It’s weird we call it muscle memory. It’s still a brain memory.
Motor movements are some of deepest knowledge we have.
Don't know if it's is a real thing, but in some CSI type show years ago there was a witness with amnesia (couldn't remember their name etc.) whose identity they found out by engaging him into a conversation to distract the consciousness from the "I can't remember" thoughts and then put a form in front of him he was supposed to sign (IIRC it could have been a witness statement) and the movement of signing something was so ingrained that it persisted even through the amnesia.
Anyone know if this is a real thing or just fiction?
It's a famous case in neurology, a man called "H.M."
Here's what's written in the chapter "Stress and memory" about H.M.:
"H.M." had a severe form of epilepsy that was entered in his hippocampus and was resistant to drug treatments available at that time. In a desperate move, a famous neurosurgeon removed a large part of H.M.'s hippocampus, along with much of the surrounding tissue. The seizures mostly abated, and in the aftermath, H.M. was left with a virtually complete inability to turn new short-term memories into long-term ones -- mentally utterly frozen in time.
Zillions of studies of H.M. have been carried out since, and it has slowly become apparent that despite this profound amnesia, H.M. can still learn how to do some things. Give him some mechanical puzzle to master day after day, and he learns to put it together at the same speed as anyone else, while steadfastly denying each time that he has ever seen it before. Hippocampus and explicit memory are shot; the rest of the brain is intact, as is his ability to acquire a procedural memory.