Spitzer M W, Semple M N
Vision, Touch and Hearing Research Centre, Department of Physiology and Pharmacology, The University of Queensland, St. Lucia, Queensland 4072, Australia.
J Neurophysiol. 1998 Dec;80(6):3062-76. doi: 10.1152/jn.1998.80.6.3062.
Transformation of binaural response properties in the ascending auditory pathway: influence of time-varying interaural phase disparity. J. Neurophysiol. 80: 3062-3076, 1998. Previous studies demonstrated that tuning of inferior colliculus (IC) neurons to interaural phase disparity (IPD) is often profoundly influenced by temporal variation of IPD, which simulates the binaural cue produced by a moving sound source. To determine whether sensitivity to simulated motion arises in IC or at an earlier stage of binaural processing we compared responses in IC with those of two major IPD-sensitive neuronal classes in the superior olivary complex (SOC), neurons whose discharges were phase locked (PL) to tonal stimuli and those that were nonphase locked (NPL). Time-varying IPD stimuli consisted of binaural beats, generated by presenting tones of slightly different frequencies to the two ears, and interaural phase modulation (IPM), generated by presenting a pure tone to one ear and a phase modulated tone to the other. IC neurons and NPL-SOC neurons were more sharply tuned to time-varying than to static IPD, whereas PL-SOC neurons were essentially uninfluenced by the mode of stimulus presentation. Preferred IPD was generally similar in responses to static and time-varying IPD for all unit populations. A few IC neurons were highly influenced by the direction and rate of simulated motion, but the major effect for most IC neurons and all SOC neurons was a linear shift of preferred IPD at high rates-attributable to response latency. Most IC and NPL-SOC neurons were strongly influenced by IPM stimuli simulating motion through restricted ranges of azimuth; simulated motion through partially overlapping azimuthal ranges elicited discharge profiles that were highly discontiguous, indicating that the response associated with a particular IPD is dependent on preceding portions of the stimulus. In contrast, PL-SOC responses tracked instantaneous IPD throughout the trajectory of simulated motion, resulting in highly contiguous discharge profiles for overlapping stimuli. This finding indicates that responses of PL-SOC units to time-varying IPD reflect only instantaneous IPD with no additional influence of dynamic stimulus attributes. Thus the neuronal representation of auditory spatial information undergoes a major transformation as interaural delay is initially processed in the SOC and subsequently reprocessed in IC. The finding that motion sensitivity in IC emerges from motion-insensitive input suggests that information about change of position is crucial to spatial processing at higher levels of the auditory system.
时变双耳相位差的影响。《神经生理学杂志》80: 3062 - 3076, 1998年。先前的研究表明，下丘（IC）神经元对双耳相位差（IPD）的调谐常常受到IPD时间变化的深刻影响，这种变化模拟了移动声源产生的双耳线索。为了确定对模拟运动的敏感性是在IC中产生还是在双耳处理的更早阶段产生，我们将IC中的反应与上橄榄复合体（SOC）中两类主要的对IPD敏感的神经元的反应进行了比较，一类是其放电对音调刺激相位锁定（PL）的神经元，另一类是非相位锁定（NPL）的神经元。时变IPD刺激包括双耳节拍，通过向双耳呈现频率略有不同的音调产生，以及双耳相位调制（IPM），通过向一只耳朵呈现纯音而向另一只耳朵呈现相位调制音产生。IC神经元和NPL - SOC神经元对时变IPD的调谐比对静态IPD更敏锐，而PL - SOC神经元基本上不受刺激呈现模式的影响。对于所有单位群体，对静态和时变IPD的反应中，偏好的IPD通常相似。少数IC神经元受到模拟运动的方向和速率的高度影响，但对于大多数IC神经元和所有SOC神经元的主要影响是在高速率下偏好IPD的线性偏移——这归因于反应潜伏期。大多数IC和NPL - SOC神经元受到模拟在有限方位范围内运动的IPM刺激的强烈影响；模拟在部分重叠方位范围内的运动引发的放电模式高度不连续，表明与特定IPD相关的反应取决于刺激的先前部分。相比之下，PL - SOC反应在模拟运动的整个轨迹中跟踪瞬时IPD，导致重叠刺激的放电模式高度连续。这一发现表明，PL - SOC单位对时变IPD的反应仅反映瞬时IPD，没有动态刺激属性的额外影响。因此，随着双耳延迟最初在SOC中处理，随后在IC中重新处理，听觉空间信息的神经元表征经历了重大转变。IC中运动敏感性从对运动不敏感的输入中出现这一发现表明，关于位置变化的信息对于听觉系统更高层次的空间处理至关重要。
