The neural correlate of (un)awareness: lessons from the vegetative state.

Consciousness has two main components: wakefulness and awareness. The vegetative state is characterized by wakefulness without awareness. Recent functional neuroimaging results have shown that some parts of the cortex are still functioning in 'vegetative' patients. External stimulation, such as a painful stimulus, still activates 'primary' sensory cortices in these patients but these areas are functionally disconnected from 'higher order' associative areas needed for awareness. Such studies are disentangling the neural correlates of the vegetative state from the minimally conscious state, and have major clinical consequences in addition to empirical importance for the understanding of consciousness.