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On left , a brain scan shows the location of a brain region that is implicated in stuttering : the arcuate fasciculus in the frontoparietal lobe ( arc-fp ). A second region involved in stuttering , the arcuate fasciculus in the temporal lobe ( arc-t ), is also shown . The graph on the right shows changes in a measure of nerve-fiber connectedness called fractional anisotropy ( FA ) in the arc-fp as children age . Connectedness of the arc-fp increases for non-stuttering children ( gray line ) and recovered stutterers ( green line ) but does not improve for persistent stutterers ( blue dashed line ). CREDIT : H . M CHOW & S . E . CHANG / HUMAN BRAIN MAPPING 2017
Chang has been trying to understand why about 80 percent of kids who stutter grow up to have normal speech patterns , while the other 20 percent continue to stutter into adulthood . Stuttering typically begins when children first start stringing words together into simple sentences , around age 2 . Chang studies children for up to four years , starting as early as possible , looking for changing patterns in brain scans .
It ’ s no easy feat to convince such young children to hold still in a giant , thumping , brainimaging machine . The team has embellished the scanner with decorations that hide all the scary parts . (“ It looks like an ocean adventure ,” Chang says .) In kids who lose their stutter , Chang ’ s team has observed that the connections between areas involved in hearing and ones involved in speech movements get stronger over time . But that doesn ’ t happen in children who continue to stutter .
In another study , Chang ’ s group looked at how the different parts of the brain work simultaneously , or don ’ t , using blood flow as a proxy for activity . They found a link between stuttering and a brain circuit called the default mode network , which has roles in ruminating over one ’ s past or future activities , as well as daydreaming . In children who stutter , the default mode network seems to insert itself — like a third person butting in on a romantic date — into the conversation between networks responsible for focusing attention and creating movements . That could also slow speech production , she says .
These changes to brain development or structure might be rooted in a person ’ s genes , but an understanding of this part of the problem has also taken time to mature .
All in the family
In early 2001 , geneticist Dennis Drayna received a surprising email : “ I am from Cameroon , West Africa . My father was a chief . He had three wives and I have 21 full and half siblings . Almost all of us stutter ,” Drayna recalls it saying . “ Do you suppose there could be something genetic in my family ?”