Heiervang E, Hugdahl K, Steinmetz H, Inge Smievoll A, Stevenson J, Lund A, Ersland L, Lundervold A
Department of Psychiatry, University of Bergen, Bergen, Norway.
Neuropsychologia. 2000;38(13):1704-13. doi: 10.1016/s0028-3932(00)00085-3.
A reduction or reversal of the normal leftward asymmetry of the planum temporale (PT) has been claimed to be typical of dyslexia, although some recent studies have challenged this view. In a population-based study of 20 right-handed dyslexic boys and 20 matched controls, we have measured the PT and the adjacent planum parietale (PP) region in sagittal magnetic resonance images. For the PT, mean left and right areas and asymmetry coefficients were compared. Since a PP area often could not be identified in one or both hemispheres, a qualitative comparison was used for this region. The total planar area (sum of PT and PP) was also compared between the two groups. A dichotic listening (DL) test with consonant-vowel syllables was administered to assess functional asymmetry of language. The results showed a mean leftward PT asymmetry in both the dyslexic and the control group, with no significant difference for the degree of PT asymmetry. Planned comparisons revealed however, a trend towards smaller left PT in the dyslexic group. In control children, but not in the dyslexic children, a significant correlation between PT asymmetry and reading was observed. A mean leftward asymmetry was also found for the total planar area, with no difference between the groups for the degree of asymmetry. Significantly fewer dyslexic children than control children showed a rightward asymmetry for the PP region. Both groups showed a normal right ear advantage on the DL task, with no significant difference for DL asymmetry. No significant correlation was observed between PT asymmetry and DL asymmetry. The present population-based study adds to recent reports of normal PT asymmetry in dyslexia, but indicates that subtle morphological abnormalities in the left planar area may be present in this condition.
颞平面（PT）正常的向左不对称性减弱或反转被认为是诵读困难的典型特征，尽管最近一些研究对这一观点提出了质疑。在一项基于人群的研究中，我们对20名右利手诵读困难男孩和20名匹配的对照组进行了研究，在矢状面磁共振图像中测量了PT和相邻的顶叶平面（PP）区域。对于PT，比较了左右平均面积和不对称系数。由于PP区域在一个或两个半球中常常无法识别，因此对该区域进行了定性比较。还比较了两组之间的总平面面积（PT和PP之和）。进行了一项包含辅音 - 元音音节的双耳分听（DL）测试，以评估语言的功能不对称性。结果显示，诵读困难组和对照组的PT均存在平均向左不对称性，PT不对称程度无显著差异。然而，计划比较显示，诵读困难组的左侧PT有变小的趋势。在对照组儿童中观察到PT不对称性与阅读之间存在显著相关性，但在诵读困难儿童中未观察到。总平面面积也存在平均向左不对称性，两组之间的不对称程度无差异。与对照组儿童相比，诵读困难儿童中PP区域出现向右不对称的情况明显较少。两组在DL任务中均表现出正常的右耳优势，DL不对称性无显著差异。未观察到PT不对称性与DL不对称性之间存在显著相关性。这项基于人群的研究进一步证实了最近关于诵读困难中PT不对称性正常的报道，但表明在这种情况下左侧平面区域可能存在细微的形态异常。
