Blindsight

Blindsight is the ability to respond to visual stimuli without consciously seeing them, usually after damage to primary visual cortex. It shows that visual information can guide behavior without ordinary visual awareness.

Primary visual cortex: The cortical region at the back of the brain that performs the first major stage of cortical visual processing. Damage here is the usual trigger for blindsight, although some visual pathways bypass it.
Patient DB: A patient with damage to primary visual cortex whose residual visual abilities helped establish blindsight. His forced-choice responses provided early evidence that unseen stimuli could still influence behavior.
Cortical blindness: Loss of vision caused by damage to visual cortex despite intact eyes and early visual pathways. Blindsight occurs within a visual field rendered blind by cortical injury.
Global neuronal workspace: A theory that conscious access occurs when information becomes globally available across distributed brain systems. The theory links blindsight to the difference between local processing and globally accessible information.
Superior colliculus: A midbrain structure involved in orienting the eyes and head toward salient stimuli. Its visual pathways can support residual orienting and localization after cortical damage.
GSR: A patient studied for residual visual abilities after damage to primary visual cortex. Experiments with GSR helped characterize blindsight beyond the earliest case reports.
Visual processing: The neural operations that extract information from light, from early feature analysis to object recognition and action. Blindsight is a case of visual processing continuing without ordinary conscious sight.
Integrated information theory: A theory proposing that consciousness corresponds to the amount and structure of integrated information in a system. Blindsight poses questions about whether residual visual processing has any corresponding conscious experience.
Pulvinar: A group of thalamic nuclei involved in visual attention and communication among cortical regions. Connections through the pulvinar are among the routes proposed to support blindsight.
Forced-choice paradigm: An experiment asks participants to choose among alternatives even when they cannot confidently identify the correct one. Above-chance choices in a blind field reveal discrimination without reported visual awareness.

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