Gustation/Olfaction

Gustation

• chemical process

• tastants as stimulus on tongue

• Why: idenitfy nutrients, avoid dangers

• Qualities:

  • sweet

  • salty

  • sour

  • bitter

  • umami

flavor

has top down influences

gustation equals taste but is not flavor

Papilae and tastebuds

papilae contain taste buds

• 3 types of papilae

• taste buds have 150 gustatory receptor cells (GRC

• tastants need to dissolve in saliva to enter taste pore

labeled line coding vs population coding for taste

• labeled line

  • each GRC respons to only one tastant and is most common

• population codiing

  • each GRC responds to multiple types of stimuli and is less common, stimuli represented by combined activation of multiple neurons

Tongue Map Inaccurate

problems are

• GRC rspond to mutiple stimuli

• GRC are even distributed across tongue

Adaptation (cake and lemonade example)

when you eat cake the sweet receptors adapt reducing the fire rate, the when u drink lemonade the sour receptors fire normall but sweet receptors fire lass

Miracle berries

activates sweet receptors, but only at low pH

Parts of the Taste Pathway (6)

1) tongue

2)GRCS

3) Thalamus

4) Insula

• codes for taste, gustatopic maps

5) OFC: affective evalutation

• codes for pleasantness of taste

6) reward circuits

Gustation vs Color Vision

• both use population coding (rely on combined activity in neurons to some degree)

• Gustation has 5 receptors for 5 tastants while vision has 3(small, medium, long) and can code for many more

• combinations vs changes

  • salty + sweet is till salty + sweet, but gree + red is now yello

Top Down influences on taste perception

think orange juice experiments, particpants were given either water/oj combo or just oj and primed visually with very sweet or less sweet and this impact the ratings

artificial vs natural sweeteners

• artificial sweeteners much more sweet

• brain distinguishes the caloric from the non-caloric sweetener. although conscious mind could not

Olfaction

• alerts us to both bad and good stimuli

• chemical mechanism (like taste)

  • stimulus is odorants

• eolutionary OLD

• shared “hardware” with breathing

Odorants

• volatile chemicals (not all chemicals are odorants

orthonsasal vs retronasal

• orthonasal

  • in through nose

• retronasal

  • from mouth

olfactory transduction

1) odorants enter naval cavity

2) dissolve in mucus

3)contact cilia of olfactory receptor neurons (ORNs)

4) ORNs depolarize

5) summate in the olfactory bulbs

6) signal tramistted to brain

Olfactory Receptor Neurons (ORNs)

• pseudogenes nonfunctional ORNs

• functional different types of ORNs

population coding: odors are identified by combined responses of many ORNs

specific anosmia

• lack ORNs(have pseudogene receptors) that code for specific odorants

Olfaction Adaptation

some receptors may alter perception of odorants that activate those receptors

olfactory localization

reason why we have two nostrils going to two different olfactory bulbs

• helps pinpoint locations of certain smells

Anosmia

losing sense of smell

• phsyical

  • hit in the head, and there is now damage to nerves

• Chemical

  • some chemicals destory olfactory receptors

• Viral

  • viruses can affect olfactory/supporting cells

inattentional anosmia

• particpants took part in highlow load visual attention task— low load were much more likely to remember smell of the room

Smokers

smokers have threshold for odors, poorer discrimination, poorer odor identification

Vision Influencs Olfaction

influences odor identification

Top Down influences on olfaction

sweat+cheese smell

labeled cheddar chess or body odors

the cheddar cheese had higher pleasantness rating

Olfaction and Memory

the different brain regions for emotion and memory are connected with the olfactory bulb