Many years ago, I worked for a neurobiologist who was doing pain research. I used to tell people my job was to design torture equipment, which always got me a few strange looks. The main purpose of most of this equipment was to figure out some basic things about how different sensations were processed by the human body. The experts in the field still don’t understand it all, and I only understand what little bit rubbed off on me while I was working there.
There’s a lot of interesting things that go on in your nervous system. For one thing, there’s an integration effect of sorts in your nerve cells. When you start to scratch, for example, at first the nerves are reluctant to fire off signals. But then, the more they fire off signals, the more they want to fire off signals, so if you scratch one area long enough you’ll feel a faint “phantom” scratching after you’ve stopped.
The integration effect also causes some other weird things. For example, if you precisely control the temperature of a small probe (which is what one of my “torture” machines could do) and you varied the temperature so that it went from 25 deg C (about room temp) to 40 deg C (not quite to the heat pain threshold, but rather warm) and alternated them back and forth at about a 1 second interval, people think that the temperature is getting hotter and hotter when it isn’t. In other words, while the temperature is going 25-40-25-40-25-40, what your nerves tell your brain is that the temperature is going 25-40-26-41-27-42-28-43 (approximately).
Another thing that happens is what engineers call “crosstalk”, which is when one signal accidentally gets coupled onto another signal. This happens all the time in electronics, and happens in your nerves too. Ever talk on the telephone and heard someone else’s conversation in the background? Same thing. If two nerves run side by side for a long time, it’s very easy for the signal for one to get coupled onto the other one. This is what causes SnakesCatLady to get confused about whether the sensation is above or below the scar. Both of those nerve signals end up in the same nerve bundle and you end up with crosstalk between them. People with sore throats often feel that their ears are itchy or sore. There’s nothing wrong with their ears, it’s just that it’s the same nerve bundle. People often feel heart attack pains in areas that are not their heart, like their shoulder or arm. Same thing. The neurobiologist did an interesting test on me once when I asked him exactly what he did with some of these machines I made for him. He put two probes on my forearm, very carefully choosing two locations that ended up in the same nerve bundle (which he didn’t tell me until later). The two spots he chose weren’t righ next to each other, either. They were a good 5 inches or so apart. Then it was a very simple test. One probe or the other would get hot. All I had to do was press a button for which probe it was. Simple enough, right? I missed 8 out of 20. I was like what? :dubious: which is when he explained the whole crosstalk in nerve bundles thing to me.
If you think the nerves themselves are complicated, once you reach the brain it gets even worse. Some parts of your nerves are processed way before your conscious brain is even aware of what is going on. This is how your reflexes work. There’s a bunch of different layers of how things are processed, and your consciousness is pretty much the last thing in a long line of stuff.