Nearly two decades ago, I participated in a Vitamin B stuttering study, I was given a daily supplement that may have been placebo and they took fMRI imagery during various speaking activities multiple times during the study. I believe this particular study didn't yield strong results, but perhaps newer studies have been more successful? In either case, I also discovered that great sleep made a massive difference for my stuttering. I tend to aim for 9 hours, but 8.5 hours is minimum for me. I'm okay for a day or two with less sleep but my stuttering gets dramatically worse quickly after that. The amount of sleep people need varies, but it's probably more than most people tolerate. It's easy to acclimate and not notice the cognitive effects. In a way, stuttering has been a physiological reminder for me to get more sleep which has been a superpower at times when some of my peers spend their days as sleepless zombies.