Furukawa Shigeto, Maki Katuhiro
Human and Information Science Laboratory, NTT Communication Science Laboratories, NTT Corporation, 3-1 Morinosato-Wakamiya, Atsugi, Kanagawa 243-0198, Japan.
Hear Res. 2006 Feb;212(1-2):48-57. doi: 10.1016/j.heares.2005.10.009. Epub 2005 Dec 1.
This study examines the extent to which the auditory middle latency response (MLR) of the guinea pig is sensitive to sound localization cues such as interaural level and time differences (ILD and ITD, respectively). The MLR was recorded with an epidural electrode placed over the auditory cortex of an anesthetized guinea pig. Click stimuli were presented monaurally or binaurally with various ILDs and ITDs. The MLR was much larger for contralateral stimulation than for ipsilateral stimulation, and its amplitude was intermediate for diotic stimulation. The MLR amplitude was sensitive to both ILD and ITD: it decreased as the ipsilateral stimulus increased in level or advanced in time relative to the contralateral stimulus. The steep slope of the amplitude-versus-ITD function fell within an ITD range of +/-330 micros, namely the guinea pig's physiological ITD range. The response reduction that resulted from increasing the relative level of the ipsilateral level could be cancelled out by advancing the contralateral onset time relative to the ipsilateral onset time. This parallels the "time-intensity trading" in sound lateralization exhibited in human psychophysics. The results imply that the binaural interaction in the guinea pig MLR reflects aspects of neural processes that are involved in sound localization.
本研究考察了豚鼠的听觉中潜伏期反应（MLR）对诸如耳间声级差和时间差（分别为ILD和ITD）等声音定位线索的敏感程度。MLR是通过将硬膜外电极置于麻醉豚鼠的听觉皮层上进行记录的。点击刺激以单耳或双耳方式呈现，具有各种ILD和ITD。对侧刺激时的MLR比同侧刺激时大得多，其幅度在双耳同时刺激时处于中间值。MLR幅度对ILD和ITD均敏感：随着同侧刺激的声级相对于对侧刺激升高或时间提前，其幅度会降低。幅度与ITD函数的陡峭斜率落在+/-330微秒的ITD范围内，即豚鼠的生理ITD范围。通过使对侧起始时间相对于同侧起始时间提前，可以抵消因同侧声级相对升高而导致的反应降低。这与人类心理物理学中声音定位所表现出的“时间 - 强度权衡”相似。结果表明，豚鼠MLR中的双耳相互作用反映了参与声音定位的神经过程的一些方面。
