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Ted Petit (310)


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University of Toronto Scarborough
Ted Petit

PSYB65 Human Brain and Behaviour Lecture 5: Sensory and motor systems and disorders (Chapter 5,6) Monday, October 22, 2012  Motor system: resides in the frontal cortex  Visual system  Humans very dependent on this system Anatomy of the Visual System: General Organization  Its function dependent upon its anatomy or organization o Discretely organized o Retina part of your CN system o Seeing things and recognizing everything around you  Retina o Anatomically divided right down the centre o Entire visual field divided down the middle ....left visual half field and right visual half field (don’t use half) o Everything begins in the retina which part of the CNS(it’s a part of the brain) o The retina grows out of the brain, it grows away from the brain and it a part of it o Retina: divided right down the middle, the part that is closest to the nose is the nasal portion. Slice the retina in half, o the half that is closest to the nose is the REITNAL portion o and the other half, that is closer to the ear is the TEMPORAL portion o The part of your retina toward the outside portion of your head referred to as your temporal portion of your retina - temporal means ‘on your sides’ o The part of your retina towards the inner portion of your head near the nose is your nasal portion  Optic nerve: o Leaves the retina o Two nerves cross, that is known as the optic chiasm (the point where the nerve at the back of each eye come together, and then go away back from each other)  Optic tract: leads to the brain  Nerve: to the pathway to the finger, the nerves that go to the brain aren’t called nerves anymore, they’re called a TRACT even though they are the same fibres  The whole visual system is a part of the CNS  Everything closest to the eye is the OPTIC NERVE, the nerves coming out of the eyes have a cross over and continue back to the brain the cross over point is called the OPTIC CHIASM, and as itmoves back towards the brain it’s called the OPTIC TRACT  The part of your retina, from the temporal portion (outside portion of the retina), as it continues back, comes to the optic chiasm, and it stays on same side as the brain o Does not cross! Stays on the same side of the brain  The nasal portion of eachretina, the one closer to your nose (that half), whenever they go toward the optic chiasm, they cross to the other side of the brain and cross over and continue to the opposite side of the brain  The temporal part of each retina continues to the back of the brain, the nasal part of the retina cross sides: the left goes to the right and the right goes to the left *Behaviour*  Image on the board DRAW IT  Something in your right visual field will hit nasal side of your right eye and hit the temporal portion of the left eye  Something in your left visual field will hit the nasal portion of your left eye and hit the temporal portionof your right eye  Everything in the left visual field goes to the right side of the brain (right cortex)  Everything in the right visual field goes to the left side of the brain (left cortex)  What you see when you look out, if your eyes are focused on him is the VISUAL FIELD  Everything to the right of him is the right visual half-field  Everything to the left of him is the left visual half-field  Visual field= what the person sees, and then what goes into the brain is different  The retina is the first entry point a spot of light that hits the receptive part inthe retina Slide 1  Damage in the visual field in each eye  Look at one eye at a time  Same image as the one drawn on the board  NOT the retina, what a person sees if you wiggle your fingers in front of them (visual field)  Left eye, fibers from the left retina continue on to the same side of the cortex  Image: each eye has its left and right visual field  Slide : the right hand side is the map of the visual field NOT what is dead in the retina  1: Normal o When your right eye is open o For example if you close your left eye, you can see everything on your right side and very little on the left side if you were to look straight ahead o Close your right eye, you can see a lot on your left, you can see some stuff on the right side; it’s crossed over  2: Monocular blindness o It’s named after what you can see in the visual field, not what part of the eye that is dead o When you Severe optic nerve on the right eye o Left eye isn’t affected o You close the right eye, you can see everything normal in the left eye o Right eye: you’re blinded, see nothing in that visual field on this side  3: Bitemporal hemianopia o If you cut through the optic chiasm: the left eye can’t see the left visual field (the nasal part of the left eye is dead o Slice through the optic chiasm (due to a tumour) o Cutting off fibers that cross over in the middle, outside fibers are not affected o Severed the fibers going across o The ones that cross is the nasal portion (close to the nose)  will be blind there o The right side, outside portion, you will be blind (right visual field) o If this left eye is blind, you will not see anything on the outside portion o The right eye, the outside portion is blind, the nose portion is dead o Won’t see anything on the right temporal side of the right visual field  4: Right nasal hemianopia o If you had a tumour, it will affect the fibers staying on the same side from the right eye  Affects temporal portion of the right eye o Nothing affected on the left eye o Affects the fibers on the outer right side which is the temporal portion of the right eye, gets info from the left visual field o Affect the nasal portion of the visual field in the right eye o Right portion of the right eye is dead o Temporal of the right eye is damaged******keep this one  5: Homonymous hemianopia o Losing the right hand side of the right eye, which means it will be blind in its left visual field in this eye o The right eye is blind in the left side of it  Because it’s been severed o Severed the fibers across o Blind on the left visual side of the left eye as well  7: Mascular sparing o Not perfect vision, you’ll still be able to see, but you see a little spot o If you go all the way to the cortex and its damagedhere  What you’ll do is the same thing as number 5 o Macular sparing: you won’t be quite blind, always a small centre spot where you can see Function Analysis of Each Level  What kind of function do things have as we move down through this system?  The more central the neuron  The neurons in the retina are capable of detecting a spot of light in a particular receptive field  The neuron build up information above the previous neuron and build up on it until it is more complex  Area 17: Primary receptor area for vision o Neurons respond to bars of light and orient it in particular direction o They take the info from the neurons in the retina and perceive the sensory information  Associational cortex: o In the infero-temporal area o These neurons respond to much more complex i
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