Schönwiesner Marc, Rübsamen Rudolf, von Cramon D Yves
Faculty of Biosciences, University of Leipzig, Germany.
Eur J Neurosci. 2005 Sep;22(6):1521-8. doi: 10.1111/j.1460-9568.2005.04315.x.
The present study investigates the acoustic basis of the hemispheric asymmetry for the processing of speech and music. Experiments on this question ideally involve stimuli that are perceptually unrelated to speech and music, but contain acoustic characteristics of both. Stimuli in previous studies were derived from speech samples or tonal sequences. Here we introduce a new class of noise-like sound stimuli with no resemblance of speech or music that permit independent parametric variation of spectral and temporal acoustic complexity. Using these stimuli in a functional MRI experiment, we test the hypothesis of a hemispheric asymmetry for the processing of spectral and temporal sound structure by seeking cortical areas in which the blood oxygen level dependent (BOLD) signal covaries with the number of simultaneous spectral components (spectral complexity) or the temporal modulation rate (temporal complexity) of the stimuli. BOLD-responses from the left and right Heschl's gyrus (HG) and part of the right superior temporal gyrus covaried with the spectral parameter, whereas covariation analysis for the temporal parameter highlighted an area on the left superior temporal gyrus. The portion of superior temporal gyrus in which asymmetrical responses are apparent corresponds to the antero-lateral auditory belt cortex, which has been implicated with spectral integration in animal studies. Our results support a similar function of the anterior auditory belt in humans. The findings indicate that asymmetrical processing of complex sounds in the cerebral hemispheres does not depend on semantic, but rather on acoustic stimulus characteristics.
本研究探讨了语音和音乐加工过程中半球不对称性的声学基础。关于这个问题的实验理想情况下涉及到与语音和音乐在感知上无关，但同时包含两者声学特征的刺激。以往研究中的刺激源自语音样本或音调序列。在此，我们引入了一类全新的类似噪声的声音刺激，它们与语音或音乐毫无相似之处，能够独立地对频谱和时间声学复杂性进行参数变化。在一项功能磁共振成像实验中使用这些刺激，我们通过寻找血液氧合水平依赖（BOLD）信号与刺激的同时频谱成分数量（频谱复杂性）或时间调制率（时间复杂性）共变的皮层区域，来检验关于频谱和时间声音结构加工的半球不对称性假设。来自左右颞横回（HG）以及右侧颞上回部分区域的BOLD反应与频谱参数共变，而对时间参数的共变分析突出了左侧颞上回的一个区域。颞上回中出现不对称反应的部分对应于前外侧听觉带皮层，在动物研究中该区域与频谱整合有关。我们的结果支持了人类前听觉带具有类似功能。这些发现表明，大脑半球对复杂声音的不对称加工并不取决于语义，而是取决于声学刺激特征。
