The relationship between consciousness and top-down attention

The relationship between selective attention and consciousness is a close one, leading many scholars to conflate the two. This chapter summarizes recent psychophysical and neurophysiological evidence arguing that top-down attention and consciousness are distinct phenomena that need not occur together and that can be independently manipulated. Subjects can attend to various aspects of perceptually invisible objects. Whether or not subjects can be conscious of unattended objects is disputed, yet evidence suggests that some types of visual processing can give rise to consciousness with little or no help from top-down attention. While neuroimaging studies in humans and nonhuman primates are uncovering the distinct hemodynamic signatures of selective attention and consciousness, optogenetic experiments in mice are beginning to isolate the specific neural mechanisms underlying top-down attention. Untangling the tight relationship between attention and consciousness is a necessary step in the ultimate elucidation of consciousness and its material substrate.