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Cognitive Psychology 2 > Taste and Smell > Flashcards

Taste and Smell Flashcards

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1
Q

what type of sense are taste and smell?

A
  • chemical senses
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2
Q

how do we taste?

A

chemicals dissolve in mouth and stimulate taste buds in the oral cavity

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3
Q

how do we smell?

A

volatile (gaseous) chemicals are inhaled into the nasal passages where olfactory receptors line the membranes

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4
Q

4 basic taste qualities or sensations

A

salty, sour, sweet and bitter

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5
Q

substances general taste and chemical compisotion

A
  • salty = produced by organic salts (e.g. NaCL)
  • sour = taste from acidic substances (e.g. vinegar)
  • sweet = produced by carbohydrates and amino acids (e.g. glucose)
  • bitter = produced by alkaloids (often poisonous) (e.g. cocaine)
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6
Q

how many taste buds does the average human have?

A

10,000

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7
Q

how many types of papillae are on the tongue

A

3 types

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8
Q

what is the lifespan of each taste bud?

A

10 days

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9
Q

what are the 3 types of afferent nerve fibres?

A
  • Chorda tympani: Front part of the tongue
  • Glossopharyngeal: back region of the tongue
  • Vagus: Throat, pharynx and larynx
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10
Q

what are the Neural Pathways for taste perception?

A
  • afferent fibres travel to nucleii in the brainstem and then via the thalamus to the primary taste
  • some fibres also project to the orbito-frontal cortex. involved in the behavioural significance significance/reward value of food and perhaps the degree of ‘‘pleasantness’ of sensory stimuli in general (e.g. Francis et al., 1999)
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11
Q

how is taste quality encoded?

A
  • most receptor cells respond to some extent to all 4 basic kinds of taste stimuli, although with different sensitivity
  • many taste responsive cells in the thalamus also respond to all tastes
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12
Q

so how does the brain differentiate between substances?

A

cross-fibre theory
- although most neurones in the taste system respond to several taste stimuli, each responds best (is ‘tuned’) to a particular substance (e.g. salt)
- consequently information about taste quality/identity can be coded in the pattern of activity within an ensemble or group of neurones

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13
Q

what do detection thresholds for taste depend on?

A

substance tested, temperature, mouth region tested, viscosity and presence other substances

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14
Q

when is taste sensitivity greatest (detection thresholds lowest)?

A

between 22 to 32 degree C regardless if taste quality

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15
Q

are all papillae equally responsive?

A

no

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16
Q

why does sensitivity to specific substances vary over the tongue surface

A
  • front = ‘sweet’ & ‘bitter’ tasting substances
  • back sides = ‘sour’
  • front sides = ‘salt’
  • soft palate maximally sensitive to bitter tasting substances
17
Q

what are two substances are intensely bitter tasting synthesised coumpounds?

A

phenylthiocarbamide (PTC)
6-n-propylthiouracil (PROP)

18
Q

what are ‘tasters’?

A

taste bitter to 50% of population

19
Q

what are ‘nontasters’?

A

tasteless or undetectable to 25% of population

20
Q

what are ‘supertasters’?

A

extremely bitter, causing choking or gagging to 25% of population

21
Q

Henning (1916) - 6 primary odour sensations

A

‘fragrant’, ‘putrid’, ‘ethereal’ (fruity), ‘burned’, ‘resinous’ and ‘spicy’
- in reality its difficult to classify odours reliably using 6 categories

22
Q

general relationship between a substance’s smell and its chemical properties

A
  • chemical stimuli for olfaction are organic, rather than inorganic, volatile substances
  • usually composed of complex mixtures of chemical compounds emitted by vegetation, decaying matter and scent-producing glands of animals
  • ability to sense these natural odours have survival value
23
Q

what are the receptors that mediate smell perception?

A
  • molecules enter nasal cavity → air warmed and humidified by baffles
  • olfactory receptors (10million humans) located on olfactory epithelium
  • Oderants are picked up by specialised odorant binding proteins in mucus and transported to receptor sites on cilia (finger-like projections) at the end of each olfactory cell
24
Q

how often are olfactory receptors replaced?

A

every 4 to 8 weeks

25
Q

why does the neural pathways of smell perception support the ‘lock and key’ hypothesis?

A
  • Specific proteins in cilia membrane (locks) have a unique 3-dimensional structure to which particular oderant molecules (keys) may bind depending on their shape and size
  • Initiates a number of biochemical processes that result in action potentials in cell axon
25
Q

how does the brain differentiate between odours?

A
  • One solution is the cross-fiber patterns of activity like those proposed for taste (Kauer, 1987, 1991)
  • Consequently information about odour quality/identity could be coded in the specific pattern of activity within an ensemble or group of neurones
25
Q

The neural pathway for smell perception

A
  • Oderant molecules interact with specific sites on membranes of cilia
  • Olfactory receptor cells send axons through holes in a bone at the top of nasal cavity, to form the olfactory nerve, to the olfactory bulb of the brain
  • Axons from the olfactory bulb project to several other regions of the brain including the olfactory cortex (below anterior portion of the frontal lobe), thalamus and lower brain centres of the limbic system (involved emotion)
25
Q

how is odour quality encoded?

A
  • Olfactory nerve fibers respond to a wide variety of different odours, but with different sensitivity (Kauer, 1991)
  • Consequently individual olfactory fibers indicate the presence of odorous substances, but alone provide ambiguous information about what it is
26
Q

what does the detection threshold for smell depend on?

A
  • Substance tested
  • odorant purity
  • the way it is delivered to the olfactory epithelium and can vary greatly from moment to moment in the same individual (e.g. Stevens et al., 1988)
27
Q

how sensitive is the olfactory system?

A
  • subjects can detect mercaptan (foul-smelling compound added to natural gas) at a concentration of 1 part per 50 billion parts of air! (Geldard, 1972)
28
Q

what other factors can odour sensitivity depend on?

A

gender and age
- Females are generally more sensitive, on average, to odours than males (e.g. Koelga & Koster, 1974) and the elderly are less sensitive than young adults (e.g. Cain & Gent, 1991)

29
Q

what is anosmia?

A
  • odour blindness
30
Q

does smell interact with taste?

A

yes, Without smell, the ability to identify foods by taste alone is poor

Cognitive Psychology 2 (22 decks)

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