Brain lateralization and corpus callosum size in children with developmental language impairment (LI)

Developmental language impairment (LI) is a condition characterized by deficits in language comprehension and/or expression in the absence of other cognitive, social, or motor deficits and in the absence of frank neurological lesions. However, the specificity of this disorder is being questioned as we learn more about the neurobehavioral and cognitive aspects of LI. The existing literature suggests that children with LI lack normal anatomical asymmetry in various areas of the brain, and white matter abnormalities have also been reported in this population. A model based on bilateral dysfunction has been proposed as a possible underlying mechanism for this disorder.; The purpose of this study was to investigate corpus callosum (CC) size and functional lateralization for verbal and nonverbal skills in children with LI. 34 children with LI and 34 typically developing children (ages 6 to 16 years) participated in the behavioral part of the study. 13 children with LI and 13 normal controls (ages 8 to 16 years) participated in the neuroanatomical study. A handedness task, a dichotic listening test, a free-vision chimeric stimuli task, and a computerized finger tapping task were administered to the participants in the behavioral study. Anatomical measurements were acquired from the midsagittal area of the CC.; The results of the behavioral study suggest that children with LI lack the normal lateralization of function to the right hemisphere for a nonverbal task, but that they exhibit the expected lateralization of function to the left hemisphere for a speech perception task and the expected lateralization of function to the dominant hand for a finger tapping task. Total CC area and proportions of (going in a rostral to caudal direction) regions 1, 2, 3, and 5 were not significantly different between the groups. The proportion of region 4, roughly interconnecting the posterior parietal and the superior temporal cortical regions across both hemispheres, was found to be significantly smaller in children with LI. The findings of both the behavioral and neuroanatomical studies are interpreted as suggestive of bilateral hemispheric dysfunction in children with LI.