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Flashcards in Midterm 3 Deck (119)
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1

do objects have colour

no they have reflectance profiles

2

is light coloured

no it only has wavelength
you construct the colour and many people experience colour differently

3

explain the electromagnetic spectrum

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

define monochroatic light

one wavelenght
eg laser

5

physical parametres of monochromatic light

wavelenght
intensity

6

define heterochromatic light

many wavelengths

7

what is spectral composition

for heterochromatic light
gives the intensity at each wavelenght

8

graphically what is the differences between mono and hetero chromatic light

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

explain the spectral composition of tungsten vs sunlight

tungsten = from light bulb, steady increase as wavefunction increases
sunlight = increases at the lower end of the spectrum then decreases

10

the spectral components of light entering the eye is the product of what two things

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

what are the three psychological dimensions of colour

hue
saturation
brightness

12

explain hue

perceived colour of the object
organised around a circle (circumference)

13

explain saturation

as colour wheel becomes whiter and whiter
is the diametre of the circle`

14

explain brightness

maps onto energy
how dark or bright

15

3D HSV colour space

circle top surface = circumference of hue, diameter of saturation and then 3D depth of value or brightness = starts bright and descends into black

16

for unimodal distributions, how do we go from physical properties of light to pscyhological dimensions of colour
hue =
saturation =
value / brightness =

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

additive vs subtractive light

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

how do monitors work eg stadium or computer screen

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

physiology of colour vision

the normal retina contains three kinds of cones (S,M and L) each maximally sensitive to a different part of the spectrum

20

trichromatic theory of colour vision

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

the principle of univariance

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

so how do we see colour

L,M and S responses
will get some output ration of three different cone types
works with mono and hetero chromatic distributions

23

how do iphone and computer monitors etc work

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

metamers

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