Chemical senses and multisensory perception

Question 1

What type of sense are both taste and smell?

Answer 1

• Taste (gustation) and smell (olfaction) are both chemosenses
- Detect chemicals

Question 2

Give features of taste

Answer 2

• Embedded into our tongue
• Circumvallate (contains taste buds)
• Core tastes: sweet, sour, salty, bitter and Umami
• Each taste bud cell contains taste receptors that respond to each

Question 3

What are taste maps?

Answer 3

• The old view – different areas of the tongue more responsive to the core tastes
• This has been disproved

Question 4

What causes the different types of taste?

Answer 4

• Sweet: sugars (fructose, glucose, saccharose) artificial sweeteners (aspartame, saccharin)
• Sour: all acids (acetic acid, citric acid, ascorbic acid, phosphoric acid, lactic acid)
• Bitter: no unique chemical class: quinine, caffeine, peptide, phenols
• Salty: salts like table salt (NaCl), or NH4Cl, KCl
• Umami: Mono sodium glutamate, Inosine 5’-monophosphate, Guanosine 6’-monophosphate

Question 5

What do supertasters have?

Answer 5

• Supertasters have more papillae and taste buds

- Detect ‘tasteless’ substance PROP (6-n-propylthiouracil)

Question 6

Give features of smell

Answer 6

• Olfaction – can discriminate up to 10,000 types of molecule
• Limited by our memory for what they indicate
• No satisfactory classification of odours

Question 7

What are the two routes for smell?

Answer 7

1. Orthonasal – via inhalation

2. Retronasal – during chewing and swallowing

Question 8

Give features of smell receptors

Answer 8

• 350 different types of olfactory receptors
• Able to discriminate large number of different smells
• Receptors of similar type project to same glomerulus

Question 9

What are the top down effects on smell?

Answer 9

• Attention
   Sniffing
   Automatic attention
• Effect of labelling
   E.g. same odour smells worse when labelled as body odour rather than cheese
• Effect of learning
   E.g. expert wine tasters identifying wine odours

Question 10

What is the close connection between smell and memory?

Answer 10

• The ‘Proust effect’ – vivid memories brought back by particular smells
• Close linkage between smell and limbic system in the brain (emotion)

Question 11

What is flavour made up of?

Answer 11

Taste and olfaction

Question 12

What are other influences on easting?

Answer 12

 Texture
 Pain
 Sound
 Vision

Question 13

Give features of texture in food

Answer 13

• Tongue well represented in somatosensory cortex

- Many foods (e.g. mushrooms) widely disliked because of the texture

Question 14

Give features of pain in eating

Answer 14

• Chilli acts on pain receptors in tongue
• Can be partly supressed by tastes:
• Best: sweet and sour liquids
• Bitter are not effective
• Salty are intermediate

Question 15

How do sounds affect taste?

Answer 15

• Foods taste crunchier and fresher when the sound is amplified or the high frequencies increased
• Foods rates as less sweet and salty in the presence of background noise

Question 16

What happens with vision and taste?

Answer 16

• Oneology students fooled by white wine with red dye

- Tastiness ratings increased for art inspired dishes

Question 17

What are multisensory receptive fields and give examples

Answer 17

• Single neurone may respond to more than one modality
• Orbitofrontal cortex – taste and smell
   Taste and sight of banana
• Posterior parietal cortex – touch, vision audition
• A cell which responds to touches to the index finger may also respond to visual stimuli close to the index finger

Question 18

What can multisensory integration do?

Answer 18

1. Can allow detection of weak stimulus in another modality
2. Can make sense of an ambiguous stimulus in another modality
3. Can alter the quality of a stimulus in another modality

Question 19

How does ventriloquism and multisensory integration work?

Answer 19

• Visual information can influence where in space we perceive a sound source
   Puppet/ puppeteer
   Visual capture’ of sound allows us to follow what is happening in TV/ cinema

Question 20

What is the McGurk effect?

Answer 20

• Watch lips moving to make sound ‘ga-ga’
• Hear sound ‘ba-ba’
• Subjects perceive ‘da-da’
• Visual information is affecting the sound that you hear

Question 21

What is Kinaesthesia?

Answer 21

illusion of speed

• Initially driving 70mph
• 10 min later after steady 70 mph feels like 50 mph
• Nervous system turns down the ‘gain’ on steady-state inputs

Question 22

How can you increase awareness of speed?

Answer 22

• Multisensory approach

- Pained/ raised lines to increase awareness of speed via vision/ audition

Question 23

What is Synaesthesia?

Answer 23

• Stimulation of a particular type which always leads to another perceptual experience

• E.g. seeing coloured letters
• Tasting shapes
• Approximately 1 in 200 people

Question 24

Give examples of cross-modal correspondences?

Answer 24

• Rounded shape is ‘Bouba’
• Sharp shape is ‘Kiki’
• Majority of people say a lemon is fast and a prune is slow
• High pitched sounds are associated with lighter stimulus, more angular shape, smaller objects, brighter visual stimulus

Question 25

Talk about synaesthesia and training

Answer 25

• Following 9 week training regime participants pass tests of genuine synaesthesia
• Participants described vivid experiences similarly to people with natural synaesthesia
• Also led to increases in IQ