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psy 14 > lecture 7: vision > Flashcards

lecture 7: vision Flashcards

1
Q

The Visual System is composed of:

A
  • The problem of perception
  • Sensation: eye and photoreceptors
  • Pathways to the brain
  • Early visual coding: striate cortex – V1, simple cells
  • Later visual coding: extrastriate cortex
  • V2, V3, V4, V5 (MT)
  • What and Where pathways
  • Specialized Faces, Places, Body Parts, Objects
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2
Q

Optical illusions show:

A

perception of the world is dependent on the mind’s ability to transform incoming
information

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3
Q

Sensation

A

Translation of external information (light, sound,
touch, odor, taste) into neural codes
Perception:
The organization and interpretation of sensations
into a coherent percept of the world

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4
Q

Perception

A

The organization and interpretation of sensations
into a coherent percept of the world

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5
Q

how are sensation and perception related

A

Sensation constrains perception

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6
Q

where does vision begin

A

Vision begins at the eye with sensation

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7
Q

what is light

A

Light is electromagnetic energy
that travels in waveforms that
have intensity (brightness) and
wavelength (color)

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8
Q

Two Types of Receptors

A

rods and cones

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9
Q

RODS

A

high-sensitivity, but low-resolution vision (poor acuity),
no color (black & white), good for low-light conditions

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10
Q

CONES

A

good for high-resolution vision, and for color vision

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11
Q

visual angle

A

how far i am from the fovea at any given time

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12
Q

fovea

A

a small depression in the retina of the eye where visual acuity is highest. The center of the field of vision is focused in this region, where retinal cones are particularly concentrated.

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13
Q

retina

A

The retina is a layer of photoreceptors cells and glial cells within the eye that captures incoming photons and transmits them along neuronal pathways as both electrical and chemical signals for the brain to perceive a visual picture

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14
Q

blind spot

A

where the nerves leave your eye to form the optic nerve that goes to the brain

The blind spot function is the ability of the eye to see objects in its blind spot. This is because the eye has a blind spot in the back of the eye where the optic nerve enters the eye. This blind spot is about the size of a pea and is not visible to the eye. When an object is in the blind spot, the eye cannot see it

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15
Q

lens

A

light passes through the lens (a clear inner part of the eye). The lens works together with the cornea to focus light correctly on the retina

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16
Q

iris

A

The iris (the colored part of the eye) controls how much light the pupil lets in.

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17
Q

pupil

A

The pupil is the opening at the center of the iris through which light passes

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18
Q

cornea

A

The cornea is the clear window on the front of your eye. It’s made of tough, transparent tissue. Together with the sclera (white of your eye), the cornea helps protect your eye. It keeps out dirt, germs and other particles

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19
Q

optic nerve

A

The optic nerve is critical to your vision. It’s an extension of your central nervous system, which includes your brain and spine. The optic nerve transmits electrical impulses from your eyes to your brain. Your brain processes this sensory information so that you can see

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20
Q

Adaptation

A

there is a gradual decline in the reaction
to any stimulus if the stimulus persists unchanged.
Sensory systems respond more to change in
stimulation.

  • Occurs in all sensory systems, both in the sensory receptors
    and the brain
  • In color vision, sensitivity of cones to specific spectrums
    become saturated. Aftereffect of staring at one color is a
    temporary increased sensitivity to opponent (or
    complementary) color
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21
Q

retinal ganglion cells

A
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22
Q

bipolar cells

A
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23
Q

amacrine cells

A
24
Q

cone receptor cells

A
25
Q

rod receptor cells

A
26
Q

horizontal cells

A
27
Q

Visual Computations in the Eye

(what order are cells in the eye?)

A
28
Q

on-center RGC

A

bright in the center and dark in the
immediate surround elicits strongest increase in activity

29
Q

off-center RGC

A

dark in the center and bright in the
immediate surround elicits strongest increase in activity

30
Q

Retinogeniculate Visual Pathway

A

The retinogeniculate visual pathway (RGVP) conveys visual information from the retina to the lateral geniculate nucleus

31
Q

Left visual field
images are
communicated
to

A

right visual
cortex

32
Q

Right visual field
images are
communicated
to

A

left visual
cortex

33
Q

how does the visual system work

A

Your visual system is “cross wired”

When light hits the retina (a light-sensitive layer of tissue at the back of the eye), special cells called photoreceptors turn the light into electrical signals. These electrical signals travel from the retina through the optic nerve to the brain. Then the brain turns the signals into the images you see

34
Q

Optic chiasm

A

Think of this like an intersection. It’s where the nerves cross over, allowing your primary cortex to get information from both eyes.

the optic nerve fibers from the nasal halves of the retinas cross to the opposite sides, where they join the fibers from the opposite temporal retinas to form the optic tracts

35
Q

V1 simple cells respond to

A

respond to orientation or lines (edges)

Simple Cells are V1 neurons that respond to stimuli with particular orientations to objects within their receptive field. Like cells in the lateral geniculate nucleus (LGN), they have clear excitatory and inhibitory regions

36
Q

lateral geniculate nucleus

A

In neuroanatomy, the lateral geniculate nucleus (LGN; also called the lateral geniculate body or lateral geniculate complex) is a structure in the thalamus and a key component of the mammalian visual pathway. It is a small, ovoid, ventral projection of the thalamus where the thalamus connects with the optic nerve.

In mammals, the visual thalamus, the lateral geniculate nucleus (LGN), relays visual information from the retina to the primary visual cortex (V1) and also receives feedback from V1. Both retinal and cortical inputs are critical to processing visual information within the LGN.

37
Q

hubel and wiesel

A

Hubel and Wiesel concluded that such plasticity is limited to early life, and called this a ‘critical period’ of visual cortex development. The discovery of critical periods demonstrated how experience shapes the developing brain’s circuitry, thus perception of the external world

38
Q

retinotopic map

A

V1 has retinotopic map that codes for
simple visual features

39
Q

Blindsight

A

some ‘vision’ via a subcortical visual pathway

Blindsight is a phenomenon in which patients with damage in the primary visual cortex of the brain can tell where an object is although they claim they cannot see it. Scientists now provide compelling evidence that blindsight occurs because visual information is conveyed bypassing the primary visual cortex.

40
Q

Perception

A

Perception combines visual stimuli (bottom-up) and expectations (top-down)

41
Q

how do visual stimuli (bottom-up) and expectations (top-down) work together for the visual system

A

One “rule” the visual system seems to
use to arbitrate between possible
interpretations is to prefer the “non-
accidental view”
(the one that’s simplest, most probable,
as opposed to least probable).
How does the visual system solve this problem?

42
Q

When in visual processing do ‘top down’ processes
influence perception?

A

Attention to regions of space can alter
or enhance responding in V1 (and even LGN), but the response properties are the same

43
Q

how does v2 work

A

V2 shows responses to ‘illusory’ lines:

V2, like V1, responds to lines and edges and has a retinotopic map,
but it also responds to ‘illusory’ lines,
suggesting it combines input from V1 and higher order cortical areas coding for expectations
based on experience

V2 (and V3) have dorsal and ventral
components, after which the visual
pathways split

44
Q

what pathway

A

(temporal lobe)

The occipital-temporal visual area refers to the ventral or “what” pathway, where your brain recognizes objects and shapes. The temporal areas provide your long-term visual memories, helping them to recall what they’ve seen before and attach meaning to it. (For example, once you’ve seen a baseball, you know what it is next time you come across one!)

Ventral damage can cause:

Impairments in contrast sensitivity, form and color vision, and depth perception
Impairments in object and face perception and route-finding

45
Q

where pathway

A

(parietal lobe)

The occipital-parietal visual area refers to the beginning of the dorsal or “where” pathway. Here, your child’s brain assesses where things are in space, like a ball zooming across a field or a puppy running toward a lap. Dorsal damage can cause: Trouble with spatial perception and perception of complex movement.

46
Q

Akinetopsia

A

Impaired motion perception due to cortical damage.

47
Q

Achromatopsia

A

Impaired color perception due to cortical damage.
Different from peripheral color blindness due to
absence of certain photoreceptors

48
Q

How does activation vary as a function of stimulus properties?

A

Color vs. Motion

49
Q

hemiachromatopsia

A

Hemiachromatopsia is defined as a disorder of impaired color perception with relative preservation of form vision in one-half of the visual field.

50
Q

what does color vision depend on

A

Depends on wavelength (cones)
and luminance (or presumed luminance)

51
Q

Color Constancy & Luminance:
the “non-accidental view”

A

Color constancy refers to our ability to perceive colors as relatively constant over varying illuminations (i.e. light sources). For example, a red apple will still look red on a sunny day or cloudy day – or in a grocery store or a home

52
Q

v5

A

codes for direction of motion

53
Q

Fusiform Face Area (FFA)

A

The fusiform face area (FFA) is a region of the cortex in the inferior temporal lobe of the brain that has been shown to respond most strongly to faces compared with other types of input (e.g., objects) for typically developing individuals.

54
Q

parahippocampal place area or PPA

A

The parahippocampal place area (PPA) is a functional region of the brain that responds more strongly to images of scenes and places compared to other classes of visual stimuli and is critical for scene and place recognition, as well as navigation

55
Q

Prosopagnosia

A

(“face agnosia”)

Prosopagnosia (also known as face blindness or facial agnosia) is a neurological disorder characterized by the inability to recognize faces

-Sometimes following
damage to fusiform area

-sometimes congenital
(from birth; runs in families)

56
Q

ffa vs ppa

A

psy 14 (21 decks)

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