Hearing Research Program, Department of Otolaryngology-Head and Neck Surgery, Medical University of South Carolina, Charleston, South Carolina, United States of America.
Visual Computing Division, School of Computing, Clemson University, Clemson, South Carolina, United States of America.
PLoS Biol. 2022 Apr 5;20(4):e3001591. doi: 10.1371/journal.pbio.3001591. eCollection 2022 Apr.
The ability to map speech sounds to corresponding letters is critical for establishing proficient reading. People vary in this phonological processing ability, which has been hypothesized to result from variation in hemispheric asymmetries within brain regions that support language. A cerebral lateralization hypothesis predicts that more asymmetric brain structures facilitate the development of foundational reading skills like phonological processing. That is, structural asymmetries are predicted to linearly increase with ability. In contrast, a canalization hypothesis predicts that asymmetries constrain behavioral performance within a normal range. That is, structural asymmetries are predicted to quadratically relate to phonological processing, with average phonological processing occurring in people with the most asymmetric structures. These predictions were examined in relatively large samples of children (N = 424) and adults (N = 300), using a topological asymmetry analysis of T1-weighted brain images and a decoding measure of phonological processing. There was limited evidence of structural asymmetry and phonological decoding associations in classic language-related brain regions. However, and in modest support of the cerebral lateralization hypothesis, small to medium effect sizes were observed where phonological decoding accuracy increased with the magnitude of the largest structural asymmetry across left hemisphere cortical regions, but not right hemisphere cortical regions, for both the adult and pediatric samples. In support of the canalization hypothesis, small to medium effect sizes were observed where phonological decoding in the normal range was associated with increased asymmetries in specific cortical regions for both the adult and pediatric samples, which included performance monitoring and motor planning brain regions that contribute to oral and written language functions. Thus, the relevance of each hypothesis to phonological decoding may depend on the scale of brain organization.
将语音映射到相应字母的能力对于建立熟练的阅读能力至关重要。人们在这种语音处理能力上存在差异，这被假设是由于支持语言的大脑区域的半球不对称性的变化所致。大脑侧化假说预测，更不对称的大脑结构有助于发展像语音处理这样的基础阅读技能。也就是说，结构的不对称性预计会随着能力的线性增加。相比之下，一个管化假说预测，不对称性会限制正常范围内的行为表现。也就是说，结构的不对称性预计与语音处理呈二次关系，具有最不对称结构的人会出现平均的语音处理。这些预测在相对较大的儿童样本（N=424）和成人样本（N=300）中进行了检验，使用 T1 加权脑图像的拓扑不对称分析和语音处理的解码测量。在经典的语言相关脑区中，结构不对称性和语音解码之间的关联证据有限。然而，在一定程度上支持大脑侧化假说，观察到小到中等的效应大小，其中语音解码准确性随着左半球皮质区域最大结构不对称性的幅度增加而增加，但右半球皮质区域没有增加，这对成人和儿科样本都适用。支持管化假说，在成人和儿科样本中，在正常范围内的语音解码与特定皮质区域的不对称性增加有关，这包括了与口头和书面语言功能有关的执行监测和运动规划大脑区域。因此，每个假说对语音解码的相关性可能取决于大脑组织的规模。
