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Psychology (7,818)
PSYB65H3 (519)
Ted Petit (310)
Lecture

PSYB65 - Lec 5 (near verbatim).docx

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Department
Psychology
Course Code
PSYB65H3
Professor
Ted Petit

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PSYB65: Lec 5  We talked about how NS put together and what can go wrong w/ it  Sensory and motor systems today SUMMARY: Sensory system is in parietal cortex and motor fxn in frontal cortex, divided by central sulcus and on either side of the sulcus are the gyri  Pre-central gyrus = primary motor output  Post-central gyrus = primary sensory input from body other than special senses TODAY: What happens when those areas get damaged (stroke, tumor etc;) Visual system = specialized = occipital cortex at back of head Temporal Lobe & Auditory cortex = primarily hearing but also speech (understanding language, decoding and re-encoding and making language) VISUAL SYSTEM:  Anatomical organization: o Down the middle of the retinas (centre of nose), they are anatomically divided  creates visual field = what you see; technically it’s divided into 2 visual half fields = right visual half field and left visual half field  shortened to right visual field and left v.f. o If you look straight ahead at a point, everything to the right is the right visual field; everything to the left of point = left visual field o Visual field is divided in 2 halves b/c retinas are divided in 2 halves o Retinal region closest to nose = nasal portion/half of retina o Other half of retina closest to outside of head = temporal portion/half of retina o Nerves are divided in exact middle of eye  Nerves from temporal portion; all nerves from 2 eyes come together as a single nerve point; 2 separate nerves leaving your eyes = optic nerves = come together after growing back and meet at single point = optic chiasm  To get to the 2 separate parts of the brain, the optic chiasm separates apart and goes into brain; part where they are separating and going to back = optic tract  Group of axons that come together: if outside the CNS = nerve; inside CNS = tract  Nerves from temporal (outside) portion of each retina remain on same side and go up to cortex  Nerves from nasal portion of each retina cross over (goes to other side of the brain) o Pupil = small opening for light to get into (review video: 15 min)  Ex) Hold hand out on right side (while you look straight on), info (the light trying to get into your eye) can only go through the little hole in your pupil and therefore it’s going to hit the nasal portion of right eye and temporal portion of left eye (b/c light doesn’t bend)  Ex) If something is in left visual field (while you look straight on), it can only hit the following portions of each eye: nasal portion of left eye and temporal portion of right eye  Remember, temporal portions stay on same side whereas the nasal portions cross over;  So, if something in left visual field, info that hits nasal portion of left eye crosses over (onto right side) whereas the info that hits temporal portion of right eye keeps going along the same side  so if info from left visual field, the right cortex receives that info  Opposite true: everything in your right visual field ends up in left cortex o Some sort of damage to the visual system (tumor, MS etc;)  Look at patient’s visual field: close one eye at a time and hold hand up in different regions of a circle 2 determine where ppl can see with each eye  Normal: don’t see a full circle b/c eyes aren’t perfect  irregular inner circle; right eye can see a bit more on the right than on the left  2) lost all nerves in that area: destroy anything that the right eye can see (blind that’s where they should be able to see but cannot that’s there visual field, NOT RETINA!); left eye open and looking at its visual field, everything fine  3) transection through middle (nerves sheared at optic chiasm = you’ve cut 2 tracts that cross; if cut the other way, would be completely blind)  the tracts that cross are of the nasal portion, so here, you’ve blinded the nasal portion of each retina  blind in peripheral portion of visual field 4) suppose MS or tumor pressing on that: only thing that’s going to be damaged due to these fibres being destroyed = temporal portion of right eye; left eye = perfectly normal -temporal portion of right eye sees things from the left so you’re blind in left portion of right eye 5) If you cut here at the right optic tract, person loses temporal portion of the right eye (can’t see on the left); also destroying crossing fibres coming in from the left eye (nasal portion of the left eye = can’t see anything on the left)  so info over there is blinded 6) Occipital Cortex: it’s almost same thing as cutting fibres at right tract  wind up not being able to see anything on the left hand side BUT there is a small circle in the middle where person can see = macular sparing = assume it has something to do w/ fibres passing through one cortex via corpus callosum -can tell where the damage is (don’t need to wait for MRI) by mapping person’s visual field (can tell whether optic nerve, optic tract, cortex and what side damage is at)  Functional organization: -the more central the neuron (ex: being in the cortex vs. the retina), aka the more advanced the area of the brain = the more complex image is excited -in the retina, a neuron responds to a spot of light falling on its receptive field (they don’t respond to hands, faces, cars etc;); neuron in area 17 (primary receptive area for vision in the occipital cortex) can decipher lines of light oriented in a specific direction; associational cortex gets info from various other neurons and integrate the info in a more complicated way, a neuron here is able to respond to something very complex (ex: specific face/hand) -goes higher and higher in order -by looking at what a person can and can’t do, can tell where the location of lesion is Damage to the Visual Cortex: -complete damage to
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