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Flashcards in Chapter 9 Deck (157):
1

Scotoma

small blind spot

2

Are we consciously aware of everything we see?

no. we are only aware of part of the visual information our brain is processing

3

Sensory receptors

specialized cells that transduce (convert) sensory energy into neural activity

4

Do sensory receptors respond to all sensory energy?

nope. they respond only to a narrow band of energy within each modality's energy spectrum

5

Vision

light energy is concerted into chemical energy in the photoreceptors of the retina and the chemical energy is concerted into action potentials

6

Auditory System

air-pressure waves are converted first into mechanical energy, which activates the auditory receptors that produce action potentials

7

Somatosensory system

mechanical energy activates receptor cells that are sensitive to touch, pressure or pain. Somatosensory receptors in turn generate action potentials

8

Taste and Olfaction

various chemical molecules carried by the air or contained in food fit themselves into receptors of various shapes to activate action potentials

9

Human sensory abilities

are average

10

Receptive field

region of the visual world that stimulates a receptor cell or neuron

11

Photoreceptor cells

in the eye; each one points in a slightly different direction and thus has a unique receptive field

12

What does the brain do with receptive fields

identify sensory information, contrast information from each receptor field, help locate sensory events in space

13

Optic flow

streaming of visual stimuli that accompanies an observer's forward movement through space

14

Auditory Flow

change in sound heard as a person moves past a sound source or asa sound source moves past a person

15

Usefulness of auditory and optic flow

tell us how fast we are going, whether we are moving or if the world is moving, what direction (straight, up, down) we are moving

16

Receptor density

determines the sensitivity of a sensory system

17

Color photoreceptors

small, densely packed to make sensitive color discrimination in bright light

18

black-white vision receptors

larger, more scattered, extremely sensitive to light

19

neural relays

all receptors connect to the cortex through a sequence of 3-4 intervening neurons; can modify information at different stages --> sensory system can mediate different responses

20

Location of relays

varies, some in brainstem, spinal cord, neocortex

21

Layers of neural relays

at each level a relay allows a sensory system to produce relevant actions that define the hierarchy of our motor behavior

22

Perceptions of speech sounds

influenced by the facial gestures of a speaker

23

Sensory coding

all sensory info from all systems is encoded by action potentials that travel along peripheral nerves in the somatic nervous system until they enter the spinal cord or brain and from there on nerve tracts within the CNS

24

How do we differentiate sensations?

different sensations are processed at distinct regions of cortex; learn through experience to distinguish them; each sensory system has a preferential link with certain kinds of reflex movements

25

synesthesia

mixing of the senses

26

topographic map

spatially organized neural representation of the external world

27

How many primary cortical areas do mammals have for each sensory system?

at least 1

28

Sensation

registration of physical stimuli from the environment by the sensory organs

29

perception

subjective interpretation of sensations by the brain

30

What sense does the brain devote most to?

vision

31

Retina

light-sensitive surface at the back of the back of the eye consisting of neurons and photoreceptor cells; initiates neural activity

32

how does light travel into the eye?

light--> pupil --> eye--> retina at the back of the eye

33

photoreceptor

specialized type of retinal cell that transduces light into neural activitiy

34

what do the photoreceptor cells and the retina do?

translate light into action potentials, discriminate wavelengths so we can see colors, work in a range of light intensities

35

how do images appear on the retina?

upside down and backward

36

what wavelengths can we see?

400-700 nanometers; shortest are deep purple, longest red

37

how is the electromagnetic wavelength measured?

nanometers

38

sclera

forms the eyeball; the white of the eye

39

cornea

eye's clear outer covering

40

iris

colored part; opens and closes to allow more or less light through a hole

41

pupil

hole

42

lens

focuses light

43

fovea

center of the retina; region of sharpest vision and has the densest distribution of photoreceptors specialized for color

44

optic disc

where blood vessels enter the eye and the axons that form the optic nerve leave the eye; has no receptors and thus forms the blind spot; conveys information from the eye to the brain

45

blind spot

region of the retina (the optic disc) where axons forming the optic nerve leave the eye and where blood vessels enter and leave; has no photoreceptors= blind

46

cornea & lens

both bend the light coming into the eye

47

normal vision

the lens focuses incoming light directly on the retina

48

myopia

can't bring distant objects into clear focus because the focal point of light falls short of the retina; caused by round eyeball--> elongated or excessive curvature of the front of the cornea

49

hyperopia

can't focus on nearby objects because the focal point of light falls beyond the retina; eyeball may be too short or the lens too flat

50

periphery

vision is not as good as in the center

51

papilloedema

swollen disc

52

optic neuritis

inflammation of the optic nerve

53

rod

photoreceptor specialized for functioning at low light levels; cylindrically shaped at one end, longer, more numerous

54

cone

photoreceptor specialized for color and high visual acuity; tapered at one end, shorter, not sensitive to dim light, less numerous

55

what happens when light strikes a photoreceptor?

it triggers a series of chemical reactions that lead to a change in the membrane potential (electrical charge) that leads to a change in the release of neurotransmitters onto nearby neurons

56

are rods and cones evenly distributed?

no; fovea only has cones, but cone density drops dramatically beyond the fovea

57

how many cone pigments are there?

3; each cone has one

58

how many total pigments do we have?

4; 3 from cones and 1 from rods

59

what do cone pigments respond to?

a range of frequencies

60

How are cones distributed?

randomly across the retina--> color perception constant across visual field

61

Red cone

gene carried in x chromosome

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what do photoreceptors connect to?

connected to two layers of retinal neurons

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first retinal layers

contains three types of cells (bipolar, horizontal, amacrine)

64

horizontal cells

link photoreceptors with bipolar cells

65

amacrine cells

link bipolar cells with the cells of the second neural layer

66

what is the second neural layer?

retinal ganglion cells

67

retinal ganglion cells

type of retinal neurons with axons that bundle at the optic disc and leave the eye to form the optic nerve

68

magnocellular (M) cell

large-celled visual-system neuron that is sensitive to moving; input from rods, sensitive to light not color

69

parvocellular (P) cell

small-celled visual-system neuron that is sensitive to form and color differences; input from cones, sensitive to color

70

Optic chiasm

junction of the optic nerve, one from each eye, at which the axons from the nasal (inside--nearer the nose) halves of the retinas cross to the opposite side of the brain

71

Do the fibers from the optic nerve enter the same side of the brain?

the left half of each optic nerve goes to the left side of the brain and the right half goes to the brain's right side

72

nasal retina

the medial path of each retina crosses to the opposite side

73

temporal retina

lateral path, goes straight back on the same side

74

Geniculostriate system

projections from the retina to the lateral geniculate nucleus to the visual cortex; formed by all of the P ganglion cell axons and some M ganglion cells

75

striate cortex

primary visual cortex (V1) is in the occipital lobe; its striped appearance when stained gives it this name

76

tectopulvinar system

projections from the retina to the superior colliculus to the pulvinar (thalamus) to the parietal and temporal visual areas; eye-->tectum--> pulvinar

77

retinohypothalamic tract

neural route formed by axons of photosensitive retinal ganglion cells from the retina to the suprachiasmatic nucleus; allows light to entrain the rhythmic activity of the SCN; third visual pathway

78

are retinal ganglion cells photosensitive?

1-3% act as photoreceptors

79

role of photosensitive retinal ganglion cells

regulating circadian rhythms; pupillars reflex

80

Visual pathways

striate cortex--> temporal lobe (ventral stream) OR parietal lobe (dorsal stream)

81

Lateral geniculate nucleus (LGN)

in the thalamus; has 6 layers; projections from the two eyes go to different layers

82

Layers 2, 3, 5 of LGN

receive fibers from the ipsilateral eye

83

Layers 1, 4, 6 of LGN

receive fibers from the contralateral eye

84

Where do axons from P cells go?

layers 3-6 (parvocellular layers); process color/form

85

Where do axons from M cells go?

laters 1 and 2 (magnocellular layers); process information about movement

86

cortical column

cortical organization that represents a functional unit six cortical layers deep and approximately .5 mm square and that is perpendicular to the cortical surface

87

what makes up the tectopulvinar pathway?

remaining M cells; send their axons to superior colliculus (tectum)

88

tectum

produce orienting movements--detect the location of stimuli and shift the eyes toward stimuli

89

where does the superior colliculus send information?

region of the thalamus called the pulvinar

90

Pulvinar

two divisions; medial pulvinar (sends connections to the parietal lobe) and lateral pulvinar (sends connections to the temporal lobe)---> "Where" function

91

occipital lobe

composed of at least 6 different visual regions: V1, V2, V3, V3A, V4, V5

92

V1

striate cortex; is the primary visual cortex

93

extrastriate cortex

remaining visual areas (outside striate) of the occipital lobe; secondary visual cortex

94

primary visual cortex (V1)

striate cortex that receives input from the lateral geniculate nucleus

95

blob

region in the visual field that contains color-sensitive neurons, as revealed by staining for cytochrome oxidase

96

neurons in blobs

take part in color perceptions

97

neurons in interblobs

participate in form and motion perception

98

what happens when info arrives at V1?

info arrives from the p-cell and m-cell pathways of the geniculostriate system and is segregated into types of info (color, form, motion)

99

what happens when information in V1 is broken down by type?

goes from region V1 to V2--inputs remain segregated

100

what happens in V2?

thick strips and pale zones receive the segregated input

101

what happens after V2?

pathways proceed to other occipital regions and then to the parietal and temporal lobes

102

ventral and dorsal streams

simple records of color, form, and motion are assembled

103

fusiform face area (FFA)

part of temporal lobe; specialized for recognizing faces

104

parahippocampal place area (PPA)

part of temporal lobe; analyzes landmarks

105

lateral intraparietal area (LIP)

part of parietal lobe; related to eye movements

106

anterior intraparieta area (AIP)

part of parietal lobe; visual control of grasping

107

facial agnosia

prosopagnosia; damage to FFA; face blindness--the inability to recognize faces

108

visual field

region of the visual world that is seen by the eyes

109

where does information from visual fields go?

input from right visual field goes to the left hemisphere, etc.; brain can easily determine whether visual information is located to the left or right

110

how do retinal ganglion cells receive information?

bipolar cells from several photoreceptors

111

ganglion cell's receptive field

the region of the retina on which it is possible to influence that cell's firing

112

where on the retina does light hit?

light from bottom (hits top); light from top (hits bottom)

113

LGN

each LGN cell has a receptive field--region of the retina that influences its activity. if two adjacent retinal ganglion cells synapse on a single LGN cell, the receptive field of the LGN cell will be the sum of the two ganglion cell's receptive fields

114

does the LGN projection to the striate cortex (V1) maintain spatial info?

yes

115

receptive field in cortex

cells in the cortex have much larger receptive fields than those of retinal ganglion cells

116

Jerison's Principle of Proper Mass

sates that the amount of neural tissue responsible for a particular function is equivalent to the amount of neural processing required for that function

117

relationship between sensory areas and cortical representation

sensory areas that have more cortical representation provide a more-detailed creation of the external world

118

Cells along the midline

look at adjacent places in the visual field; collosal connections between such cells zip the two visual fields together by combing their receptive fields to overlap at the midline. the two fields become 1

119

excitation and inhibition

the same cell may react differently depending on the stimulus; response is selective

120

neurons in the retina

do not respond to shape--> only light

121

retinal ganglion cells

a spot of light falling in the central circle of the receptive field excites some of the cells; light falling in the periphery inhibits cell; light falling across the entire field weakly increases firing rate

122

on-center cells

retinal ganglion cells that are excited by light falling in the center

123

off-center cells

retinal ganglion cells that are excited by light falling in the periphery

124

luminance contrast

the amount of light reflected by an object relative to its surroundings

125

what do V1 cells respond to?

they are maximally excited by bars of light oriented in a particular direction rathe than by spots of light; are orientation detectors; their on/off receptive field is rectangular

126

simple cells

visual cortex cells that have a rectangular receptive field

127

hpercomplex cell

maximally responsive to moving bars but also has a strong inhibitory area at one end of its receptive field

128

complex cell

maximally excited by bars of light moving in a particular direction through a visual field

129

ocular-dominance column

functional column in the visual cortex maximally responsive to information coming from one eye

130

processing shape in temporal cortex

TE neurons; maximally excited by complex visual stimuli, such as faces or hands, and can be remarkably specific in their responsiveness

131

TE neurons

responds to complex features: has a combination of orientation, size, color, texture

132

how are objects represented?

by activity of many neurons with slightly varying stimulus specificity; these neurons are grouped together into a column

133

stimulus equivalence

recognizing an object as remaining the same despite being viewed from different orientations

134

Temporal lobe's role in visual processing

not determined genetically but is subject to experience

135

neurons in Primary visual cortex

are not modified by experience--> genetically programmed

136

primary colors or light

red, blue, green

137

impression of colors

light of different wavelengths stimulates the three different cone receptor types in different ways--> the ratio of this activity of these receptor types creates our impression of colors

138

trichromatic theory

explanation of color vision based on the coding of three primary colors: red, green, and blue

139

what happens if all cones are equally active?

we see white

140

what does the trichromatic theory predict?

if we lack one type of cone receptor we cannot process as many colors as we could with all three

141

protanopia

lack of red cones

142

deuteranopia

lack of green cones

143

tritanopia

lack of blue cones

144

opponent process

explanation of color vision that emphasizes the importance of the apparently opposing pairs of colors: red versus green, blue versus yellow

145

color constancy

phenomenon whereby the perceived color of an object tends to remain constant relative to other colors, regardless of changes in illumination

146

homonymous hemianopia

blindness of an entire left or right visual field; caused by cuts in optic tract, LGN or V1

147

quadrantanopia

blindness of one quadrant of visual field

148

scotoma

small blind spot in the visual field caused by migraine or by a small lesion of the visual cortex

149

cells in the visual parietal cortex during anesthetia

are not active

150

nystagmus

constantly occurring eye motion

151

visual-form agnosia

inability to recognize objects or drawings of objects

152

achromatopsia

color agnosia

153

optic ataxia

deficit in the visual control of reaching and other movements

154

Damage to parietal cortex (dorsal stream)

can see perfectly well, yet they cannot accurately guide their movements on the basis of visual information

155

function of dorsal stream

guidance of movement

156

damage to the ventral stream

cannot see objects but can guide their movements to objects on the basis of visual information

157

function of ventral stream

perception of objects