here are the sources. 1. [ScienceDaily](https://www.sciencedaily.com/releases/2017/01/170103162356.htm) "A new study demonstrates that regional cerebral blood flow is reduced in the Broca's area -- the region in the frontal lobe of the brain linked to speech production -- in persons who stutter. More severe stuttering is associated with even greater reductions in blood flow to this region." 2. [Pubmed](https://www.ncbi.nlm.nih.gov/labs/articles/28035724/#) “We detected lower regional Cerebral Blood Flow (rCBF) at rest in the stuttering group compared with healthy controls in Broca's area bilaterally and the superior frontal gyrus. rCBF values in Broca's area bilaterally correlated inversely with the severity of stuttering and extended posteriorly into other portions of the language loop.”