Department of Cognitive Science, Johns Hopkins University, Baltimore, MD 21218, USA.
J Cogn Neurosci. 2011 Mar;23(3):552-69. doi: 10.1162/jocn.2010.21495. Epub 2010 Mar 29.
Innate auditory sensitivities and familiarity with the sounds of language give rise to clear influences of phonemic categories on adult perception of speech. With few exceptions, current models endorse highly left-hemisphere-lateralized mechanisms responsible for the influence of phonemic category on speech perception, based primarily on results from functional imaging and brain-lesion studies. Here we directly test the hypothesis that the right hemisphere does not engage in phonemic analysis. By using fMRI to identify cortical sites sensitive to phonemes in both word and pronounceable nonword contexts, we find evidence that right-hemisphere phonemic sensitivity is limited to a lexical context. We extend the interpretation of these fMRI results through the study of an individual with a left-hemisphere lesion who is right-hemisphere reliant for initial acoustic and phonetic analysis of speech. This individual's performance revealed that the right hemisphere alone was insufficient to allow for typical phonemic category effects but did support the processing of gradient phonetic information in lexical contexts. Taken together, these findings confirm previous claims that the right temporal cortex does not play a primary role in phoneme processing, but they also indicate that lexical context may modulate the involvement of a right hemisphere largely tuned for less abstract dimensions of the speech signal.
先天的听觉敏感性和对语言声音的熟悉程度对成人言语感知产生了明显的音位类别的影响。除了少数例外，当前的模型都支持高度左半球偏向的机制，这些机制主要基于功能成像和脑损伤研究，对音位类别对言语感知的影响负责。在这里，我们直接检验这样一种假设，即右半球不参与音位分析。通过使用 fMRI 来确定在单词和可发音的非单词语境中对音位敏感的皮质部位，我们发现证据表明，右半球的音位敏感性仅限于词汇语境。我们通过对一个左半球损伤的个体的研究扩展了这些 fMRI 结果的解释，该个体依赖右半球进行语音的初始声学和语音分析。该个体的表现表明，仅右半球不足以产生典型的音位类别效应，但确实支持在词汇语境中处理渐变的语音信息。总之，这些发现证实了先前的主张，即右颞叶皮质在音位处理中不起主要作用，但也表明词汇语境可能调节主要针对言语信号的不那么抽象维度的右半球的参与。
