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PSYC 102 - sensory > Post Midterm 3 > Flashcards

Post Midterm 3 Flashcards

1
Q

why is the somatosensory system important

A

reach and grasp
how we interact by motor systems in the environment
implant to control robotic arm in paralysed man
-premotor
-parietal cortex
= how robot arm controlled / where electrodes put
tongue used as a substitute for sight - grid on tongue, iphone camera used, projected onto tongue = allows to “see” `

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2
Q

skin is the …

A

heaviest organ in the body

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3
Q

layers of the skin named and explained

A

epidermis - outer layer, made of flat cells (squamous cells) then round cells (basal) then melanocytes which produce melanin. for heat etc
dermis - below epidermis and contains four kinds of mechanoreceptors that respond to stimuli such as pressure, strecthing and vibration = this bit does transduction!

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4
Q

name the 4 mechanoreceptors

A

merkel
meissner corpuscles
ruffini cylinders in collgen (elastic bit)
pacian corpustules = deep down

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5
Q

over view / organisation types of mechanoreceptors

A

temporal response properties (how quikcly adaptation to pressure occurs)
SA (slowly adapting fibres) = merkel (SA1) and ruffini (SA2), fire continuously as long as pressure is applied
RA (rapidly adapting fibres) = meissner (RA1) and pacinian (RA2), fire at onset and offset of stimulation (but not during, rapidly adapt)
1s = superficial layers of dermis
2s = deeper, in collagen and subcutaneous fat

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6
Q

merkel cells

A

specialized epithelia cell - located in superficial layers
filled with vesicles, and a nerve fibre sitting in the cell
pressre causes the release of transmitters from vesicles
found in fingertips, supports high acuity light touch
slowly adapting responds continuosly to input
as long as stimulus is on = action potentials
just like in visual system, stronger driving of cell = more action potentials per unit time

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7
Q

how have mechanoreceptors been studied

A

barely at all compared to other sense
found a way to label/ highlight each type of cell
stimulus probe
when touch = displacement = ion channel open, clacium and sodium in (this is for merkel slow adapting cells)

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8
Q

meissner corpuscle

A

close to surface
stacked cells with afferent nerve fibre running through layers
deformation of layers in corpuscles triggers action potential (allows influx of positive ions)
rapidly adapting
work similarly to merkel
as cells displaced from pressure = ion channels open. layers so displaced and mishapen
removal signal too

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9
Q

ruffini cylinder

A

deep layer
register stretch of skin - useful for detecting slippage and adjusting grip apperture
as collagen stretches (connective tissue), will allow influx of positive ions to enter nerve fibre
slowly adapting - continuous firing as long as stimulus prestent

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10
Q

pacinian corpuscle

A

deep receptor
onion like shape - pushing causes rotation of disks with each other - this rotation allows influx of positive ions
requires more stimulation to activate, and is rapidly adapting

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11
Q

receptive fields of mechani receptros

A

surface receptors have smaller repceptive fields than deep receptors
so SA1 and RA1 = small
SA2 and RA1 = big

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12
Q

pathway from skin to cortex

A

nerve fibres travle in bundles (peripheral nerves) to the spinal cord
two major pathways in the spinal cord
-medical lemniscal pathway = touch
-spinothalamic pathway = pain
these cross over to the opposite of the bosy and synapse in the thalamus, and then on to the somatosensory cortex or S1
S1 = behind central sulcous

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13
Q

explain the medial lemniscal pathway

A

consists of large fibres that carry proprioceptive and touch information

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14
Q

explain the spinothalamic pathway

A

consists of smaller fibres that carry temperature and pain information

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15
Q

maps of the body on the cortex

A

homonculus
signs travel from the thalamus to the somatosensory receiving area (S1) and the secondary receving are (S2) in the parietla lobe
body map (homonculus) on the cortes shows more cortical space allocated to parts of the body that are most sensitive to detail eg enormous hands, lips, tongue
exisits in somatosensory cortex and in motor cortex
large area = greater tactile sensistivity

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16
Q

plasitcity in S!

A

highly plastic
plasticity in neural functioning leads to flexible changes in how cortical cells are allocated to body parts
S1 is able to rapidly reorganise - even removal of body parts
eg train animal to use a particular part of its body = cortical part gets bigger
S1 doesn’t grow, just takes up more space and other bits in S1 shrink
experience dependent

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17
Q

duct taping monkeys fingers together

A

S1 mapped before and after
once monkey learned to use two fingers as one unit the receptive fields crossed the boundaries betwee the two fingers = 3rd and fourth unit as one finger both physically and in the brain

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18
Q

phantom limb dis

A

example of how S1 can reorganise very quickly
the persistent sensation of an appendage, after removal by amputation or simple denervation
Ramachandran and colleagues have shown that touching the face of a phantom limb patient leads to sensations in the missing hand or arm
this leads to the hypothesis the brian is filling in for the missing stimulation in the hand and arm representation in the somatosensory system
connections in the cortex allow hand area to be stimulate by adjacent face region = how cortical representation can cross boundary
facial cortical space branches into space taken up by missing hand / arm

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19
Q

racoon experiment with phantom limb

A

cut off fourth finger

found cortical tissue immediately started responding to third and fifth digit = neighbours

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20
Q

how ramanchandran did it

A

Phantom limbs and plasticity: Ramachandran et al. (1992) tested a patient
whose right arm had been amputated some years earlier.
In this case, touching the face caused sensation of both the face and the
missing limb.
Note the proximity of the face and hand representation in cortex. The proposed
explanation is that connections within cortex allowed the hand areas (which now
did not receive any input from the hand) to be activated by stimulation of the
adjacent face regions. This stimulation was still experienced, however, as
stimulation of the hand.

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21
Q

graziano disagreement

A

drove cells in the brain until area physically moved (eg chewing area until monkey moved)
somatosensory cortex = map of actions / potential actinos
controversial hypothesis
still thought to be honculus (passive)

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22
Q

measuring tactile acuity

A

how to measure somatosensory function
2 ways
-two-point threshold, minimum separation needed between two points (2 needles) to perceive them as two units
-grating acuity, placing a grooved stimulus on the skin and asking the participant to indicate the orientation of the grating - change dimensions to get threshold
diff parts of the body = diff so fingertips dense in merkel so very sensitive

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23
Q

3 main factors that affect tactile acuity

A

1 density correlates with acuity - more dense = higher acuity. fixed receptive field size and density, but changing the separation of points (again excitatory centre and inhibitory surround)
2 size correlates with acuity - smaller = higher acuity. fixed separation of points, changing receptive field size
3 fingertips have special extra acuity = have diff brain representation in S1

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24
Q

special fingertips

A

there is a high density of merkel receptors / SA1 fibres in the fingertips
merkel receptors are densley packed on the fingertips - similar to cones in the fovea
both 2-point thresholds and grating show greater acuity for fingertips compared to base of finger compared to palm
but density of merkel cells is not enough to explain changes in acuity
thresholds increase from to the index finger to the pinky, but the density of merkel receptors is the same accross the fingers - something else is at play = cortical area in the brain (S1). index finger = lowest mean threshold so discriminate two needles quicker with smaller distance
central sulcus = greatest cortical representation for index over pinky finger . how experience effects cortical representation

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25
Q

object perception

A

somatosensory cortex shows cells that respond maximally to orientations and directions of movement
selectivity for different features, just like in the visual system
spaciotemporal receptive field
direction selective etc
have basic features but also more complicated

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26
Q

complex motor coding

A

specific reaching and tactile inputs
this selectivity is expressed in differetial response in somatosensory cortex to grasping different objects
so same graspoing movement but different objects = fifring for one object but not another from a particular single cell

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27
Q

similarities between tactile perception and vision

A

-Center-surround receptive fields
• Receptive fields of different sizes
• Acuity (as measured with the two-point threshold) varies with location on the body
• Sensitive to movement
• Selective with respect to edge orientation and direction of
motion.

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28
Q

star nosed mole

A

mole system for sensory cortex
does not see
has a bunch of fingers it uses to see the world around - nasal rays
taken notion of having notion of having lots of small and dense receptors
sensory substitution
thumps table alot = makes image of world around
blows bubbles to smell world around him

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29
Q

pain perception - nocioceptive

A

signals imdending damage to the skin
types of nocioceptors respond to heat, chemicals, severe pressure and cold
info carried back to nervous system carried by two routes
A-delta fibres
C-fibres

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30
Q

A-delta fibres (pathway)

A

– A-delta fibers –myelinated, fast conduction times (~20meters/s),
sharp initial response to mechanical or thermal input

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31
Q

C-fibres (pathway)

A

C-fibers – non-myelinated, slow conduction times (~2meters/s),
dull slow response to most mechanical, thermal or chemical
input
eg sensation of itch - slow buring feeling

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32
Q

3 types of pain feelings on skin and descriptions

A

thermal - activated by noxious heat/ cold (via different receptors)
chemical - selective response to different compounds
mechanical - response to excess pressure or to incisions that break skin

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33
Q

inflamatory pain

A 
caused by damage to tissue and joints that releases chemicals that indirectly activate nociorecpetors
why legs hurt the day after running
why advil (anti inflamatries) work to alleviate pain
34
Q

neuropathic pain

A

cause by damage to the central nervous system, such as brain damage caused by stroke, and repetitive movements which cause conditions like capal tunnel syndrome (or disease like diabetes)
really hard to treat as can’t go in and fix it

35
Q

pain in social situations

A

– Participants watched a computer game
– Then were asked to play with two other “players” who did not exist but were part of the program
– The “players” excluded the participant
– fMRI data showed increased activity in the anterior cingulate cortex and insular areas when participants reported feeling ignored and distressed = consistent with areas associated with actual pain
idea = physical pain of ostracisation like damaging physical pain
arguments against solitary confinement

36
Q

why is taste/smell important

A

protective
- posions, ability to identify foods that were previously associated with bad outcomes
more subtle = cant taste salt / sugar because you smkoe or drink = problems with diet
on the other extreme, the destruction of taste buds can make life miserable. Following the radiationf for ENT cancers, subjects often report that everything tastes metallic and totaly unappetizing - can contribute to severe weight loss

37
Q

macrosmatic animals

A

having a keen sense of smell that is necessary for survival

eg dogs

38
Q

microsmatic animals

A

a less keen sense of smell that is not crucial to survival

eg humans

39
Q

macro vs micro smatci animals why?

A

number of receptors not sensitivity
humans = 6-10 million
dogs = 300 million to 10 billion
also additional adaptations
some dogs: Spent air exits through the slits in the sides of dogs’ noses. The exhaled air swirls out to help usher new odors into the dog’s nose. University of Oslo in Norway: a hunting dog holding its head high into the wind sniffed in a continuous stream of air for 40 seconds, spanning at least 30 respiratory cycles.
in humans, unlike some other animals, olfaction consists of a series of highly discrete “snapshots”

40
Q

human sensitivity to pheromones

A

Underarm secretions were collected from 9 donor women
• These were wiped on the upper lips of recipient women
• Results showed that menstrual synchrony occurred since:
– Secretions from the donors taken at the beginning of their cycles led to a shortened length of the recipients’ cycles
– Secretions from the ovulatory phase lengthened recipients’ cycles
• Pheromones in the secretions led to the changes, even though the women did not report smelling them
• Women do not synchronize their menstrual cycle…
suggests humans sensitive to pheromones etc… fialure to replicate etc but not managed
Yang and Schank, 2006, Human Nature replicated (in large samples) and didn’t get these results

41
Q

detection threhold of smells

A

forced-choice = two trials are given, one with odorant and one without
particiaptn indicates which smells strongest
just like with visual / auditory experiments
big hose hooked up to nose
must be done carefully controlled conc using an olfactometer
olfaction follow webers law of approx 11%

42
Q

sensitivity to diff odors

A

methanol = not super sensitive
but
mercaptin (what they add to gas to know leak) = super sensitive

43
Q

identifying odors

A

Humans can discriminate ~trillion odors but they cannot label them accurately.
• For example, humans can accurately discriminate their t-shirt from >100 other identical t-shirts worn by other people (Lord and Kasprzak 1989)
• This appears to be caused mostly by an inability to retrieve the name from memory, not from a lack of sensitivity.
no accurate labelling so no accurate encoding to memory

44
Q

localisations of smell

A

Good localization when interacting with smells, poor localization when passively perceiving (just above chance to discriminate left/right for most odorants)
Sobel insititue, Israel
= series of exp. presented odorant on left and right and determine whether came from right or left = we are bad at this, no better than chance
=person in body suit so only get odor senses and nothing else, line on grass with oderant. subjects try to sniff through environment using odor alone = humans actually good at it. so when all other sense taken away can rely on it also have to actively engage with info
–people can get better at this over subsequent trials

45
Q

humans dont trust their nose experiments

A

For example, adding color to an odorless solution increased the probability of assigning an odor to the solution (Engen 1972).
Coloring a cherry-flavored drink in orange rendered it as having an orange or apricot flavor, and also, coloring the same drink in green rendered it as lime or lemon flavor
(Dubose et al. 1980).
Even “olfactory experts” are not immune to visual dominance in olfactory decisions: A panel of 54 students of Oenology (wine experts) shifted to assigning red wine descriptors to white wine that was colored with an odorless red (Morrot et al. 2001).

46
Q

quantifying and studying odors - how do we define the space

A

researchers have found it difficult to map perceptual experience onto physical attributes of odors

47
Q

hennings odor prism

A

6 corners with the qualities putrid, ethereal, resinous, spicy, fragrant, and burned
– Other odors located in reference to their perceptual relation to the corner qualities
– Unfortunately, Henning’s prism has proven of little use in olfactory research. these dimensions are not anchored in reality. we dont know how to quantify the psych space
attempt to define analgous space to HSV

48
Q

linking chemical structure to types of smells

A

no principled means of characterizeding sensory space
initial attempts showed difficulties since
-some molecules with similar shapes have very different smells
some similar smells come from molecules with different shapes

49
Q

structure of the olfactory system

A

Olfactory mucosa is located at the top of the nasal cavity
– Odorants are carried along the mucosa coming in contact with the sensory neurons
– Cilia of these neurons contain the receptors that bind with different odorants, triggering action potentials
– Humans have about 350 types of receptors
– Receptors project to Glomeruli in olfactory bulb
– Run through Cribriform plate (bone)
- ANOSMIA = shearing of fibres through bone so no receptor relys = no info to glomeruli so no sense of smell

50
Q

periglomerular cells

A

lateral inhibition (like horizontal connections in the retina

51
Q

olfactory bulb to brain via

A

mitral and tufted cells

52
Q

special stuff about olfactory receptors

A

regenerate throughout the lifespan, with new olfactory receptor cells arising from underlying basal (stem) cells. This process likely occurs over a period of weeks.
=constant recyling of receptors

53
Q

size of olfactor bulb

A

in periform cortex
prominant structure
large bundle of axons
right above your eyes

54
Q

activating the olfactory bulb

A

olfactory mucosa is divided into 4 zones
-each zone contains many types of receptors
-however specific types of receptors in only one zone (eg 1-10 in zone 1, 11-20 in zone 2)
specific types of receptor neurons synapse with only one or two glomeruli, so bulb also arranged in zones
so olfactory bulb inherits olfactory mucosa structural organisation

55
Q

what olfactory mucosa structure means

A

so olfactory bulb (containing glomeruli) inherits olfactory mucosa structural organisation
so one smell = lots of activity in one spot
if given another odorant will have two diff patterns

56
Q

evidence distributed coding for odor

A

proposed by Malnic etr al from results of calcium imaging experiments
-odorants are coded by combination of olfactory neurons called recognition profiles
specific receptors may be part of the code for multiple odorants
sort of like a fingerprint for each odorant

57
Q

2DG technique

A

activating the olfactory bulb
2DG contains glucose, ingested by animal (rat MRI)
mouse is exposed to different chemicals
neural activation is measured by amount of radioactivity present
this technique is used with behavioural testing shows patterns of neural activation is related to perception
diff smell = diff activation
same smell = same activation

58
Q

cortical processing how we smell

A

receptors
olfactory bulb
primary olfactory cortex (priform cortex)
indirect routing through thalamus
orbitofrontal cortex (both direct and indirect projections)
-two ways into orbitofrontal cortex
-purpose of this wiring

59
Q

what happens in piriform cortex

A

very much analogous to olfactory bulb
distributed codes
smiliarity of activity patterns seems to encode odor identity

60
Q

piriform cortex study

A 
10 odorants presented
1 taken away
very similar representation
1 added 
very different representations
shows is not one cell for an orange, one for a banana, is a pattern of activation
61
Q

tongue - transduction

A

bumps = where taste buds are

  • circumvallate papillae = big back ones
  • foliate = side bumps/ ridges
  • filiform papillae = top
  • fungiform = top and side
62
Q

filiform papillae

A

more developed in other animals eg rough cat tongue
not taste buds, shaped like cones and located over entire surface - move stuff around (cleaning, circulating salavia etc)
usually stay pretty short in humans but can grow = yuck

63
Q

fungiform

A

shaped like mushrooms and found on the sides and tip of your tongue

64
Q

foliate

A

series of folds on back and sides

65
Q

circumvallate

A

shaped like flat mounds in a trench located at the back

found right infront of the tounsils

66
Q

structure of the taste system

A

taste buds are located in papallae

  • tongue contains 10,000 taste buds
  • each taste bud (little cilia) has taste cells with tips that extend into taste pore
  • transduction occurs when chemicals (eg sweet, sour etc) contact the receptors sites on the tips
67
Q

five basic taste qualities

A

salty
sour
sweet
bitter
umami = meaty, buttery or savoury and associated with MSG
sort of forgotten word but not entirely real / based in clear same experience for everyone but better
contrar to popular belief, sensations of diff qualities are not strictly localized to specific parts of the tongue

68
Q

tongue locations

A

some differential distributions for receptors of diff taste

but very much overlapping

69
Q

pathways signals from taste cells fo to brain (just names)

A

facial nerve
glossopharylgeal nerve
vagus nerve
superfirical petronasal nerve

70
Q

facial nerve

A

relays from anterior two thirds of tongue

71
Q

glossopharyngeal nerve

A

from back of tongue (circumvillate + folliate)

72
Q

vagus nerve

A

from mouth anf throat

73
Q

superficial petronasal nerve

A

from soft palate

74
Q

cranial nerves to brain route

A

cranial nerve
solitary nucleus of meduall oblongata (brain stem)
crosses into contralateral cortex, medial lemniscus (also brain stem)
relays to thalamus
primary gustatory cortex in insula

75
Q

flavour =

A

taste + smell

76
Q

where does odor stimuli from food in the mouth go

A

reaches olfactory mucosa through retronasal route

77
Q

which taste quality is not influenced by olfaction

A

MSG
related to umami
all other flavours perception changes if nose closed / clamped

78
Q

supertasters

A

35% women, 15% man
tasters = more taste buds than nontasters
tasters have specialised receptors for these compunds
supertasters appear more sensistive to bitter substances than tasters
can affect diet (dislike bitter veggies) and susceptinility to pain (burning mouth syndrome)

79
Q

how to work out if you are a supertaster

A 
whole punch
bue food dye on tongue
-taste buds dont absord die
circle on tongue
count number of papilliae (and so number of taste buds)
more than 35 = supertaster
15-35 is normal taster
80
Q

neural coding for taste

A

distributed coding - similar to olfaction
-different taste stimuli were presented to rats and recording were made from the chorda tympani (branch of facial nerve)
across-fibre patterns showed that two substances (ammonium chloride and potassium chloride) are similar to each other
basically measuring relative activity in each fibre in bundle of nerves carrying info into the brain
then
-rate trained by shocking them when they drank potassium chloride
-when given the choice they owuld hen subsequently avoid ammonium chloride
experiment provides physiological and behavioural evidence for distributed coding

PSYC 102 - sensory (4 decks)

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