The Nature of Consciousness
I like to distinguish between two different uses of the word "consciousness". There is our experience, what we are conscious of, the contents of consciousness; and there is consciousness as a faculty, the faculty of being able to experience, of having an inner mental world. Consciousness as a faculty is something common to us all, whereas our actual conscious experience varies widely.
There is little cause to doubt that our experiences -- the contents of consciousness -- are closely related to neural activity. But it is not so clear that consciousness as a faculty is also the result of neural activity. The current interest in microtubules and possible room temperature quantum coherence may, or may not, turn out to explain part of a process by which experiences arise -- I say "part" because there would probably still be a large chasm to bridge between the physical quantum state and the mental experience -- but to seek to explain the faculty of consciousness in terms of quantum coherence, or any other physical process, may not be justified.
I see no reason to suppose that consciousness as a faculty is limited to human beings. It seems absurd to suggest that a dog, for example, is purely a biological mechanism with no inner experience; as absurd as suggesting the same of another human being. Where we differ from other creatures is not in the faculty of consciousness but in the contents of consciousness.
As far as sensory experience is concerned, each species experiences the world differently according to its sensory apparatus. A dog can hear frequencies that we do not, and its sense of smell far surpasses our own. In terms of its sensory awareness of its environment, a dog may be more aware than we are. Other creatures even have sensory modalities that are absent in humans -- a dolphin's sonar, for example. They have dimensions to their experience that we know nothing of.
On the other hand we have a capacity absent in other animals (with the possible exception of whales and dolphins), namely speech. We not only speak to each other, we can also internalize our speech and engage in an inner dialog with ourselves. This gives rise to much of our thinking -- indeed, the term "thinking" is often applied to just this, our internal self-talk. It is in this -- our ability to think in words -- that the contents of human consciousness most differ from that of other creatures.
Speech and its internalization probably lies behind most of the other, non-sensory, differences between our consciousness and that of other creatures. Words conjure up associations to past experiences or classes of experience, and through them we can deliberately bring the past back to mind, independently of what is happening in the present. Other creatures may well experience associations to past experiences, but only in response to current stimuli. We can deliberately step out of the present moment. (According to many spiritual teachings we step out of the present far too much -- possibly the downside of language). In a similar way we can think about the future, and make plans and decisions in ways that are probably unavailable to other organisms.
The thinking that results from the internalization of speech may also account for self-awareness, often regarded as the paragon of human consciousness -- and sometimes equated, erroneously, with consciousness itself. We can think about our experience, reflect upon what is going on in our minds, and label it with words much as we may think about our experience of the external world. We can become conscious of the fact that we are conscious -- again something probably unavailable to organisms without symbolic language. From there it is a short step to assuming that there is within us an independent experiencing self -- although several spirtual teachings claim this is a false and misleading assumption.