Alpha rhythm in EEG is seen in

The EEG recordings show typical features of sleep which is broadly divided into two broadly different phases: 1. D-sleep (desynchronised or dreaming sleep), also called as REM- sleep (rapid eye movement sleep), active sleep, or paradoxical sleep. 2. S-sleep (synchronised sleep), also called as NREM-sleep (non-REM sleep), quiet sleep, or ohodox sleep. S-sleep or NREM-sleep is fuher divided into four stages, ranging from stages 1 to 4. As the person falls asleep, the person first passes through these stages of NREM-sleep. The EEG recording during the waking state shows alpha waves of 8-12 cycles/sec. frequency. The onset of sleep is characterised by a disappearance of the alpha-activity. Ref: A Sho Textbook of Psychiatry, Niraj Ahuja, 7th Edition, pg. no. 133