Noise on the Frequency Tuning of Mouse Inferior Collicular Neurons

In order to study the effect of weak noise on the sound signal extraction of mouse (Mus musculus Km) in ferior collicular (IC) neurons from environments, we examined the changes in frequency tuning curves (FTCs) of 32 neurons induced by a weak noise relative to 5 dB below minimum threshold of tone (reMT-5 dB) under free field stimulation conditions. The results were as follows: ① There were three types of variations in FTCs, sharpened (34.4%), broadened (18.8 %), and unaffected (46.9%), nevertheless, only the alteration of sharpened FTCs was statistically different. ② Sharpness of frequency tuning induced by a reMT-5 dB noise was very strong. Q10 and Q30 of FTCs were increased by (34.42+ 17.04)% (P =0.026, n = 11) and (46.34+22.88)% (P =0.009, n =7). ③ The changes of inverseslopes (ISs, kHz/dB) between high (IShigh) and low (ISlow) limbs of FTCs were dissymmetry. The IShigh of FTCs decreased markedly ( P = 0.046, n = 7), however, there was little change ( P = 0.947, n = 7) in ISlow. Our data revealed for the first time that the weak noise could sharpen frequency tuning and increase the sensitivity on the high frequency of sound signal in IC neurons of mouse.