Härle Markus, Rockstroh Brigitte S, Keil Andreas, Wienbruch Christian, Elbert Thomas R
Department of Psychology, University of Konstanz, Germany.
BMC Neurosci. 2004 Oct 24;5:40. doi: 10.1186/1471-2202-5-40.
How does the brain convert sounds and phonemes into comprehensible speech? In the present magnetoencephalographic study we examined the hypothesis that the coherence of electromagnetic oscillatory activity within and across brain areas indicates neurophysiological processes linked to speech comprehension.
Amplitude-modulated (sinusoidal 41.5 Hz) auditory verbal and nonverbal stimuli served to drive steady-state oscillations in neural networks involved in speech comprehension. Stimuli were presented to 12 subjects in the following conditions (a) an incomprehensible string of words, (b) the same string of words after being introduced as a comprehensible sentence by proper articulation, and (c) nonverbal stimulations that included a 600-Hz tone, a scale, and a melody. Coherence, defined as correlated activation of magnetic steady state fields across brain areas and measured as simultaneous activation of current dipoles in source space (Minimum-Norm-Estimates), increased within left- temporal-posterior areas when the sound string was perceived as a comprehensible sentence. Intra-hemispheric coherence was larger within the left than the right hemisphere for the sentence (condition (b) relative to all other conditions), and tended to be larger within the right than the left hemisphere for nonverbal stimuli (condition (c), tone and melody relative to the other conditions), leading to a more pronounced hemispheric asymmetry for nonverbal than verbal material.
We conclude that coherent neuronal network activity may index encoding of verbal information on the sentence level and can be used as a tool to investigate auditory speech comprehension.
大脑如何将声音和音素转化为可理解的言语？在本脑磁图研究中，我们检验了以下假设：脑区内部及脑区之间电磁振荡活动的连贯性表明了与言语理解相关的神经生理过程。
调幅（正弦41.5赫兹）的听觉言语和非言语刺激用于驱动参与言语理解的神经网络中的稳态振荡。在以下条件下向12名受试者呈现刺激：（a）一串难以理解的单词；（b）通过适当发音将同一串单词作为可理解的句子引入之后；（c）非言语刺激，包括600赫兹音调、音阶和旋律。连贯性定义为脑区之间磁稳态场的相关激活，并在源空间中作为电流偶极子的同时激活进行测量（最小范数估计），当声音串被视为可理解的句子时，左颞叶后部区域内的连贯性增加。对于句子（条件（b）相对于所有其他条件），左半球内的半球内连贯性大于右半球，对于非言语刺激（条件（c），音调与旋律相对于其他条件），右半球内的连贯性往往大于左半球，导致非言语材料比言语材料的半球不对称性更明显。
我们得出结论，连贯的神经网络活动可能在句子层面上为言语信息的编码提供指标，并且可以用作研究听觉言语理解的工具。
