Synapses

I am taking a class that I really enjoy. It is called Music With Children. We are learning how to introduce Music to young children. Right now we are working with First Graders. I really like this age group. They are quite fun and many of these kids are very bright.
Anyway, my instructor was explaining to us how the brain develops in children. He said that we have these neural highway connections called synapses and we start out with very few even before we are born. Gradually, we develop more and more. By the age of Three, we have the maximum number of synapses that we can possibly get. By four yrs of age, we begin to lose the ones we don't use. He said that this is why it is vitally important for kids to be exposed to music and learn to sing and make some kind of music by the age of Three. The synapses we don't use will be lost forever. It is just like any organ in the body or appendage...use it or lose it. If you keep an eye covered long enough, eventually, that eye will no longer work. If you never use one arm at all, it will atrophy and become useless. So the brain needs as many mental stimuli as it can get at a very young age.
I was fascinated by all this. I am sure that I have over simplified this topic, but I hope you get the main idea in spite of my poor ability to explain what I learned in school. So to all you parents who have newborn babies, start singing little songs to them right away and playing instruments or recordings of music for them....please!