Exam 1 Deck Flashcards
Perception Exam 1 Flashcards (237 cards)
1
Q
What is Intuition?
A
Our senses give us a true representations of the world and the things in it as they are
– We interpret those representations and make decisions based on them
– We can trust the information that we get from our senses
2
Q
Is there stuff our senses can’t pick up?
A
Yes
3
Q
Is it possible for our senses to be confused by what something is?
A
Yes, sometimes our perceptual system gives us conflicting information. We can’t tell what’s really there.
4
Q
Can experience change our perception of something even if the thing itself does not change?
A
This would not be true if what our senses was giving us was a simple reflection of the world as it is. Our experiences don’t change the world, but do change our perception of it.
5
Q
Can we perceive things that are not there?
A
Yes we can.
6
Q
We can not perceive things that are actually there. (T/F)
A
True
7
Q
Can our perceptual system get confused?
A
Yes, we can see things happening that are not actually happening. Or see things as different colors that are actually the same color.
8
Q
What is the Necker cube?
A
The Necker cube – A 'bistable' figure • Two different, incompatible interpretations – It is never ambiguous • Always one or the other percept • Flips between the two
9
Q
What is the Kaniza triangle?
A
– An apparent upside down white triangle occluding a rightside up black triangle and three black disks
• Classic example of ‘illusory contours’
10
Q
Perception is a passive process. (T/F)
A
False, it is not a passive process.
11
Q
Perception is an action that is done by the perceiver. (T/F)
A
True, in order to perceive something we have to actively be trying.
12
Q
What is perception to the perceiver?
A
The action to create a computed representation that estimates (a best guess) of the nature of an energy source in the environment by an organic computer (the brain).
13
Q
What is the retinal network?
A
• The retina is brain network made of neurons
– Rods and Cone transduce
– Bipolar cells transmit signal to ganglion cells
– Ganglion cells output to brain
– Horizontal & amacrine cells connect laterally
• This network can do computations
14
Q
What are Mach Bands?
A
An optical illusion named after the physicist Ernst Mach. It exaggerates the contrast between edges of the slightly differing shades of gray, as soon as they get in contact with each other, thus enhancing edge-detection by the human visual system.
15
Q
What is real vs. what is perceived by Mach Bands
A
• What's Real – A Stairstep pattern • Uniform intensity across color patch • What's Perceived – Stairs with ‘spikes’ at the boundaries • Bands of lighter and darker intensity where the color patches meet
16
Q
What does the visual system have to do?
A
• What does the visual system have to do?
– Discriminate one thing from another
• What distinguishes objects?
– Their boundaries
• Lateral inhibition enhances edge perception above what is really there
17
Q
Mach Bands: A Bio-Cogno-Psycho-Physical Approach… What is the Physical?
A
• Physical
– Patches of uniform intensity adjacent to patches of different intensity
18
Q
Mach Bands: A Bio-Cogno-Psycho-Physical Approach… What is the Psychological?
A
• Psychological
– Perception of lighter and darker intensity bands at patch boundaries
19
Q
Mach Bands: A Bio-Cogno-Psycho-Physical Approach… What is the Cognitive?
A
• Cognitive Model
– A computational network of convergent input with lateral inhibition
20
Q
Mach Bands: A Bio-Cogno-Psycho-Physical Approach… What is the Biological?
A
• Biological
– The retinal mosaic has horizontal cells connected between receptors and ganglion cells to provide convergence with lateral inhibition
21
Q
What is sensation?
A
– Sensation: The impact of the external world on specialized receptors on the body
22
Q
What is percept?
A
– Percept: an internal representation of something in the world
23
Q
What is perception?
A
– Perception: the process of forming that internal
representation
24
Q
What is the internal representation?
A
• That internal representation is not a direct reflection of external reality but rather the brain’s computed estimate of the source of environmental stimulation modified to be optimally adaptive
– If an organism is more likely to survive by seeing something that isn’t there or not seeing something that is, then that’s the output the perceptual system returns
25
What is dualism?
• Note part of Matrix quote: “electrical signals interpreted by your brain”
• Implies there are two things: electrical signals, and something that interprets those electrical signals
– Note here they use the term “brain” for the interpreter to try to avoid the appearance of dualism, but it's the same a saying “mind”
• This is our intuition, that there is a “true me” (whatever you call it: mind/spirit/soul) that can observe perceptions formed in the brain and can control “my” body (mechanical/meat) like a puppeteer pulling strings
– The mind and body are two separate and distinct things
• Mind: ethereal (not of the physical world)
• Body: corporeal (of the physical world)
26
René DesCartes and dualism
• Developed a theory of the relationship between mind and body known as Cartesian Dualism
– Based on hydraulic theory of nervous system
• (Also invented Cartesian coordinate system)
27
What is Cartesian Dualism?
```
• Mind and body are separate things
– Body
• Corporeal
– stuff of matter
– Occupies space in the world
• Mechanistic, predictable
– Mind
• Non-corporal
– stuff of ether
– Does not occupy space in the world
• Location of spirit, soul, free will; not mechanistic;
```
28
What is the Cartesian reflex?
```
• Involuntary
• Environmental energy moves pineal gland
• Movement of gland opens valves
• Nerve fluid flows
• Muscles contract
• No mind required
– Automatic
– Mechanistic
```
29
Cartesian voluntary action
• Information is carried from the world to the brain
– The perception part (meat)
• The mind/soul examines information in the brain and decides what to do
– Watches the show in the Cartesian "Theatre of the Mind”
– The “interpreter” in Morpheus's description
• Mind/soul animates body by pushing the pineal gland around like a joystick, allowing fluid to flow, initiating action
– The action part (meat again)
• Perhaps intuitive but not scientific
– Can't investigate things not part of the physical world
30
What introspective?
– “Look inside”
– Think about how you think
– Completely subjective
31
What is behaviorism?
– Everything we are and do reflects learned associations between stimuli or between stimuli and responses
– Measure input (stimuli) and output (responses)
– This is an experimental approach
32
What is cognitive/experimental psychology
Computational mental operations intervene between
| stimulus and response
33
What is cognitive neuroscience (biological)
– Those computations reflect activity in the brain
34
What is our perspective
• Combination of cognitive, and cognitive neuroscience, relating experimental results with the biological bases of perception
– The mind is what the functioning brain produces, not a different thing separate from the body
• This is a monistic (one thing) perspective
– The phenomena of mind are what the brain generates when it functions
• Mind and brain are both aspects of the same thing
– All thought, feeling, and behavior comes from electrochemical brain activity and nowhere else
• There is no 'ghost in the machine'
35
What is Psychophysics?
Experimental Methods Applied to Perception
– Manipulate the physical properties of the stimulus
– Query subject on their perception
• Relates individual's mental experience (Psyche) with stimulus energy (Physics)
36
What is Fechner's Law?
Fechner's Law
• We become less sensitive to change in stimuli as the stimuli become more intense
– Our perception of the stimulus intensity grows slower than the actual stimulus intensity
– The function relating stimulus intensity to perceptual sensitivity is a logarithmic curve
37
Who coined the term Psychophysics?
Gustav Fechner
38
What are some examples of Psychophysiology?
– Method of Constant Stimuli
– Method of Limits
– Method of Adjustment
– Method of Magnitude Estimation
39
What is the Method of Constant Stimuli?
• Randomly present many stimuli of varying intensities
• Find the least intense stimulus the participant can detect
– Absolute threshold
• The threshold is not a firm value that you never perceive
below and always perceive above, but is surrounded by an 'ambiguous zone'
– Near threshold, sometimes get them, sometime miss
– The 50% accuracy point is defined as the perceptual threshold
40
What is the Method of Limits?
• Stimuli aren't presented randomly
– Constantly increasing then decreasing
• Find point where subject and first detect (increasing) or can no longer detect (decreasing) stimuli
– Average across runs to correct for overshoot
• Note that subjects usually report lower intensity stimuli when decreasing than increasing
– If you’ve been saying “yes” you’re more likely to keep saying “yes”
– An example of a response bias
41
What is the Method of Adjustment?
Same as Method of Limits except participant adjusts stimulus level until they can just perceive it
42
What is Magnitude Estimation?
• Present stimuli of varying intensities
• Ask participants to assign an intensity rating of their own choosing to each stimulus
– Could be number; could be comparison
– Must be internally consistent
43
What is JND and who developed it?
Just Noticeable Difference developed by Ernst Weber.
44
What is JND?
• How small can the difference be between two weights to have them judged different?
• How close together on the skin can two points be and still be perceived as two stimuli?
– Two point threshold
45
Who discovered that the relationships between physics and psychology was lawful?
Gustav Fechner
46
What laws describe Psychophysics mathematically?
Weber's Law and Fechner's Law
47
What is Weber's Law?
• For weights
– 1/40 = .4
– 10/400 = .4
– 100/4000 = .4
48
Is JND for weights always a constant proportion for the over all weight? (Y/N)
Yes, because fuck you
49
We become more sensitive to change in stimuli as the stimuli becomes less intense. (T/F)
False. We become LESS sensitive to change in stimuli as the stimuli becomes MORE intense.
50
Our perception of the stimulus grows faster than the stimulus intensity. (T/F)
False. Our perception of the stimulus grows SLOWER than the stimulus intensity.
51
Stevens' Power Law
• Using Magnitude Estimation, Stevens found that some perceptions didn't follow Fechner's law
– e.g. we become MORE sensitive to electric shock as the intensity increases
• Stevens generalized Fechner's law for any kind of exponential function
– Not just the logarithm special case of exponential function
52
What is so special about Fechner's Law?
• Fechner's law showed for the first time that the mind followed lawful relationships too, and thus could be predicted
– You could test someone on several trial weights, find out how sensitive they were at those weights, then mathematically predict how sensitive they'd be to some weight they'd never experienced before
• Because the mind follows lawful rules and we know the rule
53
What is response biases?
– Different people may respond differently and the same person can respond differently at different times depending on all sorts of factors
• e.g. they may really not want to miss any stimuli so they respond even when they're not sure they perceived something, just to be sure
• Or they may want to be sure they never make any wrong responses so they don’t respond even when they’re pretty sure they did perceive something, leading to the opposite bias
54
Are our neurons always firing?
Neurons are always firing whether there's a stimulus there or not -- how do we know that they're firing because there's something there?
55
What Perceptual Sensitivity?
• Our ability to distinguish signal+noise from noise alone is our perceptual sensitivity
– Called d' (“dee prime”)
• The better we can distinguish signal+noise from noise, the higher our d'
56
What is Response Criterion?
• We set some level of perceptual certainty (how sure we are there’s a signal in there) as our response criterion
– Above that level of perceptual certainty, we respond “Yes: signal present”
• “signal present” = “target”
– Below we say “no: no signal, just noise”
• “no signal” = “rejection”
57
What are the 4 types of responses?
2 correct, 2 incorrect
58
You can do something about your sensitivity but you can't change your response criterion. (T/F)
False. You CAN'T do anything about your sensitivity but you CAN change your response criterion.
59
How can you change the proportion of missed targets to false alarms for the same perceptual sensitivity?
By changing the confidence level required for a response you change the proportion.
60
What is the sensory transducer?
• Transforms environmental stimulus to electrochemical activity in the brain
61
Separate Parts of the Brain Perform Different Perceptual Computations. What are the separate parts of the brain?
```
Vision
Audition
Somatosensation
Taste
Smell
```
62
What are parts of the brain for vision in perceptual computations?
```
Primary = Occiptal
Higher = Temporal, Parietal
```
63
What are parts of the brain for audition in perceptual computations?
Temporal
64
What are parts of the brain for somatosensation in perceptual computations?
Parietal
65
What are parts of the brain for taste in perceptual computations?
Parietal and Insular
66
What are parts of the brain for smell in perceptual computations?
Orbitofrontal
67
What is Neuroanatomy?
The structure of the Nervous System
68
What is the Hierarchic structure of the nervous system
```
• CNS =
– Brain
– Spine
• PNS =
– Somatic
• External world
– Touch
– Temperature/pain
– Autonomic
• Internal body
• Sympathetic
– arouse
• Parasympathetic
– Relax
```
69
What is system I/O?
It is the different nervous systems methods of input and output.
70
What is input?
```
• Input (sensory)
– Afferent nerves
• Brings information to the CNS from the periphery
• "arrive"
• Perception
```
71
What is output?
```
• Output (motor)
– Efferent nerves
• Takes commands out from the CNS to the periphery
• "exit"
• Action
```
72
Information enters and exits the CNS via __# of spinal and __# of cranial nerves (bundles of fibers which carry information -- think cable)
30 spinal, 12 cranial
73
What is the purpose of Spinal Nerves? What do they do?
```
• Somatosensation
• Each of the spinal nerves serves one part of the body
– A dermatome
• Spinal nerves are 'mixed'
– Carry both sensory and motor signals
```
74
What is the purpose of Cranial Nerves? What do they do?
• Facial somatosensation and the other four senses
– Some sensory
– Some motor
– Some mixed
75
The Nervous System starts as a hollow tube. (T/F)
True. A developing fetus's nervous system starts out as a hollow tube.
76
What do the 3 swellings the hollow tube of the nervous system develop into?
– Forebrain
– Midbrain
– Hindbrain
77
What happens to the rest of the hollow tube of a developing fetus after the 3 swellings have developed?
The rest becomes the spine.
78
What is found inside the spine of a developing fetus?
Cerebro-spinal fluid
– Ventricles
– Aqueducts
79
What Brain structures make up the Hindbrain?
```
• Medulla oblongata
– Respiration, muscle tone
• Cerebellum
– Smooth motor action
– Timing?
– Learning?
• Pons
– Sleep and arousal
• Reticular Formation
– In both hind and midbrain
```
80
What Brain structures make up the Midbrain
```
• Tectum (roof)
– Superior colliculus
• Visual orienting
– Inferior colliculus
• Auditory orienting
• Tegmentum (floor)
– More reticular formation
• Arousal
– Periaqueductal gray
• Pain regulation
– Red nucleus
• Motor
– Substantia Nigra
• Motor
```
81
What Brain structure makes up the Forebrain: Diencephalon?
```
• Thalamus
– Contains sensory relay nuclei (among other things)
• Hypothalamus
– Homeostasis
– Hormone regulation
– Control of species-typical behaviors
• The "four 'F's
```
82
What does the Basal Ganglia (Forebrain) regulate?
```
• Motor regulation
– Projections to Basal Ganglia from Substantia Nigra
damaged in Parkinson’s
• Reward motivation
• Other cognitive functions
• Memory, attention
• Not well understood
```
83
What does the Limbic System (Forebrain) handle?
* Emotions
| * Memory
84
What does the Neocortex (Forebrain) manage?
```
• Gray matter
– Neuron cell bodies
• White matter
– Fiber tracts (axons)
• Gyri
– Humps
• Sulci
– Valleys
• Fissures
– Big valleys
```
85
What are Neurons?
The brain's computational and signaling units
86
What is the Basic Neuron Structure?
```
• Soma (cell body)
– Metabolic center
• Dendrites
– Primary input to cell
• Axon
– Output pathway (nerves are bundles of axons)
• Single output from soma
• Multiple terminal branches (sometimes thousands)
• Myelin sheath
– Insulates axon
• Terminal buttons
– Output terminal
```
87
What are the 3 general types of neurons
Unipolar, Bipolar, Multipolar
88
What do Unipolar neurons do?
– One process from cell body
| – Sensory, primarily touch and pain
89
What do Bipolar neurons do?
– Two processes
| – Primarily sensory transduction
90
What do Multipolar neurons do?
– Multiple processes
– Many different configurations
– Ubiquitous in nervous system
91
Do Neurons connect with each other at synapses? (Y/N)
Yes
92
What are the 4 synapses neurons can connect with each with called?
Axo-dendritic
Axo-somatic
Axo-axonic
Dendro-dendritic
93
List in order the most common type of synapse to neuron connectors from most common to rarest.
Axo-dendritic - Most common
Axo-somatic - Common
Axo-axonic - Important for learning
Dendro-dendritic - Rare
94
The "skin" of a neuron does not have holes in it. (T/F)
False they do have holes in their "skin"
95
What is the Neuron membrane made out of?
Membrane is made out of lipids (fat)
96
Describe the process that neurons let things in and out and initiate activity in the cell.
```
• Proteins structures are imbedded in the membrane
– Channel proteins
• Lets things in and out
– Signal proteins
• Initiates activity in the cell
```
97
What are the 5 different kinds of Ions?
```
A- ions (large protein anions)
Cl- (chloride) ions
Na+ (sodium) ions
K+ (potassium) ions
Na+ and K+
```
98
Describe what A- ions do.
– Negative charge
– All inside cell
– Source of resting potential
• - 70 mV inside
99
Describe what Cl- ions do.
– Negative charge
– More outside cell
– Post-synaptic potentials
100
Describe what Na+ ions do.
– Positive charge
| – More outside cell
101
Describe what K+ ions do.
– Positive charge
| – More inside cell
102
Describe what Na+ and K+ ions do.
They are incharge of the action potential.
103
What forces act on critical ions?
```
• Na+ (more outside neuron)
– Diffusion in
– Electrostatic in
• Wants to move into cell, if it could
• K+ (more inside neuron)
– Diffusion out
– Electrostatic in
• Wants to move out of cell, if it could
```
104
How can we measure a membranes potential?
With an electrical stimulant we can inject positive or negative electrical charge into the axon while we measure the membrane potential.
105
What happens to the membrane potential if we inject a positive current? What is this process called?
The membrane potential moves towards 0. This is called Depolarization.
106
What happens to the membrane potential if we inject a negative current? What is this process called?
The membrane potential moves away from 0. This process is called Hyper-polarization.
107
What changes occur in the membrane if you depolarize it enough?
– The membrane potential shoots up to about + 40 mV with no further stimulation
– The potential then drops back down to the resting potential
• This is the Action Potential
– The basis of neural signaling
108
What does action potential do and how is it set off?
– channels in the membrane open when the membrane is depolarized enough
– Allows ions to pass through the membrane
– There are channels for both Na+ and K+
109
Describe the rising phase of the action potential?
• When the membrane has depolarized about 10 mV, Na+ channels open
– Remember, Na+ wants to go into cell along concentration and electrostatic gradients
• Na+ ions flow into cell raising the voltage from negative to positive
110
Describe the end of the rising phase.
• At the action potential peak (~+40 mv), Na+ channels close so no more positive charge can enter the cell
111
Describe the termination of the action potential.
• During the rising phase K+ channels open
– K+ wants to flow out of cell along concentration gradient
– Also, it’s now positive inside the cell, repelling the positive K + ions
• K+ ions flow out of the cell taking positive charge with them
• After the Na+ channels close, the exiting positive charge returns the cell voltage to the resting potential
112
How does the signal "go down the wire"?
• Conduction of the action potential down the axon
113
How do action potentials get started in the brain?
• When a neuron fires, it changes the membrane potential of the neuron(s) it has synapses on
114
Neurotransmission is not electrochemical. (T/F)
False, neurotransmission IS electrochemical
115
How does neurotansmission work?
* The arrival of an action potential at the presynaptic membrane (electrical) causes neurotransmitter chemicals to be released into the synapse (chemical)
* The arrival of a neurotransmitter chemical at the postsynaptic membrane (chemical) causes changes in the membrane potential of the postsynaptic neuron (electrical)
116
Describe transmitter release.
• The arrival of the action potential at the terminal button causes vesicles (little packages of neurotransmitter chemicals) to merge with the cell membrane, dumping their contents into the synapse
117
Describe the process of neurotransmission.
• Transmitter molecules diffuse across the synaptic cleft
– This doesn't take long, the cleft is only ~20 nm (20 billionths of a meter)
• Transmitter molecules bind with receptor proteins in the postsynaptic membrane
– Remember, 2 types of membrane proteins
• Channel
• Signal
118
What are channel receptors and what do they do?
• Channel receptors are chemically gated ion channels
– Work just like a voltage gated channel proteins except it’s a chemical (the transmitter molecule) that opens the channel rather than electrical charge
– Allows ions to enter or exit post-synaptic neuron,
depolarizing (exciting) or hyperpolarizing (inhibiting) the postsynaptic neuron
• Signal receptors are “G-Protein Linked Receptors”
– Use ‘second messenger’ chemicals to open channels
– Or initiate metabolic changes in receiving neuron
119
How is transmission ended?
• Reuptake
– Transmitter is reabsorbed into presynaptic button,
repackaged, and reused
• Deactivation
– An enzyme in the synapse reacts with transmitter rendering it ineffective for receptor binding
120
How do Psychoactive drugs alter synaptic transmission?
• Example: Prozac:
– Inhibits the reuptake of serotonin into the sending neuron
– Allows serotonin to remain active in the synapse longer
– More serotonin makes some people feel better (sometimes)
• Prozac is an SSRI
– Selective Serotonin Reuptake Inhibitor
121
What are the components of the visual system?
Light, The Eye, The Retina, and Phototransduction
122
What are the 2 different natures of light?
Light as particles and light as waves
123
Describe light as particles.
– Light comes in individual, discrete packets
• Photons
– Each photon is one quanta (piece) of light
124
Describe light as waves.
– Light comes in continuous undulations
• Like waves in the ocean
– Different wavelengths of light correspond to different perceived colors
125
List the 5 different ways light can interact with matter.
```
Absorbed
Diffracted
Reflected
Transmitted
Refracted
```
126
What happens when light is absorbed?
It is taken up by something and is not transmitted at all.
127
What happens when light is diffracted?
It is bent or spread out by something
128
What happens when light is reflected?
It is redirected when it strikes a surface, usually back to its point of origin.
129
What happens when light is transmitted?
It is passed through a surface (neither reflected nor absorbed by the surface, like a window)
130
What happens when light is refracted?
It is altered as it passes into another medium (like making a rainbow).
131
What wavelengths in the electromagnetic spectrum is our visual system sensitive to?
Wavelengths between 400 - 700 nm (nm = nano-meter).
132
Name 6 different parts of the eye?
```
Cornea
Aqueous humor
Crystalline lens
Pupil
Vitreous humor
Retina
```
133
What is the purpose of the cornea perform?
It is the transparent "window" into the eyeball.
134
What is the purpose of the Aqueous humor?
It is the watery fluid in the anterior chamber.
135
What is the purpose of the crystalline lens?
It is the lens inside the eye, which enables changing focus.
136
What is the purpose of the pupil?
It is the dark circular opening at the center of the iris in the eye where light enters.
137
What is the purpose of the vitreous humor?
It is the transparent fluid that fills the vitreous chamber in the posterior part of the eye.
138
What is the purpose of the retina?
It is a light-sensitive membrane in the back of the eye that contains rods and cones, which receive an image from the lens and send it to the brain through the optic nerve.
139
What is necessary in order for our eyes to focus?
• Refraction is necessary to focus light rays on the retina
– Done by the lens under control of ciliary muscle
• The lens can change its shape, and thus alter the refractive power
140
What is emmetropoia?
No refractive error in the eye
141
What is myopia?
– Focus in front of the retina
– distant objects cannot be seen sharply
– nearsightedness
142
What is Hyperopia?
– focus behind the retina
– Near things cannot be focused
– farsightedness
143
Is there a way for us to fix our focus?
Yes through artificial lenses (glasses/contacts).
144
Describe the process of the Retinal Network.
• Light passes through a network of neural cells to get to the transducers
– Rods and Cone transduce
– Horizontal, bipolar, & amacrine cells process
– Ganglion cells output
145
What are phototranducers?
Rods and cones
146
In terms of rods and cones, what does the outer segment consist of in the eye and where is it in the eye?
– Contains the 'disks’
147
What is the process of phototransduction?
– Light hits rod or cone
– Membrane potential changes
– Changes transmitter chemical release from terminal
– Light to electrochemical signal
148
Does the retinal have color in the dark? (Y/N)
Yes.
149
If you expose the retina to light, it gains color. (T/F)
False, if you expose the retina to light it LOSES color.
150
If you put the retina back in the dark does color return? (Y/N)
Yes.
151
What is bleaching?
Light induced chemical change in the receptors.
152
What does photosensitive mean?
Light sensitive.
153
What is the photosensitive chemical in the rods?
Rhodopsin.
154
What 2 molecules is rhodopsin made of?
Opsin and Retinal
155
Retinal Exists as Two Isomers.
• Isomers have the same chemical formula
– C20H28O
– Same number of the same atoms and similar bonds
• Have different physical three-dimensional shape
156
Bleaching to transmission.
```
• Dark
– Rhodopsin inactive
– NA+ channels open
– NA+ flows in, depolarizing membrane
– Transmitter released
• Light
– Rhodopsin active
– NA+ channels close
– NA+ blocked
– Transmitter release stopped
```
157
What are our 2 spectral sensitivity curves?
Scotopic
| Photopic
158
What is scotopic
Low light conditions
159
What is photopic
High light conditions
160
What is the primary focus of rods?
Primary receptor of the scotopic (low light) system
161
What is the primary focus of cones?
Primary receptor of the photopic (high light) system
162
What are the 3 types of cones?
– Short (“blue”)
– Middle (“green”)
– Long (“red”)
163
Where are cones located in the retina?
• The Cones are located mostly at the center of the retina
| – The fovea
164
Where are the rods located in the retina?
• The Rods are out towards the sides (periphery) of the retina
– None at the fovea
165
What is the fovea?
• A cone rich area of the retina with the “retinal network” pushed away
– At the focal point of the eye "camera"
• Specialized area for high light photopic vision
166
How do photopic and scotopic systems connect differently?
```
• Photopic (high light)
– Low convergence (few to one)
• Poor sensitivity
– Can’t detect faint signal
• Good acuity
– Can tell the difference between things
• Via midget bipolar cells to midget ganglion cells
– Fire slow
• Scotopic (low light)
– High convergence (many to one)
• Good sensitivity
– Can detect faint signal
• Poor acuity
– Can’t tell the difference between things
• Via diffuse bipolar cells to parasol ganglion cells
– Fire fast
```
167
What is the purpose of the optic nerve?
• Processed visual information leaves the eye via the optic nerve
– Axons of the retinal ganglion cells
• There is a 'hole' in the retina where the optic nerve leaves the eye
• This creates a blind spot in our vision
– When one eye is closed
– Scotoma
168
How do you find your blind spot?
• Finding your blind spot
– Close one eye
– Fixate on 'F'
– Move book closer and farther from eye
– At some point the red dot will disappear
– At that point, the red dot is falling on your blind spot, the place where your optic nerve leaves your retina
169
What is the output unit of the eye called?
Ganglion cells.
170
What do rods and cones do?
Tranduce
171
How do the Horizontal, Bipolar, & Amacrine cells modify the input?
– Convergence
| – Lateral inhibition
172
What is lateral inhibition?
– Stimulation in the center excites the output cell
– Stimulus in the surround inhibits the output cell via lateral inhibition
• This is the same mechanism that created the Mach bands
173
What is the pathway from the eye to the brain called?
The Geniculo-Striate Pathway
174
Describe The Geniculo-Striate Pathway.
• About half of the axons of the optic nerve decussate (cross over) at the optic chiasm
– Left visual field projects to right hemisphere
– Right visual field projects to left hemisphere
• Retinal ganglion cells synapse at the lateral geniculate nucleus (LGN) of the thalamus
– The “geniculo” part
• All sensory input to cortex, except olfactory, make an initial synapse at a thalamic nucleus
• Most LGN cells project to striate cortex (AKA primary visual cortex, V1, Brodmann's area 17, calcarine fissure of occipital lobe)
– The “striate” part
175
What is visual field separation?
• Each eye gets input from the right and left visual fields
– But each visual field projects to the contralateral hemisphere
• The optic chiasm separates the visual field input to both eyes to the contralateral hemisphere
– Left visual field to right hemisphere
– Right visual field to left hemisphere
176
Describe the way that damage to visual pathway can be caused.
```
• Before chiasm
– Still see full visual field
• Reduced field on same side as damage
• After chiasm
– Can only see half of visual field
• No vision on opposite side as damage
• Contralateral Hemianopia
```
177
What Kind of Stimuli Make a Ganglion Cell Fire?
• Mapping the Receptive Field of a Retinal Ganglion Cell
– Record the firing of a single retinal ganglion cell
– Move a spot of light across the visual field
– The part of the visual field in which the light changes the firing of the ganglion cell is the receptive field of that ganglion cell (the video showing via light the path way the cells fired).
178
What is the receptive field of the cell?
• That part of the visual field that can change the firing rate of the cell (up or down) if the proper stimulus falls within it
179
Retinal Ganglion Cell Receptive Fields are Circular Center/ Surround
* On-center/ Off-surround
| * Off-center/ On-surround
180
Eyes to layers.
```
• Input from different eyes goes to different layers
– Layers 1, 4, 6
– Contralateral eye input
– Layers 2, 3, 5
– Ipsilateral eye input
– Ipsilateral eye input
• Different layers have different kinds of cells
– Layers 1, 2
• Magnocellular
– Large fast cells
– Layers 3, 4, 5, 6
• Parvocellular
– Small slow cells
```
181
define: lesion (Ch.4)
1. a region of damaged brain
| 2. to destroy a section of the brain
182
define: agnosia (Ch.4)
a failure to recognize objects in spite of the ability to see them. Agnosia is typically due to brain damage.
183
define: inferotemporal (IT) cortex (Ch.4)
part of the cerebral cortex in the lower portion of the temporal lobe, important in object recognition
184
define: homologous regions (Ch.4)
brain regions that appear to have the same function in different species
185
define: Gestalt (Ch.4)
means "form" in German. a school of thought stressing that the perceptual whole could be greater than the apparent sum of the parts
186
Two visual systems are maintained from eye to cortex. What are they?
• One low acuity, high sensitivity, fast
– spatial location, motion: “where”
• One high acuity, low sensitivity, slow
– object recognition: “what”
187
Do neurons adapt to stimulation?
Yes they do, like wearing a watch; you notice it at first but after a while your neurons stop alerting you of its presence.
188
What do we know so far how the visual system works and constructs images?
• Bottom-up processing
– The visual system initially responds to dots of light
– From those dots it builds edges
– From the edges it builds corners
– From those dots and edges and corners it can build complex features
– From those features it can build objects
• This is the structuralist view
– The perception of a thing is the sum of its parts
189
What are the 5 Gestalt Laws of perceptual organization?
```
Law of simplicity
Law of proximity
Law of similarity
Law of good continuation
Law of common fate
```
190
What is the law of proximity?
Things that are closer together belong together.
191
What is the law of similarity?
Things that are alike get grouped together.
192
What is the law of good continuation?
Things that result in straight or smoothly curving lines, rather than abrupt angles, get grouped together.
- We see a curved line over a straight, not two lines with abrupt angles.
193
What is the law of common fate?
Things that move together get grouped together.
194
What are some other grouping principles?
Closure
Common region
Connectedness
Parallelism & symmetry
195
What is closure?
We group things that are close
196
In terms of rods and cones, what does the inner segment consist of in the eye and where is it in the eye?
– Closer to front of eye
| – Metabolic stuff
197
define: feed-forward process (Ch.4)
a process that carries out a computation (e.g., object recognition) one neural step after another, without need for feed-back from a later stage to an earlier stage
198
define: middle (midlevel) vision (Ch.4)
a loosely defined stage of visual processing that comes after basic features have been extracted from the image (low-level, or early, vision) and before object recognition and scene understanding
(high-level vision)
199
define: illusory contour (Ch.4)
a contour that is perceived even though nothing changes from one side of it to the other in an image
200
define: structuralism (Ch.4)
a school of thought believing that complex objects of perceptions could be understood by analysis of the components
201
what are Gestalt grouping rules? (Ch.4)
they are a set of rules describing which elements in an image will appear to group together. The original list was assembled by members of the Gestalt school of thought.
202
what is "good continuation"? (Ch.4)
A Gestalt grouping rule stating that two elements will tend to group together if they seem to lie on the same contour
203
define: prosopagnosia (Ch.4)
an inability to recognize faces
204
define: congenital prosopagnosia (Ch.4)
a form of "Face blindness" apparently present from birth, as opposed to "acquired prosopagnosia" which would typically be the result of an injury to the nervous system
205
What are the 2 models of sensory organization?
Old Model and the New Model
206
What are the 3 organization systems in the old model
Hierarchic
Functionally homogeneous
Serial
207
What are the 3 organization systems in the new model?
Hierarchic
Functionally segregated
Parllel
208
What is common region?
Things that are enclosed together belong together.
| - Can over come proximity.
209
What is connectedness?
Things that are connected to each other belong together.
| - Can also overcome proximity.
210
define: texture segmentation (Ch.4)
carving an imagine in to regions of common texture properties
211
define: similarity (Gestalt) (Ch.4)
a gestalt grouping rule stating that the tendency of two feature to group together will increase as the similarity between them increases.
212
define: proximity (Gestalt) (Ch.4)
a Gestalt grouping rule stating that the tendency of two features to group together will increase as the distance between them decreases
213
define: parallelism (Gestalt) (Ch.4)
a rule for figure-ground assignment stating that parallel contours are likely to belong to the same figure
214
define: ambiguous figure (Ch.4)
a visual stimulus that gives rise to two or more interpretations of its identity or structure
215
define: Necker cube (Ch.4)
an outline that is perceptually bi-stable. Unlike the situation with most stimuli, two interpretations continually battle for perceptual dominance
216
define: accidental viewpoint (Ch.4)
a viewing position that produces some regularity in the visual image that is not present in the world
217
define: figure-ground assignment (Ch.4)
the process of determining that some regions of an imagine belong to a foreground object and other regions are part of the background
218
define: surroundedness (Ch.4)
a rule for figure-ground assignment stating that if one region is entirely surrounded by another, it is likely that the surrounded regions is the figure
219
define: relatability (Ch.4)
the degree to which two line segments appear to be part of the same contour
220
define: heuristic (Ch.4)
a mental shortcut
221
define: non-accidental feature (Ch.4)
a feature of an object that is not dependent on the exact (or accidental) viewing position of the observer
222
define: global superiority effect (Ch.4)
the finding in various experiments that the properties of the while object take precedence over the properties of parts of the object
223
define: Bayesian approach (Ch.4)
a way of formalizing the idea that our perception is a combination of the current stimulus and our knowledge about the conditions of the world -- what is and is not likely to occur.
224
Bayes' theorem (Ch.4)
P(A|O)=P(A) x P(O|A)/P(O) it enables us to calculate the probability (P) that the world is in a particular state (A) given a particular observation (O)
225
define: parahippocampal place area (Ch.4)
a region of extrastriate visual cortex in humans that is specifically and reliably activated more by images of places than by other stimuli
226
define: fusiform face area (Ch.4)
a region of extrastriate visual cortex in humans that is specifically and reliably activated by human faces
227
define: extrastriate body area (Ch.4)
a region of extrastriate visual cortex in humans that is specifically and reliably activated by images of the body other than the face
228
define: middle temporal area (Ch.4)
an area of the brain thought to be important in the perception of motion
229
define: naive template theory (Ch.4)
the proposal that the visual system recognizes objects by matching the neural representation of the image with a stored representation of the same "shape" in the brain
230
define: structural description (Ch.4)
a description of an object in terms of the nature of its constituent parts and the relationships between those parts
231
define: geon (Ch.4)
in Biederman's recognition-by-components model, any of the "geometric ions" out of which perceptual objects are built
232
define: recognition-by-components model (Ch.4)
Biederman's model of object recognition, which holds that objects are recognized by the identities and relationships of their component parts.
233
define: viewpoint invariance (Ch.4)
1. A property of an object that does not change when observer viewpoint changes.
2. a class of theories of object recognition that proposes representations of objects that do not change when viewpoint changes
234
define: entry-level category (Ch.4)
for an object, the label that comes to mind most quickly when we identify it (e.g. "bird"). At the subordinate level, the object might be more specifically named (e.g. "Eagle"); at the superordinate level, it might be more generally named (e.g. "animal")
235
define: double dissociation (Ch.4)
the phenomenon in which one of two function, such as hearing and sight, can be damaged without hard to the other and vice versa
236
What is parrellelism and symmetry?
We group 2 with 3 & 7 with 8
- 2 and 3 = parallel
- 7 and 8 = symmetric
237
define: symmetry (Gestalt) (Ch.4)
a rule for figure-ground assignment stating that symmetrical regions are more likely to be seen as figure.
