The key question for a 'science of consciousness' is: how can neural processes generate our experiences - how does brain give rise to mind? This question is sometimes referred to as the 'problem of consciousness', and was recently described by EO Wilson as 'the master unsolved problem of biology'. Some contemporary neuroscientists believe that we are approaching a solution using conventional methods, others doubt that the problem will ever be fully amenable to scientific enquiry while a third camp argues that the 'problem' is ill-posed and in need of redefinition. These disagreements stem at least partly from the the complexity of the concept of consciousness, and its hinterland of 'associated beliefs' which remain strongly influenced by religion: a recent survey of Edinburgh students indicates that a majority believe that the mind and the brain are separate, that each of us has a soul which is separate from the body and that some spiritual part of us survives after death. This talk aims to clarify some dimensions of the concept of consciousness which often generate confusion, by way of a series of contrasts.
First 'consciousness' comprises two partly distinct functions: 'wakefulness' and 'awareness'. The former, arousal, function has been clarified by studies of the electrical correlates of conscious states ­ distinguishing wakefulness, slow wave (stages 1-4), rapid eye movement sleep and pathological variants ­ and of their regulation by the activating systems of the brain stem and thalamus. The neural basis of awareness, the 'content' of consciousness, has been the more or less explicit target of a vast programme of research in neuroscience involving all our major psychological capacities but especially perception (from which I will draw examples). A quite separate, second, set of contrasts is opened up by the distinction between 'consciousness' and 'self-consciousness': the latter is used to refer, among other things, to the 'idea of me' (possession of a concept of self) and the 'awareness of awareness' (possession of a theory of mind). A third contrast, between 'consciousness narrow' and 'consciousness broad' highlights the distinction between the full-blooded adult human expression of consciousness, permitting self-report and the control of action, and a variety of unconscious or preconscious relatives of consciousness: much current research focuses on the 'contrastive analysis' of these two categories. A fourth distinction, between consciousness 'inner' and consciousness 'outer' picks out the distinction between consciousness considered as a fundamentally private, solipsistic phenomenon and consciousness considered as the result of a process of exploration and interaction with our physical, social and cultural surroundings. The strength of our attachment to the 'inner' view is likely to determine our reaction to the final contrast I shall draw, between the 'easy' and 'hard' problems of consciousness. This distinguishes questions amenable to objective science (for example which brain events subserve normal vision and which subserve blindsight?) from a question which some consider to be of a different kind (how do the brain events subserving normal vision give rise to the conscious experience of sight?).
A wide range of disciplines and interests converge on the multi-faceted problem of consciousness: the study of conscious states, content-rich psychological processes, unconscious states, artificial intelligence, religion, the Arts, the philosophy of mind. This convergence creates a rich opportunity for cross-fertilisation - and for cross-purposes. Recent work supplies ample evidence for the feasibility of a science of wakefulness and conscious states, a science of conscious processes, such as perception, and a science of self-awareness (for example of theory of mind). The feasibility of a comprehensive science of consciousness depends on our view of its target: are we studying a private event or an objective set of interactions? To clarify our goal, scientists and philosophers need to renew their old alliance.

Selected references:
Zeman A. Consciousness: A User's Guide. Yale University Press, 2003
Zeman A. Theories of visual awareness. Prog Brain Res. 2004; 144:321-9
Zeman A. Consciousness. Brain. 2001; 124:1263-89