I’m afraid you are not going to find anything in the brain except “dead molecules”. There isn’t anything in there except the laws of physics and chemistry acting out like clockwork.

But in terms of the scale of how “decisions” work. Then, yes, far simpler decisions (perhaps better to say “reactions”) happen with relatively few neurons. The complete brains of small insects have been mapped by researchers, maybe several million neurons. They can detect movement reactions happening in response to stimuli.

This though is a very different thing to what people mean when referring to their conscious decision to do something.