Chemical Senses

Question 1

anosmia and effects

Answer 1

loss of sense of smell can result in a decrease in quality of life, decrease in motivation to eat, increase in risk of hazardous events (cannot smell fire, more food poisoning)

Question 2

chemical senses

Answer 2

taste (molecules bind to receptors on tongue)
smell (moleculen bind to receptors in olfactory mucosa)
flavour (combination of taste and smell)

Question 3

functions of taste and smell

Answer 3

detect and distinguish things that are important for survival and things that are bad for us
affective component: things that are good for us tend to taste/smell good

Question 4

how often are taste receptors re-generated

Answer 4

every 1-2 weeks

Question 5

how often are olfactory receptors regenerated

Answer 5

every 5-7 weeks

Question 6

what is different about chemical senses vs. vision, hearing, touch

Answer 6

receptors are directly exposed to the environment and are easily damaged (so undergo neurogenesis)

Question 7

basic tastes

Answer 7

salty (sodium chloride)
sweet (sucrose)
sour (hydrochloric acid)
bitter (quinine)
*umami (MSG)

Question 8

which tastes are innate and why

Answer 8

sweetness is inherently rewarding - has high caloric/nutritive value = survival-based
bitterness is inherently rejected - associated with poisons (but this response can. be altered with habituation to foods like coffee, beer)

Question 9

what are the types of papillae and where are they found?

Answer 9

filiform - all over the tongue (for texture detection, no taste buds)
fungiform - sides and tip
circumvallate - back to hold tastants before they are swallowed
foliate - back on sides to trap tastants

Question 10

structure of the fungiform papillae

Answer 10

shaped like a mushroom with taste buds protruding
the taste bud has a taste pore where tastants bind (contains taste cells with nerve fibers)
taste cell has receptor sites for the four basic tastes - where transduction occurs

Question 11

pathways to the brain from the tongue

Answer 11

chorda tympani nerve (front and sides of tongue)
glossopharyngeal nerve (from back of tongue)
superficial petrosal nerve (from soft palate)
vagus nerve (from mouth and throat)

Question 12

pathway of tastants

Answer 12

to brain stem (nucleus of the solitary tract) - thalamus - frontal lobe (insula, frontal operculum, orbital frontal cortex)

Question 13

population coding evidence for taste

Answer 13

recording from chorda tympani - 13 fibers responded in across-fiber patterns to produce perception of taste

Question 14

specificity coding evidence for taste

Answer 14

giving mice a PTC-bitter receptor = avoid PTC
removing the bitter-Cyx receptor in mice = stop avoiding Cyx
giving rats amiloride (blocks sodium from entering receptors) lowers response from solitary tract neurons that respond to salty but not neurons that respond to salty-bitter combination

Question 15

when do we use population and specificity coding for taste

Answer 15

population for subtle differences in tastes and specificity for basic tastes

Question 16

evidence for individual differences and genetic impacts on taste

Answer 16

cats don’t have sweet receptors (lack a functional gene)
tasters can taste PTC, nontasters cannot (specialized receptors)
some people can taste PROP (higher densities of taste buds, specialized receptors)
tasters of PTC and PROP may be more sensitive to bitter substances (more avoidance)

Question 17

microsmatic

Answer 17

weak sense of smell that is nonessential to survival

Question 18

macrosmatic

Answer 18

well-developed sense of smell that is essential for survival
humans have 10 million receptors, dogs have 1 billion)

Question 19

forced-choice method for detection threshold of smell

Answer 19

giving Ps one weak odourant and no odourant and they must choose which smells stronger

Question 20

why are smells difficult to explain/classify

Answer 20

physical properties (chemical structure) don’t always relate to perception (similar structures can result in very different perceptions, and different structures can result in similar perceptions)
smells in our environment are combinations of molecules

Question 21

steps for creating odour objects

Answer 21

perceptually organizing molecules into sources
1. analyzing in olfactory mucosa and bulb (transform into neural activity)
2. synthesizing into objects in the olfactory cortex (learning and memory)

Question 22

pathway of smell

Answer 22

molecules - olfactory mucosa (olfactory receptors - electrical signals in olfactory receptor neurons) - olfactory bulb (glomeruli) - piriform cortex - orbitofrontal cortex, amygdala, hippocampus
*each olfactory receptor responds to a narrow range of odourants (we have 350-400) and each ORN contains one type of olfactory receptor
*1 type of ORN sends signals to 1-2 glomeruli = different patterns of activation

Question 23

recognition profiles for odorants

Answer 23

patterns of activation in individual receptors (differences in recognition profiles account for differences in perception sweet vs. rancid)

Question 24

chemotopic/odour/odotopic map

Answer 24

map of odorants in the olfactory bulb based on molecular features of odorants (not conserved in the piriform cortex, where activity becomes widespread)

Question 25

formation of odour objects takes place in…

Answer 25

the piriform cortex by learning (creating neuronal connections which become recognized patterns of activity)
neurons in the PC can discriminate odour objects with exposure/training

Question 26

Proust effect

Answer 26

taste and olfaction “unlock” memories (typically from childhood)

Question 27

odour-evoked autobiographical memories

Answer 27

often from first 10 years of life, evoke strong emotions, associated with mental time travel (amygdala and hippocampus connections)

Question 28

retronasal pathway

Answer 28

chemicals in food/drink reach the olfactory mucosa through the nasal pharynx

Question 29

oral capture

Answer 29

sensations from olfaction and taste are perceived as from the mouth (tactile receptors)

Question 30

orbitofrontal cortex neurons

Answer 30

has bimodal neurons (respond to more than one sense) which often respond to similar qualities
- for percetual representations of food and flavour
- expectation also affects flavour (cost of food, label, presentation of food)

Question 31

sensory-specific satiety

Answer 31

after eating a particular food, odour of that food is perceived as less pleasant
reflected in the insula, amygdala, orbitofrontal cortex

Question 32

correspondences

Answer 32

property of a chemical sense is associated with properties of other senses (with pitches, instruments, colours, textures)

Question 33

influences

Answer 33

stimuli from one sense affect our perception of another sense (consonant music = sweeter chocolate, colour influences flavour, odour can have priming effects)

Question 34

where do correspondences and influences come from

Answer 34

learning and associations, pleasure, emotions (lemon-yellow, bright colours = happiness = pleasant odours = pleasant feelings = soft fabrics)

Question 35

developmental dimension of taste

Answer 35

mother’s food changes flavour of amniotic fluid = infant’s preferences
also the food she eats while breastfeeding and choice of first solid foods