On the relationship between consciousness and attention

Over the last 20 years, our understanding of the neuronal basis of perceptual consciousness and selective attention has greatly progressed. This advancement was facilitated by research using visual illusions and task designs that keep sensory input constant yet vary internal factors such as top-down attention and subjective visibility. To isolate the neuronal mechanisms of consciousness and attention, however, it has become increasingly clear that keeping the sensory input constant is not enough. Unless manipulated independently, consciousness and attention usually covary. Recent studies that independently vary both consciousness and attention have found that the behavioral and neuronal effects of consciousness and attention can be dissociated, implying that their neuronal mechanisms may be largely independent. Yet, even if independent neuronal mechanisms underlie consciousness and attention, there remains a conceptual dispute over the exact relationship between these processes. It is now generally accepted that subjects can selectively attend to attributes of events or objects without becoming aware of them. Whether the converse is also true is much more contentious