By means of exercise the brain actually grows, very much like a muscle. If you exercise your brain in various ways, it will get larger. The brain needs connections between the various neurons in order to handle new information so the process can be one of increasing the blood supply and increasing the information (via blood supply).
Everything we learn to do, we do repetitively. So, we do Neurofeedback repetitively. Changes slowly develop, because each time we exercise our brain, we build. With HEG, this applies primarily to the development of new blood pathways. This is angiogenesis, developing the available blood supply. This process leads to dendritic growth—a bulking up of the brain. Herschel Toomin, inventor of the HEG, thought that using the HEG increased IQ by 10% within 20-40 sessions.