Dopamine and its role in stuttering

Dopamine and its role in stuttering We hear a lot about dopamine in relation to stuttering. I’m sure you’ve heard it brought up at some point. I want to provide some clarity on what the role dopamine is playing in stuttering. Firstly, reducing dopamine in the brain has been shown to improve fluency. But the question is, what is dopamine doing to lead to stuttering to begin with? I’ll attempt to provide an explanation. In the brain there is this relay station that we call the basal ganglia that receives motor commands when we want to move or speak. In the basal ganglia, we have 2 pathways, a direct pathway and an indirect pathway. How this relay station works is that a motor command will be received and the direct pathway will cause the initiation of that motor command, it’s associated with “go”. While the indirect pathway is responsible for “no-go”, but it’s also responsible for inhibiting competing motor commands that we don’t want. This is where dopamine plays a role. **Dopamine inhibits the indirect pathway via D2 receptors.** This leads to competing motor commands not being suppressed. Dopamine also excites the direct pathway via D1 receptors, which leads to an overactive direct pathway. So there is an imbalance. An under-active indirect pathway and an overactive direct pathway. The main issue lies in the competing motor commands not being suppressed. This is why reducing dopamine in this particular region of the basal ganglia, the dorsal striatum, leads to fluency by balancing out the direct and indirect pathways. A question you might ask is why only speech? Why aren’t all movements impaired? Huntingtons disease has an impairment in the same region, but they have global motor impairments, not just speech impairments. So what's going on? I believe this is because there is a lack of blood flow in brocas area in people who stutter, this area is responsible for speech. This might explain why it's so targeted, but this is just me speculating. I’ve thrown a lot at you here, but I am more than happy to answer any questions Here are some references if you’d like to read more. 1. This is a reference to a lack of blood flow in developmental stuttering [https://pubmed.ncbi.nlm.nih.gov/28035724/](https://pubmed.ncbi.nlm.nih.gov/28035724/) 2. Here is a review on the basal ganglia circuitry, the involvement of dopamine and how dopamine contributes to stuttering. [https://www.frontiersin.org/journals/psychology/articles/10.3389/fpsyg.2019.03088/full](https://www.frontiersin.org/journals/psychology/articles/10.3389/fpsyg.2019.03088/full)