Q. Global alteration of brain functioning - Sleep?

Sleep involves a global alteration of brain functioning, and occupies one third of our lives, The transition from waking to sleep is one of the most dramatic natural alterations in consciousness. Sleep is differentiated from waking state by reduction in neuronal responsiveness, inattention to sensory stimuli, and loss of consciousness. These two states differ fundamentally in most physiological parameters including the activity of a variety of key neurotransmitter systems.

Sleep Structure: Electroencephalogram (EEG) recordings reveal the two most basic states of sleep - REM (Rapid Eye Movement) sleep and NREM sleep. NREM comprises of four stages (Stages1 to 4). EEG pattern of wakeful state and different stages of sleep is explained further.

Active wakefulness: It is accompanied by low amplitude, high frequency beta waves. In relaxed wakefulness with eyes closed, the brain emits alpha waves. Alpha waves are low amplitude brain waves of about 8 to 13 cycles per second.