Damages to the visual system Flashcards
what does a cut to the right optic nerve do?
1) cause right monocular blindness
what does a cut to the optic chiasm do?
2) cause bitemporal blindness
this is when both temporal fields are damaged (the outside ones)
what does a cut to the right optic tract do?
3) left homonyous hemianopia (left visual field blindness)
what does a cut to 4 do?
4) left homonyous hemianopia with macular sparing (preserves vision in the center of the visual field)
what are the two sides of the retina?
nasal (inside of the retina so inside half of visual field) and temporal (outside of retina so outside of visual field)
patient DB had?
left homonymous hemianopia with macular sparing and blindsight
(DB skips V1)
What is akinetopsia?
absence of motion vision
- damage to V5 - extreme
What is Achromatopsia?
absence of colour vision - see greys/dream in greys
due to damage to V4
What is visual Agnosia?
failure of recognition
due to damage to pathways to occipital lobe (which assembles incoming vision)
what is apperceptive agnosia?
failure of recognition due to failure of perception - struggle to see shapes
- poor copying/ matching
can look like peppery mask
what can cause apperceptive agnosia?
carbon monoxide poisoning/ mercury poisoning
Dorsal Simultagnosia?
failure of object recognition due to spatial perceptual impairment
- can recognise objects but no more than 1
could be in different spatial positions
Ventral simultagnosia?
failure of object recognition due to complex perceptual impairment
- can only identify 1 object but knows there are multiple unidentifiable objects
where and what is the dorsal stream?
located in the parietal lobe
is important for spatial recognition - of objects etc
where and what is the ventral stream?
located in the temporal cortex - temporal lobe
is important for object recognition (what)
what is blindsight?
patients can point to objects they swear they cannot see - due to damage in temporal lobe
(can locate object they ‘can’t’ see)
what does damage to the middle and inferior temporal gyrus do?
- achromatopsia
- akinetopsia
- ventral simultagnosia
- associative agnosia (difficulty understanding the meaning of what they are seeing
what does damage to the superior temporal gyrus do?
auditory region…
- deafness
- wekenickes aphasia
- auditory agnosia
Damage to the pathway from the right lateral geniculate nucleus to the right primary visual cortex results in…
homonymous hemianopia
what is associative agnosia?
failure of recognition - but no deficit in perception
- difficulty with the meaning/understanding of what they are seeing
difference between associative and apperceptive agnosia?
patients with associative agnosia are able to copy/ match/ draw objects but patients with apperceptive agnosia cannot
associative agnosia is the highest form of agnosia
why do patients with apperceptive agnosia sometimes see a peppery mask?
they are scotoma all over the visual field… V1 Retinotopically mapped so scotomas are present all over this visual field.