I suppose there is a concept of sentience from outside and a different concept from internal sentience. The movie "Johny Got His Gun" by Dalton Trumbo discusses a situation where a badly injured soldier in WW1 is considered brain dead by outsiders while he's fully conscious and sentient internally.
I haven't studied neuroscience so I don't know how you define consciousness. I have read Julian Jaynes's "The Origin of Consciousness..." which in my untrained opinion makes a compelling case that consciousness is a hard term to define.
That's not how we define conscious anywhere.
You can process the world around you, feel and introspect. Even if your judgment is off and you forget your actions, you're conscious in that moment.
From a neuroscience perspective, what you're suggesting is absolutely false btw.