PSYB65H3 Lecture Notes - Lecture 5: Optic Chiasm, Optic Tract, Optic Nerve

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Lecture 5
x Retina is part of the CNS (grows out of the brain, thus part of
the brain)
x Retina is part of the CNS not periphral
x Retina is divided down the middle
o Each half has a different name
๎‚ƒ Nasal portion
x closest to the nose
๎‚ƒ Temporal portion
x Closer to temporal lobes
o Info from each of the halves form a specific connection
that conveys information
x Nerve
o ๎‚‰๎€‚๎‚šZร๎€‚ร‡๎€ƒ}ยต๎‚š๎‚]๎€š๎€ž๎€ƒ๎‚šZ๎€ž๎€ƒ๎€’E^๎€ƒ~(]vP๎€ž๎‚ŒY๎€ยต๎‚š๎€ƒ}v๎€๎€ž๎€ƒu}ร€๎€ž๎‚๎€ƒ]v๎€ƒ
CNS, referred to as tract)
x Tract
o pathway inside the central nervous system
x Optic nerve
o everything closest to the eye is called optic nerve
o even though it is all part of the CNS since the retina
grows out of the brain, but it is done for simplicity
x Optic chiasm
o where the paths cross, but as moves back towards the
๎€๎‚Œ๎€‚]vU๎€ƒ]๎‚š[๎‚๎€ƒ๎‚šZ๎€ž๎€ƒ}๎‚‰๎‚š]๎€๎€ƒ๎‚š๎‚Œ๎€‚๎€๎‚š
x nasal portion of ๎‚Œ๎€ž๎‚š]v๎€‚Y๎‚šZ๎€ž๎€ƒfibres cross
x the temporal portion of retina goes on its (same side)
x if wiggle right hand fingers, it is going to hit the left side of
the retina of each eye
x something in right visual field will hit the nasal portion of the
right eye and temporal portion of left eye
o information from the right visual field ends up in the
left cortex
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o goes to the other hemisphere
x everything you see is your visual field
o the middle object/point is the dividing line
o to the right of it is your right half visual field
x The fibers from the nasal portion of the retina cross each
others fibers i.e. (nasal from right and from left will cross to
the other side of the brain)
x The further you are into the periphery of the visual system,
the more simple it is
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x When get to area 17 (primary cortex of occipital lobe), the
neurons responds to a particular line or orientation and do
not respond to lines of different orientations
x When get to associational cortex, the neurons respond to
much more complex situations. i.e. objects, hands, etc
x Behavioural deficit in a person is directly related to where
the problem is i.e. if damage in associational cortex, what
goes wrong is completely complex
x รฎX๎€ƒD}v}๎€ยตo๎€‚๎‚Œ๎€ƒ๎€o]v๎€šv๎€ž๎‚๎‚๎€ƒ~๎€๎€‚v[๎‚š๎€ƒ๎‚๎€ž๎€ž๎€ƒ๎€‚vร‡๎‚šZ]vP๎€ƒ]v๎€ƒ๎‚Œ]PZ๎‚š๎€ƒ๎€žร‡๎€žV๎€ƒ
either left or right visual field)..eye is removed
x 3. If cut retina in half, will only affect nasal portion of each
eye
o The left eye will not be able to see anything in the left
visual field
o Cannot see anything in the left visual field
x If get complete damage to occipital cortex
o Complete blindness on opposite visual field
o Posterior artery is damaged *then kills whole occipital
cortex
x If get incomplete damage, blindness will occur in some
portion of the opposite visual field
x Macular sparing (not complete blindness, but sparing right
in the centre)
x If get little tiny area that is damaged, get a scatoma (small
area of blindness) caused by a small area of damage
o D}๎‚๎‚š๎€ƒ}(๎€ƒ๎‚šZ๎€ž๎€ƒ๎‚š]u๎€ž๎€ƒ๎€š}v[๎‚š๎€ƒ๎€žร€๎€žv๎€ƒv}๎‚š]๎€๎€ž๎€ƒ]๎‚š๎€ƒ๎€๎€ž๎€๎€‚ยต๎‚๎€ž๎€ƒ๎€๎‚Œ๎€‚]v๎€ƒ
makes up for it
๎‚ƒ Small scatomas are NOT noticed
o We all have a naturally occurring blindspots
x Damage into each side has different consequences
o Right side: patterns
o Left: perception of language, visual items
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