Hunting the ghost: Toward a neuroscience of consciousness.
Document Type:Book Chapter
Topics:Neural Correlates of Consciousness
Deposited by:Dr. Petra Stoerig
Date of Issue:2007
Title of Book:Cambridge Handbook of Consciousness
Number of Pages:60
Publisher:Cambridge University Press
Place of Publication:New York
ISBN:978 0 521 85743 7
Official URL:http://www.cambridge.org/978052185743 7
Abstract:Consciousness is a term with many meanings. In one sense, we use the term to indicate whether or not an organism is in a conscious state. In this sense, consciousness is what is altered, reduced, or even lost when we faint or undergo deep general anaesthesia. In a second sense, it is a trait, an attribute of a psychological process; we may think, desire, hear, see, and feel consciously, thereby becoming conscious of thoughts, wishes, voices and music, of colours and textures. Local anaesthesia, by abolishing conscious sensations of touch in the affected limb, thus interferes with the consciousness of something. Within trait consciousness, I draw a further distinction between conscious representations and conscious access. Conscious representations are of objects or contents of perceptions, desires, or actions; they are usually phenomenal, like a strawberry that is red, sweet. and heart-shaped and that I see, smell, and desire to eat. To describe the strawberry’s looks and taste or to resist its temptation, conscious access to its representation is required (Block, 1995). This chapter reviews evidence pertaining to the neural basis of state and trait consciousness (Stoerig, 2002). As we (still?) lack an objective marker of conscious representations that is independent of the subjects’ overt behaviour, we can assess conscious representations only when our subjects can access and (verbally or non-verbally) express them. The same applies to the conscious state, because it is only observable conscious access that precludes a diagnosis of unconsciousness. If conscious representations as well as state consciousness are attributed on the basis of evidence for conscious access, the neuronal processes that mediate conscious access in its many forms are likely to contaminate what we learn about those that mediate conscious representations and states. A prominent candidate for mediating conscious access is a network of frontoparietal cortical regions that play an important role in attentional and behavioural selection of incoming and stored information. As these regions allocate processing resources and guide behavioural selection, it is not surprising that they are activated both when vegetative state patients recover and when healthy subjects perform demanding perceptual tasks. Although the frontoparietal network has been implicated in the mediation of the conscious state, of conscious representations, and of conscious access, I argue that these different manifestations of consciousness may well depend on different neuronal processes.