WWC1 and aging: Wang D. et al. (2013) also observed KIBRA-related differences in volumes in specific frontal regions, including medial prefrontal cortex and bilateral anterior cingulate cortex. However, unlike Wang D. et al. (2013), volume changes were observed only in frontal white matter but not cortical gray matter. Declines in brain structure and metabolism in frontal regions have been linked to both healthy cognitive aging and mild cognitive impairment (Loessner et al., 1995; Davatzikos et al., 2008; Bennett et al., 2010; Giorgio et al., 2010).