Like, I can be there just sitting and think. “Now I’m gonna move my middle finger”, and just do it, no reason at all. How does the brain know what muscle is each, how does a signal is determined to make you move the finger you want? Does the brain have a “map” or something of every muscle in your body?
In: Biology
Kind of a map, the motor cortex is a region in your brain and different places on it are associated with different movements. But how your brain takes conscious thought and changes it into movement I don’t think anybody really knows.
You are exactly right that there is a map in the brain. If you look up images of “motor cortex homunculus” you can see a diagram showing which parts of the brain control which areas of the body. The individual neurons in the brain connect like wires through other nerves in the spinal cord which eventually go out to several muscle cells right next to each other. When the neuron fires, it causes chemicals to release that cause the muscle cells connected to it to contract. If the brain fires off a signal in all the neurons going to, say, the biceps, then the entire biceps will contract
I read about something like this in my psychology textbook the other day, so I’m not an expert but this is what I found: there are 2 pathway systems when it comes to sensing touch: the “what” system, and the “where” system. The “what” system is a pathway in touch that provides information about the properties of surfaces/objects. The “where” system is a pathway that provides info about a location in external space that is being touched, or a location on the body that is being stimulated. Separate from that are things in your brain called “basal ganglia” which direct intentional movements. Within the basal ganglia is something called the “striatum” which controls posture and movement. So it seems like these structures do make a sort of “map” in your brain of where all of your body parts are and how they are positioned. So while my answer isn’t an entire answer to your question, that’s all I know as a wee college student.
I think it learns which nerve moves which muscle. For example, I had shoulder surgery, and my skins nerves kinda got “switched”. I would touch here, but would feel it there. It took a while, but my brain eventually rewired itself so touching where I thought I would touch, felt the correct location.
As a fetus your DNA wires up your muscles to a bunch of unlabeled ‘buttons’ in your brain. Slightly later in development your brain is bored and starts mashing buttons to see what happens, and starts labeling the buttons. Some people never find the ‘wiggle your ears’ button, for example. As a baby your brain develops enough to start arranging button presses into goals — crawl over there, grab that dangerous item someone left in your reach, put it in your mouth.
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