I think that people (children, mostly) who recover - their brains start firing right probably through natural development. But training like therapy, you can ease SOME of the symptoms over time. You can retrain the brain (not perfectly, but you may see improvement). My son has a speech disorder (non stutter) and other non-neurotypical issues they do a bit of brain imaging studies on. There are DEFINITE differences in small and large brain structures alike. And it looks like people do study brain structures in sutterers. As seen in the following links: https://academic.oup.com/brain/article/132/10/2747/330765 ; https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3574760/ I'm excited to see how my daughter develops. She does have a stutter. It ebbs and flows in severity, but she's just like her mama (me). It got worse and probably peaked around puberty. By age 20 I could fly under people's radars. I work really hard to be fluent, and I never shied away from talking (even though it was frightening sometimes). I think it helped me coordinate my speech better.