Cortical asymmetry and its developmental change have distinct relationships with brain connectivity

More asymmetric cortical regions—defined as greater left-right difference in association tract overlap across 74 homotopic pairs—show lower connectional density to cortical and non-cortical targets across three birth-to-22 cohorts.

• Why it matters: It remains unclear whether structural hemispheric asymmetry reflects reduced connectivity and whether connectivity also shapes how asymmetry develops from childhood to early adulthood.
• What they did: Across three independent cohorts spanning birth to 22 years, the authors quantified asymmetry as tract-overlap magnitude differences and related it to connectional density and to age-related change, including corpus callosum involvement as a moderator.
• The result: Callosal involvement showed no consistent inverse relationship with regional asymmetry, but conditioned age effects: in two older cohorts, mean asymmetry predicted more positive age effects where callosal overlap was appreciable (standardized interactions +0.42 and +0.56), while it was weak or negative with little overlap. In the youngest cohort, regions converged toward the mean, narrowing between-region spread by 12%, with no detected callosal moderation.