Quiz 1

Question 1

Describe the steps in the sensory process

- 3 steps + examples

Answer 1

3 steps:

1. Physical stimulus (eg. light, sound, odour)
2. physiological response (pattern of electrical activity in sensory receptors, nerves, brain)
3. sensory experience (see/hear/smell something)

Question 2

list the techniques available to study each part of the sensory process.

Answer 2

a) physical –> physiological
- animal single-unit recording
- human brain imaging (MEG, PET, fMRI)
- event-related potentials

b) physiological –> sensory
- animal lesions
- human clinical studies
- human brain imaging

c) physical –> sensory
- behavioural techniques (ask them to describe their experience)
* easier to do behavioural since physio is expensive)

Question 3

why is having a quantified spectrum of visible light useful?

Answer 3

• able to quantify colour based on wavelength
• people assigned words to wavelengths
• good to have it quantified because it is hard to prove that the “blue” one person sees is the same as the “blue” another person sees

Question 4

What did Fechner invent?

Answer 4

Fechner came up with a way to define quantitative relationships between physical and psychological (subjective) events
- physical –> sensory = psychophysics

Question 5

absolute threshold
(what about a psychometric function? what does it mean if you have a low threshold?)

Answer 5

the minimal amount of stimulation necessary to just detect the presence of a stimulus
- weakest stimulus you can detect

when it’s for a psychometric function, the absolute threshold is the minimum amt of stimulation needed for a person to detect a stimulus 50% of the time
- becomes a statistic rather than just a value!

*low threshold = high sensitivity (good!)

Question 6

psychometric function

Answer 6

a graph of stimulus value (eg. intensity) on the horizontal axis vs the subject’s responses (eg. proportion “yes”) on the vertical axis
- measures a single person multiple times (since every person is different!)

Question 7

ogive

Answer 7

typical S shape of a real psychometric function

- never really a sharp change from not seeing a stimulus to seeing it –> varies from person to person

Question 8

difference threshold

Answer 8

discrimination (type of perception), not just detection!
- the smallest difference between stimuli or a change in a stimulus that the observer noticed 50% of the time (aka JND –> just noticeable difference)

eg. if you say they look the same but they’re not, that stimulus is below your difference threshold

Question 9

suprathreshold stimulus

Answer 9

above absolute threshold –> always detectable

Question 10

Detection

(i) the method of constant stimuli

Answer 10

• select stimulus intensities above and below expected threshold
• present many trials of each intensity in random order
  plot psychometric function
• find where the 50% detection point is on the graph

Question 11

Detection

(ii) the method of limits

Answer 11

a) descending series: stimulus intensity decreased in equal increments until response changes to “no”
b) ascending series: stimulus intensity increase in equal increments until response changes to “yes”

• alternate between ascending and descending + vary start point (so that people don’t just count trials)
• crossover point calculated for each series
• absolute threshold = avg of all crossover points

Question 12

Detection

(iii) the method of adjustment

Answer 12

observer adjusts stimulus intensity using a potentiometer (volume, dimming, heat control, etc)

• experimenter randomly adjusts starting point
• calculate avg (mean) of these threshold adjustments

*some people take really long to fine-tune, others don’t

Question 13

Discrimination

(i) the method of constant stimuli

Answer 13

• standard (fixed value) vs comparison (value that changes) stimuli presented together
  magnitude of comparison (values above or below standard) varied in random order with many trials of each value
• plot % “stronger” response vs comparison magnitude
• 0.75 point is the upper limit, 0.25 point is the lower limit (from graph)
• JND = (upper - lower)/2
• 0.50 point on graph is point of subjective equality (PSE) –> measure of accuracy (perfect accuracy would mean that PSE = standard)

Question 14

Discrimination

(ii) the method of limits

Answer 14

• standard and comparison stimuli presented together
• descending: response changes from stronger to equal to weaker (stop)
• ascending: response changes from weaker to equal to stronger (stop)
• alternate between descending and ascending series; vary starting pt
• upper limit is crossover pt between stronger and equal on each series
• lower limit is crossover pt between equal and weaker on each series
  eg. 9 = equal, 8 = weaker –> crossover point = 8.5
• JND = (avg upper - avg lower)/2
• PSE = (avg upper + avg lower)/2

Question 15

Discrimination

(iii) the method of adjustment

Answer 15

• observer adjusts the comparison stimulus until it matches the standard stimulus
• experimenter randomly varies starting point
• JND = SD of the matches x 0.6745

Question 16

advantages (2) and disadvantages (4) of the method of constant stimuli

Answer 16

pros: accurate and repeatable threshold values
cons: time-consuming (have to pick all the values beforehand), not good for tracking thresholds that change over time (eg. drug effects), not good for children or clinical patients (attention span), lots of data collected is far from threshold (inefficient since you have to throw away a lot of unrelated data)

Question 17

advantages (2) and disadvantages (2) of the method of limits

Answer 17

pros: saves time (efficient), don’t have to tract out whole psychometric function
cons: error of habituation (alternate series reduces this, but requires extra series –> participants may forget to change their response of stronger/equal/weaker), error of anticipation (varying start point reduces this, but requires extra stimulus levels –> participants may count the number of times they say yes and do that every time)

Question 18

advantages (2) and disadvantages (2) of the method of adjustment
- reason for use

Answer 18

pros: quick, participants like it (they’re in charge)
cons: not very accurate (within a person you will get diff threshold values each time) or repeatable (threshold all over the place)
* lots of ppl use this method as a preliminary method for the other two (rough estimate in order to pick values)

Question 19

Describe how to measure detection thresholds with the staircase method

• adaptive method
• absolute threshold
• modern improvement

Answer 19

• starts out like method of limits
• stimulus intensity decreased in equal steps until you can’t detect
• then, stimulus intensity increased until you can detect
• keep going back and forth
• adaptive method: stimuli kept hovering around threshold by adapting test sequence to participant’s responses
• absolute threshold is the average of the cross over points at response reversals
• modern improvement for differences: make differences smaller and smaller –> when they can’t tell the difference anymore then make the difference bigger

Question 20

advantages (3) and disadvantages (3) of the staircase method

Answer 20

• pros: efficient, most data collected around threshold; can be used to track threshold changes over time (if the staircase is going up or down over time) –> can measure drug effectiveness
• cons: researcher must change what they present based on participant’s response (cannot predesign expt); errors of habituation and anticipation (if there is only one staircase they realize what is going on –> interweave 2 staircases together –> computer decides trial)

Question 21

Distinguish between “yes-no” and 2-alternative forced-choice paradigms

• worst performance possible?
• absolute threshold?

Answer 21

yes no is what everything we have done so far –> participant reports –> very subjective (cannot verify)

2-alternative forced-choice paradigm: more objective

• Participants must prove they can detect or discriminate the stimulus (circle on left or right? in which interval are the two stimuli different?)
• worst performance can be is 50% (chance) –> this paradigm measures % correct
• 75% is the absolute threshold, while 50% is the guess rate

Question 22

explain the advantages offered by the two-alternative forced-choice paradigm

Answer 22

• lower thresholds –> performance is better (able to detect things they normally wouldn’t if they just have to say “yes” or “no”
• reduces non-sensory differences between participants (bias or criterion differences = guessing)
• can be used with the method of constant stimuli, limits, staircase method, but not the method of adjustment –> can’t leave it up to the participant

Question 23

Weber’s law

Answer 23

• difference threshold is a constant proportion of the physical magnitude of the stimulus –> JND is larger for larger stimuli

delta i = ki
delta i = JND
i = physical magnitude of stimulus
k = constant (weber’s fraction) = delta i / i

Question 24

Fechner’s law

• description
• equation
• variables
• comparison to weber’s law (graphical relationship)
• delta S

Answer 24

• suggested using JNDs (as a unit) to describe perceived intensity (quantify) –> describes the relationship between stimulus magnitude and resulting sensation magnitude (scaling)

S = k log R

S = sensation
k = Weber fraction --> delta I / I
R = stimulus level = I

• Weber’s law had JND (delta I) is larger for larger stimuli (I) –> linear
• Fechner used Weber’s findings to describe sensation –> assumed JNDs produced equal steps in sensation (delta S)
• sensory steps at the upper end of the scale required larger increases in stimulus intensity –> logarithmic relationship
• as stimulus intensity increases, sensation intensity increases rapidly at first, but then more slowly
• the change in S is constant, but the higher level the delta S is, the larger the change in I needs to be
• to calculate delta S find both S using the formula and then subtract
• to find the difference in JNDs do (bigger - smaller)/JND of smaller
  (since it is in reference to how big the difference is compared to the smaller value)

Question 25

Describe Stevens’ power law and a magnitude estimation experiment. Discuss reasons for the discrepancy between Stevens’ and Fechner’s scaling results.

Answer 25

- relationship between stimulus magnitude and resulting sensation magnitude --> magnitude of subjective sensation is proportional to the stimulus magnitude raised to an exponent (power) ``` S = aI^b S = sensation a = constant I = stimulus intensity b = exponent (determines shape of curve) ``` if b > 1 = bends up if b < 1 = bends down if b = 1 = straight line (linear) - steven's law and fechner's law are same for b < 1 but not other --> Fechner's assumes all JNDs equal (not true) - magnitude estimation more subjective than JNDs

Question 26

what is d'? | - perfectly sensitive vs completely insensitive

Answer 26

d' = the statistic that reflects a perceivers sensitivity (ease with which they can tell diff btwn presence and absence) perfectly sensitive: hit rate = 1, FA rate = 0 completely insensitive: hit rate = FA rate

Question 27

criterion

Answer 27

beta --> response bias within a perceiver; depends on expectations and motivation - non-sensory - cannot study this with staircase bc we need catch trials for FAs (stimuli are always be present so there would be no FAs) (sensitivity is d', bias is beta)

Question 28

expectations: - 50% presence vs 90% presence vs 10% presence - lax vs strict criterion

Answer 28

50%: medium-high hits, medium-low FAs 90%: really high hits, high FAs 10%: low hits, really low FAs - manipulation of expectations - the higher B is, the stricter the criterion is for saying yes (less likely to say yes) - lower probability for presence = stricter criteria - lax criterion = high hits, high FA - strict criterion = low hits, low FAs - strong motivation = small B (lax) --> affects behaviour, not sensitivity - response pattern is what changes, not d' (sensitivity stays the same because stimulus stays the same)

Question 29

List the 7 sensory cranial nerves and show how they illustrate the doctrine of specific nerve energies

Answer 29

doctrine: the nature of sensation depends on which nerves are stimulated, not on how the nerves are stimulated (will carry the signal to brain) --> we only know the activity of nerves, not what is actually out in the world --> brain only sees APs not really world ``` SENSORY: I. olfactory: smell II. Optic: vision VIII. Vestibulocochlear: spatial orientation, balance, hearing - 2 nerves --> auditory and vestibular ``` BOTH: V. Trigeminal: face, sinuses, teeth VII. Facial: tongue, soft palate IX. Glossopharyngeal: posterior tongue, tonsils, pharynx, pharyngeal muscles X. Vagus: heart, lungs, gastrointestinal tract, bronchi, trachea, larynx

Question 30

Compare and contrast the 4 neuroimaging techniques for studying human brain function - MRI

Answer 30

1. structural MRI: large magnet obtains high res images of body based on differences in water content - fMRI: uses same machine - neural activity = inc blood flow = inc O2 consumption = inc O2 in venous blood (gets redder) = stronger MRI signal - grey image = MRI, coloured parts = statistics - non-invasive, best spatial resolution, but response changes very slowly (poor temporal resolution --> not good for changes over time)

Question 31

Compare and contrast the 4 neuroimaging techniques for studying human brain function - EEG

Answer 31

2. EEG: electrodes on scalp, subject performs perceptual task --> measures potentials (voltage changes) - maps signal strength over time across scalp --> has good temporal resolution (fast) but poor spatial resolution (very noisy, don't know where signals are coming from) - avg waveforms = event-related potentials

Question 32

Compare and contrast the 4 neuroimaging techniques for studying human brain function - MEG

Answer 32

3. MEG: array of SQUIDS (measuring device) measures magnetic fields created by flow of ion currents btwn neurons --> records same activity as EEG, but not using electricity --> mag fields don't get distorted like EEG = good spatial resolution (when used with MRI) - high temporal resolution, not good for measuring signals deep in the brain

Question 33

Compare and contrast the 4 neuroimaging techniques for studying human brain function - PET

Answer 33

4. PET: radioactive tracer (usually oxygen-15) injected --> tracer decays and positrons emitted are picked up by scanner --> areas of radioactivity are associated with neural activity (based on blood flow) --> inc in blood flow to active parts of brain - good for studying disease (eg cancer) /chemicals - poor spatial resolution (improved with MRI); invasive procedure (not good for healthy ppl/generic studies) --> expensive

Question 34

- frequency - phase - amplitude - sound pressure level

Answer 34

- measured in cycles per second (Hz) - 90 = 1/4th, 180 = hump, 270 = 3/4th, 360 = full wave - phase often used to compared the timing of 2 sound waves (sound localization) - amplitude measured in dynes/cm2 or pascals 0.0002dynes/cm2 = absolute threshold (1000Hz) pressure converted to log scale --> compressed higher level numbers - measured in dB dB = 20*log(P/Po) P = pressure of tone, Po = reference pressure = 0.0002 dynes/cm2 - humans cannot hear higher freq than 20,000Hz - can hear lower than 0dB - above 115dB = high risk, above 135dB = pain threshold

Question 35

Fourier's theorem

Answer 35

- only pure tones are sine waves, but complex sounds can be described as a set of sine waves - for pure tones, frequency corresponds to perceived pitch, and amplitude corresponds to perceived loudness Fourier's analysis: mathematical procedure for separating a complex pattern into component sine waves that vary over time (hearing) or space (vision) fundamental: lowest sine wave frequency in a complex sound (line furthest to the left on a spectrum graph) harmonics: higher freq sine wave --> integer multiples of fundamental freq timbre: diff instruments have diff timbre which is why they sound diff even tho they playing the same note (same freq) --> diff sine wave components

Question 36

Describe 4 types of computational models that have been applied to the study of sensation and perception

Answer 36

Efficient coding models: used to discover predictability and structure —> an efficient system should note spend a lot of resources on inputs that are predictable/redundant —> encode world Bayesian models: coding model that attempts to build a model of the world (estimate) —> use predictive coding —> if there is a prediction error the model is adjusted to improve future predictions Artificial neural networks: aka connectionist models —> written connections —> weight inc/dec depending on experience (how nodes contribute to network’s success) —> like a synapse Deep neural networks (DNNs): type of machine learning —> computer programmed to learn something —> many layers and nodes in artificial neural networks —> network trained, then can provide answers from inputs never seen before

Question 37

Identify the structures in the outer, middle and inner ears.

Answer 37

outer: - pinna - ear canal - eardrum (tympanic membrane) middle: - ossicles: malleus, incus, stapes - muscles: stapedius and tensor tympani - round window and oval window inner: - semicircular canals - vestibular canal, cochlear duct, tympanic canal - helicotroma - cochlear partition: tectorial/basilar membranes, organ of corti (everything inside middle canal) - reissner's membrane - cochlea - auditory nerve - eustachian tube: equalizes air pressure btwn middle and outer ear

Question 38

Describe 2 ways in which the middle ear functions to amplify the sound pressure reaching the inner ear. Define the acoustic reflex and name the 2 muscles involved.

Answer 38

impedance matching: - tympanic membrane larger than stapes footplate --> inc amplitude of pressure change at oval window by 17 times due to the change in volume (eg. high heels) - ossicles act like levers --> increases force at stapes by a factor of 1.3 (teeter totter) acoustic reflex: in response to prolonged loud sounds, tensor tympani and stapedius muscles contract to dec vibration of ossicles --> reduces magnitude of auditory signal transmitted to ear - can reduce by 30dB but will take 30 sec - cannot protect from fast loud sounds; reflex --> not voluntary

Question 39

Compare and contrast the anatomical arrangement, innervation and function of the inner and outer hair cells.

Answer 39

inner hair cells: sound receptors --> contain stereocilia --> in contact with tectorial membrane (rest against it) - in a single row - converts sound into electrical signals --> do not have axons or fire APs, but do release NTs (glutamate) --> synapses with auditory nerve fibers - convey most sensory info about sound to the brain --> receptor cells like visual rods and cones - 90% of afferent fibers are connected to inner hair cells outer hair cells: - 3 rows, V shape arrangement of stereocilia - tallest embedded in the tectorial membrane - modulate signal from inner hair cells --> feedback from efferent fibers causes contraction and elongation (electromotility) - 10% of afferent fibers are connected to outer hair cells - efferent fibers carry info from CNS to inner ear (most synapsing w outer hair cells)

Question 40

Describe the transduction of mechanical energy into action potentials in the cochlea

Answer 40

- transduction occurs when stereocilia are bent --> when basilar memb moves up and down, hair cell stereocilia are bent back and forth against tectorial membrane - cilia connected together by tip-links 1. stereocilia bend 2. tip-links open K+ channels 3. K+ ions enter hair cell 4. cell depolarizes (graded potential) 5. calcium channels open 6. neurotransmitter released at synapse with auditory nerve fiber 7. auditory nerve fiber fires APs - endolymph is K+ rich so its mostly K+ involved - when tectorial membrane goes back everything is undone --> channels close, hyperpol, dec NTs) graded potential: slow change --> not all or nothing ---> size effects how much NTs are released and whether or not AP is produced AP: rapid depol (all or nothing) --> auditory nerve fibers

Question 41

Describe the response of the basilar membrane to sounds of different frequencies - low vs high freq - active process

Answer 41

waves peak at diff places for each frequency of sound - have a peak amplitude then die out basilar memb has a stiff and narrow base, and a wide and loose apex - peak occurs near oval window for high freq, and near helicotrema for low freq - basilar membrane's physical properties cause more activation for low freq sounds (since its wide and loose) BUT peak is much narrower and higher in living ear --> means that its not ONLY the basilar memb but something in the intact living ear is sharpening and amplifying the response active process: sharpens and amplifies response of basilar membrane relative to response based on passive, physical properties of basilar membrane --> likely due to electromotility of outer hair cells (stiffening response of tectorial/basilar memb --> contract and elongate

Question 42

Describe the two types of otoacoustic emissions and discuss how they are related to the active process that sharpens the mechanical tuning of the basilar membrane.

Answer 42

- sounds emitted by healthy ears - evoked emission: occur in response to auditory stimulation --> depend on freq of stimulating sound, now used clinically as a quick indicator of inner ear damage --> what goes in also comes out - spontaneous emissions: occur without stimulation --> less than 20dB, 1000-2000Hz - due to elongation and contraction of outer hair cells (related to active process)