Loss of the ability to maintain awareness of self and environment combined with markedly reduced responsiveness to environmental stimuli. (From Adams et al., Principles of Neurology, 6th ed, pp344-5).
The question, then, is whether activity (perception) occurs in the mind (brain) during unconsciousness. Can or does perception continue? Do we interact with the mind-objects, the concepts we have acknowledged (gained knowledge of) even after the sensation of space-objects is shut off?