The neurobiological approach to consciousness moves from the assumption that all 
phenomenal experiences are based on neuronal activity in the brain. 
Consciousness has two main components: wakefulness and awareness. While it may 
be relatively easy to determine the neuronal correlates of wakefulness, it is 
not the same for awareness, of which the neural correlates are poorly 
understood. Knowledge of the circuitry and the neurochemistry of the sleep/wake 
condition is necessary but not sufficient to understand the circuitry and 
neurochemistry of consciousness. Disorders of consciousness (DOCs) include coma, 
vegetative state and minimally conscious state. The study of DOCs and of the 
electrophysiological changes underlying general anaesthesia-induced loss of 
consciousness may help in understanding the neuronal correlates of 
consciousness. In turn, the understanding of the neural bases of consciousness 
may help in designing interventions aimed at restoring consciousness in DOC 
patients. Sporadic cases of recovery from a DOC have been reported after the 
administration of various pharmacological agents (baclofen, zolpidem, amantadine 
etc.). This review provides an overview of such drugs, which are from various 
and diverging classes but can be grouped into two main categories: CNS 
stimulants and CNS depressants. The available data seem to suggest an awakening 
effect obtained with CNS depressants rather than stimulants, the latter being 
more effective at improving functional cognitive and behavioral recovery in 
patients who have spontaneously regained an appreciable level of consciousness. 
There is a need for more rigorous systematic trials and further investigation of 
the above treatments, with particular attention paid to their mechanisms of 
action and the neurotransmitters involved.