Lack of awareness despite complex visual processing: Evidence from event-related potentials in a case of selective metamorphopsia

Visual awareness is thought to result from integration of low- and high-level processing; instances of integration failure provide a crucial window into the cognitive and neural bases of awareness. We present neurophysiological evidence of complex cognitive pro- cessing in the absence of awareness, raising questions about the conditions necessary for visual awareness. We describe an individ- ual with a neurodegenerative disease who exhibits impaired visual awareness for the digits 2 to 9, and stimuli presented in close proximity to these digits, due to perceptual distortion. We identi- fied robust event-related potential responses indicating 1) face detection with the N170 component and 2) task-dependent target-word detection with the P3b component, despite no aware- ness of the presence of faces or target words. These data force us to reconsider the relationship between neural processing and vi- sual awareness; even stimuli processed by a workspace-like cog- nitive system can remain inaccessible to awareness. We discuss how this finding challenges and constrains theories of visual awareness.