Figure 4. Age-associated increase in spontaneous use of semantic clustering is partially accounted by the volume of the right caudal middle frontal lobe.

A. Volume of the right caudal middle frontal lobe partially explained the effect of age on total semantic clustering score during recall as evident by a significant indirect effect (standardized β = 0.05, SE = 0.03, 95% bias-corrected bootstrapped CI [0.01, 0.13]). Numbers for each path shown in the figure are the standardized beta weights. SE, standard error; CI, confidence interval. *indicates significant paths with a 95% bias-corrected bootstrapped CI that does not overlap with zero. Number in parenthesis indicates direct effect of age on semantic clustering. B. Total semantic clustering score during recall trials for each participant is depicted as a function of participant’s right caudal middle frontal lobe volume. The values depicted were standardized residuals adjusted for sex. Total semantic clustering score showed a significant relation with volume in this region (r = −0.30, p = 0.001, FDR q = 0.008), smaller volumes were associated with greater use of semantic clustering during recall.