Vision

Front 1

Sensory receptors

Back 1

specialized neuron that detects a particular category of physical events

Front 2

*Sensory transduction

Back 2

process by which sensory stimuli are transduced into slow, graded receptor potentials

Front 3

Receptor potential

Back 3

slow, graded electrical potential produced by a receptor cell in response to a physical stimulus

Front 4

Vision stimulus

Back 4

eyes detect the presence of light; electromagnetic radiation wavelength 380-760 nm is visible to humans

Front 5

Wavelength

Back 5

distance between waves; perception of color

Front 6

Intensity

Back 6

how strong is the wave; perception of brightness

Front 7

*Hue

Back 7

dominant wavelength, longer = more red, shorter= more blue

Front 8

*Brightness

Back 8

intensity; more intense= brighter color

Front 9

*Saturation

Back 9

purity; how many wavelengths are mixed together (e.g. all wavelengths= no hue sensation, appears white)

Front 10

3 types of eye movements

Back 10

vergence movement, saccadic movement, pursuit movement

Front 11

Vergence movement

Back 11

cooperative movement of the eyes; ensures that image of an object falls on identical portions of both retinas

Front 12

Saccadic movements

Back 12

rapid, jerky movements of the eyes used in scanning a visual scene

Front 13

Pursuit movement

Back 13

the movement the eyes make to maintain an image of a moving object on the fovea

Front 14

Sclera

Back 14

white outer coat of the eye; does not permit in light

Front 15

Orbits

Back 15

bony pockets in front of skull

Front 16

Conjunctiva

Back 16

mucous membranes that line the eye and fold back to attach the eye

Front 17

Extraocular muscles

Back 17

movement of the eyes

Front 18

Iris

Back 18

regulates amount of light that reaches the retina; contractile tissue, donut shaped, give eyes color

Front 19

*Pupil

Back 19

how light enters the eye; hole in iris, size responds to changes in illumination, compromise between sensitivity (detect presence of dimly lit objects) and acuity (ability to see details of objects)

Front 20

*High illumination

Back 20

sensitivity is not important, pupils constrict, sharper image, greater depth of focus

Front 21

*Low illumination

Back 21

receptors are activated successfully, pupils dilate to let more light in, worse acuity and depth of focus

Front 22

Lens

Back 22

behind the pupil, focuses incoming light on the retina, direct attention to something near

Front 23

Ciliary muscles

Back 23

contract- reduce tension on ligaments holding lens, helps the lens refract (bend) light, brings close objects into focus

Front 24

Accommodation

Back 24

process of bringing images into focus on the retina

Front 25

Convergence

Back 25

eyes move so that a point is projected to corresponding points on both retinas

Front 26

Binocular (retinal) disparity

Back 26

the difference in position of the same image on the 2 retinas, cocktail sausage illusion

Front 27

Vision process

Back 27

light passes through lens, goes through vitreous humor (clear glassy liquid), falls on retina

Front 28

*Retina

Back 28

interior lining of back of the eye, location of photoreceptors (rods and cones)

Front 29

*Macula

Back 29

center of retina

Front 30

*Fovea

Back 30

central portion of macula; region for acute vision, only contains cones (equal number of ganglion cells and cones); central vision

Front 31

*Cones

Back 31

6 million in retina, day time vision, small features, high acuity, color vision

Front 32

Visual distortion

Back 32

see wavy words, letters are distorted as in a funhouse mirror= damage to retina

Front 33

*Come and go vision

Back 33

small areas of vision loss that come and go= macular degeneration

Front 34

Better night vision

Back 34

rod cells are unaffected by macular degeneration, located in the peripheral retina and used in lower levels of light

Front 35

Peripheral vision sensitivity

Back 35

can see a speck of dirt on the floor, cannot recognize faces, damage to central retina impairs vision straight ahead but can use peripheral vision

Front 36

*Rods

Back 36

120 million in retina, more sensitive to light, used in dim light, color blind and lack foveal vision in dim light

Front 37

Optic disc

Back 37

location of exit point from retina of fibers of ganglion cells that form the optic nerve; responsible for the blind spot, no receptors there

Front 38

*Blindspot

Back 38

gap in the receptor layer where axons leave the eye

Front 39

Completion (vision)

Back 39

visual system uses info from receptors to fill in gaps in retina

Front 40

Layers of retina

Back 40

photoreceptors form synapses with bipolar cells; bipolar cells form synapses with ganglion cells, ganglion cells axons go through optic nerve to brain

Front 41

Horizontal and Amacrine cells

Back 41

combine messages from photoreceptors, responsible for lateral communication

Front 42

Transduction

Back 42

photopigments responsible for transduction, special molecules in photoreceptor lamellae (membrane)- Opsin (protein), retinal (lipid derived from vitamin A)

Front 43

Rhodopsin

Back 43

found in rods, pinkish hue, exposure to light breaks it into two component parts: rod (red) opsin and retinal, splitting causes change in membrane potential of photoreceptor, changes release rate of glutamate

Front 44

Hyperpolarization of photoreceptor

Back 44

-> depolarization of bipolar cells -> excitation of ganglion cells

Front 45

Dorsal lateral geniculate nucleus (LGN)

Back 45

thalamus; contains 6 layers of neurons, receives input from only one eye, cell bodies of inner 2 layers are larger than outer 4 layers

Front 46

*Magnocellular layers

Back 46

inner two layers of LGN (rods)

Front 47

*Parvocellular layers

Back 47

outer 4 layers in LGN (cones)

Front 48

Koniocellular sublayers

Back 48

ventral to each of the magno and parvo layers

Front 49

Optic nerve

Back 49

nerves join at base of brain to form optic chiasm

Front 50

*Optic chiasm

Back 50

x-shaped, joining of optic nerves

Front 51

*Vision through optic chiasm

Back 51

ganglion cell axons from inner half of retina (nasal), cross through the chiasm, ascend to contralateral LGN, ganglion cell axons from outer half of reina (temporal) remain on ipsilateral side= info from both eyes goes to both sides of the brain; image of the world on the retina is inverted

Front 52

Meyers loop

Back 52

axons from LGN go to primary visual cortex via optic radiations

Front 53

*Primary visual cortex

Back 53

V1; region surrounding the calcarine (spur shaped) fissue; also called striate cortex bc of dark striations (layers of cells); nerve fibers carry info from V1 to extrastriate areas (V2, V3, V4, and V5, MT (middle temporal))

Front 54

*Blindsight

Back 54

after damage to V1, some patients have the ability to respond to visual stimuli while reporting not seeing (e.g. person who is blind can walk through a room and avoid objects in the way, but can't report seeing them)

Front 55

*Receptive field

Back 55

portion of the visual field in which the presentation of visual stimuli will not produce an alteration in the firing rate of a particular neuron; part of visual field a neuron 'sees'; use microelectrodes to investigage individual neurons in receptive field; if neuron receives info in fovea= fixation point, periphery of retina= off to one side

Front 56

Periphery of retina

Back 56

many receptors converge on a simple ganglion cell, brings info from large area of retina and large part of visual field; peripheral vision not very precise

Front 57

*3 types of ganglion cells

Back 57

(Hartline, 1938, frog retina)

On cells- excitatory, burst when retina illuminated

Off cells- respond when light is off

On/Off cells- respond when light goes on and again when light goes off

Front 58

*Form of ganglion cells

Back 58

(Kuffler, 1952-3, cat retina)

receptive field is a circle surrounded by a ring

On cells- excited by light in center, inhibited by light in surround

Off cells- opposite

On/Off cells- briefly excited when light turned on or off

Front 59

Rebound effect

Back 59

neurons that are inhibited when light is on, have burst of excitement when light goes off and vice versa

Front 60

Center surround

Back 60

good for seeing edges (contrasts), detect outlines even when contrast between items is low; visual system adds borders

Front 61

Additive effects of color mixing

Back 61

mixing colors of light= white; mixing colors of paint= brown/gray

Front 62

Photopigment

Back 62

special molecule embedded in lamallae, 2 parts: opsin and retinal; different opsins absorb different wavelengths

Front 63

*Photoreceptors for cones

Back 63

3 types: blue, green, red; based on amount of light absorbed by photopigment

Front 64

Genetic defects in color vision

Back 64

result from problems in one or more of the 3 types of cones; 2 involve genes on the x chromosome= more common in men, females have a normal gene on the other x chromosome to compensate

Front 65

Protanopia

Back 65

red and green hues confused; see world in shades of blue and yellow; red and green appear yellowish; visual acuity is normal- correct number of cones, red cones are filled with green cone opsin

Front 66

Deuteranopia

Back 66

red and green confused; visual acuity is normal, correct number of cones; green cones filled with red opsin

Front 67

Tritanopia

Back 67

not on x chromosome ( = likely for male and female)

rate, hues with short wavelengths are confused, see world in reds and greens; clear blue sky is bright green, yellow looks pink; blue cones lacking or faulty

Front 68

Negative afterimage

Back 68

image seen after a portion of retina is exposed to an intense visual stimulus, consists of colors complementary to those of the physical stimulus

Front 69

Complimentary colors

Back 69

colors that make white or grey when mixed together (e.g. red/green, yellow/violet, blue/orange)

Front 70

Striate cortex

Back 70

V1, contains dark staining layer, 6 layers, contain nuclei of cell bodies and dendritic trees; 25% analyzes foveal info, neurons in visual cortex respond selectively to specific features

Front 71

Hubel & Weisel

Back 71

Nobel prize winners; described neurons in V1, studied in cats

Front 72

*Simple cell

Back 72

receptive field is organized in an opponent fashion; respond best to bars of light of a particular orientation

Front 73

*Complex cell

Back 73

responds to the presence of a line segment with a particular orientation located within its receptive field, especially when line moves perpendicular to its orientation; detects movement

Front 74

*Hypercomplex cell

Back 74

responds to the presence of a line segment with a particular orientation that ends at a particular point within the cells receptive field

Front 75

Sine wave grating

Back 75

a series of straight parallel bands varying continuously in brightness according to a sine wave function, along a line perpendicular to their lengths; fuzzy, unfocused parallel bars

Front 76

Spatial frequency

Back 76

the relative width of the bands in a sine wave grating

Front 77

*Neurons in V1

Back 77

respond to orientation, movement, spatial frequency, retinal disparity, color

Front 78

Visual association cortex

Back 78

where info is received, combined, and analyzed; receives fibers from striate cortex and the superior colliculi-> projects to the inferior temporal cortex

Front 79

*Dorsal stream (vision)

Back 79

system of interconnected regions of visual cortex involved in perception of spatial location; begins in striate cortex, ends in posterior parietal cortex; "where" pathway, guides action

Front 80

*Ventral stream (vision)

Back 80

System of interconnected regions of visual cortex involved in perception of form, begins in striate cortex, ends in inferior temporal cortex; "what" pathway

Front 81

Parvo and Konio cellular system

Back 81

only found in primates

Front 82

*Parvocellular system

Back 82

receives info about wavelength from cones- analyze color; high spatial resolution, low temporal resolution; detect fine details but response is slow and prolonged

Front 83

*Magnocellular system

Back 83

found in all mammals; color-blind, does not detect fine detail, can detect small differences between light and dark, sensitive to movement

Front 84

*V4

Back 84

Zeki (1980); responds to color; regulates color constancy: relatively constant appearance of colors of objects viewed under varying light conditions, visual system compensates for source of light, not strictly a response based on the wavelength of the light reflected

Front 85

Cerebral achromatopsia

Back 85

inability to discriminate among different hues; caused by damage to area V8

Front 86

Visual agnosia

Back 86

deficits in visual perception in the absence of blindness; caused by brain damage

Front 87

Apperceptive visual agnosia

Back 87

failure to perceive objects, failure in high level perception, visual acuity is relatively normal (e.g. can't identify object without touching it); cannot copy

Front 88

Associative visual agnosia

Back 88

inability to identify objects that are perceived visually, disconnect between the perceptions and visual systems, form of perceived object can be drawn or matched with similar objects (can be copied)

Front 89

Prosopagnosia

Back 89

failure to recognize particular people by the site of their faces

Front 90

Object agnosia

Back 90

failure to recognize objects

Front 91

*Fusiform face area

Back 91

FFA; region of visual association cortex located in inferior temporal cortex (ventral stream); involved in perception of faces and other complex objects that require expertise to recognize

Front 92

Extrastriate body area

Back 92

EBA; region of visual association cortex located in lateral occipitotemporal cortex; involved in perception of the human body and body parts other than faces

Front 93

Parahippocampal place area

Back 93

PPA; region of medial temporal cortex; involved in perception of particular places (scenes)

Front 94

*Experience dependent plasticity

Back 94

integration of environmental stimuli into the normal patterns of development- more activity to stimuli have more experience with

Front 95

V5 (MT)

Back 95

responds to movement; receives input directly from striate cortex and several regions of extrastriate cortex; neurons in V5 respond much faster than those in V4

Front 96

Akinetopsia

Back 96

inability to perceive movement, caused by damage to area V5 (also called MST) of visual association cortex

Front 97

Optic ataxia

Back 97

difficulty in reaching for objects under visual guidance; can see it and recognize it but can't reach it

Front 98

Ocular apraxia

Back 98

inability to fixate on certain points in the peripheral visual field despite intact eye movements

Front 99

Simultanagnosia

Back 99

difficulty in perceiving more than one object at a time; even if you cross two items, subject only sees one

Front 100

Balint's syndrome

Back 100

syndrome caused by damage to parieto-occipital region (i.e. dorsal stream), includes optic ataxia, ocular apraxia, and simultanagnosia

Front 101

Intraparietal sulcus

Back 101

IPS; end of the dorsal stream of the visual association cortex, involved in perception of location, visual attention, control of eye and hand movements