When you go to sleep, your brain frequency slows down, all the way to about half a cycle per second in the deepest levels of natural sleep. This is known as the Delta level.
In between Beta, (the waking state), and Delta, (the deep sleep state), there are yet two other levels of mental activity.
When you are in a light level of sleep or in meditation you are in the Alpha range, which is 7 to 14 cycles per second.
Going to the alpha level or centering is essentially the same thing as meditating. When someone meditates, scientifically, they are simply reducing their brain wave frequency to Alpha. The Alpha level is the level we use to activate our minds.
This is no different from training your physical body and getting into shape. If you exercise your body only once per month you get very different results than if you exercise daily. The same principle applies when you train and exercise your mind. The more you go into alpha, learn to visualize, relax, and tune into your intuition, the healthier and better your life becomes