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Neural patterns of conscious visual awareness in the Riddoch syndrome.

Ahmad Beyh, Samuel E Rasche, Alexander Leff, Dominic H Ffytche, Semir Zeki

Journal of Neurology November 2023 DOI: 10.1007/s00415-023-11861-5 (opens in new tab)

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AI-extracted from the abstract
Characteristics Case study Case report Peer reviewed
Sample size 1
Population Patient ST, who has Riddoch syndrome following lesions to the primary visual cortex
Keywords Awareness Blindsight Consciousness Mt + Neural patterns Statokinetic dissociation V5 Visual motion
Key findings In patient ST, conscious perception of visual motion in the blind field was associated with intact V5 receiving direct subcortical input and with decodable neural patterns in V5 that emerged only during conscious perception. Moving stimuli activated medial visual areas but remained unperceived without decodable V5 activity. High-confidence motion discrimination at chance levels correlated with inferior frontal gyrus activity, and hallucinatory motion correlated with hippocampal activity.

Abstract

The Riddoch syndrome is one in which patients blinded by lesions to their primary visual cortex can consciously perceive visual motion in their blind field, an ability that correlates with activity in motion area V5. Our assessment of the characteristics of this syndrome in patient ST, using multimodal MRI, showed that: 1. ST's V5 is intact, receives direct subcortical input, and decodable neural patterns emerge in it only during the conscious perception of visual motion; 2. moving stimuli activate medial visual areas but, unless associated with decodable V5 activity, they remain unperceived; 3. ST's high confidence ratings when discriminating motion at chance levels, is associated with inferior frontal gyrus activity. Finally, we report that ST's Riddoch Syndrome results in hallucinatory motion with hippocampal activity as a correlate. Our results shed new light on perceptual experiences associated with this syndrome and on the neural determinants of conscious visual experience.

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