Specht Karsten, Rimol Lars M, Reul Jürgen, Hugdahl Kenneth
Department of Biological and Medical Psychology, University of Bergen, Jonas Lies vei 91, 5009 Bergen, Norway.
Neurosci Lett. 2005;384(1-2):60-5. doi: 10.1016/j.neulet.2005.04.057.
A problem in current studies of brain activation in speech perception is that most studies use stimuli that are sampled from different categories. This study presents a new approach in creating acoustic stimuli by filtering real words in different ways, thus this enables one to 'morph' the sounds gradually from something like tones to real words while preserving temporal characteristics ("soundmorphing"). This will make it possible to explore steps between tone and speech processing on a gradual scale. This study aimed to investigate more closely the network, involved in the perception of speech and the decoding of auditory (speech-)stimuli. Sets of auditory stimuli were created by dividing real words into several frequency-bands and creating a randomised rearrangement of these components. Four different sets of stimuli were used, containing 1, 2, 3 or 4 frequency bands (total range: 0-2500 Hz). Only the latter one contained intelligible words. During the fMRI session, these four trial types were presented pseudo-randomised. In all conditions, significant activations of auditory cortex were observed. The number of activated voxels and their significance increased over the four trial types. In addition, Broca's area, SMA, left thalamus, and right cerebellum were activated in the most complex and most speech-like condition. Comparing these complexes with the tone-like trials, only the left auditory cortex, left SMA, and cingulate gyrus became significant. These activations reflect the bilateral processing of the auditory stimuli, but only the left temporal areas demonstrated an increasing BOLD response with an increasing number of presented frequency components.
当前言语感知中大脑激活研究的一个问题是，大多数研究使用的刺激是从不同类别中采样的。本研究提出了一种新方法，通过以不同方式过滤真实单词来创建声学刺激，从而能够在保留时间特征的同时将声音从类似音调的东西逐渐“变形”为真实单词（“声音变形”）。这将有可能在渐变尺度上探索音调与言语处理之间的步骤。本研究旨在更深入地研究参与言语感知和听觉（言语）刺激解码的神经网络。通过将真实单词划分为几个频段并对这些成分进行随机重排来创建听觉刺激集。使用了四组不同的刺激，包含1、2、3或4个频段（总范围：0 - 2500赫兹）。只有最后一组包含可理解的单词。在功能磁共振成像（fMRI）过程中，这四种试验类型以伪随机方式呈现。在所有条件下，均观察到听觉皮层的显著激活。激活的体素数量及其显著性在四种试验类型中逐渐增加。此外，在最复杂且最像言语的条件下，布洛卡区、辅助运动区、左侧丘脑和右侧小脑被激活。将这些复合体与类似音调的试验进行比较时，只有左侧听觉皮层、左侧辅助运动区和扣带回变得显著。这些激活反映了听觉刺激的双侧处理，但只有左侧颞叶区域随着呈现的频率成分数量增加而表现出增强的血氧水平依赖（BOLD）反应。
