Sensation And Perception 2 Flashcards
(123 cards)
1
Q
Optic Ataxia
A
- Damage to the where stream
- Damage to the parietal lobe
- Inability to use visual information to guide movement
- Cannot match orientation of card in hand to that of a slot with the same orientation
- BUT can push the card through the slot
2
Q
How do ‘what’ and ‘where’ stream relate to LGN?
A
- Layers 1-2 project to the dorsal pathway (where)
2. Layers 3-6 project to the ventral pathway (what)
3
Q
What is Object perception
A
- Perceiving objects and separating them from their backgrounds seems easy and automatic
- But it’s quite difficult
- Hard for computers
- Information organized into coherent units
4
Q
Images on the retina can be ambiguous, blurred or hidden
A
- Ambiguous because a particular shape, like a circle on the retina, can be created by objects that are aren’t circular
- Hidden meaning people understand objects continue to exist even if an object is partially covered
5
Q
Gestalt psychology
A
- Gestalt: essence of an entity’s complete form
2. The whole is different than the sum of our parts
6
Q
Gestalt principles of perceptual organization
A
- Similarity: similar things appear to be grouped together
- Continuity: things partially covered by other objects are seen as continuing behind the covering object
- Proximity: things that are near each other appear to be grouped together
- Common fate: things that are moving together appear as a group (same direction)
- Closure: connected region of the same visual properties, color, texture, motivation n, is perceived as a single unit
- Familiarity
- Figure-ground: when we see a separate object, it is usually seen as figure that stands out from its background, called the ground
7
Q
Figure-ground segregation
A
- Process by which objects are separated from their backgrounds
- Borders of shape are assigned to a figure
8
Q
Figural cues
A
- Symmetry: symmetrical regions more likely to be seen as figure
- Convexity: convex (not concave) more likely to be seen as figure
- Closure: enclosed regions more likely to be seen as figure
- Small area: regions with a smaller area more likely to be seen as figure
- More likely to perceive lower area as figure vs. upper area
- Familiarity: regions that are familiar more likely to be seen as figure
9
Q
Object perception in the brain i.e. What types of neurons
A
- Neurons in inferior temporal cortex fire in response to whole objects
- Fire to specific objects
- IT neurons have large receptive fields
- IT neurons can prefer to have certain objects in their receptive field like an apple, square, or faces
10
Q
Specificity coding
A
- IT neurons fire in response to objects, and fire in response to specific objects
11
Q
Types of neurons in IT
A
- Size specific: small # of objects of a particular size
- Location specific: small # of objects of a particular location
- View specific: small # of objects shown in a particular view
- Size variant: many different sizes of a small group of objects
- Location invariant: small group of objects located in many different places in visual field. These neurons have very large receptive fields
- View invariant: small # of faces seen in many different views
12
Q
Face perception
A
- Some neurons in IT respond selectively to faces
2. Area referred to as the fusiform face area (FFA, in temporal lobe)
13
Q
Damage to FFA
A
- Prosopagnosia: can perceive faces but cannot recognize them
- Evidence for unconscious recognition: increased skin conductance when viewing picture of significant other
14
Q
Grandmother cells
A
- Neurons that increase their firing rate in response to a very specific stimulus
EX. picture of grandma regardless of angle or facial expression - Experimentally tested: cell that fires to Jennifer Aniston but no other famous people or non famous people
15
Q
Real motion
A
- When there is actually motion
2. Continuous smooth movement over space and time
16
Q
Illusory motion
A
- When there is not actually motion
2. 4 types: apparent motion, induced motion, motion aftereffects, peripheral drift
17
Q
Apparent motion
A
- Illusion of movement between 2 objects separated in space when the objects are flashed rapidly on and off, and separated by a time interval
- Set of discrete displacements
- Brain activation for real and apparent motion occupied in the same region of the brain
- Ex. Motion pictures
18
Q
Induced motion
A
- Stationary object appears to be moving due to the presence of other moving objects nearby
- Ex. Clouds moving over the moon makes the moon appear like it’s moving too, but it is not.
19
Q
Motion aftereffects
A
- The perception of motion after looking at a moving stimulus and looking away (or once the motion stops)
- Ex. Waterfall Illusion
20
Q
Peripheral drift
A
- The Illusion of motion in the periphery when your eyes are moving or blinking
21
Q
Motion perception at the retina
A
- Retinal neurons fire in response to motion in their RF
2. But there is motion perception beyond the retina
22
Q
Where in the brain is motion processed?
A
- Area MT (medial temporal)
2. Located in dorsal ‘where’ pathway
23
Q
Newsome et al. Study on monkeys
A
- Presented monkeys with moving dot display
- Asked monkeys to indicate direction of motion
- Goal: investigate relationship between monkeys ability to perceive motion and the response of a neuron in MT
- Higher motion coherence = greater activity in MT
- Result: Area MT is involved in motion perception
24
Q
What if MT is damaged: Newsome study with monkeys
A
- Monkey can detect motion at 1-2% coherence
2. With MT lesion, monkey can’t detect motion until 20% coherence
25
MT damage in humans looks like?
1. Bilateral MT damage = akinetopsia: motion blindness
2. All perceptual/ cognitive functions intact...only motion perception is impaired
3. Photographic snap shots of motion
26
What if MT is stimulated?
1. Electrodes implanted into the brain of an awake monkey
| 2. Stimulation to MT neurons changes perception (may change direction of motion)
27
When we follow something with our eyes, is there movement on the retina/ cortex? And what 2 bits of info are needed?
1. No movement on retina or cortex
| 2. 2 bits of information: whether eyes are moving and what the image on the retina is
28
Corollary discharge theory
1. 2 types of signals sent to the brain regarding motion
2. Corollary discharge signal (CDS): signal that tells the brain an eye movement has occurred.
- to initiate eye movements, brain sends motor signals (ms) to eye
muscles (moving your eyes to follow a moving object)
- the ms causes the CDS to be sent to the cortex
3. Image displacement signal (IDS): signal that tells the brain that something has moved across the retina (no eye movement)
- movement across retinal receptors sends IDS to the cortex
29
What happens when CDS or IDS signals are sent?
1. Motion is perceived
30
What happens when CDS and IDS signals are sent?
1. No motion is perceived
31
Neural evidence for CDT
1. Bar moves across receptive field
2. Bar stationary and eye movement causes receptive field to move across bar
3. Results: different neural responses in visual cortex
4. Neurons fire in response to real movement, not any movement
5. Real motion neurons
32
Biological motion
1. Movement of an animate object (like a human) EX. walking, skipping
33
Neural correlates of biological motion
1. Superior temporal sulcus (STS) responds more to biological motion than scrambled motion
2. Knocking out STS via TMS = impaired biological motion perception
34
Area MT: major findings from Newsome study with monkeys
1. Area MT is involved in motion perception: higher activity with higher motion coherence
2. Area MT is necessary in motion perception: impairment to MT= can't perceive motion
35
Distributed Attention
1. Broad focus on no particular object
36
Divided attention
1. Focus on a few particular areas/objects
2. We can not multitask, we are only switching back and forth between tasks quickly
3. Exception is supertaskers
4. Ex. Driving and talking on phone = delayed brake time, impaired object perception, increased accident rates.
37
Selective attention
1. Focus on a particular area/object
38
Why is attention important/necessary?
1. Need help dealing with all the mess of info in the world
| 2. Processing everything at one is bad i.e autism
39
Saccades
| How does it affect attention?
1. Selective attention task
2. Eye movements that can occur unconsciously (200 ms)
3. Eye tracker: detects contrast between pupil and cornea in order to track saccades
4. Can have saccades without attention
5. Can have attention without saccades
40
Bottom up influences involved in attention
1. Stimulus salience: the features that stand out due to physical properties (contract, brightness, familiarity, drawing our attention)
41
Top down influences in attention
1. Task: where we focus our attention depends on the task.
2. Experience: where we focus our attention depends on how much we know about the situation i.e someone who knows a lot about sports
42
Eye movements and autism
1. Autistic children have trouble detecting facial expressions
2. Saccades when viewing faces much different than individuals without autism
3. Perhaps due to differences in eye movements
43
Can attention enhance perception?
1. Yes, attention improved reaction times to a target
44
Object based attention
1. Attention is automatically drawn to objects and spreads within them
2. Attention enhancing perception
45
Can attention hinder perception?
1. Yes, attention is limited: you can only focus on one thing at once
2. Attention is a spotlight
46
Change blindness
1. Failure to perceive something due to breaks in your visual scene
47
Inattentional blindness
1. Failure to perceive something due to your attention being allocated elsewhere
2. Ex. Magic trick thief or following an assigned task
48
Processing unattended stimuli
1. Using interocular suppression: 2 different images shown to each eye
2. Results: attention unconsciously directed towards opposite gender
3. For men, attention was directed away from same gender (but not for women)
4. Attention can be directed unconsciously, we process stimuli unconsciously
49
Binding: function of attention (what is the purpose of attention?)
1. Process by which features (individual lines, colors, motion) are assembled to form a coherent object
2. Attention helps to assemble or bind these features
3. To perceive objects, need to put features together that are processed by V1 (location, depth, color, form)
50
Feature integration theory (FIT)
1. Features are bound in two stages
1. Preattentive stage: individual features are processed (lines, color, orientation) -no attention required
2. Focused attention stage: features are combined - attention is required
3. Attention is the glue that combines 'what' and 'where' info
4. Linear theory: object > preatt. Stage > focused stage > perception
51
Evidence for FIT
1. Illusory conjunctions: wrongly binding the features of 2 objects into 1
Ex. Present brief Visual stimuli of red circle and green square > participant reports green circle
2. Visual search: feature search: find red T amongst all blue L's
3. Visual search: conjunction search: find red T amongst mixed red and blue T and L's
4. Patients with damage to 'where' stream (parietal) can do feature search but not conjunction search
52
Selecting and gating information: function of attention
1. Attention helps us to understand our visual world by focusing our resources on a particular area/object/event
2. Necessary because world is cluttered and confusing
3. Attention helps neuron select which stimulus to fire in response to
4. Attention acts as a gate, visual information must pass in order to be processed
53
Top down/ bottom up physiology for attention
1. Top down: Directed attention
2. Prefrontal cortex
3. Look over there out the window
1. Bottom up: stimulus driven
2. Sensory cortex in parietal
3. Phone ringing catching your attention
4. What we expect to perceive
54
Attention and neural activity
| What did the study find?
1. Colby 1995: recorded from neuron in monkey parietal cortex
2. Results: attention enhances neural firing
3. Attention increases fMRI activity
4. Attention increases gamma synchrony
55
Attentional deficits
1. ADHD attention deficit hyperactivity disorder: inattention and hyperattention
2. ADD attention deficit disorder: only inattention
3. Risk factors: genetics, alcohol/smoking during pregnancy, low birth weight, premature birth, diet (food coloring, dyes)
4. Pathophysiology: reduction of brain volume in left prefrontal cortex, elevated dopamine levels, low arousal threshold
56
What is sound?
1. Pressure changes in the air or other medium (i.e. Water)
| 2. Sound is the experience we have when we hear
57
What are the two parts to sound stimulus?
1. Condensation: increase in pressure
2. Rarefaction: decrease in pressure
3. Air molecules don't move far, they just shift back and forth slightly (vibrate)
58
What are the two properties of sound waves?
1. Width: frequency (# of times per section pressure changes repeat, space between waves)
- Cycles per second measured in Hertz.
- This is how we hear pitch.
- humans hear from 20 and 20,000hz (optimal 2,000-4,000)
2. Height: amplitude (pressure, how tall a wave is)
- amplitude: difference in pressure between the middle and peak of a sound wave
- this is how we perceive loudness (measured in decibel)
59
Can two tones have the same frequency? Why?
1. Yes, because they have different timbres
| 2. Timbre: quality of a tone
60
Process of hearing
1. Sound waves travel into pinna and down ear canal
2. Pressure from these waves vibrates the ear drum (tympanic membrane)
3. Movement of tympanic membrane causes ossicles to move
4. Ossicle movement pushes the fluid in the cochlea
5. Fluid movement in cochlea vibrates basilar membrane
6. Hair cells (within organ of corti) on basilar membrane transduce signal
61
Ossicles
1. Smallest bones in the human body
2. The middle ear: malleus, incus, stapes
3. Purpose to help transport and amplify sound
62
Tympanic membrane
1. Eardrum
| 2. Vibrates in response to sound
63
Cochlea
1. Primary organ for hearing
2. Inner ear
3. Snail shaped and fluid filled
64
Cross section of cochlea (picture for labeling)
1. Middle section: cochlear duct
2. Basilar membrane: under cochlear duct
3. Organ of corti: under cochlear duct, above basilar membrane
4. Tectorial membrane: inside cochlear duct
5. Cochlear near: leaves cochlear duct to the brain
65
Basilar membrane
1. vibrates differently in response to different frequencies
2. Tonotopic organization: base responding to high frequency, apex responding to low frequency
3. Inside cochlea
66
Organ of corti
1. Sits on the basilar membrane within the cochlea
2. Contains hair cells (receptors of hearing)
3. Is covered by the tectorial membrane, which touches the cilia of the hair cells
67
Tonotopic organization of sound
1. Base responds to high frequencies
| 2. Apex responds to low frequencies
68
Hair cells
1. Transduce the auditory signal and send it down the auditory nerve to the brain
2. Inner hair cells: transduce signal, provide information on pitch
3. Outer hair cells: amplify response from inner hair cells and send info to auditory cortex
69
Transduction: inner hair cells
1. Movement of fluid inside cochlea cause hair cells to move (tip over)
2. This movement opens ion channels (Na+), causing cell to depolarize
3. This signal is sent down the auditory nerve to the brain
70
Which fibers fire? Inner hair cells and basilar membrane
1. Hair cells that fire depend on their location on the basilar membrane
2. Which depends on the frequency of the sound
71
Pinna: outer ear
1. Funnels and enhances sound, protects tympanic membrane
72
Tectorial membrane
1. Extends over the hair cells
73
Hearing loss
1. Conductive hearing loss: sound can't reach receptors
2. Noise-induced hearing loss: damage to hair cells
3. Cortical hearing loss: damage to A1
4. Presbycusis: age related hearing loss (old ear)
74
Cochlear implants
1. Aid in hearing, but not entirely restore it
| 2. Only helps with inner ear hearing loss
75
From ear to brain, what are the relay stations?
1. Ear > brain stem > medial geniculate nucleus (MGN) > A1
76
A1
1. primary auditory cortex (temporal lobe)
2. Encodes frequency info, like basilar membrane
3. If damaged, difficulty detecting frequency changes
4. Has a tonotopic map to maintain
77
Effects of experience on sound
1. Auditory cortex is plastic, changes with experience
2. Musical training: enlarged part of auditory cortex where tones are processed- musicians have 25% more cortex activated to music than non musicians
3. Increases neural activity in response to sound: 2x more activity in musicians vs non musicians
78
Sound localization
1. Knowing where sounds are located in our auditory space
2. More difficult than we think
3. Less info to work with than vision
4. Cochlea does not gather location information (retina does)
79
Coordinate system for sound localization
1. Localizing along the azimuth (left and right)
2. Localizing along the elevation (up and down)
3. Localizing distance
80
Azimuth: localization of sound
1. Binaural cues: requires the use of both ears
2. Interaural time difference ITD
3. Interaural level difference ILD
4. Binaural cues work together
Ex. Sound at 90 degrees: hits right ear first (ITD) and is higher in pressure at the right ear (ILD)
81
Interaural time difference ITD
1. The difference in the amount of time it takes for a sound to reach the left vs the right ear
2. Difficult to localize a sound coming from directly in front of you or directly behind you (180 degrees directly behind or straight ahead, 90 degrees from the side)
82
Interaural level difference ILD
1. Difference in the sound pressure level reaching the left vs. right ear
2. Difference apparent only for higher frequency sounds
3. Acoustic shadow: sound waves disrupted by the head
4. Behind the head is a shadow where sound waves don't reach
5. Affects perception of sound in shadowed ear
6. ILD occurs for high frequencies only
83
Cone of confusion
1. ITD and ILD do not provide information about elevation
2. To a listener: audio sources A (up high) and B (down low) and C (off to right) and D (off to left) have identical ITD and IDL
84
Elevation: localization of sound
1. Monoaural cues: requires one ear
2. Spectral cue:distribution of frequencies reaching the ear associated with specific locations of a sound
3. Interaction of sound with the head/outer ear provides info on location
85
Distance: localization of sound
1. Sound level: lower pressure = greater distance
2. Frequency: atmosphere absorbs high frequencies, more muffled = greater distance
3. Reverberations: sounds reflecting off a surface. Direct sound = sound reaching ear directly from source. Indirect sound = sound reaches ear after hitting a wall
86
Precedence effect
1. Sounds coming from 2 sources (and a bit delayed in time) are perceived as coming from only 1 source
87
Principles of auditory organization
1. Onset time: sounds that arrive at different times are probably coming from different sources
2. Location: sounds that are separated in space are probably coming from different sources
3. Proximity in time: sounds that are very close to one another are probably coming from the same source
4. Auditory continuity: sounds that stay constant are probably coming from the same source (we can fill in missing info)
5. Similarity of timbre and pitch: sounds that have the same pitch/timbre are probably coming from same source
7. Experience: our ability to segregate sounds in our environment is affected by our experience Ex. Hearing familiar melody in noisy environment
88
Damage to auditory cortex
1. Impairs sound localization ability (temporal lobe)
89
'What' stream for sound
1. Sound recognition/ identification: understanding the pattern of sounds and how they are assembled to make a whole, coherent percept i.e. Music
2. Location in brain: ventral stream: anterior auditory cortex > frontal lobe
90
'Where' stream for sound
1. Sound localization: understanding from where a sound is originating
2. Location in brain: dorsal stream. Posterior auditory cortex > parietal > frontal lobe
91
Double dissociation in auditory cortex streams (damage)
1. Damage to 'what' stream: impaired recognition but intact localization
2. Damage to 'where' stream: impaired localization but intact recognition
92
Jeffress Model
1. Neurons in auditory cortex respond to specific ITD's
2. Neurons receive input from both ears
3. These neurons have narrow tuning curves
93
Broad tuning curve neurons
1. Neurons in auditory cortex that respond to information entering the contralateral ear
2. Not specific to ITD's, just to ear receiving input
3. Distributed coding
94
Ventriloquism effect
1. Error in sound localization
| 2. Ex of visual perception influencing sound perception
95
Speech perception
1. Speech perception is how we make sense of the sounds people utter in order to communicate with us
2. Seems easy, but computers have a hard time, even humans too
96
Acoustic signal
1. The physical stimulus is the acoustic signal
2. Based on frequencies of the sound
3. influenced by how sound is created
4. More complex than complex sounds, the air pushed by lungs past vocal cords and in vocal tract
97
Articulators
1. Lips, jaw, teeth, etc
2. Affect shape of vocal tract
3. Allow for differentiation of vowels and consonants
98
Acoustic signal: vowels
1. Produced by vibrations of vocal cords
2. Vibration occurs at various frequencies
3. Vowel sound is based on formants and the articulators
99
Formants
1. Frequencies (associated with vowels) that make up an acoustic signal
2. Vowels are characterized by series of formants
100
Formants transitions
1. Rapid shifts in frequency preceding or following formants
101
Acoustic signal: consonants
1. Produced by a constriction of the vocal tract
102
Phoneme
1. Most basic unit of speech
2. Shortest segment of speech that can change the meaning of a word
3. 47 phonemes in American English
103
Voice onset time (VOT)
1. Delay between when sound begins and vocal cords begin vibrating
2. Can lead to changes in perception
3. Ex. VOT is shorter for 'da' than 'ta'
104
Phonetic boundary
1. Study Eimas and Corbin 1973
2. Slowly increase VOT
3. At some point, perception shifts from da to ta
4. This is phonetic boundary
105
Influence on phoneme perception: context
1. The d in din and du sound the same but have different acoustic signals
2. Coarticulation: overlap between articulation of neighboring phonemes
106
Influence on phoneme perception: speakers
1. Between speakers, lots of variability in
| 2. Pitch, speed, accents, pronunciation
107
Influence on phoneme perception: visual cues
1. What we see influences what we hear
| 2. Ex. video of man saying ba, but it looks as if he is saying fa
108
McGurk effect
1. Audiovisual perception
2. Calvert study:
3. FMRI while subjects watched and repeated lip movements
4. Results: activation in auditory cortex
5. Similar to actually perceiving speech
6. Same areas activated for lipreading and speech perception
109
Influence on phoneme perception: experience
1. Brain fills in missing information
2. Based on prior knowledge
3. Phonemic restoration
4. Experience dependent plasticity: infants can discriminate between all sounds, by age of 1 they lose this ability (Japanese lose L and R sound, Americans get better at L and R
110
Phonemic restoration
1. perceptual phenomenon where under certain conditions, sounds actually missing from a speech signal can be restored by the brain and may appear to be heard
111
Top down/ bottom up speech perception
1. Top down: knowledge meaning
2. Bottom up: acoustic signal
3. Working together for speech perception
112
Speech segmentation
1. Perception of individual words in a stream of speech
2. Surprisingly difficult
3. Spectrographs can not even reveal much about speech segmentation (acoustic signal)
4. Not based on pauses between words
5. Based on experience: we learn that some sounds are more likely to follow each other than others
6. Ex. 'Pre & tty,' 'ba & by,' but not 'tty & ba'
113
Statistical learning
1. Speech segmentation occurs via statistical learning where we learn the transitional probabilities between syllables (chance on sound will follow another)
114
Testing segmentation in babies
1. Present two items one word 'golabu' and one part word 'bupado'
2. Results: babies listen more to new items
3. Listened more to part words
4. Babies learned transitional probabilities and thus were able to segment the speech stream
115
Aphasia
1. Language impairment
116
Brocas aphasia
1. Speech production: damage to inferior frontal gurus
117
Wernicke's aphasia
1. Speech perception/comprehension: damage to superior temporal lobe
118
Aphasia double dissociation
1. Brocas aphasia: deficit in production, intact comprehension (trouble producing words) (non fluent aphasia)
2. Wernicke's aphasia: deficit in comprehension, intact production (can produce words, but words won't make sense, word salad) (fluent aphasia)
119
What and where stream for speech
1. Ventral: recognizing speech
2. Dorsal: producing speech
3. Speech processing distributed across cortex
120
Motor theory of speech perception
1. Motor mechanisms involved in producing sounds activate mechanisms for perceiving sounds (and vice versa)
2. In monkeys, audiovisual mirror neurons (in Broca's area) fire when a monkey carries out an action that produces a sound, or just hears the sound itself
121
Speech production and perception: TMS studies
1. In humans, TMS studies show link between production and perception
2. Stimulation of motor areas involved in producing phonemes enhanced perception of those phonemes
122
Parietal lobe speech perception
1. Damage = difficulty discriminating between syllables, but word comprehension ok
123
Superior temporal lobe in speech perception
1. FMRI used to find voice area
| 2. Activated by voices more than by other sounds
