Midterm 3 Flashcards
(119 cards)
1
Q
do objects have colour
A
no they have reflectance profiles
2
Q
is light coloured
A
no it only has wavelength
you construct the colour and many people experience colour differently
3
Q
explain the electromagnetic spectrum
A
energy is described as by a wavelength
spectrum ranges from short gamma (10^-3) to long radio waves (10^15)
visible light = 400-750 nanometres
frequency = speed/ wavelength so wavelength = distace between two peaks
4
Q
define monochroatic light
A
one wavelenght
eg laser
5
Q
physical parametres of monochromatic light
A
wavelenght
intensity
6
Q
define heterochromatic light
A
many wavelengths
7
Q
what is spectral composition
A
for heterochromatic light
gives the intensity at each wavelenght
8
Q
graphically what is the differences between mono and hetero chromatic light
A
mono = vertical bar down at specific wavelenght
hetero = horizontal line across then white light at all wavlengths present
or steep up and acorss = none of some wavelenghts but the other wavelengths are there
9
Q
explain the spectral composition of tungsten vs sunlight
A
tungsten = from light bulb, steady increase as wavefunction increases sunlight = increases at the lower end of the spectrum then decreases
10
Q
the spectral components of light entering the eye is the product of what two things
A
the illuminant and the surface reflectance of objects
so illuminant = light type, mono or hetero and if hetero which wavelenghts
surface reflectance = what is reflected is what we see
so purple, blue, green, yellow, orange, red = (low to high wavelength)
11
Q
what are the three psychological dimensions of colour
A
hue
saturation
brightness
12
Q
explain hue
A
perceived colour of the object
organised around a circle (circumference)
13
Q
explain saturation
A
as colour wheel becomes whiter and whiter
is the diametre of the circle`
14
Q
explain brightness
A
maps onto energy
how dark or bright
15
Q
3D HSV colour space
A
circle top surface = circumference of hue, diameter of saturation and then 3D depth of value or brightness = starts bright and descends into black
16
Q
for unimodal distributions, how do we go from physical properties of light to pscyhological dimensions of colour
hue =
saturation =
value / brightness =
A
hue = peak, centre, of spectral distribution so where peak is saturation = spread (variance) of spectral distribution so narrow vs fat peak brightness = height of spectral distirbution so stumpy is dark and tall is bright
17
Q
additive vs subtractive light
A
additive = white lights add to make white light, so how monitors (RGB work)
subtractive = add to give black so paint
for pigments so subtractive - in the mixture, the only wavelengths reflected by the mixture are those that are reflected by all the components in the mixture
18
Q
how do monitors work eg stadium or computer screen
A
RGB
only three colours - phosphors
almost any colour can be generated by adding different amounts of the three primary colours (red, green, blue)
works because we have three types of photoreceptor (S,M,L cones) (short is vaguely blue, medium is green and long is red)
19
Q
physiology of colour vision
A
the normal retina contains three kinds of cones (S,M and L) each maximally sensitive to a different part of the spectrum
20
Q
trichromatic theory of colour vision
A
young-helmholtz
our ability to distinguish between different wavelengths depends on the operation of three different kinds of cone receptors, each with a unique spectral sensitivity
each wavelenght of light produces a unique pattern of activation in the three cone mechanisms
No blue, red, green cones!
perceived colour = the relative amount of activity - the pattern of activity - in the three cone mechanism
21
Q
the principle of univariance
A
the absorption of a photon of light by a cone produces the same effect no matter what wavelength of light generates the response
so m cones for example will respond equally to a dim green light as a bright red light - as far as just M cones alone, these are exactly the same
so we need 3 cones to tell the difference
so
22
Q
so how do we see colour
A
L,M and S responses
will get some output ration of three different cone types
works with mono and hetero chromatic distributions
23
Q
how do iphone and computer monitors etc work
A
so slide showed heterochromatic light source activating s,m and l to specific extents
as long as the monochromatic light source acts on the three cones in excatly the same way = then see the same colour
=metamers
24
Q
metamers
A
two diff lights
some arbitrary distribution of light you can mix 3 monochromatic light sources in a way to produce the same outputs across the cone types = same perceived colour
on any arbitrary disribution
how iphones etc work
relies on our 3 cones
based on trichromatic theory of colour
so can mix the three primary colours to make amy colour at all (worked this out before discovered the three photoreceptors match onto this
25
herring's argument against trichromacy
never see a yellowish blue or greenish red
base on colour after effects
red and green are fundamentlaly opposite and so are yellows and blues so dont see these together
= opponent processing
26
opponent process theory
colour vision is influences by the activity of two opponent processing mechanisms
= a yellow / blue opponent process
so see loads of yellow, M and L isomerise so calm down, then white light shown = perceived as blue as no yellow opponent process on
= a red / green opponent provess
stare at red, part of retina looking at red drives long wave cones maximally, isomerise and turn off. then white light shown and will perceive as green as no opponent red
27
complete how we see colour combining two theories
trichromacy = metameric matching
see all colours with 3 cone types
can predict on hue, saturation and brightness
second layer of opponent processing
second order wiring
certain combinations of colours are not perceived based on neuron wiring
28
name and explain types of colour blindness
monochromat- person who needs only one wavelength to match any colour - pure colour blindness = rods only = rare
dichromat - person needs only two wavelengths to match any colour
anomalous trichromat - needs three wavelenghts in different proportions in different proportions than normal trichromat
unilateral dichromat - trichromat vision in one eye and dichromat in other eye
pure colour blindness = rods only = rare
29
colour experience of monochromats
```
very rare, heridatary
only rods and no functioning cones
ability to perceive only in white, gray and black cones
true colour blindness
poor visual acuity
very sensitive to bright light
only output of one colour receptor, touches on principle of univariance
no concept of colour
```
30
colour experience of dichromats
are missing one of the three cone systems
3 types
protanopes - no L
see in blues to yellows (red - green colour)
dueteranopes - no m
see in blues to yellows (red - green colour)
tritanopes - no S
see in red to green (so blue yellow colour blind)
not true colour blindness, just see colour differently as onl output from two cones
31
how audition differs from vision
vision - space for free (map created in periheral receptors in retina)
audition - no spatial map, must compute space centrally
-some acoustic information about sound location, but no spatial information at the cochlear
sound (and thus the process of hearing) is inherently temporal in how it physically occurs / provides information - unfolds over time
32
physical sound is...
compression of air molecules in space
33
how do loud speakers produce sound
the diaphragm of the speaker moves out, pushing air moecules together
the diaphragm also moves in pulling air molecules apart
the cycle of this process creates alternating high and low pressure regions that ravel through the air
= sound waves
34
sound waves
pure tone created by a sine wave
| period = whole wave = tone
35
amplitude of a sound wave
height above atmospheric pressure
| difference in pressure of high and low peaks
36
frequency of a sound wave
how may waves are packed in over time
number of repeating cycles in a given second
where wave returns to the same spot
37
```
physical properties of a sound wave
frequency
amplitude
timbre
result in what perceptual elements of sound
```
frequency (period)- pitch
amplitude - loudness
complexity - timbre (how we tell between a clarinet and a flute), relative to harmonics. dependent largely on relative energy in different frequency bands of sound's spectrum. relative power accross the harmonics
38
reflectance
multiple paths / path lenghts of an acoustic signal; same sound will be variabley decayed / decay thus same sound arrives at ear at different times with different acoustic properties
39
clarinet demo
the harmonic structure caused timbre to change
| pitch and loudness otherwise the same
40
how we measure / depict sound
waveform - frequency by amplitude
decibels
spectogram
41
decibels
measure amplitude / sound pressure - perceptual correlate = loudness
10dB increase = perceived doubling of loudness
doubling distance = 6 dB loss in perceived loudness
50-65 dB =average amplitude of human speech
but loudness is not based purely on sound pressure / amplitude
-duration
-frequency
takes a higher decibel to yield the same perceived loudness level in a person for a different frequency
42
spectrogram
most useful way of visually depicting sound
| plots relative power of a given sound across time and its frequency spectrum
43
fundamental frequency
lowest frequency / base frequency at which there is distinct power for a sound
harmonic structure of a sound is necessary based on what the fundamental is
each harmonic above it is a mutliple of the fundamental
the base frequency band at which a sound has power
determines the structure of the harmomics which will determine the timbre / harmonic structure (bands are multiples of the fundamental frequency)
44
ear converts
sound waves in the air into electrical impulses
| this is interpreted by the brain
45
track route of sound entering the ear
enters through external auditory canal
timpanic membrane
this vibrates in response to the sound
three bones - auditory osciles (malius, incus, stapes in that order)
movements of timbanic membrane vibrate the osicles passing on the information of frequency and amplitude
three bones pivot togther on amplitude = series of ligaments holding middle ear in place (anterior malial, posterior incutal ligament = important)
footplate of stapes
stapes moves with piston like structure into labrinth
filled with paralimbth
round window flexibility - allows for pressure change
so vibrations enter the labrinth
cochlear - vibration from stapes into cochlear then out to round window
asecending (scala vestibuli) and descending paths (scala tympani)
cochlear duct between the two - filled with endolympth
resner membrane separates and so does basal
organ of corti on basal membrane - this sends impulses to the brain by the cochlear nerve - hair cells do the trandsuction
tactorial membrane covers hair cells
basal membrane moves variabley
specific areas along the basal membrane move specifically for different frequencies
-low frequencies = at apex
-high frequencies = base
=tonatopic orientation
46
vibrations on timpanic membrane
low pitch / frequency = slower vibrations
| lower volume / amp = less dramatic
47
shape of timbanic membrane
cone shaped
48
pinna
bit that sticks out
functions to collect sounds at certain frequency ranges and amplify a certain frequency range of those sounds
2-5 thousand hertz = where conversational speech lies
amplfiy frequencies most salient for us as humans who talk
49
ear canal
```
external auditory meatus
3 cm long
funnel and ampliy sounds
protect sensitive ear drum
ear wax lives there - antimicrobe, fungal, moisturising etc, so dont need to clea out
```
50
ear drum
tympanic membrane
at base of ear canal
vibrates in response to compression waves of air moleules (sound)
first transformation - compression waves in air to a mechanical movement of the airdrum
51
middle ear
air filled space
eustachian tube opening and closing = pressure changes allowed, opens in throat
2 cubic cm cavity
three ossicles inside
transduce sound from air compression waves into mechanical movements
increase gain of the sound ( compensates for sound that is lost when you transmit sound into muddier vibrations) - middle ear muscles = move window with increased pressure into the cochlear
52
ossicles
3 of the smallest bones in the human body - (hammer, anvil and stirrup) malius, incus and stapes in the right order
attached to timbanic membrane
malius moves based on timbanic membrane
incus transmits to stapes
stapes transmits to inner ear through oval windonw - door to the cochlear
53
comparative middle ear
some reptiles and amphibians only have one middle ear cavity
we adpated to have two to increase info in higher frequencies as air over water now so inherently more info in air than water at higher frequencies
54
inner ear
cochlear
fluid filled snail-like structure set into vibration by the stapes (stapes attatches to scala vestibuli and round window at scala tympani
cochlear - spiral space (the chamber space bit!)
scala vestibuli
middle - basal membrane (cochlear partition extends from stapes thick end to apex)
scala tympani
55
inner hair cells
part of organ of corti
one row of inner hair cells, 3 rows of outer hair cells
1 row
embedded in tectorial membrane
synapse directly onto auditory nerve / spiral ganglion fibres
basal membrane moves whole tectorial mebrane which moves hair cells
different to outer hair cells as synapse directly
56
outer hair cells
active amplifier
active due to motility
dont directly send info to auditory nerve
activates protein prestin
-motor protein embedded in OHCs
discovered by genetically removing from mice and finding when it wasnt there there was a 30dB loss in sensitivyt and cells less tuned to specific frequencies
57
how transduction works in hair cells
cilia bend in response to movement from the organ of corti and tectorial membrane
- movement in one direction opens ion channels
- movement in the other direction closes the channel
- causes rhythmic bursts of electrical activity
58
name of two theories of how cochlear takes in frequencies and processes them into useful info
frequency theory
| bekeskys place theory of hearing
59
frequency theory
the cochlear as a whole (specifically the basal membrane) will vibrate in response to the frequency of the sound waves that are stimulating it
basal membrane doesn't vibrate equally along the length of it = problematic
60
bekeskys place theory of hearing
which fibres are responding = frequency of sound is indicated by the place on the organ of corti that has the highest firing rate
bekesys determined this in two ways
-direct observation of he basiliar membrane in a cadaver
-building a model of the cochlear using the physical properties of the basilar membrane
wider and floppier the closer to the apex
61
frequency vs place theory in the cochlear
post mortem cochlear
-obviously basic response was consisitent with place theory, can see specific bits exciting and not just the whole thing (apart from at low frequencies)
but frequency theory has a role - studied in cochlear implant frequencies
perceived pitch increases linearly no matter where on the basilar membrane according to frequency but only up to 400 Hz
so both play a role - but neither really accounts for pitch perception, just frequency decomposition
62
basilar membrane as a frequency analyser
the cochlear automatically breaks down complex tones into their component frequencies - it is performing fourier analysis
so complex tone - outer ear - middle ear - basiliar membrane = firing at specific places along it - out comes different hz into separate auditory nerve fibres
63
auditory nerve fibre
8th cranial nerve
carries electrical infor from cochlear to subsorticqla brain structures
when they fire action potentials do so in a reliable and consistent manner
respond at certain times corresponding to peak in waveform / pressure
=frequency specificity and phase locking
nerve becomes more and more sensitive to a specific frequency
64
pathway to the cortex
cochlear nuclues (one per ear)
superios olivary complex info from ears crosses here, first area to receive info from both ears
-in brainstem
-binaural signals first occur at SOC from bot cochlear nuclei (coincidence detection)
inferior colliculus (has timing from both ears)
-analogous to superior collicious for vision
-midbrain
medial geniculate body of the thalamus
primary auditory cortex (a1) = really hard to reach with electrodes - why we dont know loads about it
65
preservation of tonotopicity
similar to vision
| basiliar membrane encodes different frequencies at different spots along its length
66
brainstem and audition
groups of neurson can encode sound with microsecond precision
frequency following response (FFR) - can record
some of the fastest, most precise neurons in the brain
67
auditory cortex
A1 analgous to V1
-sensitive to pure tones
tonotopic organization so like basilar membrane
tucked into fold so hard to record from
hierarchical - core to belt to parabeit
-belt and parabelt (as you progress higher and higher - next stage in cortical processing) only weakly responsive to single tones, get more complicated
- areas all responsive to different
68
what vs where stream
what = ventral
-starts anterior portion of the core and belt and extends to the prefrontal cortex
-responsible for identifying sounds
where = dorsal
-starts in posterior core and belt and extends to the parietal and prefrontal cortices
-responsible for locating sounds
69
auditory object perception
| -perceptual
a sound readily attributable to a particular physical source
consequence of the auditory systems interpretation of acoustic events (spaciotemporal regularities)
spectral and temporal
70
auditory object perception
| -vocalizations
particularly species specific sounds that the brain has evolved to hear pop out of the background
ability to be sensitive to salient sounds based on its spectral profile
71
audition is...
constructive, use different cues and rules to make inferences about the auditory landscape
72
using auditory stimuli to replace sight
Prosthetic devices being created
auditory scene analysis to tell people where objects are in the environment
sesnory substution device
can learn to see by hearing certain frequencies
73
auditory space
surrounds an observer and exists wherever there is sound
74
azimuth coordinates
position left to right
75
elevation coordinates
position up and down
76
distance coordinates
position from observer
77
where are we most accurate in auditory ocalization
right in front of us
then alright to the side
and rubbish behind
78
3 primary cues for auditory localization
interaural time difference
interaural level difference
head-related transfer function
79
why is localization harder for audition than vision
on the eye there is the map on the retina = info comes for free
on the basilar membrane all the sound info is combined and organized by frequency
so bir tweeting high and cat going meow = all we will be told is there is high and low frequency stuff and not their position in space
80
binaural cues
location cues based on the comparison of the signals recevied by the left and right ears
81
interaural time difference
difference between the times sounds reach the two ears
-when distance to each ear is tha same, there are no differences in time (like circle over head / nose)
-when the source is to the side of the observer, the times with differ
fraction of a milisecond difference (0.6-0.8)
82
interaural level difference
difference in sound pressure (amplitude) level reaching the two ears
reduction in sound level occurs for sounds in the far ear
the head casts and acoustic shadow
trick they use in speakers
-is best for high frequency sounds becuase low frequency sounds are not attenuated much by the head
think about how low frequency sounds pass through the wall from your neighbour next door)
83
the cone of confusion
set of locations that have the same interaural time difference and interaural level difference
is a cone coming out from each ear
84
are ITD and ILD any good at judgin elevation
no
since many locations may be zero
- ie when a source is right infront of you or right behind you
owls get around this by having two offset ears
85
head related transfer function
the pinna and head affect the intensities of freuencies
measurements have been performed by placing small microphones in ears and comparing the intensities of frequencies with those at the sound source
-the difference is called the head-related transfer function
-this is a special cue since the information for location comes from the spectrum of frequencies
pinna is asymetrical and a different shape for all of us = distorts sounds differently depending on its location in the environment
fixes cone of confusion problem
86
experiment investigating spectral cues
listeners were measured for performance locating sounds
then fitted with a mold that changed the shape of their pinnae
performance was poor - particularly elevation
after 19 days = back to original performance level = learnt reshaped outer ear
once the molds were removed performance stayed high
this suggests there might be two different neuronal maps - the new set doesnt overwrite the old set
87
where is the first place in the brain that is getting input from both ears
superior olivary nucleus
88
physiological representation of auditory space
ITD detector - neurons that respond to specific interaural time differences
-they are found the first nucleus (superior olivary) in the system that receives input from both ears
topographic maps - neural structure that responds to location in space
89
topographic maps
barn owls have neurons in the brainstem that respond to locations in spce
thses neurons have receptive fields for sound location
like retinotopic maps
90
evidence of topographic maps
in subcortical areas of mamls no evidence to date
91
panoramic neurons
have been found in the cat auditory cortex that signal location by their pattern of firing
92
phonetics
sounds
93
phonology
phonemes
94
morphology
words
95
syntax
phrases, structure
96
semantics
literal meaning and sentences
97
pragmatics
meaning in context
98
phones
individual units of speech sounds
there are many phones that are not used in english
eg ng at beginning of words never used in english or african clicks
99
phonemes
the smalest unit of speech that change meaning in a word
specific to a language
24 consonant and 13 vowel phonemes in the english language
100
creation of speech sounds
| vowels vs consonants
vowels - no construction in arflow, just vocal fold vibrating
consonants - constriction in airflow
101
how vowel sounds are created
caused by resonant frequency of the vocal cords and produce peaks in pressure at a number of frequencies called formats
the first format has the lowest frequency, second has the next highest etc
shown on spectogram
tend to have lower frequencies
102
how consonant sounds are produced
by the constriction of the vocal tract
format transitions - rapid changes in frequency preceding or following consonants
tend to have higher frequencies
103
what is the variability problem
there is no simple correspondence between the acoustic signal (is a spectrum but only a given number of phonemes in a language) and individual phonemes
- coarticulation - overlap between articulation of neighbouring phonemes cause variation (we dont pause between phonemes)
- variability comes from a phonems context, the speaker etc (different speaker, diffeent communicative environment etc)
104
spectogram of coarticulation
di vs du
| different spectoram representations as following vowel sound changes d articulation
105
what does coarticulation allow us to do
allows speecht o be produced very smothly
| enables us to communicate at about five syllables a second
106
variability in a speaker
speakers differ in pitch, accent, speed in speaking and pronounciation
different pronounciations have the same menaing but very different spectograms
107
solution to variability in speech
categorical perception
occurs when a wide range of acoustic cues results in the perception of a limited number of sound categories
simplifies perception = collapses near infintie variablity to a finite set of possible phonems
comes from VOT experiments
108
VOT experiment
even if we continuously vary VOT, we only hear one phonmem or the other, never a blend of the two (experiments done using computerized speech)
demonstrates the auditory system is is simplifying input to filter out mush of the complexity
109
top down speech percpetion
categorical perception facilitated by top down knowledge
| eg we recognize words faster than non-words becuase of top down knowledge
110
the segmentation problem
there are no physical breaks in the continuous acoustic signal
must use top down knowledge to disambiguate
the fact we can easily resolve each word despite the ocntinuous nature of the signal implies that top down knowledge of word / sentence structure of guiding perception
111
evidence of word segmentation
taught 4 made up words
probability of one syllable following another
infants responded differntly to the words
7 month old infants
112
EEG recap
recording electrical activity from the scalp
excellent remporal resolution and poor spatial resolution
so N400 = negative goin wave peaking at 400 miliseconds after starting
113
using top down knowledge in speech comprehension
| neural data study
```
N400 = very sensitive to meaning integration
showed world (top-down) knowledge is integrated at about the same time as word meaning
```
114
principles of grouping in auditory scene analysis
```
location
proximity in time
good continuation
similarity
streaming
```
115
pitch perception
pitch occurs in a variety of sounds
-music
-speech (tonal languages very important)
-environmental sounds (sometimes weaker pitch percept)
generally correlated with the period of the signal
116
pitch invariance - missing fundamental
multiple stimuli = same percept of pitch
sound with fundamental frequency removed = perceived pitch of a sound is not due to a ocmbination of all the frequencies making them up
so is not average frequency alone but fundamental has alot to do with it
frequency content getting lower but sounds have been altered so that fundamental frequency is rising and rising = we hear it as rising and rising
117
what areas do pitch perception in the brain
different areas postulated = pitch selective neurons in A1
f0 = fundamental
neuron fires to complexes with the same fundamental = shows how brain identifies pitch and correctly perceive it
118
cochlear implants
used to create hearing in people with damaged hair cells
work best for people who receive them early in life or have lost their hearing after being able to hear for a long period in time
pretty rubbish signal eg never report enjoying listening to music
device =
a microphone worn behind the ear that receives sounds from the environment
a sound processor that divides the sound into frequency bands
a transmitter mounted on the mastoid bone
electrodes along the cochlear that stimulate different ner cells based on the intensity of frequencies received
119
noise exposure
sounds become worrysome at +85 dB = potential for damage, maximum allowed in the sound is 8 hours a day
every +3dB time halves
when young hair cells bounce back
recovery happens less and less as you age
