Sensation And Perception Flashcards
1
Q
Sensation example
A
The sound waves emitted by fallen tree
2
Q
Perception example
A
Sound waves as interpreted by our brains
3
Q
Perception defined
A
- The psychological response to physical stimuli
- Not only light hitting eye, sound hitting ear, brick hitting face
- Behind scenes processing taking place (7 steps from text)
4
Q
Perceptual process
A
- Detection of stimulus
- Transduction
- Transmission
- Higher level processing
- Perception
5
Q
Detection of stimulus
A
- what’s in the environment: thermal energy, mechanical energy, acoustic energy, light energy, electromagnetic energy
6
Q
Transduction
A
- conversion of physical energy to electrical energy.
- Brain reads electrical signals, so transduction allows brain to take in sensation and turn them into a perception
- Stimulus in environment stimulates receptors Ex. Light hitting the retina
- Receptors fire in response to that stimulation
7
Q
Transmission
A
- Electrical signal has been created, now it needs to be relayed throughout brain
8
Q
Higher level processing
A
- Acting on and interacting with the signals in the brain
2. Applying prior knowledge to the perception
9
Q
When does knowledge exert influence?
A
- Bottom up: detect stimulus > access knowledge > perception
Ex. Brown tall thing > trees are brown and tall > perceive tree - Top down: access knowledge > detect stimulus > perception
Ex. I’m in forest and forest has trees > brown tall thing > perception - Both processes working together!
10
Q
Higher level processing
A
- Top down processing us internally driven
- Bottom up processing us externally driven
- Top down: prior experience, expectations, and context all change the way we perceive things
- Top down allows brain to fill in missing information, without us knowing or trying
Ex. Seeing spider on our leg when we feel an itch
11
Q
Psychophysical approach
A
- Investigates relationship between physical stimulus and psychological response
Ex. I see the sun
12
Q
Physiological approach
A
- Investigates relationship between physical stimulus and physiological response
Ex. Squinting at the sun
13
Q
Ways to measure perception
A
- Describe: I see something large and bright
- Recognize: I recognize that object as the sun
- Response time: how long does it take to respond to the sun
- Detection: I detect sunlight
14
Q
Absolute threshold
A
- Minimum physical stimulus intensity that can be just detected (psychological or physiological)
Ex. Threshold for seeing a light is the intensity at which light can just barely be seen
15
Q
Measuring threshold
A
- Method of limits
- Method of constant stimuli
- Method of adjustment
16
Q
Method of limits
A
- Ascending series: start well below threshold, increase in steps while subject responds at each step
- Descending series: start well above threshold, decrease in steps while subject responds at each step
- Threshold is midpoint between yes and no responses
17
Q
Problems with method of limits?
A
- Does not eliminate the problem of habituation, subjects will habituate to yes or no responses. It becomes hard to change your response
18
Q
Method of constant stimuli
A
- Present stimuli in random order instead of ascending/ descending order
- Threshold is intensity that results in detection on 50 percent of the trials.
- Removes habituation and anticipation
19
Q
Method of adjustment
A
- Subject controlled
- Level of stimulation adjusted until barely noticed
- Ex. Adjusting volume knob on stereo
20
Q
Webers Difference threshold
A
- The smallest difference between two stimuli that can be detected, the just noticeable difference
- Scales with size/ intensity of the stimulus
- Bigger/ more intense stimulus = harder to detect a difference
- K = DL/S
- K = webers constant DL = difference threshold (just noticeable difference) S = value of standard stimulus
21
Q
Webers Law
A
- Ability to detect difference between 2 stimuli (standard and comparison) depends on the size of the standard stimulus
- Bigger stimulus = bigger jnd
- Smaller stimulus = smaller jnd
- For given stimulus (light) Weber number (k) is constant
22
Q
Ex. Of Webers Law
A
- K = 1 and is constant
- A stack of papers weigh .5 lbs. how much paper would you have to add to the stack to notice a different in weight? (What is the DL?)
- 1 = x/.5
- DL = .5
- It would take .5 lbs added to that stack to notice a difference in its weight
- The bigger the stimulus, the larger the jnd
23
Q
Webers Law applications in real life
A
- Explains why you don’t notice your headlights are on in the daytime
- Adding a large weight to your weightlifting machine
24
Q
Magnitude estimation
A
- Technique used to measure what an observer perceives of experiences
- Physical measure or estimation
- Ex. Brightness of a light, loudness of a tone
25
Response compression
1. As the intensity increases, the perceived intensity increases less
2. Ex. When observers asked to estimate intensity of 20, perceived brightness is 28. When intensity of 40, perceived brightness is 36.
26
Response expansion
1. As intensity increases, perceived intensity increases even more
2. Ex. Intensity of a shock at 30, perceived at 20. Intensity of 40, perceived at 50.
27
Aristotle on the mind
1. Intelligence (the mind) is rooted in the heart
2. Brain is the cooling mechanism
3. 4th century BC
28
Galen on the mind
1. Health, thoughts, emotions emanate from the ventricles
| 2. 2nd century
29
Descartes
1. Pineal gland is responsible for the interaction between mind and brain
2. 1630's
30
Thomas Willis
1. Dissections of human and animal brain suggest that the brain is where mental functioning originates
2. 1664
31
Central and peripheral nervous system
1. Central: brain, spinal cord and eyes
| 2. Peripheral nerves throughout body
32
Main Brain regions (4)
1. Frontal lobe (front)
2. Occipital lobe (back)
3. Temporal lobe (low side)
4. Parietal lobe (between frontal and occipital, top middle)
33
Occipital functions
1. Low level vision
34
Parietal functions
1. Touch, temperature, pain, attention, spatial processing
35
Temporal functions
1. High level vision, memory, hearing
36
Frontal function
1. Coordinates info across all senses, planning, and strategy, goal directed behavior, inhibition
37
Right brain vs. left brain
1. Brain functioning is not this straightforward
| 2. No one area in brain responsible for one function, works systematically
38
Modular organization
1. Idea that one area is responsible for one function
Ex. Language in the left frontal lobe
1. Multiple areas involved in language as seen on fmri
39
Dendrites
1. Receive signal
| 2. Long arm looking branches
40
Cell body (soma)
1. Process signal
| 2. Main cell body
41
Axon
1. Conduct signal
| 2. Covered in myelin sheath
42
Axon terminal
1. Transmit/send signals
43
Axon hillock
1. Place between soma and axon where signal begins (action potential)
44
Myelin
1. Protects and accelerates the signal
| 2. Breakdown of myelin causes muscular dystrophy
45
Nodes of Ranvier
1. Between myelin, regenerates the signal
46
Receptors
1. Neurons of perception
47
How do neurons communicate?
1. Action potential
2. Atoms that are positively or negatively charged
3. Stimulation > action potential > electrochemical signal
48
Cation
1. Positively charged ion in action potential
49
Anion
1. Negatively charged ion in action potential
50
Action potential: resting potential
1. Resting potential is -70mv
2. Outside of cell: more positive (more Na+)
3. Inside of cell: more negative (more K+)
4. This makes the cell polarized
5. Sodium-potassium pump maintains resting membrane potential
51
Action potential: depolarization
1. Neuron is stimulated
2. If threshold is reached, stimulation causes Na+ channels to open
3 N+ rushes into cell, causing membrane to depolarize (become more positive)
52
Action potential: repolarization
1. K+ channels open
2. Na+ channels close
3. K+ rushes out of cell, causing cell to re polarize (become less positive)
53
Action potential: hyperpolarization
1. Slight dip below resting potential, after repolarization
54
Action potential: recovery
1. K+ channels close
| 2. Membrane is returned to resting state (back to -70mv)
55
Important notes about action potentials
1. All or none: action potential either happens or not
2. Nondecremental: does not diminish as it travels down axon
3. Has refractory period: cannot fire again for a brief time afterwards
4. Very fast: 5 ms
56
After action potential?
1. Signal sent to next neuron
2. Connection between two neurons: synapse
3. Chemicals (neurotransmitters) cross the synapse
57
Neurotransmitters
1. Small molecules stored that are released across the synapse
2. Excitatory NTs: causes depolarization (increase in positivity), increases ability for post synaptic neuron to fire
3. Inhibitory NTs: causes hyperpolarization (decrease in positivity) decreases the ability for the post synaptic neuron to fire
58
Synaptic transmission
1. Transfer of signal from one neuron to the next
2. Action potential in presynaptic neuron causes vesicles to migrate toward synapse; mediated by calcium influx
3. Vesicles release NTs into synaptic cleft
4. NTs bind to receptor sites on post synaptic neuron, causing ion channels to open
59
Types of neuroimaging techniques
1. PET
2. EEG
3. tDCS
4. fMRI
5. Single-cell recording
6. TMS
60
Positron emission tomography (PET)
1. Detects changes in brain activity through change in blood flow
2. Good spatial resolution
3. Measured via radioactive tracer
61
Electroencephalogram EEG
1. Measures electrical activity on scalp
| 2. Great temporal resolution (bad spatial)
62
Functional magnetic resonance imaging (fMRI)
1. Detects changes in blood flow
| 2. Great spatial resolution, poor temporal resolution
63
Single cell recording
1. Microelectrode measures activity from a single neuron
| 2. Hodgkin and Huxley recorded from a squid giant acorn
64
Transcranial magnetic stimulation (tMS)
1. Brief magnetic pulse is sent to the brain
2. Pulse either inhibits a brain region or expires it
3. Used for migraines, stroke victims
65
Visual perception
1. Ability to interpret information from visible light reaching the eye
2. More of the brain is devoted to vision than to any other sense (in humans)
66
Electromagnetic spectrum
1. Continuum of electromagnetic energy that is produced by electrical charges and is radiated as waves
67
Wavelength
1. Distance between the peaks of the electromagnetic waves
68
Visible light
1. Energy within the electromagnetic spectrum that humans can perceive
2. Has wavelengths ranging from 400-700nm
3. Short waves appear blue, middle wavelengths green, long wavelengths yellow, orange, and red
69
Photon
1. One packet of light energy = photon
| 2. Light described as consisting of small packets of energy
70
Pupil
1. Light reflected from objects in environment enters eye through pupil
71
Cornea
1. Transparent tissue that covers the eye
2. Responsible for transmitting and focusing light into the eye
3. Fixed in place, cannot adjust its focus
72
Lens
1. Transparent structure in the eye situated immediately behind Iris
2. Forms sharp images on the back of the retina
3. Changes shape to adjust the eyes focus for objects located at different distances
73
Fovea
1. Point of central focus
2. Contains only cones
3. When we look at an object, objects image falls on the fovea
74
Retina
1. Network of neurons that covers the back of the eye
2. Contains receptors for vision
3. Maintains spatial organization of the visual scene
75
Cones and rods
1. Visual receptors that contain light sensitive chemicals
2. Sensitive chemicals are called visual pigments
3. Also known as photoreceptors
76
Accommodation
1. The changing of the lens's shape that in increases the bend of light that passes through the lens so the focus point is pulled back to hit the retina at the right spot, sharp focus
2. Prevents blurring of images when looking at objects far away
77
Presbyopia
1. Old eye
2. Distance of the near point that increases as we age
3. Ex 10cm for 20yo, 100cm at 60 yo
4. Happens because lens hardens and ciliary muscles weaken
5. Image focused behind the retina
78
Myopia
1. Nearsightedness: inability to see distant objects clearly
2. Most common
3. Rays of light focus at a point in front of the retina, image reaches retina as blurred
4. Cornea and lens is bending light too much
5. Eyeball is too long
79
Hyperopia
1. Farsightedness: can see distant objects clearly, but has trouble seeing close up
2. Focus point for light is located behind the retina
3. Eyeball is too short
4. Cornea too flat
80
Astigmatism
1. Blurriness due to irregular cornea shape
2. Cornea may be oval shaped
3. Image distributed across retina (rather than focused)
81
LASIK
1. Laser assisted in situ keratomileusis
| 2. Laser adjusts the shape of the cornea
82
Rod characteristics
1. Low visual acuity
2. No color detection
3. Light sensitive, used in dim light settings
4. 120 million
5. Located among the peripheral retina
83
Cone characteristics
1. High visual acuity
2. Yes, color vision
3. Light sensitive, no
4. 6 million cones in retina
5. Used in light settings
6. Located on the fovea
84
Visual acuity
1. Sharpness of the image that we perceive
2. In fovea: visual acuity is good
3. In peripheral retina: visual acuity is awful
85
Blind spot
1. Area in the retina where there are no receptors
2. This is where the optic nerve leaves the eye
3. No receptors= blind spot
86
Optic nerve
1. Carries neural impulses from the eye to the brain
87
Photoreceptor properties
1. Outer segment: (top of cone, top of rod) of photoreceptors contains discs
2. Each disk has thousands of visual pigment molecules which span the disc membrane
3. In rods: rhodopsin (detects light/ dark)
4. In cones: color pigments (detects color)
5. Each visual pigment has two parts: a long opsin protein, and each opsin protein contains one retinal
88
Phototransduction in the dark
1. (At rest, in dark) rods and cones are depolarized
2. They're active (-40mv)
3. Sodium inflow in outer segment
89
Photoransduction in the light
1. Rods and cones hyperpolarize
2. Light deactivates them (-70mv)
3. Closing of Na+ channels
90
Steps of phototransduction
1. Light reaches eye
2. Retinal absorbs one photon of light
3. Retinal separates from posing
4. Isomerisation: change in shape that causes chemical chain reaction to create electrical signals
5. Chain reaction causes Na+ channels to close
6. Closure of Na+ channels causes hyperpolarization (only one isomerized pigment to hyperpolarize entire cell)
7. Hyperpolarization of multiple cells leads to perception
91
How many visual pigments need to be isomerized in order to perceive light?
1. 1 photon of light = 1 visual pigment isomerized
2. 1 visual pigment isomerized = 1 cell hyperpolarize
3. Hecht's experiment: method of constant stimuli
1. Presented flashes of light
2. Could detect light that contained 100 photons
3. Of those 100, only 50 reach the retina
4. Of those 50, only 7 absorbed by retinal
* only 7 visual pigments need to be isomerized to perceive light
92
Transduction in the retina, where does it start?
1. Transduction: transformation of light energy into electrical energy (for vision)
2. Light first moves to the back, hitting retina (photoreceptors), then moves forward towards the ganglion cells
93
Visual pigment bleaching
1. In light environments: After the shape change, the retinal separates from the opsin part of the molecule, causing the molecule to become lighter in color
2. When pigments are in their lighter color, they are no longer useful for vision (inactive). Incoming light can longer be detected
3. Threshold for bleaching is lower for rods than cones
4. In dark environments: recovery from bleaching must occur, rods become functional again, dark adaptation
94
Ganglion cells
1. Gather the signals tranduced by photoreceptors and send them out for processing via the optic nerve
2. One ganglion cell processes signal for multiple photoreceptors: neural convergence
95
Receptive field
1. Area on the receptors that influences the firing rate of a neuron
2. The firing rate of a retinal ganglion increases in response to visual stimulation in a certain area if the visual field (certain group of receptors on the retina)
96
Convergence
1. The direct pathway from the receptors to the ganglion cells
2. Rods: signals converge more, 120 million rods
3. Cones: converge less, 6 million cones. Each ganglion receives signal from only one cone, no convergence
97
Why do rods have better sensitivity?
1. Takes less light to generate a response from individual rod receptor than from individual cone receptor
2. The rods have greater convergence
98
Receptive field
1. Area on the receptors that influences the firing rate of a neuron
2. Firing rate of a retinal ganglion cell increases in response to visual stimulation in a certain area of the visual field (certain group of receptors on the retina)
99
Center-surround receptive fields
1. On-center-off-surround: increases in response to stimulation in the center. Decreases in response to stimulation immediately surrounding that ref
2. Off-center-on surround: vice versa
100
Lateral inhibition
1. Inhibition by nearby cells
| 2. The surround inhibits the center
101
Herman grid
1. appearance of gray dots produced by lateral inhibition
2. White: high brightness
3. Black: low brightness
4. The higher the brightness, the higher it's inhibition on its neighboring cells
102
Why do dots on Herman grid disappear when we move our eyes to that area?
1. Receptive fields are smaller at the fovea than in the periphery
103
Causes of Blindness
1. Cataracts: clouding of the lens
2. Glaucoma: damage to optic nerve
3. Detached retina: when retina becomes detached to from pigment epithelium (traumatic injury to the eye)
4. Photoreceptor damage
5. Macular degeneration: destruction of cone rich fovea and small area surrounding it, creating a blind spot, often occurs with age
104
Restoring vision
1. Corneal transplant
2. Implanted electrodes: patient wears special camera that stimulates photoreceptors
3. Stem cells to grow new cornea
105
How do we perceive color?
1. Light reflecting off of an object for opaque (non see through) objects
2. Light transmitting through an object for transparent objects
3. Specific color we see is dependent upon the wavelength of light reflected/transmitted
106
How many colors can we see?
1. Book says 200
| 2. Other's say 1000
107
Reflectance curve of colors and wavelengths
1. Plots of the percentage of light reflected versus wavelength
2. The actually wave appearance on graph
108
Chromatic hues
1. Wavelengths reflected more than others: blue, greens, and reds
109
Achromatic
1. All wavelengths reflected equally
| 2. Black, gray, white
110
How is Hue (color) determined?
1. Determined by wavelength
2. Short waves = high frequency = blue = high pitch sound
2. Medium = green
3. Long = low frequency = red = low pitched sounds
111
How is Intensity (brightness) determined?
1. Determined by amplitude
2. Great amplitude = Bright colors = loud sounds
3. Small amplitude = dull colors = soft sounds
112
Mixing light
1. All wavelengths reflected are seen
2. Additive
3. Blue reflected (S,M) + yellow reflected (M,L) = white seen (S,M,L)
113
Mixing paint
1. Only wavelengths in common are seen
2. Subtractive
3. Blue (S,M) + yellow (M,L) = green (M)
114
Perceptual/ color constancy
1. We perceive color and lightness as constant despite viewing circumstances and even under changing circumstances
2. Ex. The blue/black dress: we see one color under sunlight or artificial light differently depending on how the sweater is being illuminated. Need to consider the interaction between the wavelengths produced by the illumination and the wavelengths reflected from the sweater.
115
Color adaptation
1. Prolonged exposure to chromatic color impairs perception of other colors
2. Ski goggles: bleaches your cone pigments, decreasing sensitivity to 'red light' for example
116
Trichromatic theory
1. Color vision depends on activation of 3 different types of receptors (cones on the retina)
2. Blue, green, red cones
3. Light stimulates these cones to differing degrees
4. Adjusting proportions of three wavelengths results in ability to match
117
Opponent process theory
1. Color vision is caused by opposing responses generated by blue and yellow, and red and green, black and white
2. Afterimages, simultaneous contrast
118
Which theory about color vision is right?
1. Both!
2. Receptors respond to different wavelengths of light (trichromatic)
3. Then opponent neurons integrate this info
119
Color deficiency: dichromacy
1. Only 2 types of cones
2. Protanopia: missing red (L) cone (most common, red green color blind)
2. Dueteranopia: missing green (m) cone
3. Tritanopia: missing blue (S) cone (very rare)
120
Color deficiency: monochromacy
1. Only 1 type of cone
2. No chromatic color perception
3. Achromatic colors only (black, grey, white)
4. Can only see lightness and darkness
121
Color deficiency: cerebral achromatopsia
1. Impairment in the cortex rather than on the retina
| 2. No chromatic color perception
122
Color in different species
1. Dogs and cats: dichromats (2 cones, green and blue)
2. Fish and birds: tetrachromats (4 types of cones)
3. Pigeons and butterflies: pentachromats (5 types of cones)
123
Color take home message
1. Color does not exist out in the world
2. Completely in our heads
3. A psychological property, not a physical property
4. Color experience is created by the nervous system
124
How do we perceive depth and size?
1. Image on our retina is 2D, how do we see in 3D?
2. Need cues (heuristics) to help
3. Implicit cues: generated from inside ourselves: oculomotor cues
4. Explicit cues: out in the environment: monocular cues and binocular cues
125
Oculomotor cues
1. Our bodies can sense the position of our eyes and muscle use
2. Can use this information to determine depth
3. Created by convergence and accommodation (changing of the lens occurring when we focus on objects at various distances)
126
Convergence
1. The inward movement of the eyes that occurs when we look at nearby objects
2. You can feel this movement (and accommodation too)
127
Monocular cues
1. Requires the use of just one (mono) eye
2. Linear perspective: looking down parallel lines and converging in the distance
3. Occlusion/overlap: one object is in front of the other
4. Texture density gradient: elements that are equally spaced in a scene appear to be more closely packed as distance increases
5. Atmospheric perspective: distant objects appear less sharp than nearer objects
6. Familiar size: judging distance based on prior knowledge about sizes of objects (if a dime is the same size as a quarter, the dime is probably closer)
7. Relative size: two objects of equal size, the one farther away takes up less of field if view
8. Shadows: decreases in light intensity caused by blockage of light
128
Binocular cues
1. Requires use of both eyes
129
Binocular disparity
1. Each retina receives a slightly different angle (depth cue)
2. Corresponding retinal points: same place on each retina
3. Horopter: imaginary surface where corresponding points line up
4. Points are non-corosponding: image on each retina is different, points lie outside of horopter
5. Degree to which these points deviate from the horopter is called absolute disparity
130
Stereopsis
1. The impression of depth that results from information provided by binocular disparity
2. Perception of depth, experience of depth created by disparity
131
Front face eyes and disparity
1. Depth perception from disparity
132
Side facing eyes and disparity
1. Not disparity information because they do not have overlapping fields of view, but better peripheral vision
133
Physiology of depth perception: binocular depth cells
1. Neurons in the brain that respond differentially to binocular disparity, responding differentially to objects at different depths
2. Primary visual cortex, in ocular region
3. Disparity selective neurons are responsible for stereopsis
134
Blake and Hirsch
1. Selective rearing in kittens
2. Kittens saw out of one eye every day
3. 6 months later recorded from visual cortex
4. Results: no binocular vision, could not use binocular disparity to perceive depth, and impaired oculomotor convergence
5. Eliminating binocular neurons, eliminates stereopsis
135
Visual angle
1. The angle of an object relative to your eye
2. Takes into account actual size of an object and viewers distance away from the object
3. Tells us how large the image will be on the retina
4. Large objects can have the same image on our retina as small objects, if the large object is farther away
136
Size constancy
1. Perception of an objects size remains constant, even though the image on the retina changes size
2. Size and depth perception balance each other out
But
3. Size constancy can be affected when depth info is lacking (or messed up)
137
Ames Illusion, How does it work?
1. It's the image on your retina (small man > walks to the right > becomes super large man)
138
Muller-Lyer Illusion
1. Lines with arrows >-<
| 2. The end arrows give the lines an appearance of depth
139
Unilateral
1. One side
140
Bilateral
1. Both sides
141
Ipsilateral
1. Same side
142
Contralateral
1. Opposite side
143
What hemisphere is the left visual field processed? Right visual field?
1. In both eyes, information in the left visual field is processed in the right hemisphere.
2. In both eyes, information in the right visual field is processed in the left hemisphere
3. Information crosses in the optic chasm (front center of brain)
144
Visual system organization in split brain patient
1. Hemispheres cannot communicate
| 2. Severed Corpus callosum means severed optic chiasm
145
Lateral Geniculate Nucleus
1. Located in the thalamus
2. Acts as a relay station for visual information
3. Processes multitudes of information: from cortex, retina, thalamus and brain stem
4. Organized by eye (6 layers, altering ipsilateral eye, contralateral eye)
5. Have center/surround receptive fields, like retinal neurons do
146
How is information represented in the LGN?
1. Locations on the cortex correspond to locations on the retina
2. Electronic map of the retina on the cortex is called retinotopic map
147
How are LGN neurons organized
1. Organized by spatial location
2. Adjacent LGN info from adjacent retinal neurons
3. Perpendicular tracks: all neurons have receptive fields in same overlapping retinal locations
148
After information is transmitted through the LGN, where does it go?
1. Proceeds to the cortex, specifically primary visual cortex (v1)
2. 80% of the cortex responds to visual stimulation
149
Role of V1
1. First place visual info is processed in the cortex
| 2. Processes components, parts, features of a stimulus
150
Hubel and Wiesel 1959
1. Recorded neuron in cat V1
2. Found neurons in V1 have side by side receptive fields
3. Discovered roles of simple and complex cells
4. Neurons are adaptable and can change with experience
152
Neurons in V1
1. V1 neurons have receptive fields (like retina and LGN)
2. Receptive fields are side by side, not center surround
3. Organized by retinotopic map: nearby areas of cortex receive input from nearby areas of retina
4. Organized by more than retinotopic map..
5. Feature detectors, motion detectors, orientation detectors, necessary for vision
153
Complex cells in V1
1. Respond to particular orientation of light that is moving in a particular direction
154
Why are simple and complex V1 neurons important?
1. Demonstrates that V1 neurons only respond to small features (oriented bars of light), but specific features
2. From simple features, representation of a whole object can be constructed
155
Cortical surface
1. Layer of gray matter on the outside of the brain
156
Location columns
1. V1 neurons organized into location columns that are perpendicular to the surface of the cortex, so that all of the neurons within a location column have their receptive fields at the same location on the retina
157
Orientation column
1. Cortex organized into orientation columns, with each column containing cells that respond best to a particular orientation
158
Ocular dominance column
1. Column that corresponds to each eye, left eye right eye
159
Cortical blindness "Blindsight"
1. Damage to V1: photons still transduced at the retina, but not processed by the brain
2. Evidence these patients still have conscious perception
3. They can correctly guess, upon being asked, that they see something in their blind spot, but cannot tell you that they see something
160
Simple cells in V1
1. Respond to particular orientation of light
161
Ungerleider and Mishkin Monkey study
1. Object discrimination: differentiate between two shapes
2. Landmark discrimination: relative to food wells
3. Ablation of temporal lobe: impairs object discrimination/ normal landmark discrimination
4. Ablation of parietal lobe: impaired landmark discrimination/ normal landmark discrimination
5. Determined the what and where of an object
162
Monkey study double dissociation
1. Object recognition impaired if temporal lobe impaired
| 2. Spatial vision impaired if parietal lobe impaired
163
Higher level processing "what and where region"
1. What = Ventral stream (temporal lobe)
| 2. Where = dorsal stream (parietal lobe)
164
What stream
1. Ventral visual stream
2. Extends from visual occipital to temporal lobe
3. Puts together features established by V1, determine what object is
165
Damage to 'what' stream
1. Object agnosia: inability to recognize objects
166
'Where' stream
1. Dorsal visual stream
2. From visual occipital lobe to parietal lobe
3. Determine where objects are in space and how to guide ourselves to them
4. Spatial vision and attention
167
Damage to the 'where' stream
1. Hemispatial neglect: inability to maintain awareness of one side of the visual field
168
'What' and 'where' pathways work together?
1. Yes! Interactive system
2. Information flows forward: feedforward
3. Information flows backwards: feedback
