A persistent vegetative state (PVS) is a medical condition where a person loses cognitive function and awareness but retains some basic bodily functions. This state can occur after severe brain injury, leading to a lack of response to the environment, although the individual may still have sleep-wake cycles and reflexive movements. Patients in PVS do not show signs of conscious awareness or purposeful behavior. They may breathe independently and maintain heart function, but they cannot communicate or respond to stimuli in a meaningful way. PVS is different from a coma, as individuals in PVS can remain in this state for months or even years.