Figure 7. Asymmetry associations with general cognitive ability (first principal component [PC1]), handedness, sex, and intracranial volume (ICV) in UKB, in clusters exhibiting population-level areal (upper) and thickness asymmetry (lower).

(A, D) Significance of associations (negative logarithm; corrected [p<7.4e^–5] and uncorrected threshold [p=0.01] shown by dotted and non-dotted line, respectively). X-axis displays the test for each cluster-association. As maximum sample size was used to test each association, effects of general cognitive ability were tested in separate models with fewer observations (N=35,198; separated association plots) than handedness, sex and ICV (N=37,569). (C) Visualization of the found association between leftward areal asymmetry in the large supramarginal cluster with general cognitive ability. The line of null association is shown for comparison (dotted) (B, E) Right plots denote effect sizes, 95% confidence intervals (error bars) and cortical location of associations surpassing Bonferroni-corrected significance. Individual AIs in rightward clusters were inversed. Right handers and females are coded 0, such that a negative effect for general cognitive ability / handedness / sex / ICV / reflects less asymmetry in higher cognition / left handers / males / larger brains. Associations with ICV are shown in Figure 7—figure supplement 2. Yellow and blue clusters denote leftward and rightward asymmetries, respectively.

Figure 7—figure supplement 1. Cognitive associations.

(A) Association of reduced leftward areal asymmetry in the large supramarginal cluster upon general cognitive ability (PC1 across 11 cognitive tests). The line of null association is shown for comparison (dotted). (B) Post-hoc association tests between cognitive scores on the 11 separate tests in UKB and areal asymmetry in our 14 robust clusters (labelled under plot, leftward and rightward clusters in yellow and blue text, respectively). Black circled points highlight the association tests for the leftward cluster (visualized) wherein we find the association with general cognitive ability (i.e. PC1). Corrected (p<7.4e-5) and uncorrected threshold (p=0.01) shown by dotted and non-dotted line, respectively. As these tests are a post-hoc confirmation and not independent of the initial analysis using PC1 across tasks, the correction level is the same as in the main paper (note the association with PC1 survives regardless [p=7.4e-7]).

Figure 7—figure supplement 2. ICV effects (continuation of Figure 7).

Asymmetry effect sizes with general cognitive ability (first principal component [PC1]), handedness, sex, and intracranial volume (ICV) in UKB, in clusters exhibiting population-level areal (left) and thickness asymmetry (right). Effect sizes, 95% confidence intervals (error bars) and cortical location of associations with ICV surpassing Bonferroni-corrected significance (see Figure 7 for associated p-values). Individual AIs in rightward clusters were inversed. Right handers and females are coded 0, such that a negative effect size for handedness / sex / ICV / cognition reflects less asymmetry in left handers / males / larger brains / higher cognition. Blue and yellow clusters denote leftward and rightward asymmetry, respectively.