How do brainwaves differ in a sleeping state than when we are awake?
How we describe sleeping waves from us using brainwaves is complicated. But when brainwaves were first discovered, by a chap called Hans Berger, he immediately identified and classified some of the frequencies that could be seen. So, if you put electrodes onto somebody and get them to close their eyes and they are relaxed, then generally they will produce what is called alpha rhythm and that is 8 to 12 cycles per second activity. Not particularly high voltage, very, very obvious, for the most part. When one is in deep sleep one has a situation where one is getting roughly a quarter through to two cycles per second activity; very high voltage is being produced and if you just compare those to alpha sleep and delta sleep, the slow wave sleep, then you can say well that is the big difference between the two. In fact, there are all kinds of shades in between that make it more complicated but, for the most part, alpha sleep is defined by the frequency, delta sleep by the frequency, there is also theta sleep. Theta is a bit faster than delta, there is also beta sleep which is faster than theta. So the slowest frequency is delta, then theta, then alpha, then beta.
