Conscious awareness of cognitive processes and their dysfunction

Conscious awareness is the state in which external and internal stimuli are perceived and can be intentionally acted on. Although various investigations have provided new insights into the neural mechanisms of conscious awareness, its whole network in human remains to be solved. Anosognosia for visual dysfunction and unconscious processing of visual stimuli are good examples of dissociation between cognitive processes and conscious awareness. Anton syndrome, anosognosia for blind or deaf, could be observed in blindness caused by cerebral as well as ophthalmological diseases, when general cognitive function or attention is impaired. Unawareness of hemianopia is not an exception but a common phenomenon, which seems to be related to a completion phenomenon and macular sparing. Patients with visual agnosia are not consciously aware of the nature of their visual dysfunction but have a vague feeling of visual impairment. Blindsight, unconscious visual processing in the blind field, might be partly related to the dorso-dorsal visual stream that takes roles in the control of actions "on line" without awareness of spatial perception. In patients with unilateral spatial neglect, unconscious processing of visual stimuli on the neglected space was also observed. Better understanding of neural mechanisms of conscious awareness would provide insights into various neurological disorders and therapeutic approaches.