Developmental Changes in Neural Lateralization for Visual-Spatial Function? Evidence From a Line-Bisection Task

Studies of hemispheric specialization have traditionally cast the left hemisphere as specialized for language and the right hemisphere for spatial function. Much of the supporting evidence for this separation of function comes from studies of healthy adults and those who have sustained lesions to the right or left hemisphere. However, we know little about the developmental origins of lateralization. Recent evidence suggests that the young brain represents language bilaterally, with 4-6-year-olds activating the left-hemisphere regions known to support language in adults as well as homotopic regions in the right hemisphere. This bilateral pattern changes over development, converging on left-hemispheric activation in late childhood. In the present study, we ask whether this same developmental trajectory is observed in a spatial task, that is, strongly right-lateralized in adults-the line bisection (or "Landmark") task. We examined fMRI activation among children ages 5-12 years as they were asked to judge which end of a bisected vertical line was longer. We found that young children showed right-lateralized activation in the same parietal and posterior temporal areas as has been shown among adults, with no significant effects of age on lateralization within the age range we tested. We discuss potential underlying mechanisms and suggest that understanding the development of lateralization for a range of cognitive functions can play a crucial role in understanding general principles of how and why the brain comes to lateralize certain functions. SUMMARY: -Functional MRI was used to examine neural activation associated with a line bisection task in children ages 5-12 years. -Children showed right-lateralized activation in the same areas previously identified among adults. -There were no effects of children's age on the degree of right-lateralization. -This illustrates stable lateralization over development for the line bisection task and contrasts with findings of increasing lateralization over age in the domain of language.