How the hell can he claim a brain is not conscious just because it's not being stimulated, when consciousness is so very badly understood to begin with?
Not just because it is not being stimulated, but rather because it has never been stimulated. That's a rather large difference.
This seems significant:
http://www.theguardian.com/science/2015/aug/18/first-almost-fully-formed-human-brain-grown-in-lab-researchers-claim