Cluttering has similar brain regions involved to stuttering, but there seem to be subtle differences. Cluttering has lowered activation of brocas area like stuttering, and has abnormalities in the basal ganglia but they're a little different. Some research has speculated that cluttering is associated with high dopamine but I'm unaware of any studies confirming it. Here's a review: [https://pubmed.ncbi.nlm.nih.gov/25662409/](https://pubmed.ncbi.nlm.nih.gov/25662409/)