不同最佳频率的下丘神经元的声反应特性和方位敏感性  

Response properties and azimuthal sensitivity of inferior collicular neurons with different best frequency to sound stimulation

作　　者：李安邦[1] 吴飞健[2] 陈其才[2] 

机构地区：[1]华中师范大学物理系,武汉430079 [2]华中师范大学生命科学学院,武汉430079

出　　处：《华中师范大学学报（自然科学版）》2001年第4期445-452,共8页Journal of Central China Normal University：Natural Sciences

基　　金：国家自然科学基金 (#3 9740 0 0 2 );国家教育部科技重点基金 (#96-1 46)资助

摘　　要：在自由声场刺激条件下 ,从 2 0只昆明小鼠 (Kunming Mus Musculus)下丘 (Inferior Col-liculus,IC)记录到 1 93个神经元 .将这些神经元按其最佳频率 (best frequency,BF) (k Hz)分为(5 ,1 0 ],(1 0 ,1 5 ],(1 5 ,2 0 ]和 (2 0 ,3 1 ]4个频率段 ,观察和分析它们的声反应特性 ,并用最小阈值(minimum threshold,MT)和放电率 (firing rate)标准对这些神经元前听空间俯仰方位(Elevation) 0平面的 7个水平方位 (Azimuth)角 (同侧 90°、60°、3 0°,0°,对侧 3 0°、60°、90°)的敏感性进行了研究 .结果表明 :1、IC神经元的放电率和潜伏期基本随刺激强度的增加而增加和缩短 ,其函数表现为三种基本不同的形式 :单调型、非单调型以及放电率函数的不规则型和潜伏期函数的饱和单调型 .非单调函数神经元数目高于单调函数神经元 .三种函数形式的神经元数目分布与 BF之间无明显相关 ;2、BF较高的 IC神经元的潜伏期与 BF较低的神经元的潜伏期之间未发现显著性差异 ;3、用低 MT和最大放电率指标检测 IC神经元的方位特性发现 ,在神经元的最敏感角度展现出低 MT和高放电率 ,虽然最佳敏感角度的分布随频率段而不同 ,但绝大部分神经元的最敏感角度位于对侧 ,其中以对侧 60°所占比例最大 .用低A total of 193 neurons responding to presented acoustic stimuli were recorded on 20 Kunming Mus Musculus under free field sound stimulation conditions. Best frequencies (BF) (kHz) of these neurons were divided into four ranges: (5, 10], (10, 15]?(15, 20] and (20, 31] and their acoustic response features, minimum thresholds (MT) and firing rates, and directional sensitivity of 7 azimuth angles (90°, 60°, 30° ipsilateral; 0°; and 30°, 60°, 90° contralateral), were examined. Our results is provided as following: 1. Firing rates and latencies of IC neurons increased and shortened with increasing stimulus intensity. There are three basic types of intensity rate functions and intensity latency functions i.e. monotonic, nonmonotonic, and irregular for intensity rate function or saturational monotonic for intensity latency function. Number of nonmonotonic neurons was more than that of monotonic neurons. There was no significant correlation between BFs and types of intensity rate functions and intensity latency functions. 2. There was no significant difference between latencies of IC neurons with higher BF and lower BF. 3. Directional sensitivity of each IC neuron recorded was investigated by determining its variation of minimum threshold (MT) and firing rate with a sound broadcast at 7 selected azimuthal angles. Most of IC neurons had a contralateral best sensitive angle at which it showed the lowest MT and the highest firing rate of 10 dB above MT. The neurons sensitive to 60° contralateral appeared higher proportion than others though the proportion of best sensitive angle of IC neurons in different BF span was different. Best sensitive angles determined by lowest MT were more sensitive than those determined by maximum firing rate of 10 dB above MT. That the animal keeps higher directional sensitivity to lower sound intensity could have very important biological significance for avoiding predators and searching accompanier or helpmate.

关 键 词：下丘神经元 方位敏感性 小鼠 声反应特性 声信号处理机制 声源定位 声调频率 

分 类 号：Q429.8[生物学—神经生物学]