Stecker G Christopher, Middlebrooks John C
Kresge Hearing Research Institute, University of Michigan, Ann Arbor, MI 48109-0506, USA.
Biol Cybern. 2003 Nov;89(5):341-9. doi: 10.1007/s00422-003-0439-1. Epub 2003 Nov 12.
Although the auditory cortex plays an important role in sound localization, that role is not well understood. In this paper, we examine the nature of spatial representation within the auditory cortex, focusing on three questions. First, are sound-source locations encoded by individual sharply tuned neurons or by activity distributed across larger neuronal populations? Second, do temporal features of neural responses carry information about sound-source location? Third, are any fields of the auditory cortex specialized for spatial processing? We present a brief review of recent work relevant to these questions along with the results of our investigations of spatial sensitivity in cat auditory cortex. Together, they strongly suggest that space is represented in a distributed manner, that response timing (notably first-spike latency) is a critical information-bearing feature of cortical responses, and that neurons in various cortical fields differ in both their degree of spatial sensitivity and their manner of spatial coding. The posterior auditory field (PAF), in particular, is well suited for the distributed coding of space and encodes sound-source locations partly by modulations of response latency. Studies of neurons recorded simultaneously from PAF and/or A1 reveal that spatial information can be decoded from the relative spike times of pairs of neurons - particularly when responses are compared between the two fields - thus partially compensating for the absence of an absolute reference to stimulus onset.
尽管听觉皮层在声音定位中起着重要作用，但这一作用尚未得到充分理解。在本文中，我们研究了听觉皮层内空间表征的本质，重点关注三个问题。第一，声源位置是由单个调谐尖锐的神经元编码，还是由分布在更大神经元群体中的活动编码？第二，神经反应的时间特征是否携带有关声源位置的信息？第三，听觉皮层的任何区域是否专门用于空间处理？我们简要回顾了与这些问题相关的近期研究工作，以及我们对猫听觉皮层空间敏感性的研究结果。综合来看，它们强烈表明空间是以分布式方式表征的，反应时间（尤其是首次放电潜伏期）是皮层反应的关键信息承载特征，并且不同皮层区域的神经元在空间敏感性程度和空间编码方式上都存在差异。特别是后听觉场（PAF），非常适合空间的分布式编码，并且部分通过反应潜伏期的调制来编码声源位置。对同时从PAF和/或A1记录的神经元的研究表明，空间信息可以从成对神经元的相对尖峰时间中解码出来——特别是当比较两个区域的反应时——从而部分弥补了缺乏对刺激起始的绝对参考的问题。
