Brain structures associated with executive functions during everyday events in a non-clinical sample

Abstract

Executive functions involve control processes such as goal-oriented planning, flexible strategy generation, sustaining set maintenance, self-monitoring, and inhibition. Executive functions during everyday events (EFEEs) are distinct from those measured under laboratory settings; the former can be severely impaired while the latter remain intact. Non-routine everyday problems due to executive dysfunctions affect individual functioning in everyday life and are of great clinical interest. Despite the importance of anatomical bases underlying better EFEEs, such bases have never been investigated among non-clinical samples. Using voxel-based morphometry to measure regional gray matter volume (rGMV) and regional white matter volume (rWMV) and diffusion tensor imaging to determine fractional anisotropy values, we identified the anatomical correlates of better EFEEs using the Dysexecutive Questionnaire in 303 normal young subjects (168 men and 135 women). Better EFEEs were associated with a smaller rGMV in the orbitofrontal cortex (OFC) spread across Brodmann areas (BA) 25, 11, and 12 and larger rWMV in the WM area of OFC adjacent to BA 11. Furthermore, individual EFEEs were positively associated with rWMV in the temporal areas, primarily the inferior longitudinal fasciculus and inferior fronto-occipital fasciculus, the latter of which connects OFC and posterior regions. Thus, our findings suggest that brain structures involving OFC, together with other regions, contribute to the maintenance of effective EFEEs among non-clinical subjects.

Fig. 1

The associations between rGMV and EFEEs. a A region of positive association between rGMV and DEX scores (negative association between rGMV and EFEEs). Results are P < 0.05, corrected for multiple comparisons at the non-isotropic adjusted cluster level with an underlying voxel level of P < 0.0025, uncorrected. The region of significant correlation is overlaid on a “single-subject T1” SPM5 image. The regions with significant associations are seen mainly in the posterior and medial parts of OFC, which include BAs 25, 11, and 12. b The panel shows a scatter plot of the relationship between DEX scores and mean rGMV within a significant cluster in OFC. The blue line represents the regression line for males, and the red line represents the line for females. r values (correlation coefficients) and P values are for the correlation between DEX scores and mean rGMV within the significant cluster of OFC for males and females (simple regression analyses)

Fig. 2

Associations between rWMV and EFEEs. Regions of negative association between rWMV and DEX scores (positive association between rGMV and EFEEs). Results are shown with a height threshold of uncorrected P < 0.0025 and an extent threshold of 500 voxels. Regions of significant correlation are overlaid on a “single-subject T1” SPM5 image. Regions with significant associations are shown in an area in the left OFC that is adjacent to BA 11 and in WM in the bilateral temporal areas. The association of OFC may look small under the threshold in the figure, but when the uncorrected threshold of P < 0.05 was used, the cluster including this area had an extent of 6,068 mm³. The panels show scatterplots of the relationships between DEX scores and mean rWMV b within the significant cluster of WM in the left temporal area, c within the significant cluster of WM in the right temporal area, and d within the cluster formed around the significant voxels (under the SVC) of OFC under the threshold of P < 0.0025, uncorrected. The blue lines represent the regression lines for males, and the red line represents the line for females. r values (correlation coefficients) and P values are for correlations between DEX scores and mean rWMV within the clusters (simple regression analyses)