Patterns of structural lateralization in cortical language areas of older adolescents.

Structural lateralization of cortical language areas has been extensively studied in the past, with the conclusion that there is a predominant left lateralization in the majority of typically developing adolescents. However, lateralization in this age group has often been examined using cortical volumetric measures, without taking into account the independence of surface area and thickness. Utilizing structural MRI data in a relatively large sample size, the lateralization of cortical volume, surface area, and thickness was analysed across regions of interest (ROIs) known to support language processing in 118 typically developing adolescents, ages 13;9 to 18;9 using a laterality index. Results showed that the laterality index scores for volume and surface area were more strongly correlated than volume and thickness. Results also showed that not all language regions were left lateralized, with some ROIs being significantly right lateralized. Results also showed that surface area and thickness did not always share direction of lateralization. Taken together these results indicate that cortical ROIs supporting language are not all strongly left lateralized in adolescents. These data also show that cortical surface area and cortical thickness need to be treated independently in future studies characterizing language and lateralization in the adolescent brain.