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Published on: August 11, 2016
Neural substrates of blindsight after hemispherectomy
1Cognitive Neuroscience Unit, Montreal Neurological Institute and Hospital, McGill University, Montreal, Canada. alain.ptito@mcgill.ca
Summary
Blindsight, the ability to process visual information without awareness, is confirmed in hemispherectomized patients. Research implicates the superior colliculi in this phenomenon, overcoming previous criticisms of blindsight studies.
Area of Science:
- Neuroscience
- Visual Perception
- Cognitive Science
Background:
- Blindsight allows hemianopic patients to process visual information unconsciously.
- Previous blindsight studies faced criticism regarding methodology and lesion artifacts.
- Hemispherectomized patients offer a unique model to study blindsight due to extensive brain removal.
Purpose of the Study:
- To investigate residual visual abilities in the blind field of hemispherectomized patients.
- To address criticisms of previous blindsight research by using a more robust patient group.
- To explore the neuronal mechanisms underlying blindsight, focusing on the superior colliculi.
Main Methods:
- Studying hemispherectomized patients with extensive cerebral hemisphere removal or disconnection.
- Employing precise behavioral paradigms with strict controls for artifacts (light scatter, fixation, criterion effects, macular sparing).
- Utilizing advanced neuroimaging techniques like diffusion tensor imaging tractography.
Main Results:
- Demonstrated residual visual processing in the blind field of hemispherectomized patients.
- Provided strong evidence for blindsight independent of spared visual cortex islands.
- Identified the involvement of the superior colliculi in mediating blindsight phenomena.
Conclusions:
- Blindsight is a genuine phenomenon that can be studied in hemispherectomized patients.
- The superior colliculi play a crucial role in the neural circuitry of blindsight.
- This research strengthens the understanding of visual processing pathways and awareness.
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