Blindsight Flashcards
Blindsight.
Ability of a blind person to accurately sense a light source or other visual stimuli, despite being unable to see it consciously.
Type 1 blindsight.
Blind subjects have no conscious awareness of any stimuli but can still predict aspects of a visual stimulus.
Type 2 blindsight.
Blind subjects have some conscious awareness of a stimuli without visual perception, perhaps because they can feel their eyes tracking movement.
Striate cortex (V1).
In the occipital lobe and receives sensory input.
Benefits of blindsight studies.
- Allows for distinction between conscious and unconscious perception.
- Allows for distinction between multiple parallel processing streams.
Perimetry.
A systematic measurement of visual field function that can detect dysfunction.
Scotoma.
Visual field abnormality.
Visual pathway.
Retina -> optic nerve -> optic chiasm -> optic tract -> lateral geniculate body -> optic radiation -> primary visual cortex.
Optic chiasm.
Nasal visual field of eyes cross to the opposite side.
Lesion in optic nerve.
Loss of vision in that eye.
Lesion in optic chiasm.
Bitemporal hemianopia (right half of right eye and left half of left eye is blind).
Radiation/cortex/lateral geniculate root lesion.
Homonymous hemianopia (loss of right half in both eyes or loss of left half in both eyes).
Anopsie.
Large visual field deficits.
Lesion in Meyer’s loop.
Loss of sight in a quartile of the eye.
Macular sparing.
Vision loss preserving centre vision.
Occipital lobe lesions.
Macular sparing.
Paradoxical vision.
Sensing light, motion, etc. whilst being blind.
Stray-light hypothesis.
Stray light from the light source to be located helps the patient locate the target. More strong light = stronger accuracy.
Stray light.
Unwanted light that interferes with performance of optical systems.
Blind spot.
Where the optic nerve is leaving the retina without rods and cones.
Hemi-decorticated.
Lacking cerebral cortex of one hemisphere.
Retino-tectal pathway.
From Superior Colliculus. Residual motion and location detection.
Geniculo-extrastriate pathway.
From LGN to V2 and V4. Residual form and colour discrimination.
Saccade.
Rapid movement of eye between fixation points.
