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PSYCH 275 > Chapter 9: Sense and Perception > Flashcards

Chapter 9: Sense and Perception Flashcards

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1
Q

What is blindsight?

A

patient can’t identify objects in blind area

but can accurately tell about changes in visual field

patient not conscious that they can register changes in visual field

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2
Q

What is the relationship between blindsight and perception?

A

NS must construct images from bits of information

the brain must bind it all together, whole image perception

selective awareness: we can only access some part of the information our brain is currently processing

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3
Q

What is the nature of sensation and perception?

A

the only input our brain receives from the “real” world is a series of action potentials originating from external energy that are transduced by our sensory receptors

this info is passed along sensory neurons that form specific pathways

how we end up perceiving one set of nerve impulses as vision and another set as hearing is unknown

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4
Q

How are sensory system diverse?

A

vision, touch, taste, etc.

lead to different perceptual experience

but each sensory system is organized similarly

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5
Q

What are sensory receptors?

A

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

each sensory system’s receptors are designed to respond only to a narrow band of energy

vision: light energy produces chemical energy
auditory: air pressure produces mechanical energy
somatosensory: mechanical energy
taste and olfaction: chemical molecules

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6
Q

What is the receptive field?

A

region of sensory space (e.g. skin surface) in which a stimulus modifies a receptor’s activity

what the open eye sees is the receptive field of that eye

each photoreceptor in the eye points in a slightly different direction, so each one has a unique receptive field

RF helps us sample sensory information and can locate events in space

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7
Q

What is the relationship between sensory receptors and the receptive field?

A

sensory receptor receptive field can contrast the information each receptor is providing

adjacent receptive field may overlap

the contrast between their responses to events help us localize sensations

this spatial dimension of sensory information produces cortical patterns and maps that form each person’s sensory reality

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8
Q

What is receptor density and sensitivity?

A

sensory receptors are not evenly distributed across the body or its organs

density is important for determining the sensitivity of a sensory system, visual receptors packed towards the center of our visual field, peripheral vision is poorer

differences in receptor density determine the special abilities of many animals

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9
Q

What are neural relays?

A

all receptors connect to the cortex through a sequence of intervening neurons

sensory information is modified at each stage in the relay, each region constructs different aspects of the sensory experience

neural relays allow sensory systems to interact

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10
Q

What is sensory coding?

A

after transduction, sensory information is encoded by action potentials that travel along peripheral nerves to the CNS

from there, action potential travel on nerve tracks within the CNS, each bundle carries the same kind of signal

presence of a stimulus can be encoded by an increase or a decrease in discharge rate (the amount of increase/decreases can encode stimulus intensity)

changes in the visual field can be encoded by activity in different neurons or different levels of discharge within a neuron

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11
Q

What is representation of sensory coding?

A

the neocortex represents the sensory field of each sensory modality as a spatially organized neural representation of the external world

topographic map is a spatially organized neural representation of the external world

in mammals, each sensory system has at least one primary cortical area

these may project to secondary areas

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12
Q

What is the topographic map in the sensorimotor cortex?

A

the size of its features represent the relative proportions of the parts of the human brain responsible for motor and somatosensory function

the features that are most exaggerated have the largest correlate representations in the brain

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13
Q

What is sensation?

A

registration of physical stimuli from the environment by the sensory organs

sensory impressions are influenced by context, emotions, and memory

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14
Q

What is perception?

A

subjective interpretation of sensations by the brain

our visual experience is not an objective reproduction of what is out there, rather it is a subjective construction of reality that is manufactured by the brain

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15
Q

What is the cornea?

A

clear outer covering

controls and focuses the entry of light into the eye

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16
Q

What is the iris?

A

opens and closes to allow in more or less light

the hole in the iris is the pupil

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17
Q

What is the lens?

A

focuses light

bends to accommodate near and far objects

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18
Q

What is the retina?

A

where light energy initiates neural activity

light-sensitive surface at the back of the eye, consists of neurons and photoreceptor cells

translates light into action potentials

discriminates wavelengths (colors)

works in a wide range of light intensities

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19
Q

What is the fovea?

A

region at the center of the retina that is specialized for high acuity

receptive field at the center of the eye’s visual field

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20
Q

What is the acuity across the visual field?

A

vision is better in the center of the visual field than at the margins, or periphery

letters at the periphery must be much larger than those in the center for us to see them as well

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21
Q

What is the blind spot?

A

region of the retina where axons forming the optic nerve leave the eye and where blood vessels enter and leave

has no photoreceptors

visual fields overlap: left eye can see the right eye’s blind spot, brain compensation

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22
Q

What are photoreceptors?

A

the retina’s photoreceptor cells convert light energy first into chemical energy and then into neural activity

light arriving at photoreceptor triggers a series of chemical reactions

leads to a change in membrane potential

leads to a change in the release of neurotransmitters onto nearby neurons

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23
Q

What are rods?

A

more numerous than cones

sensitive to low levels of light (dim light)

used mainly for night vision

one type of pigment only

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24
Q

What are cones?

A

highly responsive to bright light

specialized for color and high visual acuity

in the fovea only

three types of pigment

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25
What are the three types of cone pigments?
absorb light over a range of frequencies blue, or short wavelength green, or middle wavelength red, or long wavelength there are approximately equal numbers of red and green cones, but fewer blue cones
26
What are the types of retinal neurons?
bipolar cell: receives input from photoreceptors into ganglion cells horizontal cell: links photoreceptors and bipolar cells amacrine cell: links bipolar cells and ganglion cells retinal ganglion cell (RGC): gives rise to the optic nerve
27
What are the two types of ganglion cells?
magnocellular cell (M-cell) parvocellular cell (P-cell)
28
What are magnocellular cells?
magno-, large receives input primarily from rods sensitive to light and moving stimuli
29
What are parvocellular cells?
parvo-, small receives input primarily from cones sensitive to color
30
What is the optic chiasm?
junction of the optic nerves from each eye axons from the nasal (inside) half of each retina cross over to the opposite side of the brain axons from the temporal (outer) half of each retina remain on the same side of the brain information from the left visual field goes to the right side of the brain, information from the right visual field goes to the left side of the brain
31
What are the three routes to the visual brain?
two main pathways lead to the visual cortex in the occipital lobe geniculostriate pathway for processing the object's image (made by all P ganglion axons and some M ganglion axons) tectopulvinar pathway for directing rapid eye movements (made by remaining M ganglion axons) another smaller pathway tracks into the hypothalamus
32
What is the geniculostriate system?
projections from the retina to the lateral geniculate nucleus to layer IV of the primary visual cortex bridges the thalamus (geniculate) and the striate cortex)
33
What is the striate cortex?
the primary visual cortex (V1) in the occipital lobe shows striped (striations) when strained two visual paths emerge from the striate cortex: one route goes to vision-related region of the parietal lobe, one route goes to vision-related regions of the temporal lobe
34
What is the tectopulvinar system?
projections from the retina to the midbrain's superior colliculus to the pulvinar (thalamus) to the parietal and temporal visual areas
35
What is the retinohypothalamic tract?
synapses in the tiny superachiasmatic nucleus in the hypothalamus roles in regulating circadian rhythms and in the pupillary reflex contains photosensitive RGCs
36
What is the dorsal visual stream?
visual processing pathway from V1 to the parietal lobe guides movement relative to objects the how pathway (how action is to be guided toward objects)
37
What is the ventral visual stream?
V1 to the temporal lobe object identification and perceiving related movements the what pathway (identifies an object)
38
What is the lateral geniculate nucleus?
thalamus right LGN: input from right half of each retina left LGN: input from left half of each retina
39
What are the six layers of the lateral geniculate nucleus?
projections from the eyes go to different layers layers 1,4, and 6: input from contralateral retina layers 2, 3, and 5: input from ipsilateral retina layers 1 and 2: input from magnocellular cells layers 3 to 6: input from parvocellular cells
40
What is the geniculostriate pathway?
P and M retinal ganglion cells send separate pathways to the thalamus segregation continues in the striate cortex left and right eyes also send separate pathways to the thalamus pathways remain segregated in the striate cortex
41
How is separate visual input maintained?
after info is segregated in the LGN it maintains this segregation in the primary visual cortex pattern: alternating regions of the left and right eye
42
How is the tectopulvinar pathway made up of M cells?
formed by the axons of remaining M cells (some form the geniculostriate pathway along P cells) M cells are sensitive to light but not color, sensitive to movement but not fine detail M cells from the retina project to the superior colliculus (in the midbrain's tectum) function: orienting movements to detect and focus the eyes towards stimuli superior colliculus sends connection to the pulvinar region of the thalamus
43
What are the medial and lateral pulvinar in the tectopulvinar pathway?
medial pulvinar: sends connections to the parietal lobe lateral pulvinar: sends connections to the temporal lobe provide information regarding location (where) damage in this pathway prevents individuals from identifying the location of stimuli
44
What is the primary visual cortex (V1; striate cortex)?
striate cortex receives input from the lateral geniculate nucleus
45
What is the secondary visual cortex (V2 to V5, extrastriate cortex)?
visual cortical areas outside the striate cortex each region processing specific features of visual input
46
What is the heterogenous layering in the V1 area?
Blob (V1): region in the visual cortex that contains color-sensitive neurons interblob (V1): region that separates blobs, participates in the perception of form and motion within the V1 region, visual input is segregated by info type: color, form, motion, and projected into the V2 region
47
What is the heterogenous layering in the V2 region?
thick and thin stripes mixed with pale zones the thick stripes receive input from the movement-sensitive neurons in region V1 the thin stripes receive input from V1's color-sensitive neurons pale zones receive input from V1's form-sensitive neurons visual pathways proceed from V2 to other occipital/temporal regions
48
What is the visual field?
region of the visual world that is seen by the eyes divided into left and right fields information in the left visual field goes to the right hemisphere information in the right visual field goes to the left hemisphere
49
What is the coding location in the retina?
each retinal ganglion cell (RGC) responds to stimulation on just a small circular patch of the retina, the cell's receptive field the receptive field represents the outer world as seen by a single cell the visual field is composed of thousands of receptive fields light falling on one place on the retina will activate one ganglion cell, and light falling on another place will activate a different ganglion cell
50
What is the relationship between the location in the LGN and region V1?
cells in the lateral geniculate nucleus (LGN) also have receptive fields each LGN cell represents a particular place projects to V1 (striate cortex), forming a topographic map, spatially guided visual representation
51
What is the topographic organization of region V1?
receptive fields of cells in the cortex are typically larger than those of retinal ganglion cells more cortical tissue is devoted to cells in the fovea than in the periphery (higher acuity)
52
What is receptive-field hierarchy?
the receptive fields of many retinal ganglion cells combine to form the receptive field of a single LGN cell the receptive fields of many LGN cells combine to form the receptive field of a single V1 cell
53
What is the neuronal activity associated with seeing shape?
place a straight line positioned at a 45 degree angle in front of the eye the cell can respond to this stimulus either by increasing or decreasing its firing rate, cell could show excitation to one stimulus, inhibition to another, or no reaction at all in either case, the cell is generating information about the line, cell's response to a particular stimulus is selective
54
What are retinal ganglion cells?
respond only to the presence or absence of light, not to shape concentric circle arrangement center and surround (periphery)
55
What are on-center cells?
excited when light falls on the center portion of the receptive field, inhibited when light falls on the surround (periphery) of the receptive field light across whole receptive field produces weak excitation
56
What are off-center cells?
excited when light falls on the surround of the receptive field, inhibited when light falls on the center of the receptive field light across the whole receptive field produces weak inhibition
57
What are overlapping receptive fields?
neighboring retinal ganglion cells receive their inputs from an overlapping set of photoreceptors a small spot of light shining on the retina is likely to produce activity in both on-center and off-center ganglion cells
58
What does processing look like in retinal ganglion cells?
luminance contrast: ganglion cells tell the brain about the amount of light hitting a certain spot on the retina relative to average amount of light falling on surrounding retinal regions this allows input from RGCs to tell the brain about shape, this system emphasizes differences in luminance
59
How is shape processed in the primary visual cortex (V1)?
V1 neurons receive input from multiple RGCs, V1 neurons have a much larger receptive field than RGCs, V1 neurons respond to stimuli more complex than light on or light off cells behave like orientation detectors, excited by bars of light oriented in particular directions
60
What are simple cells in V1?
receptive field with a rectangular on-off arrangement
61
What are complex cells in V1?
maximally excited by bars of light moving in a particular direction through the receptive field
62
What are hypercomplex cells in V1?
like complex cells, maximally responsive to moving bars also have a strong inhibitory area at one end of the receptive field
63
How does receptivity in V1 compare to RGC?
RGC responds maximally to spots of light (not orientation) V1 input comes from ganglion cells aligned in a row
64
How is shape processed in the temporal cortex?
temporal cortex cells are maximally excited by complex visual stimuli (eg. faces or hands), very selective (eg. particular facial expressions, etc.) complex features are necessary for activation of most neurons in area TE, include a combination of characteristics such as orientation, size, color, and texture neurons with similar but not identical responsiveness to particular features tend to cluster in columns
65
What is stimulus equivalence?
recognizing that an object is the same across different viewing orientations
66
What is the process of seeing color?
subtractive color mixing obtains entire range of colors by mixing only three colors of paint (red, blue, and yellow) property of the cones in the retina light of different wavelengths stimulates the three cone receptor types in different ways ratio of activity of these three receptor types forms our impressions of colors
67
What is the trichromatic theory?
explanation of color vision based on the coding of the three primary colors red, green, and blue the color we see is determined by the relative responses of the different cone types, all three types equally active results in use seeing white can explain different types of color blindness: lacking one cone receptor type = color blindness
68
What are the limitations of the trichromatic theory?
four basic colors: red, green, yellow, and blue cannot explain afterimages (red-green, blue-yellow)
69
What is opponent processing?
explanation of color vision that emphasizes the importance of the opposition of colors (red vs. green, blue vs. yellow) opponent processing occurs in retinal ganglion cells, on-off and center-surround receptive fields, about 60% retinal ganglion cells cells excited by red are inhibited by green (and vice versa)
70
What is the opponent-color contrast response?
the center of the receptive field is excitatory in some cells, inhibitory in other cells stimulation to the periphery has the opposite effect, the center is responsive to one wavelength and the surround is responsive to another
71
What is the opponent processes in neurons in cortical region V4?
do not respond to particular wavelengths but are responsive to various perceived colors, center of the receptive field is excited by a certain color, and the surround is inhibited may be important for color constancy. perceived color is constant relative to other colors, regardless of changes in illumination
72
What is the neuronal activity in the dorsal stream?
involved in processing visual information for action, the "how" stream neurons in this area are silent to visual stimulation when a person is under anesthesia some cells in this area process the visual appearance of an object to be grasped, these cells will fire even when a monkey watches another monkey picking an object
73
What is monocular blindness?
destruction of the retina or optic nerve of one eye, producing loss of sight in that eye
74
What is homonymous hemianopia?
blindness of an entire left or right visual field caused by cuts in the optic track, LGN or V1
75
What is quadrantanopia?
blindness of one quadrant of the visual field
76
What is scotoma?
small blind spot in the visual field caused by a small lesion or migraines of the visual cortex
77
What is visual-form agnosia?
inability to recognize objects or drawings of objects
78
What is color agnosia (achromatopsia)?
inability to recognize colors
79
What is face agnosia (prosopagnosia)?
inability to recognize faces
80
What is optic ataxia?
deficit in the visual control of reaching and other movements damage to the parietal cortex retention of the ability to recognize objects normally
81
What are the characteristics of damage to the dorsal visual stream?
people with damage to the parietal cortex in the dorsal visual stream can see perfectly well yet they cannot accurately guide their movements on the basis of visual information
82
What are the characteristics of damage to the ventral visual stream?
people with damage to the ventral stream cannot perceive objects because object perception is a ventral stream function yet these same people can guide their movements to objects on the basis of visual information

PSYCH 275 (11 decks)

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