Language greatly enhances conciousness. Humans think in a language, or sometimes two three. The deaf often think in sign language. A person that grows up without learning a language will have greatly impaired cognitive skills, even if his brain is normal.
An internal language will be important for high functioning brain clones and other artificial intelligences. It may even be a human language. However, we really don't have any idea how to introduce this inner voice into our artificial intelligences. When we do, it will likely move us much closer to achieving conciousness.