Lecture 2: taste and smell

Question 1

What are taste and smell?

Answer 1

Chemical compounds

Question 2

Outline Wedekind 1995

Answer 2

*dirty t shirts

Question 3

Outline McCulloch et al 2006

Answer 3

*dogs can pick up diseases in people through their sense of smell

Question 4

How do we recognise smell?

Answer 4

• combination receptor code

- each odour has a different spatial pattern

Question 5

How does adaptation to recognising smells work?

Answer 5

Receptors stop firing as much if repeatedly exposed

Question 6

How does adaptation to recognising smells work?

Answer 6

Receptors stop firing as much if repeatedly exposed

Question 7

Taste

Question 8

Taste sensitivity

Answer 8

**
some people increased liking with increased sweetness, others prefer intermediate levels (Callaghan and Weingarten, 1992).

Question 9

Taste buds

• how long do they last?
• what happens to food molecules
• how many tastes per cell?

Answer 9

• Only last about 10 days
• Food molecules dissolve in the mouth and bind to receptors.
• One cell – one taste.
• Tastes buds all capable of receiving different tastes (several cells).

Question 10

Taste: what is involved in neural relay

Answer 10

• Cranial nerve fibres relay this information to the brain.
– Preference for one taste by may respond to others.
• To thalamus – gustatory cortex (anterior insula and frontal operculum).
• Or straight to amygdala- emotion!

Question 11

How does cortical processing work?

Answer 11

• Cortical cells can respond to all flavours.
• Scott and Plata-Salaman (1999)
– Cortical responses to taste.
– Single cell recordings – tuning preference.
– 1= responds to all tastes, 0=only responds to one taste.
– Average = 0.7
Most cortical cells respond to a variety of tastes but have a preference for one.

Question 12

Taste adaptation

• what happens
• what happens to water taste after having salt solution on tongue

Answer 12

• *
• can adapt to specific tastes, eg rate tastes as less sour over time

-salt solution on tongue for a while makes pure water taste sweet

Question 13

What is flavour?

Question 14

What percentage of taste comes from how we think it smells?

Answer 14

Between 75-95%

Question 15

What is retronasal olfaction

Answer 15

=smells coming from the mouth

Question 16

What is orthonasal olfaction

Answer 16

=via the nose

Question 17

Murphy et al (1977)

Answer 17

**

Question 18

Stevenson et al (2004)

Answer 18

Caramel odorants can enhance sweetness but also diminish sour tastes.
Oral referral
Olfactory and gustatory stimuli are congruent – get flavour experience
Smell may be “referred” to the mouth.

Question 19

Taste and Fizz

Answer 19

**

Question 20

Taste and music

Answer 20

• music influencing choice of wine purchase
• enjoyment of sugar can be enhanced by loud music
• oysters eaten while listening to the ‘sound of the sea’ taste significantly more pleasant than oysters eaten while listening to farm yard nosied

Question 21

Understanding multi sensory integration

Answer 21

**

Question 22

Taste primaries

Answer 22

= a theory of taste coding based on the idea that perceived taste can be broken down into basic qualities, each uniquely associated with activity in a specific neural pathway

Question 23

Umami

Answer 23

A Japanese word meaning ‘good taste’, recent evidence indicates that it is a fifth basic taste quality

Question 24

Olfactory receptor neuron

Answer 24

A specialised neutron that produces electrical responses to door molecules

Question 25

Olfactory epithelium

Answer 25

A patch of muscoous membrane in the roof of the nasal cavity containing olfactory receptor neurons, in humans contains 6 million receptor neurons

Question 26

Free nerve ending

Answer 26

A brand of a sensory nerve cell that has no specialised receptor process, but is embedded directly in tissue

Question 27

Mitral cell

Answer 27

A neuron in the olfactory bulb that receives signals from olfactory receptor neurons and relays them to the brain, 50,000 mitral cells in the human olfactory bulb

Question 28

Olfactory bulb

Answer 28

A mass of neural tissue protruding from the brain behind the nose, which conveys neural signals from the olfactory epithelium to the brain

Question 29

Olfactory glomerulus

Answer 29

A dense, spherical accumulation of dendrites and synapses, where approx 200 olfactory receptors make contact with a single mitral cell

Question 30

Primary olfactory cortex

Answer 30

The cortical destination of mitral cell fibres, thought to mediate perception of smell

Question 31

Amygdala

Answer 31

A necleus lying deep in the brain, forming part of the limbic system, involved in emotional, sexual and automatic responses

Question 32

Anosmia

Answer 32

Lack of sensitivity to door

Question 33

Taste receptor

Answer 33

A chemoreceptor cell found on taste buds in the mouth, tongue and throat, there are 50-150 recpetors on each bud

Question 34

Taste bud

Answer 34

A cluster of cells embedded in the skin of the tongue and mouth, housing taste receptors. The human tongue contains approx 5000 taste buds