Consciousness and attention: on sufficiency and necessity.

Selective attention and consciousness, once thought to be tightly linked, can be dissociated. Psychophysical and neurophysiological evidence shows that people can attend to objects they do not consciously see. More debated is whether people can become conscious of an isolated object or a scene's gist with almost no top-down attention. Recent studies that independently manipulate attention and consciousness reveal paradoxical effects, including cases where the two have opposing influences. Neuroimaging using EEG, MEG, and fMRI has identified distinct neural correlates for each, suggesting attention acts as an analyzer and consciousness as a synthesizer. Separating these processes is crucial for understanding the neural substrates of consciousness.

Study at a glance

Abstract

Recent research has slowly corroded a belief that selective attention and consciousness are so tightly entangled that they cannot be individually examined. In this review, we summarize psychophysical and neurophysiological evidence for a dissociation between top-down attention and consciousness. The evidence includes recent findings that show subjects can attend to perceptually invisible objects. More contentious is the finding that subjects can become conscious of an isolated object, or the gist of the scene in the near absence of top-down attention; we critically re-examine the possibility of "complete" absence of top-down attention. We also cover the recent flurry of studies that utilized independent manipulation of attention and consciousness. These studies have shown paradoxical effects of attention, including examples where top-down attention and consciousness have opposing effects, leading us to strengthen and revise our previous views. Neuroimaging studies with EEG, MEG, and fMRI are uncovering the distinct neuronal correlates of selective attention and consciousness in dissociative paradigms. These findings point to a functional dissociation: attention as analyzer and consciousness as synthesizer. Separating the effects of selective visual attention from those of visual consciousness is of paramount importance to untangle the neural substrates of consciousness from those for attention.