Stuttering speech can stem from hyperactivity in the brain

Individuals suffering from developmental speech disorders may get a clearer insight into the brain's role, according to a new MRI study from Germany.  

Researchers from the Max Planck Institute for Human Cognitive and Brain Sciences and the University Medical Center Göttingen in Germany have recently discovered that a hyperactive network in the front right hemisphere of the brain inhibits the flow of speech, according to a recent Max Planck Institute release.  

Currently, 1 percent of all adults and 5 percent of adults have a speech development disorder, according to the study. Researchers conducted MRIs on a handful of adults who have had stutters since childhood. During the study, participants were asked to imagine themselves saying the names of the months, which is an "imaginary speaking" method. They then scanned participants' brains for modified fiber tracts in the brain's right hemisphere region.  

"Parts of the right inferior frontal gyrus are particularly active when we stop actions, such as hand or speech movements", said Nicole Neef, MD, neuroscientist at the Max Planck Institute and lead author of the study. "If this region is overactive, it hinders other brain areas that are involved in the initiation and termination of movements." 

According to the study, the right inferior frontal gyrus (IFG) stops the flow of speech, while the left one supports it. In people who stutter, researchers found that the right IFG is activated, interrupting speech flow and inhibiting activity in the left IFG. Furthermore, Neef explained that if the left IFGs and left motor vortex regions of the brain are affected and contain stronger frontal aslant tracts, speaking articulately is nearly impossible.  

"The stronger the frontal aslant tract, the more severe the stuttering. From previous studies we know that this fiber tract plays a crucial role in fine-tuning signals that inhibit movements", Neef said. "The hyperactivity in this network and its stronger connections could suggest that one cause of stuttering lies in the neural inhibition of speech movements."