Mediation model of central atrophy (latent variable) predicting processing speed (observed) and GDT net-score (observed) . Model fits were adequate according to RMSEA (root mean square approximation), CFI (Bentler's Comparative Fit Index), TLI (Tucker-Lewis Index), SRMR (Standardized Root Mean Square Residual), and χ2. Coefficients (standard errors) are standardised. GDT: Game-of-Dice Task; ICR: Intercaudate ratio; TVR: Third ventricle ratio. * p < 0.05; ** p < 0.01.