University Medical Center Hamburg-Eppendorf, Department of Systems Neuroscience, Martinistraße 52, 20246 Hamburg, Germany.
Neuroimage. 2012 Jan 2;59(1):788-99. doi: 10.1016/j.neuroimage.2011.07.025. Epub 2011 Jul 21.
Repetition has been shown to activate the so-called 'dorsal stream', a network of temporo-parieto-frontal areas subserving the mapping of acoustic speech input onto articulatory-motor representations. Among these areas, a region in the posterior Sylvian fissure at the temporo-parietal boundary (also called 'area Spt') has been suggested to play a central role particularly with increasing computational demands on phonological processing. Most of the relevant evidence stems from tasks requiring metalinguistic processing. To date, the relevance of area Spt in natural phonological operations based on implicit linguistic knowledge has not yet been investigated. We examined two types of phonological processes assumed to be lateralized differently, i.e., the processing of syllabic stress versus subsyllabic segmental processing. In two ways, subjects modified an auditorily presented pseudoword before reproducing it overtly: (a) by a prosodic manipulation involving a stress shift across syllable boundaries, (b) by a segmental manipulation involving a vowel substitution. Manipulation per se was expected to engage area Spt. Segmental compared to prosodic processing was expected to reveal predominantly left lateralized activation, while prosodic compared to segmental processing was expected to result in bilateral or right-lateralized activation. Contrary to expectation, activation in area Spt did not vary with increased phonological processing demand. Instead, area Spt was engaged regardless of whether subjects simply repeated a pseudoword or performed a phonological manipulation before reproduction. However, for both segmental and prosodic stimuli, reproduction after manipulation (compared to repetition) activated the left intraparietal sulcus and left inferior frontal cortex. We propose that these parieto-frontal regions are recruited when the task requires phonological manipulation over and above the more automated transfer of auditory into articulatory verbal codes, which appears to involve area Spt. When directly contrasted with prosodic manipulation, segmental manipulation resulted in increased activation predominantly in left inferior frontal areas. This may be due to an increased demand on phonological sequencing operations at the subsyllabic phoneme level. Contrasted with segmental manipulations, prosodic manipulation did not result in increased activation, which may be due to a lower degree of morphosyntactic and to syllable-level processing.
重复已被证明可以激活所谓的“背侧流”，这是一个 temporo-parieto-frontal 区域的网络，用于将声音言语输入映射到发音运动表示上。在这些区域中，颞顶边界的后西尔维安裂（也称为“区域 Spt”）中的一个区域被认为在语音处理的计算需求增加时发挥着核心作用。大部分相关证据来自需要元语言处理的任务。迄今为止，尚未研究区域 Spt 在基于隐含语言知识的自然语音操作中的相关性。我们检查了两种类型的语音过程，这些过程被认为是不同的偏侧化，即音节重音的处理与子音节段的处理。通过两种方式，受试者在公开再现之前修改了听觉呈现的假词：（a）通过涉及音节边界上重音转移的韵律操作，（b）通过涉及元音替换的音段操作。操作本身预计会涉及区域 Spt。与韵律处理相比，音段处理预计会产生主要的左侧激活，而与音段处理相比，韵律处理预计会导致双侧或右侧激活。与预期相反，区域 Spt 的激活不随语音处理需求的增加而变化。相反，无论受试者是否简单地重复一个假词，或者在再现之前进行语音操作，区域 Spt 都会被激活。然而，对于音段和韵律刺激，在操作后再现（与重复相比）会激活左侧顶内沟和左侧下额叶皮质。我们提出，当任务需要在更自动地将听觉转化为发音口头代码的基础上进行语音操作时，这些顶前区域会被招募，这似乎涉及到区域 Spt。与韵律操作直接对比时，音段操作导致主要在左侧下额叶区域的激活增加。这可能是由于在子音节音位水平上对语音序列操作的需求增加所致。与音段操作相比，韵律操作不会导致激活增加，这可能是由于形态句法和音节级处理程度较低所致。
