<P> The arcuate fasciculus is the area of the brain between Wernicke's area and Broca's area that connects the two through bundles of nerve fibers . This portion of the brain serves as a transit center between the two areas dealing most largely with speech and communication . </P> <P> Recent studies have shown that the rate of increase in raw vocabulary fluency was positively correlated with the rate of cortical thinning . In other words, greater performance improvements were associated with greater thinning . This is more evident in left hemisphere regions, including the left lateral dorsal frontal and left lateral parietal regions: the usual locations of Broca's area and Wernicke's area, respectively . </P> <P> After Sowell's studies, it was hypothesized that increased performance on the verbal fluency test would correlate with decreased cortical thickness in regions that have been associated with language: the middle and superior temporal cortex, the temporal--parietal junction, and inferior and middle frontal cortex . Additionally, other areas related to sustained attention for executive tasks were also expected to be affected by cortical thinning . </P> <P> One theory for the relation between cortical thinning and improved language fluency is the effect that synaptic pruning has in signaling between neurons . If cortical thinning reflects synaptic pruning, then pruning may occur relatively early for language - based abilities . The functional benefit would be a tightly honed neural system that is impervious to "neural interference", avoiding undesired signals running through the neurons which could possibly worsen verbal fluency . </P>

The two lobes of the brain associated with language are