Spironelli C, Penolazzi B, Vio C, Angrilli A
Department of General Psychology, University of Padova, Via Venezia 8, 35131 Padova, Italy.
Neuropsychologia. 2006;44(14):2814-21. doi: 10.1016/j.neuropsychologia.2006.06.009. Epub 2006 Jul 31.
The phonological deficit hypothesis of dyslexia has been investigated in the present research by analysing language-related lateralization of the EEG theta band in a sample of dyslexic children. To this aim, a paradigm based on word-pair visual presentation was used in which the same words were processed in Semantic and Phonological tasks. Theta band amplitude, a cortical index that has been related to working memory processing, was analysed during four different phases of word elaboration, thus allowing to measure also the temporal dynamics of word reading/encoding in the verbal working memory. Control subjects showed a specific (and therefore efficient) task-related and time-dependent cortical activation: a peak of theta activity during word reading was found that decayed during the next inter stimulus interval. Furthermore, during word presentation in the Phonological task, theta amplitude was greater on the left hemisphere. Dyslexics evidenced an altered pattern of theta activation both in the temporal dimension and in the cortical space: their peak of activity was delayed to the first inter stimulus interval after word offset and was shifted to the right hemisphere throughout the whole epoch of Phonological task and in two phases of the Semantic task. Analysis of alpha band failed to replicate the complex pattern of lateralization found for theta band in the two groups, a result that suggests a specific functional role of theta band, which cannot be interpreted as a simple marker of cortical inhibition. Results point to a deficit, in dyslexic children, to recruit left hemisphere structures for the elaboration of the phonological component of the verbal working memory. This deficit was marked by a different, unspecific and dysfunctional hemispherical asymmetry of theta activation to language, a deficit that involved also the time course of phonological linguistic elaboration.
在本研究中，通过分析诵读困难儿童样本中与语言相关的脑电图θ波段的偏侧化，对诵读困难的语音缺陷假说进行了研究。为此，使用了一种基于单词对视觉呈现的范式，其中相同的单词在语义和语音任务中进行处理。在单词加工的四个不同阶段分析了θ波段振幅，这是一种与工作记忆加工相关的皮质指标，从而也能够测量言语工作记忆中单词阅读/编码的时间动态。对照组受试者表现出特定的（因此也是有效的）与任务相关且随时间变化的皮质激活：在单词阅读期间发现了一个θ活动峰值，该峰值在接下来的刺激间隔期间衰减。此外，在语音任务中的单词呈现期间，左半球的θ振幅更大。诵读困难者在时间维度和皮质空间上都表现出θ激活模式的改变：他们的活动峰值延迟到单词偏移后的第一个刺激间隔，并且在整个语音任务阶段以及语义任务的两个阶段都转移到了右半球。对α波段的分析未能重现两组中θ波段所发现的复杂偏侧化模式，这一结果表明θ波段具有特定的功能作用，不能将其解释为皮质抑制的简单标记。结果表明，诵读困难儿童在为言语工作记忆的语音成分加工招募左半球结构方面存在缺陷。这种缺陷的特征是θ激活对语言的半球不对称不同、非特异性且功能失调，这种缺陷还涉及语音语言加工的时间进程。
