Fig. 11.5.

In a group of 57 alcoholics, lower working memory scores were selectively correlated with high mean diffusivity (MD) in the genu but not the splenium, whereas lower visuospatial test scores were selectively correlated with high MD in the splenium but not the genu. Selectivity of these relations was established with multiple regression analysis. As reported in Pfefferbaum et al. (2006, p. 1004), “Genu and splenium MD values of the focal regions were entered as simultaneous predictors of working memory and accounted for 13% of the variance. Genu MD made a significant independent contribution to the variance (partial F = 4.10, p < 0.05), whereas splenium MD did not (partial F = 1.18, p > 0.70). For matrix reasoning, both genu MD (partial F = 3.55, p < 0.07) and splenium MD (partial F = 4.92, p = 0.03) were independent contributors to the total variance (26%). When all four regional DTI [diffusion tensor imaging] measures (i.e., genu fractional anisotropy (FA) and MD and splenium FA and MD) were entered as predictors of matrix reasoning, 28% of the variance was accounted for but only splenium MD made a significant independent contribution (partial F = 4.28, p < 0.05) to the overall variance. (For a detailed description of DTI methods, see Chapter 17 in this volume.)