Salmelin R, Service E, Kiesilä P, Uutela K, Salonen O
Low Temperature Laboratory, Helsinki University of Technology, Espoo, Finland.
Ann Neurol. 1996 Aug;40(2):157-62. doi: 10.1002/ana.410400206.
Dyslexia is most often attributed to phonological impairments, manifested in abnormal activation of the left temporal and temporoparietal cortex in response to auditorily presented language and possibly associated with anomalies in the cytoarchitecture and hemispheric symmetry of the plana temporale. The immediate cortical correlate of the severely impaired reading process has, however, remained obscure. Here we report on the distinct time courses of cortical activation in dyslexic and control subjects during passive viewing of single words, tracked with whole-head magnetoencephalography. A striking difference was found in the left inferior temporo-occipital region where intracranial recordings have recently identified word-specific responses within 200 msec after stimulus onset: controls showed a sharp activation at about 180 msec after word presentation, whereas dyslexics failed to activate this area entirely, or showed a slowly increasing late response. Perception of words as specific units thus seems to be impaired in dyslexics.
诵读困难通常归因于语音障碍，表现为在听到语言时左颞叶和颞顶叶皮质异常激活，可能与颞平面的细胞结构和半球对称性异常有关。然而，严重受损阅读过程的直接皮质关联仍不清楚。在此，我们报告了用全头磁脑图追踪的诵读困难者和对照组在被动观看单个单词时皮质激活的不同时间进程。在左颞枕下部区域发现了一个显著差异，颅内记录最近在此区域识别出刺激开始后200毫秒内的单词特异性反应：对照组在单词呈现后约180毫秒出现急剧激活，而诵读困难者则完全未能激活该区域，或表现出缓慢增加的晚期反应。因此，诵读困难者似乎将单词作为特定单元的感知能力受损。
