Imagine you had a conversation with your friend today. How long do you think you will be able to remember the whole conversation? It is likely that you will forget it very soon. You might still remember that you had a conversation and perhaps what it was about but if you are asked to remember the exact facts of the conversation, like who said what, your brain will have already forgotten it. Now compare that to riding a bicycle, or swimming, or knitting. You may not cycle for years on an end, but when you do, you will be able to remember just how to do it. Your brain will not tell you that it has forgotten how to cycle. This long-term memory that remembers skills is called muscle memory.
If it is just about storing information in the brain, how can it be so easy to remember certain things and forget others? Neurobiologists give us the answer to that question. Our brain does not store all the information in the same way. Human memory is made up of different systems. What was said in a conversation is a fact. Facts are stored in declarative memory. Having a conversation is a life event. That is stored in episodic memory. Declarative and episodic memory are conscious memories. Muscle memory, also called procedural memory, forms part of the unconscious memory system.
Even the simplest everyday actions involve a complex sequence of tensing and relaxing many brain muscles. We can perform these actions smoothly and accurately because we have repeated them several times in life. With continual practice, actions as complicated as riding a bike, knitting, or even playing a tune on a musical instrument, can be performed without thinking about it.
Our brain is an amazingly complex organ. It does not simply store a new skill, but changes with it. Every time we learn a new skill, the brain muscles that are used in that activity become stronger. Doing the same thing over and over again changes the muscles of the brain, making it more permanent than other systems of memory.