University of California, Irvine, Irvine, CA 92697, USA.
J Cogn Neurosci. 2010 Apr;22(4):632-9. doi: 10.1162/jocn.2009.21196.
Although it is generally acknowledged that at least two processing streams exist in the primate cortical auditory system, the function of the posterior dorsal stream is a topic of much debate. Recent studies have reported selective activation to auditory spatial change in portions of the human planum temporale (PT) relative to nonspatial stimuli such as pitch changes or complex acoustic patterns. However, previous work has suggested that the PT may be sensitive to another kind of nonspatial variable, namely, the number of auditory objects simultaneously presented in the acoustic signal. The goal of the present fMRI experiment was to assess whether any portion of the PT showed spatial selectivity relative to manipulations of the number of auditory objects presented. Spatially sensitive regions in the PT were defined by comparing activity associated with listening to an auditory object (speech from a single talker) that changed location with one that remained stationary. Activity within these regions was then examined during a nonspatial manipulation: increasing the number of objects (talkers) from one to three. The nonspatial manipulation modulated activity within the "spatial" PT regions. No region within the PT was found to be selective for spatial or object processing. We suggest that previously documented spatial sensitivity in the PT reflects auditory source separation using spatial cues rather than spatial processing per se.
尽管人们普遍认为灵长类动物皮质听觉系统中至少存在两个加工流，但后顶流的功能仍是一个备受争议的话题。最近的研究报告称，相对于非空间刺激（如音高变化或复杂的声音模式），人类颞上回（PT）的某些部分对听觉空间变化具有选择性激活。然而，之前的工作表明，PT 可能对另一种非空间变量敏感，即同时在声信号中呈现的听觉对象的数量。本 fMRI 实验的目的是评估 PT 的任何部分是否相对于呈现的听觉对象数量的操作表现出空间选择性。通过比较与位置变化的听觉对象（来自单个说话者的语音）相关的活动与保持静止的听觉对象相关的活动，定义了 PT 中的空间敏感区域。然后，在非空间操作期间检查这些区域内的活动：将对象（说话者）的数量从一个增加到三个。非空间操作调节了“空间”PT 区域内的活动。在 PT 内没有发现对空间或对象处理有选择性的区域。我们认为，先前在 PT 中记录的空间敏感性反映了使用空间线索进行听觉源分离，而不是空间处理本身。
