week 2 (psychophysics + touch) Flashcards
(44 cards)
1
Q
define: difference threshold (or JND)
A
- just noticeable diff.
- represented by ΔI
- how much a stim. needs to change in order to prod. a detectable change
2
Q
describe: 2 alternative forced choice
A
- 2 stim. presented side by side
- subjects must make comparative judgement
- MUST PICK
3
Q
define: perceptual equivalence point
A
- 2 stim. feel the same to a participant
- ex. saying weight is heavier 50% of time
⤷ they don’t actually know the diff.
4
Q
define: weber’s law
A
ΔI = k * I
ΔI = just noticeable diff.
k = constant proportion
I = stim. intensity
5
Q
question: are JND constant?
A
- no
- differ based on diff. standard stim. intensity
6
Q
question: what does a smaller k mean for JND?
A
- smaller k = smaller weber fraction
- very sensitive
- need to add very little to OG stim. to be able to detect change
7
Q
define: weber-fechner’s law
A
S = k * log(I)
S = psychological sensation/perception
k = constant (not same as weber law)
I = stim. intensity
8
Q
question: what does the weber-fechner law say?
A
- increasing the difference in threshold results in same size change in sensation
- psychological exp. increases slower than physical stim. increases
9
Q
define: scaling vs magnitude estimation
A
- scaling: psychophysical was to estimate amount of something related to perception
- magnitude estimation: scaling but subjects provide direct ratings
⤷ provide numerical rating
10
Q
define: power law (for relationship between stim. and sensation)
A
S = a * I^b
S = sensory exp.
a = scaling constant
I = initial intensity
b = exponent
⤷ diff. for each sensory exp.
11
Q
question: does fechner’s law work for exponents greater than 1?
A
- no
- use power law instead
- bc if larger than 1 exponent, graph is no longer log
⤷ becomes accel. graph (exponential)
12
Q
define: sensory transducer theory
A
- idea that transduction of physical stim. into biological stim. is the basis of power law
- basically: size of recep. potential influences sensitivity
13
Q
define: cross-modality matching
A
- compare stim. from 1 sensory modality to stim. of another modality
⤷ ex. comparing electric shock vs brightness
14
Q
define: signal detection theory
A
- tanner and swets
- theory that takes into account nonsensory factors that affect signal detection
⤷ ex. cognitive factors
general idea: sensitivity of sensory system + judgement by subject both matter in decision
15
Q
name: example of noise vs signal
A
- ex. mammogram
⤷ noise = fuzzy regions
⤷ signal = clearer fuzzy white region = cancer - ex. shower
⤷ noise = water/shower noises
⤷ signal = phone ringing
16
Q
explain: shower and phone ringing scenario (reference graph)
A
- sensation magnitude starts in the middle
⤷ already perceiving loudness of shower - ringtone playing= added to the noise
⤷ graph shifts right - need to decide on a criterion B (beta)
⤷ decide how loud the overall sound needs to be before you jump out of the shower
⤷ criterion B = where the original graph meets the graph w/ ringtone
17
Q
name + explain: possible outcomes of a signal detection theory experiment (4)
A
1. correct rejection
⤷ no signal, rejected
2. false alarm
⤷ no signal, yes reaction
3. miss
⤷ yes signal, no reaction (rejected)
4. hit
⤷ yes signal, yes reaction
18
Q
question: what is d’ in sensitivity?
A
- measure of sensitivity
- if 3 ppl w/ diff. sensitivities to same signal
⤷ d’ = measure of indiv. detection sensitivity - if 1 person w/ diff. sensitivities to 3 diff. signal strengths
⤷ d’ = measure of separation between 2 distributions
19
Q
question: whatn the criterion beta change?
A
- yes
- change based on expectation and motivation
- liberal criterion = expect stim. 70% time
- conservative criterion = expect stim 30% time
20
Q
question: how are the false alarms and hits changed with liberal and conservative criterions?
A
LIBERAL
- more false alarms but also more hits
CONSERVATIVE
- less false alarms but also less hits
21
Q
question: can an ROC curve ever bend towards the 4th quadrant (bottom right)?
A
- no
- bc would mean more false alarms than hits
⤷ which can only occur when up to chance - A of false alarm will never be greater than A of hits
22
Q
recap: what are beta and d’ in an ROC curve?
A
B = how nonsensory factors influence judgements
d’ = relative sensitivities of different individuals
23
Q
question: what is an ROC curve and what are the axes?
A
- receiver operating characteristic curve
- plots false alarms on x and probability of hits on y
24
Q
define: touch
A
- sensation caused by stimulation of skin, muscles, tendons, and joints
25
name + define: types of somatosensory and proprioception touches (5, 2)
SOMATOSENSORY
**1. tactile**
⤷ sensation caused by mech. displacement of skin
**2. itch**
**3. pain**
⤷ body tissues are (potentially) damaged
**4. thermal**
⤷ perception of thermal changes
**5. pleasant**
⤷ stroking
PROPRIOCEPTION
**1. kinesthesia**
⤷ internal sensation from musc., tendons, joints, too inform about positions and mvts of limbs
**2. vestibular**
⤷ balance
26
question: epidermis vs dermis?
EPIDERMIS
- outermost layer
- protection
- several sublayers
- constantly replenished
DERMIS
- bulk of skin tissue
- has touch receptors
27
question: how to touch receptors differ? (4)
**1. type of stim.**
⤷ ex. vibration, pain, mech.
**2. transmission speed**
⤷ dep. on afferent fiber
**3. rate of adaption**
⤷ resp. on continuous stim.
**4. size of receptive field**
⤷ extent of body area that elicits recep. resp.
28
explain: structure of touch receptor
- pseudo-unipolar
- can be myelinated or not
- can have specialized ending (capsule) or ion channels to help tune the afferent fiber to a particular feature of touch
29
question: what is the axon diameter, myelination, and conduction speed of proprioceptors, mechanoreceptors, paint/temp, and pleasant/pain/temp receptors?
PROPRIO = A-alpha
- thickest
- most myelin
- fastest conduction
MECHANO = A-beta
- slightly thick
- second most myelin
- moderately high conduction speed
PAIN/TEMP = A-delta
- relatively thinner
- little myelination
- slower conduction
PLEASANT/PAIN/TEMP/ITCH = C
- thinnest
- no myelination
- slowest
30
name + explain: types of mechanoreceptors (4)
**1. pascinian corpuscle**
- fast changes to skin deformation
- high freq. vibrations
- deep (dermis)
**2. ruffini capsule**
- sensitive to skin stretch
- designed to transmit sustained downward pressure
- dermis and deeper tissue
- ex. holding things
**3. meissner corpuscle**
- transmit low freq. vibrations
- stable grasp
- superficial (between dermis and epidermis)
**4. merkel cell**
- sustain pressiore
- very low freq.
- coarse textures, patters, finer details
- in fingerprint region
- superficial (between dermis and epidermis)
31
explain: pathway of transduction by mechanoreceptors
- stim. deforms Pacinian corpuscle -> stretches mem. of nerve fiber
- allows ions to flow in -> depol. -> increases to reach AP threshold -> sends sig.
32
question: slow adapting vs fast adapting receptors?
SLOW ADAPTING
- lower temporal resolution
- best of info about unchanging stim,
FAST ADAPTING
- high temporal resolution
- best for stim. that vary over time
33
define: tactile receptive field
- patch of body where stim. will prod. resp.
- smaller RF = greater capacity for spatial resolution
34
explain: thermoreceptors (where, what type)
- in dermis and epidermis
- C fibers
⤷ thin, no myelin, slow
- A-delta
⤷ thin, lightly myelinated
- have warm and cold fibers
- activated by changes from physiological 0
35
question: how do thermoreceptors sense heat or cold?
- transient receptor potential channels (TRP)
- thermoTRPs detect entire thermal range
- heat/cold causes ion channel to open -> ions in -> depol. -> AP
36
question: which TRPs are for hot vs cold?
HOT - mainly TRPV1 and TRPV2
COLD - mainly TRPA1 and TRPM8
37
define: nociceptors
- receptors sensitive to noxious stim.
- potential to cause damage (pain)
- free nerve endings in skin, joints, musc., organs
- subtypes
1. myelinated A-delta = strong psi or heat
⤷ slow and fast adapting
2. unmyelinated C = strong pst, intense temp, noxious chem.
⤷ slow adapting
38
explain: pleasant touch (type of stim., fiber type)
- light, slow-moving, stroking
- C fibers
⤷ unmyelinated
⤷ diff. from the pain/itch ones
39
explain: kinesthetic receptors (where, why)
- terminal ends of nerve fibers of sensory neurons
- info transmitted to CNS through A-alpha
⤷ thickest, most myelin
- endings have mechanically stretch gated channels
- make sense of where limbs are
40
question: where are the somatosensory neurons?
- bodies in dorsal root ganglion
- axons all converge on single spinal nerve
path: AP travel from peripheral end -> along axon to central end -> enter spinal cord at dorsal horn
41
question: what are signals transferred in the spinal cord?
- dorsal horn = organized into laminae (layers)
- somatotopical
- nerve fibers appear as labeled lines
⤷ stay separate until cerebral cortex
42
question: how do each type of mechanoreceptor get signal from neuron to brain?
PROPRIO AND MECHANO (A-alpha and A-beta)
- dorsal column medial lemniscal pathway (DCML)
PAIN AND TEMP (A-delta, C)
- spinothalamic pathway
43
explain: DCML pathway
- path for sig. of proprioceptors and mechanoreceptors
- 1st-order DRG neurons send axons up white matter of cord
- dorsal column
- central axons of DRG neurons synapse on dorsal column nuclei in medulla
- medial lemniscus
- axons of 2nd-order neurons decussate and ascent to thalamus
- internal capsule
- thalamic relay (3rd order) neurons project to cerebral cortex
44
explain: spinothalamic pathway
- path for sig. of pain and temp receptors
- 1st-order DRG neurons synapse in dorsal horn
- axons of 2nd-order dorsal horn neurons cross midline and cord and ascend
- spinothalamic tract
- most axons terminate on relay nuclei in medulla, midbrain, thalamus
⤷ project to cortex in diffuse way
