Normal

Alert; responds appropriately to environment

Dementia

Normal amount of consciousness but loss of higher, intellectual function, with impaired interaction

Delirium

Dramatic disruption of higher, intellectual function, with inappropriate response to the environment

Lethargy

Little spontaneous activity; lies quietly or sleeps in the absence of stimuli; will interact with the environment when stimulated, but quality and quantity of interaction are depressed

Obtundation

Appears asleep in the absence of stimulation; can be briefly aroused to minimal interaction

Stupor

Requires vigorous stimulation to provoke arousal and response with movement or vocalization, but there is no appropriate interaction 

Coma

Unconscious; cannot be aroused even with vigorous or painful stimuli (note that general anesthesia is a drug-induced coma)