Spatial tuning to virtual sounds in the inferior colliculus of the guinea pig.
Spatial tuning to virtual sounds in the inferior colliculus of the guinea pig.
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豚鼠下丘虚拟声音的空间调谐。
DOI：
10.1152/jn.00348.2003
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发表时间：
2003
期刊：
影响因子：
--
通讯作者：
Hoffmann,Klaus-Peter
中科院分区：
文献类型：
--
作者：
Sterbing,SusanneJ;Hartung,Klaus;Hoffmann,Klaus-Peter
下丘(IC)神经元如何编码声音的空间位置？我们已经使用虚拟听觉环境解决了这个问题。为此，在覆盖上半球的122个位置的自由场条件下，测量了18只豚鼠的个体头部相关传递函数(HRTF)。在257个神经元中，94%的神经元对声压级为70分贝的短时(50ms)白噪声刺激有反应。在这些神经元中，80%的神经元空间调谐的感受野小于半视野(70db)。其余的反应为全向反应或感受野断裂。大多数神经元偏爱对侧大脑半球的方向。然而，偏爱前排或后排位置和高海拔的情况经常发生。对于70dBSPL的刺激，根据半最大反应，感受野的平均直径不到上半球的四分之一。偏爱正面方向的神经元对后方方向反应较弱或没有反应，反之亦然。因此，在IC的单个神经元水平上存在前/后辨别。当非个体HRTF被用来产生刺激时，大多数神经元的空间感受野变大，分裂成几个部分，位置改变，或反应变得全方位。在阈值以上20~40分贝范围内，绝对声强的变化对神经元的择优方向影响不大。随着强度的增加，大多数感受野保持不变或扩大。此外，我们还测试了双耳去相关和刺激带宽对空间调谐的影响。在双耳不相关噪声的刺激下，绝大多数特征频率较低的神经元(<；2.5 khz)失去了空间调谐，而高频单位几乎不受影响。大多数在宽带刺激(白噪声和1倍频程宽噪声)下表现出空间调谐的神经元在1/3倍频程宽噪声刺激下呈现全向调谐。
How do neurons in the inferior colliculus (IC) encode the spatial location of sound? We have addressed this question using a virtual auditory environment. For this purpose, the individual head-related transfer functions (HRTFs) of 18 guinea pigs were measured under free-field conditions for 122 locations covering the upper hemisphere. From 257 neurons, 94% responded to the short (50-ms) white noise stimulus at 70 dB sound pressure level (SPL). Out of these neurons, 80% were spatially tuned with a receptive field that is smaller than a hemifield (at 70 dB). The remainder responded omnidirectionally or showed fractured receptive fields. The majority of the neurons preferred directions in the contralateral hemisphere. However, preference for front or rear positions and high elevations occurred frequently. For stimulation at 70 dB SPL, the average diameter of the receptive fields, based on half-maximal response, was less than a quarter of the upper hemisphere. Neurons that preferred frontal directions responded weakly or showed no response to posterior directions and vice versa. Hence, front/back discrimination is present at the single-neuron level in the IC. When nonindividual HRTFs were used to create the stimuli, the spatial receptive fields of most neurons became larger, split into several parts, changed position, or the response became omnidirectional. Variation of absolute sound intensity had little effect on the preferred directions of the neurons over a range of 20 to 40 dB above threshold. With increasing intensity, most receptive fields remained constant or expanded. Furthermore, we tested the influence of binaural decorrelation and stimulus bandwidth on spatial tuning. The vast majority of neurons with a low characteristic frequency (<2.5 kHz) lost spatial tuning under stimulation with binaurally uncorrelated noise, whereas high-frequency units were mostly unaffected. Most neurons that showed spatial tuning under broadband stimulation (white noise and 1 octave wide noise) turned omnidirectional when stimulated with 1/3 octave wide noise.
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