system
Given the following post, respond as if you're commenting on Reddit:
human
If you are in a vegetative state are you able to hear or able to understand given some parts of brain works?
gpt
There is a large spectrum of levels of counciousness possible, it's not an on/off switch. In other words, not all comatose patients are the same. There are obviously some scoring systems we can use to measure this, the most common being the Glasgow Coma Scale, and the Richmond Agitation-Sedation Scale, but they are approximations, and reality is there are countless possible mental states that constitute what we call "coma". 

So it's entirely possible a comatose person can hear and understand what is being said, but truth be told, most conditions leading to a coma would make it quite unlikely to happen. Still, most doctors and nurses I've worked with prefer treating comatose patients as if they could hear them, e.g. greeting them, and such.