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PSYB65H3 (519)
Ted Petit (310)
Lecture 5

PSYB65- Lecture 5.docx

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University of Toronto Scarborough
Ted Petit

PSYB65- Lecture 5  Sensory systems  Retinas are divided anatomically right down the middle; a visual field is what a person can see; visual fields are split into two half-fields of left and right; consists of nasal portion of retina is the half that is closest to one’s nose, and the other portion of the retina that is to the outside of the head are referred to as the temporal portion; the nerves are divided exactly at the middle of the eye; the two separate nerves leaving your eyes are referred to as the optic nerves; the point at which they come together is referred to as the optic chiasm; they separate apart again and head towards the brain which is referred to as the optic tract; the nasal portion of the retina crosses, while the temporal potions stay on the same side when heading back to the left and right cortex; something in your right visual field crosses over to the left cortex, and everything in your left visual field goes to your right cortex; macular sparing refers to the little bit in the center that you can see when the damage is near the cortex  The more central the neuron (associational vs. primary), the more advanced the area of the brain, the more complex is the image that excites it; the more complex images excite it; for example in the retina, a neuron respond to a spot of light falling on its receptive field; by the time you get to area 17,lines of light oriented in a specific direction; when you get to associational cortex, these neurons integrate information from other neurons, and it responds to complex images like a face, hand  Complete damage to the right occipital cortex (major stroke), you will get complete blindness in the left visual field except for the tiny little bit of macular sparing; smaller amount of damage in the right occipital cortex, you get partial blindness in the opposite visual field; a little tiny area of damage produces something called a schitoma which is a small area of blindness in the visual field; lesions to higher visual processing areas (20,21) cause problems of perception of complex visual material such as faces, patterns  Visual agnosia is the inability to recognize objects for what they are; cannot figure out what to do with it or what it is used for; typically caused by damage to the left occipital lobe  Prosopagnosia is when a person cannot recognize faces; also may not be able to recognize other complex objects; typically from bilateral damage from areas 18 and 19  Colouragnosia is when the colours seem less intense to people, and in extreme cases, they can lose colour vision completely after a stroke; typically caused by bilateral damage to the occipital- temporal area  Somatosensory information comes into the post central gyrus; damage to this area results in altered sensory thresholds; cannot distinguish as precisely as people without damage as to where they are being touched exactly or how many points are touching them;  Stereognosis is where a person cannot tell you what a shape is; a person is impaired in their tactile/feeling; cannot distinguish shapes will enough because their sensation
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