Findings related to white matter extent and microstructure further support the idea that alcohol acts as a neurotoxin in the context of adolescent brain development. Most studies of alcohol effects on white matter have not reported changes in white matter volumes (7). We found that cortical white matter extent, particularly in right hemisphere regions associated with motor function (precentral gyrus), complex visual processing/visual integration (lingual gyrus), recognition memory (middle temporal gyrus) and conflict monitoring/cognitive control (anterior cingulate cortex) failed to show the expected rate of increase over time in alcohol initiators. These relative developmental distinctions between groups cohere with other findings regarding the integrity of major fiber tracts in adolescent alcohol users. Work in this area is sparse to date. The few current studies of alcohol effects on brain white matter in human adolescent samples have reported decreased fractional anisotropy and/or increased mean diffusivity throughout the brain. McQueeney et al. (31) reported that binge-drinking adolescents, as compared to controls, had significantly lower FA values in 18 brain regions, including multiple areas of the corpus callosum, the superior longitudinal fasciculus, the
