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Psych 3 > Vision (Lecture 5) > Flashcards

Vision (Lecture 5) Flashcards

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1
Q

vision pathway

A

light enters through the pupil and reaches the retina, the cornea refracts light onto the fovea (center of the retina with highest acuity)

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2
Q

equivalent of light

A

waves of photons

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3
Q

Photons

A

-emitted with different energies resulting in different wavelength and different quantities resulting in different amplitudes of waves

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4
Q

Visible Light Spectrum

A
  • we only see (380-760nm)

- we perceive different wavelengths as different colors which is a creative process of the brain

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5
Q

light enters they eye through….

A

the pupil

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6
Q

lens

A

attached to ciliary muscles, important for contraction and reflection of light to the back of the eye

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7
Q

cornea

A

-refracts the light onto the fovea

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8
Q

ciliary muscle

A
  • contort lens to focus on fovea
  • far objects —> relax ciliary muscles
  • close objects —> contract cilary muscles –> fat lens
  • this is ACCOMMODATION
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9
Q

fovea

A
  • center of the retina with highest acuity (ability to see details)
  • focuses objects in center of visual field
  • CONES ONLY
  • thinning of ganglion cell layer reduces distortion
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10
Q

emmetropia

A

PERFECT??

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11
Q

hyperopia

A

images appear behind the retina, farsightedness

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12
Q

hyperopia correction

A

-convex lens

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13
Q

myopia

A

images appear before the retina, nearsightedness

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14
Q

myopia correction

A

-convave lens

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15
Q

convergence

A

-eyes must turn slightly inward when objects are close

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16
Q

binocular disparity

A

difference between the images on the two retinas = 3D vision

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17
Q

RETINA

A

thin strip of tissue (contains the fovea) along the back of the eye where light is converted to neural signals that can be sent to the brain through the optic nerve (blind spot)

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18
Q

blind spot

A

areas of no photoreceptors in the retina

  • located at the optic disk
  • completion
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19
Q

optic disk

A

-where axons of retinal ganglion cells gather together and leave the eyeball (optic nerve)

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20
Q

ganglion cells

A

-primary visual neurons

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21
Q

optic nerve

A

projects to brain

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22
Q

horizontal, bipolar, and Amacrine cells

A

-process info from rods and cones

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23
Q

photoreceptors

A

-rods and cones
-detect light
-contain light sensing photopigments in discs within their outer segments
middle (cell body), and synaptic ending-makes contact with bipolar cells

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24
Q

lateral communication

A

the synaptic points
(amacrine cell between ganglion and bipolar)
(horizontal cell between photoreceptors and bipolar)

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25
Q

ganglion cell axons

A

-project to forebrain

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26
Q

rods

A
  • scotopic (nighttime vision)
  • high-sensitivity to light because more photopigment (larger outer segment) allowing for low-acuity vision in dim light, but lacks detail and color information
  • only one type
  • in bright daylight rods are saturated and the cell can not be further hyper polarized
27
Q

cones

A
  • photopic (daytime) vision
  • high acuity color information in good lighting
  • different opsin proteins that are differentially activated by specific wavelengths of light
28
Q

rods ratio

A

-many:1 ratio with retinal ganglion cells

29
Q

Why do rods and cones differ in sensitivity and acuity?

A
  1. differences in amount of light sensing photopigments

2. convergence

30
Q

cones ratio

A

-1:1 ratio with retinal ganglion cells

31
Q

less of a light signal (dim/fewer photons)=

A
  • greater change of exciting a rod-fed ganglion cell = greater sensitivity
  • ganglion cell carries less information about where photons were revieced = less acuity
32
Q

visual transduction

A

conversion of light to neural signals by photoreceptors

33
Q

in dark the cell is depolarized and releases….

A

glutamate

34
Q

light causes cell to hyper polarize glutamate….

A

-rate of release is reduced

35
Q

lack of light (pathway)

A
  1. second messenger (cGMP) na+ channels open
  2. cell is depolarized
  3. glutamate is being released
36
Q

optic nerve

A

-formed by asons of ganglion cells

37
Q

optic chiasm

A
  • the part of the brain where the optic nerves partially cross (located at the bottom of the brain below the hypothalamus)
  • where part of image crosses over to opposite side
38
Q

optic tract

A

continuation of the optic nerve and runs from the optic chiasm to the lateral geniculate nucleus

39
Q

visual fields

A
  • travel to contralateral(opposite) cortex
  • fields are not defined by the eyes; cortex recieves info from ipsilateral (same side) and contralateral (opposite side) eye
40
Q

retina-geniculate-striate system

A

-90% of axons of retinal ganglion cells

information received at adjacent portions of the retina remains adjacent = retinotopic

41
Q

lateral geniculate body/nucleus (thalamus/LGN)

A
  • thalamic relay center nucleus that deals with visual information
  • asons from retinal ganglion cells synapse on other neurons here
42
Q

P(parvocelluar) layers

A
  • small cell bodies
  • color and fine details
  • stationary objects
  • input from cones
43
Q

M(magnocellular) layers

A
  • large cell bodies
  • detect movement
  • primary input from rods
44
Q

do retinal cell project anywhere else?

A

-some axons from the optic nerve go out of main pathway and relay into the hypothalmus(important fro sleep/wake cycle) and superior colliculus (orientation reflex)

45
Q

primary visual cortex (occipital lobe)

A
  • V1
  • brodmann’s Area 17
  • Striate Cortex
  • axons from LGN (M?P cells) terminate in layer 4 of V1
  • info arriving in layer 4 remains segregated(i.e. is either from one eye or the other) until it travels to other cortical layers for further processing
  • most neurons in V1 are either simple or complex
46
Q

Hubel and Wiesel (1979)

A

-mapped receptive fields of retinal ganglion cell, LGN cells, and layer 4 V1 cells

47
Q

receptive field

A

-area in visual field within which it is possible for a visual stimulus to influence that neurons firing

48
Q

receptive field of foveal areas vs periphery

A

foveal areas are smaller than those in periphery (due to convergence)

49
Q

neurons receptive fields

A
  • circular in shape
  • neurons are monocular
  • many neurons at each level had receptive fields with excitatory and inhibitory area
50
Q

center-surrounded receptive fields

A

-bipolar and retinal ganglion cells and neurons in V1 layer 4

51
Q

on-center (off-surround)

A
  • cells fire more when light is in center of receptive field

- firing it inhibited when light is shone in surrounding receptive field

52
Q

off-center (on-surround)

A
  • cells fire more when light is shone in surround

- firing is inhibited when light is shone in center of receptive field

53
Q

lateral inhibition

A
  • capacity of excited neuron to reduce the activity of its neighbors
  • used in vision to sharpen signals to the brain, it increases the contrast and sharpness in visual response
54
Q

simple visual cortex receptive fields

A

-rectangular
-on and off regions (like cells in layer IV)
-orientation and location sensitive
all are monocular

55
Q

complex visual cortex receptive fields

A

-rectangular
-do not have static on and off regions
not location sensitive
-motion sensitive
-many are binocular
larger receptive fields

56
Q

secondary visual cortex

A

-association cortex

57
Q

dorsal steam

A
  • “how” pathway
  • processing objects spatial location
  • specialized for motion
  • “where” stimuli are for the “control of behavior”
58
Q

ventral steam

A
  • specialized for attributes

- “what” stimuli are for “conscious perception”

59
Q

posterior parietal cortex (dorsal stream)

A
  • cells selective for linear motion, radial motion, or circular motion
  • brain lesion in this area–>
60
Q

inferior temporal lobe (ventral steam)

A
  • cells are orientation selective and color selective
  • important for shape and color perception
  • what would happen if you sustain a brain lesion in this area???
61
Q

fusiform face area

A
  • specialized face recognition circuit

- shows enhanced activation in fMRI when subjects shown faces as opposed to other shapes

62
Q

prosopagnosia

A
  • damage to fusion face areas

- damage to other object recognition areas but no FFA results in recognition of face and not other objects

63
Q

retinotropic

A

mapping of visual information from retina to neurons within the visual system

Psych 3 (13 decks)

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