On the precision of neural computation with interaural level differences in the lateral superior olive
On the precision of neural computation with interaural level differences in the lateral superior olive
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DOI：
10.1016/j.brainres.2013.05.008
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发表时间：
2013-11-06
期刊：
影响因子：
2.9
通讯作者：
Marsalek, Petr
中科院分区：
文献类型：
--
作者：
Bures, Zbynek;Marsalek, Petr
耳间声级差(ILD)是声源空间定位的基本线索之一。由于头部投射的声影，内侧平面外的声源导致近耳处的声级增加，而远耳处的声级降低。在哺乳动物的听觉脑干中，ILD是由外侧上橄榄核(LSO)的双耳神经元组成的神经元回路处理的。这些神经元接受同侧的主要兴奋性投射和对侧的主要虹膜抑制投射。由于声级主要由神经元的放电率编码，因此LSO神经元的主要功能是估计和编码兴奋性和抑制性输入的放电率之间的差异。这一操作的两个一般机制在生物学上是可信的：(1)减去较长时间间隔内的累计放电率，(2)检测较短时间间隔内单个棘波的重合。然而，ILD评估的确切机制尚不清楚。此外，考虑到神经元活动的随机性，目前尚不清楚该电路如何实现实验观察到的ILD评估的显著精度。我们使用概率模型和互补的计算机模拟来研究这两种一般机制是否能够达到预期的性能。引入理想观测器的概念，我们根据相互作用的棘波序列的统计数据、总的放电率、探测时间、会聚纤维的数目以及神经机制本身，确定了用刚刚可察觉的差异(JND)来表示的理论ILD精度。我们证明JND依赖于尖峰定时的精度；然而，在适当的参数设置下，最低理论值与实验值相似或更好。此外，基于兴奋性和抑制性符合检测的机制可能比减去放电率得到更好的结果。(C)2013爱思唯尔B.V.保留所有权利。
Interaural level difference (ILD) is one of the basic binaural clues in the spatial localization of a sound source. Due to the acoustic shadow cast by the head, a sound source out of the medial plane results in an increased sound level at the nearer ear and a decreased level at the distant ear. In the mammalian auditory brainstem, the ILD is processed by a neuronal circuit of binaural neurons in the lateral superior olive (LSO). These neurons receive major excitatory projections from the ipsilateral side and major irihibitory projections from the contralateral side. As the sound level is encoded predominantly by the neuronal discharge rate, the principal function of LSO neurons is to estimate and encode the difference between the discharge rates of the excitatory and inhibitory inputs. Two general mechanisms of this operation are biologically plausible: (1) subtraction of firing rates integrated over longer time intervals, and (2) detection of coincidence of individual spikes within shorter time intervals. However, the exact mechanism of ILD evaluation is not known. Furthermore, given the stochastic nature of neuronal activity, it is not clear how the circuit achieves the remarkable precision of ILD assessment observed experimentally. We employ a probabilistic model and complementary computer simulations to investigate whether the two general mechanisms are capable of the desired performance. Introducing the concept of an ideal observer, we determine the theoretical ILD accuracy expressed by means of the just-noticeable difference (JND) in dependence on the statistics of the interacting spike trains, the overall firing rate, detection time, the number of converging fibers, and on the neural mechanism itself. We demonstrate that the JNDs rely on the precision of spike timing; however, with an appropriate parameter setting, the lowest theoretical values are similar or better than the experimental values. Furthermore, a mechanism based on excitatory and inhibitory coincidence detection may give better results than the subtraction of firing rates. (C) 2013 Elsevier B.V. All rights reserved.