taste

Question 1

flavour = a mix of sensory data including

Answer 1

1. taste
2. smell
3. sound
4. texture
5. temperature
6. pain

Question 2

tastant

Answer 2

• any molecule that elicits taste
• Water soluble (lipophilic) chemicals
• Dissolve in saliva
• Activate tastant receptors / ion channels on taste receptor cells

Question 3

gustation process (food -> nerve)

Answer 3

• tastants dissolve in saliva and bathe papillae
• tastant molecule binds to receptor on TRC of tastebud (found on microvilli of TRC in the papillae folds)
• binding causes depolarisation and neurotransmitter release from TRC onto sensory nerve cells → AP cranial nerves

Question 4

gustation process (receptor -> brain)

Answer 4

• tastant binding causes depolarisation and neurotransmitter release from TRC onto sensory nerve cells → AP cranial nerves
• brainstem centres → thalamus → primary gustatory cortex, OFC, & also to hypothalamus & amygdala

Question 5

kokumi - taste modality?

Answer 5

• kokumi refers to a mouthfeel of richness and cannot be pinpointed to one singular molecule or type of molecule
• not a specific taste sensation triggered by chemical binding to taste receptors

Question 6

types of cells in taste bud

Answer 6

• BASAL cell
• GUSTATORY cell
• SUPPORTING cell

Question 7

3 types of TRCs

Answer 7

• Type 1: detects low salt
  
  • actually a glial cell
• Type 2: detects high salt, sweet, bitter, umami & kokumi
• Type 3: Detects sour
  
  • H+ channels

Question 8

how are different tastes detected across the tongue?

Answer 8

= difference in sensitivity, but by taste not by area
- All tastes are sensed by all parts of the tongue, just different sensitivity thresholds

Question 9

what is the role of olfaction in taste?

Answer 9

normal smell pathway + pathway from olfactory receptors at top of throat to primary gustatory cortex + integration at OFC → smell has significant contribution to flavour perception

Question 10

What coding schemes are thought to contribute to gustatory perception?

Answer 10

• specialist coding: one neuron for one type of taste receptor cell with one type of receptor on it
• combinatory coding:
  
  • TRC with multiple types of receptors
  • OR neuron that carries info from multiple types of TRCs

Question 11

evidence for coding schemes in gustation

Answer 11

• evidence for both: specialist and combination cells at all levels of encoding
  
  • Some sensory fibres respond best to one tastant [specialist]
  • Sensory fibres can be broadly tuned or narrowly responsive [combinatory]

Question 12

brain processing regions for taste

Answer 12

Cranial nerves project to brainstem nuclei → thalamus → gustatory (insular) cortex & OFC [integration] & also to hypothalamus & amygdala

Question 13

Specific Hungers Theory (Curt Richter, 1940s)

Answer 13

• Posits that deficiency of a given nutrient drives hunger for that nutrient
  
  • in humans, only sweet and salty

Question 14

hedonic vs homeostatic eaters

Answer 14

• homeostatic: to maintain energy balance, driven by hormone signalling, and innate approach/avoidance behaviours for specific flavours (e.g. bitter = poisonous, sweet = fuel)
• hedonic: for pleasure, driven by reward system

Question 15

threshold and JND with adaptation

Answer 15

adaptation: perceived intensity decreases (relative threshold), but JND increases

Question 16

non-taste contributions to flavour

Answer 16

• temp
• texture
• pain (e.g. chilli)
• sound
• appearance

Question 17

multisensory integration - WHERE?

Answer 17

OFC: inputs from gustatory and olfactory pathways, as well as other sensory pathways

Question 18

multisensory integration - role?

Answer 18

role in decision making, preference, reward value, avoidance/approach behaviours — takes into account multiple modes of sensory info, informs response

Question 19

superadditivity

Answer 19

• superadditivity = individually weakly effective (i.e. near-threshold) stimuli combining to give rise to multisensory experiences that are more intense, and richer, than would be predicted by the simple linear combination of their individual parts
• observed in OFC in response to congruent olfactory, gustatory and visual stimuli
• e.g. smell + taste + sight of cookie = COOKIE