Fig. 1: Systematic longitudinal changes occur in multiple structural whole-brain asymmetry patterns spanning white matter, cerebellum, and cortical structures.

A Previously established whole-brain asymmetry patterns enable investigation into structural brain asymmetry change. Structural asymmetry patterns describe concurrent left-right deviations across white matter, cerebellum, and cortical structures. These asymmetry patterns have previously been discovered and delineated in work by Saltoun and colleagues (2023). We apply these established asymmetry pattern definitions²⁸ to extract measures of structural asymmetry for individuals across multiple imaging visits, with an average of over 2 years between visits. Comparing asymmetry pattern expression between timepoints in an individual enables two complementary viewpoints of structural brain asymmetry change in adults. The magnitude of brain asymmetry change (MBAC) captures how much the structural imbalance between hemispheres progressed in individuals. Longitudinal Brain Asymmetry Change (LBAC) captures how structural imbalance between hemispheres progresses, including which hemisphere showcases greater change. B Asymmetry patterns exhibiting large asymmetry changes across the population draw upon distinct combinations of brain features spanning the whole brain. Shows brain feature contributions of the 10 asymmetry patterns with the largest LBACs (border). The square size (center) represents the relative amount of change amongst the top 10 patterns encapsulated by the given asymmetry pattern. Brain maps show cortical and subcortical, major white matter tracts, and cerebellum contributions to the specified asymmetry pattern. Brain features shown on the right hemisphere represent right hemisphere homologues exhibiting larger longitudinal shifts than left hemisphere counterparts in the positive direction, and the reversed configuration in the negative direction. Asymmetry patterns with negative mean directional change (LBAC) are illustrated with blue coloured brain maps. This corresponds to the reversed configuration of brain feature changes as delineated above, with brain features shown on the right hemisphere exhibiting either diminished R > L asymmetry or increased L > R asymmetry with time. Source data are provided as a Source Data file.