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PSYB65H3 (519)
Ted Petit (310)
Lecture 5

Lecture 5.docx

8 Pages
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Department
Psychology
Course Code
PSYB65H3
Professor
Ted Petit

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Description
Notice that the left dotted line crosses over to the right This would be nasal part of optic nerve On the right hand side is what we actually see in our visual field 1. It is NOT the retina It is what we can actually see in the world and what is blind and our visual field Pics are what actually see if we were to wiggle our fingers in front of them 2. We also have to look at one eye at a time We cannot do two eyes at a time Optic nerve is coming out from the retinas Retina really is part of CNS - part of the brain, that grows away from it Normally "tract" is word for CNS But we call it optic nerve The two nerves cross at the optic chiasm And then they head towards the brain Once they pull away, it is the optic tract Part of retina from the temporal portion as it continues back, it goes to the chiasma it stays on the same side of the brain - IT DOES NOT CROSS Right stays right They go away from the chiasma staying on the same side of the brain Nasal portion: they actually CROSS at the optic chiasma and go over to the other side Left retina goes to the right hand side of the brain When we look at something in our right visual field: It goes through the nasal portion of our right eye and the temporal portion of our left It will thus collect from both parts at the LEFT temporal lobe Like how right hand is controlled by left cortex Left visual field: Hits temporal portion of the right eye Hits nasal portion of the left eye Will collect at the right cortex Close one eye Try and point things out What can they see Just by looking what and where they can see, identify location of tumor 1. Normal Midline is our nose If we were to close our left eye, we could see a lot of things on our right but very little on our left 2. Monocular blindness Sever the optic nerve on the right eye Left eye is not affected at all. It can see everything perfectly normal Essentially blind in the right eye Wag the fingers, we will see nothing in the areas where we normally see 3. Bitemporal hemianopia Slice right through the optic chiasm Vertical cut Cutting the fibers that cross over - the ones that cross would cross in the middle The ones on the outside are not hurt The nasal portions have been gone Right hand side of right gone, left hand side of left visual field is gone The temporal would be fine 4. Right nasal hemianopia Tumor on the right hand outside portion Destroying the left most part of the right visual field Everything else will be fine It is really affecting the temporal portion. The fibers on the outside Remember, the right temporal is taking in information from the left, so naturally this is where damage will be Temporal portion of the right retina is dead Left visual field is damaged The visual field is what each retina can see. So, the left part of that right visual field is gone (Think of it when you close one eye) 5. Homonymous hemianopia Losing the right hand side of the right eye, meaning it is blind in the left Severing the temporal portion Also blind to the left since you severed the nasal nerve 6. Quadranticanopia 7. Macular Sparing If we have damage in the cortex Little part in middle that is sparing, otherwise it is same as 5 You are not quite blind Little spot in center we are able to see. Should not be there, but it is Small areas of damage in occipital cortex: we lose only portions of the opposite visual field Damage very small: scotoma: Small area of blindness caused by damage to occipital cortex We all have a natural scotoma Natural blind spot Each eye has a left and right visual field The left visual field of the right eye is damaged in number 4 As we move down the system, what functions exist? Peripheral: Retina Detect a single spot of light falling on a single receptive field Each neuron builds on the information from those above it Dots of light Once enough dots are there, it will fire The more central something is, i.e. the closer it is to the cortex Area 17 Primary receptive area Respond to bars of light and orient it in a particular direction Has to have a specific orientation Once that orientation is there, it will fire Associational cortex : Responds to complex images: hand Will respond only to the specific Each step along the way will become more specific and more complex SOMATOSENSORY SYSTEM Nonspecific, body senses Goes into the parietal lobe in the postcentral gyrus Think of the sensory homunculus: think of organization Sensory strip lighting up Damage to these areas: Altered sensory thresholds: where damage is from any part of the body Trouble distinguishing whether or not you are touching them softly or hardly Trouble separating out if they are being touched at one or two points. Has to be touched further apart to tell it is two Face or lips: very easy to tell that it is two points Back: not sensitive, have to get really far apart to tell it is separate points Tumor or stroke to somatosensory system: More damage with these points I.e. the lips would lose this sensitivity Losing the location of where touch is. They might not be able to tell you which specific finger you are touching, but know it is your hand Loss of ability for fine detail Stereoognosis: Difficulty in determining the shape you are feeling It's like "Operation" The normal person could feel out the shape of what needs to be put in Stroke here, postcentral gyrus, would have a problem Trying to feel and get sensory information from the hands - the trouble with doing this is stereoognosis Also, putting circle in a pile of wooden blocks and trying to pick it out Also, difficulty in placing objects in
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