Delta Delta is the slowest electrical frequency that may sometimes be trained using neurofeedback. The rhythm generator for the delta rhythm is the brain stem and hind-brain—so it does not part of the autonomic nervous system.  Delta is unconscious. Generally, delta in the 0-2 Hz range indicates that part of the brain is in a state of deep sleep. At times this is not good.  Delta in the range of 2-5 Hz indicates drowsiness and may be the result of […]