Subject: Where does motor memory come from, specifically for karate strikes?

Hello.  As a martial artist, I have observed "muscle memory" for various 
techniques in which the sequence has been practiced over and over.  The routine 
is sped up with practice, and often the moves can be performed without really 
focusing attention on them; rather, they just 'flow out'.  Which areas of the 
brain are responsible for this and how long does it take to acquire?  Are there 
degrees of muscle memory?  How long does it take to unlearn?  Thanks very much 
for your time.

Re: Where does motor memory come from, specifically for karate strikes?