Chemical senses and multisensory perception Flashcards
What type of sense are both taste and smell?
• Taste (gustation) and smell (olfaction) are both chemosenses
- Detect chemicals
Give features of taste
- 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
What are taste maps?
- The old view – different areas of the tongue more responsive to the core tastes
- This has been disproved
What causes the different types of taste?
- 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
What do supertasters have?
- Supertasters have more papillae and taste buds
- Detect ‘tasteless’ substance PROP (6-n-propylthiouracil)
Give features of smell
- Olfaction – can discriminate up to 10,000 types of molecule
- Limited by our memory for what they indicate
- No satisfactory classification of odours
What are the two routes for smell?
- Orthonasal – via inhalation
2. Retronasal – during chewing and swallowing
Give features of smell receptors
- 350 different types of olfactory receptors
- Able to discriminate large number of different smells
- Receptors of similar type project to same glomerulus
What are the top down effects on smell?
- 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
What is the close connection between smell and memory?
- The ‘Proust effect’ – vivid memories brought back by particular smells
- Close linkage between smell and limbic system in the brain (emotion)
What is flavour made up of?
Taste and olfaction
What are other influences on easting?
Texture
Pain
Sound
Vision
Give features of texture in food
- Tongue well represented in somatosensory cortex
- Many foods (e.g. mushrooms) widely disliked because of the texture
Give features of pain in eating
- 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
How do sounds affect taste?
- 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
What happens with vision and taste?
- Oneology students fooled by white wine with red dye
- Tastiness ratings increased for art inspired dishes
What are multisensory receptive fields and give examples
- 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
What can multisensory integration do?
- Can allow detection of weak stimulus in another modality
- Can make sense of an ambiguous stimulus in another modality
- Can alter the quality of a stimulus in another modality
How does ventriloquism and multisensory integration work?
- 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
What is the McGurk effect?
- 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
What is Kinaesthesia?
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
How can you increase awareness of speed?
- Multisensory approach
- Pained/ raised lines to increase awareness of speed via vision/ audition
What is Synaesthesia?
• Stimulation of a particular type which always leads to another perceptual experience
- E.g. seeing coloured letters
- Tasting shapes
- Approximately 1 in 200 people
Give examples of cross-modal correspondences?
- 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
Talk about synaesthesia and training
- 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
