Diagnostic criteria for the vegetative state (VS): loss of cognitive ability, no conscious activity, inability to execute commands; ability to open eyes automatically or under stimulation; sleep-wake cycle; purposeless eye tracking; inability to understand and express language; maintenance of voluntary respiration and blood pressure; basic preservation of subthalamic and brainstem functions; persistent vegetative state (PVS) diagnostic criteria: vegetative state lasting more than one month Persistent vegetative state (PVS) can only be defined as persistent vegetative state.