南方医科大学学报

南方医科大学学报 ›› 2021, Vol. 41 ›› Issue (11): 1672-1679.doi: 10.12122/j.issn.1673-4254.2021.11.11

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背景噪声对清醒小鼠初级听皮层神经元听觉响应特征的影响

宋长宝，赵 岩，柏 林   

  1. 南方医科大学生物医学工程学院数学物理系，基础医学院生理学教研室，广东 广州 510515
  • 出版日期:2021-11-20 发布日期:2021-12-10

Effects of background noise on auditory response characteristics of primary auditory cortex neurons in awake mice

SONG Changbao, ZHAO Yan, BAI Lin   

  1. Department of Biomedical Engineering, Department of Basic Medical Science, Southern Medical University, Guangzhou 510515, China
  • Online:2021-11-20 Published:2021-12-10

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摘要： 目的 探究不同强度持续噪声背景对清醒小鼠初级听皮层神经元听觉反应特征的影响。方法 以清醒小鼠初级听皮层（A1）第4层神经元为研究对象，采用细胞外贴附式记录方式，研究清醒状态下A1神经元在不同强度背景噪声下对声刺激发生响应的声强调谐、频率调谐和时间调谐特征的变化。总计44例神经元均进行5种目标声刺激序列扫描，根据神经元的声强响应特征和目标声序列扫描完成情况，将神经元分为4组：单调性-声强组20例、非单调性-声强组6例，完成声强-噪声强度序列扫描；单调性-频率组25例，完成频率-噪声强度序列扫描；单调性-延时组15例完成延时-噪声强度序列扫描。 结果 给予持续宽带白噪声刺激，44例A1听神经元仅在给声后10~40 ms内出现瞬态的尖峰响应，不同强度的背景噪声对A1神经元的发放率无明显影响（P>0.05）；单调性和非单调性-声强组，给予不同声强的目标声叠加持续背景噪声时，当背景噪声增强到一定程度，26例神经元对目标声刺激发生响应的声强阈值随背景噪声强度变化表现出线性增大（线性回归R2值均>0.90，P值均<0.05），各神经元的阈值变化斜率差异较大，但单调性和非单调性神经元群体之间的阈值变化趋势无明显差异（P>0.05）；A1非单调性神经元的最佳声强也随背景噪声增强而增大，其变化斜率与该神经元声强阈值的变化趋势呈正相关（相关系数0.944，P<0.001)；单调性-频率组，给予不同频率的目标声叠加持续背景噪声时，随背景噪声强度增大，神经元频率响应带宽减小（P<0.001），平均发放率减小（P<0.001），而最佳频率基本不变（P<0.001）；单调性-延时组，噪声背景的增强使得神经元对同一声刺激的响应延时增大（P<0.05），但首个动作电位发放时间的精确性不发生改变（P>0.05）。结论 在不断增强的噪声背景中，清醒小鼠A1神经元的声强响应阈值表现出线性升高，其变化斜率存在较大的个体差异，但与神经元的声强响应特征（单调或非单调）无关。增强的背景噪声压缩了A1神经元的频率响应范围，延长了神经元对目标声的响应时间，但神经元的频率选择性和对同一目标声发生反应的时间精确性不受噪声背景的干扰而保持稳定。

关键词: 背景噪声；初级听皮层；清醒小鼠

Abstract: Objective To study the effects of different continuous background noises on auditory response characteristics of primary auditory cortex (A1) neurons in awake mice. Methods We performed in vivo cell-attached recordings in layer 4 neurons of the A1 of awake mice to investigate how continuous background noises of different levels affected the intensity tuning, frequency tuning and time characteristics of individual A1 neurons. According to the intensity tuning characteristics and types of stimulation, 44 neurons were devided into 4 groups: monotonic-intensity group (20 monotonic neurons), nonmonotonic-intensity group (6 nonmonotonic neurons), monotonic-frequency group (25 monotonic neurons) and monotonic-latency group (15 monotonic neurons). Results The A1 neurons only had transient spike response within 10 to 40 ms after the onset of continuous wild-band noise stimulation. The noise intensity had no significant effects on the background firing rates of the A1 neurons (P>0.05). The increase of background noise resulted in a significant linear elevation of the intensity threshold of monotonic and nonmonotonic neurons for tone-evoked response (R2>0.90, P<0.05). No significant difference was observed in the slopes of threshold changes between monotonic and nonmonotonic neurons (P>0.05). The best intensity of nonmonotonic neurons increased along with the intensity of the background noise, and the variation of the best intensity was positively correlated with the change of the threshold of the same neuron (r=0.944, P<0.001). The frequency response bandwidth and the firing rate of the A1 neurons decreased as the noise intensity increased (P<0.001), but the best frequency almost remained unchanged (P<0.001). The increase of background noise intensity resulted in an increased first spike latency of the neurons to the same tone stimulus (P<0.05) without affecting the time accuracy of the first action potential (P>0.05). Conclusion The acoustic response threshold of the A1 neurons increases linearly with the increase of background noise intensity. An increased background noise leads to compressed frequency band-width, a decreased firing rate and a prolonged spike latency, but the frequency selectivity and the time accuracy of auditory response to the same noise remain stable.

Key words: background noise; primary auditory cortex; awake mice