Center for Cognitive Neuroscience and Department of Cognitive Sciences, University of California, Irvine, CA 92697, USA.
Cereb Cortex. 2010 Oct;20(10):2486-95. doi: 10.1093/cercor/bhp318. Epub 2010 Jan 25.
Hierarchical organization of human auditory cortex has been inferred from functional imaging observations that core regions respond to simple stimuli (tones) whereas downstream regions are selectively responsive to more complex stimuli (band-pass noise, speech). It is assumed that core regions code low-level features, which are combined at higher levels in the auditory system to yield more abstract neural codes. However, this hypothesis has not been critically evaluated in the auditory domain. We assessed sensitivity to acoustic variation within intelligible versus unintelligible speech using functional magnetic resonance imaging and a multivariate pattern analysis. Core auditory regions on the dorsal plane of the superior temporal gyrus exhibited high levels of sensitivity to acoustic features, whereas downstream auditory regions in both anterior superior temporal sulcus and posterior superior temporal sulcus (pSTS) bilaterally showed greater sensitivity to whether speech was intelligible or not and less sensitivity to acoustic variation (acoustic invariance). Acoustic invariance was most pronounced in more pSTS regions of both hemispheres, which we argue support phonological level representations. This finding provides direct evidence for a hierarchical organization of human auditory cortex and clarifies the cortical pathways supporting the processing of intelligible speech.
人类听觉皮层的层次组织可以从功能成像观察中推断出来，这些观察表明核心区域对简单刺激（音调）有反应，而下游区域则对更复杂的刺激（带通噪声、语音）有选择性反应。人们认为核心区域编码低级特征，这些特征在听觉系统的更高层次上组合，以产生更抽象的神经编码。然而，这一假设在听觉领域尚未得到严格评估。我们使用功能磁共振成像和多元模式分析评估了对可理解和不可理解语音内的声音变化的敏感性。背侧上颞叶的核心听觉区域对声音特征表现出高度的敏感性，而在前上颞回和后上颞回（pSTS）双侧的下游听觉区域对语音是否可理解的敏感性更高，对声音变化的敏感性（声音不变性）更低。在两个半球的更多 pSTS 区域，声音不变性最为明显，我们认为这支持语音水平的表示。这一发现为人类听觉皮层的层次组织提供了直接证据，并阐明了支持可理解语音处理的皮质通路。
