Goeckel Tom, Führ Hartmut, Lakemeyer Gerhard, Wagner Hermann
Institute for Biology II, RWTH Aachen University, Mies-van-der-Rohe-Strasse 15, 52056, Aachen, Germany,
J Comput Neurosci. 2014 Feb;36(1):1-17. doi: 10.1007/s10827-013-0460-x. Epub 2013 May 29.
Multiplication-like sound localization models are subjected to phase ambiguities for high-frequency tonal stimuli as multiplication creates several equivalent response peaks in tuning curves. By increasing the bandwidth of the stimulus, phase ambiguities can be reduced, which is often referred to as side peak suppression. In this study we present a Jeffress-based sound localization model, and determine side peak suppression analytically. The results were verified with an implementation of the same model, and compared to physiological data of barn owls. Three types of stimuli were analyzed: pure-tone stimuli, two-tone complexes with varying frequency distances, and noise signals with variable bandwidths. As an additional parameter we also determined the half-width of the main response peak to examine the scaling of tuning curves in azimuth. Results showed that side peak suppression did not only depend on bandwidth, but also on the center frequency and the distance of the side peak to the main response peak. In particular, the analytical model predicted that side peak suppression is a function of relative bandwidth, whereas half-width is inversely proportional to center frequency, with a proportionality factor depending on relative bandwidth. The analytical approach and the implementation yielded equivalent tuning curves (deviation < 1%). Moreover, the electrophysiological data recorded in barn owls closely matched the predicted tuning curves.
对于高频音调刺激，类似乘法的声音定位模型会受到相位模糊的影响，因为乘法会在调谐曲线中产生几个等效的响应峰值。通过增加刺激的带宽，可以减少相位模糊，这通常被称为旁峰抑制。在本研究中，我们提出了一种基于杰弗里斯的声音定位模型，并通过分析确定旁峰抑制。结果通过相同模型的实现进行了验证，并与仓鸮的生理数据进行了比较。分析了三种类型的刺激：纯音刺激、频率间距不同的双音复合体以及带宽可变的噪声信号。作为一个额外的参数，我们还确定了主响应峰值的半高宽，以研究方位角上调谐曲线的缩放比例。结果表明，旁峰抑制不仅取决于带宽，还取决于中心频率以及旁峰与主响应峰值的距离。特别是，分析模型预测旁峰抑制是相对带宽的函数，而半高宽与中心频率成反比，比例因子取决于相对带宽。分析方法和实现产生了等效的调谐曲线（偏差<1%）。此外，在仓鸮中记录的电生理数据与预测的调谐曲线紧密匹配。
