Human Brain Research Center, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan.
Department of Psychology, Graduate School of Letters, Kyoto University, Kyoto 606-8501, Japan.
Neuroimage. 2017 Oct 1;159:185-194. doi: 10.1016/j.neuroimage.2017.07.055. Epub 2017 Jul 27.
Interaural time (ITD) and level differences (ILD) constitute the two main cues for sound localization in the horizontal plane. Despite extensive research in animal models and humans, the mechanism of how these two cues are integrated into a unified percept is still far from clear. In this study, our aim was to test with human electroencephalography (EEG) whether integration of dynamic ITD and ILD cues is reflected in the so-called motion-onset response (MOR), an evoked potential elicited by moving sound sources. To this end, ITD and ILD trajectories were determined individually by cue trading psychophysics. We then measured EEG while subjects were presented with either static click-trains or click-trains that contained a dynamic portion at the end. The dynamic part was created by combining ITD with ILD either congruently to elicit the percept of a right/leftward moving sound, or incongruently to elicit the percept of a static sound. In two experiments that differed in the method to derive individual dynamic cue trading stimuli, we observed an MOR with at least a change-N1 (cN1) component for both the congruent and incongruent conditions at about 160-190 ms after motion-onset. A significant change-P2 (cP2) component for both the congruent and incongruent ITD/ILD combination was found only in the second experiment peaking at about 250 ms after motion onset. In sum, this study shows that a sound which - by a combination of counter-balanced ITD and ILD cues - induces a static percept can still elicit a motion-onset response, indicative of independent ITD and ILD processing at the level of the MOR - a component that has been proposed to be, at least partly, generated in non-primary auditory cortex.
耳间时间（ITD）和强度差（ILD）是声音在水平面上定位的两个主要线索。尽管在动物模型和人类中进行了广泛的研究，但这两个线索如何整合为一个统一的感知仍然远未清楚。在这项研究中，我们的目的是用人的脑电图（EEG）来测试，动态 ITD 和 ILD 线索的整合是否反映在所谓的运动起始反应（MOR）中，这是由移动声源引起的诱发电位。为此，我们通过线索交易心理物理学单独确定 ITD 和 ILD 轨迹。然后，当受试者呈现静态点击序列或包含动态部分的点击序列时，我们测量 EEG。动态部分是通过将 ITD 与 ILD 结合来创建的，要么一致地引起向右/向左移动声音的感知，要么不一致地引起静态声音的感知。在两个实验中，个体动态线索交易刺激的推导方法不同，我们观察到在运动起始后约 160-190 毫秒，对于一致和不一致条件，都存在至少具有变化 N1（cN1）成分的 MOR。仅在第二个实验中，对于一致和不一致的 ITD/ILD 组合，发现了一个显著的变化 P2（cP2）成分，在运动起始后约 250 毫秒达到峰值。总之，这项研究表明，通过平衡 ITD 和 ILD 线索的组合而产生静态感知的声音仍然可以引起运动起始反应，这表明在 MOR 水平上进行独立的 ITD 和 ILD 处理 - 已经提出该成分至少部分是在前脑听觉皮层之外生成的。
