Summary All the lectures of Sensory Science

Principles of Sensory Science
Lecture 1: Smell and trigeminal

Food perception
 Influenced by:
- Outside mouth
o Vision
o Smell
o Audition
o Texture
- Insde mouth
o Taste
o Smell
o Trigeminal
o Texture
o Audition

Functions of smell
- Food
 Smell influence the taste
o Important to flavor perception
- Social life
o Hygiene and perfumes
o Pheromones/body odors
 Based on smell; there can be sexual attraction, recognition
o Emotions and memory
 Sense of smell is very close to the emotion and memory area in the brain
- Safety
 Smell can be a warning
- Symptoms of disease
 Losing sense of smell can be a symptom of a disease

Anatomy and physiology of the olfactory system
From nose to brain
o Odor molecules in the air
 binds to odorant receptors
 Cranial nerve I
 Glomerulus

,  Signals are transferred to higher brain regions via
olfactory bulb
o Odor receptors
 Different types
 One glomerulus receives
the signals from one type
of receptors
 Combination of activated
receptors are causing a
smell
 Family of olfactory receptors (OR)
genes
 Part of GPCR family
 Receptors recognize only
small, structural features
on each molecule
 All have the same in the cell membrane, but differ of functional
structure
 One odor can activate multiple neurons (=odor receptors)
 Odor identity = a pattern of activated glomeruli codes
In the brain
 From the bolb straight to the piriform
cortex (= is closely connected to the limbic
system), does not pass the thalamus
 Orbitofrontal cortex
Odor quality coding
Overlapping activation in the piriform cortex,
but per odor unique.
 Can change based on learning/experience
o Coding in the brain changes

In summary:




Odor perception and measurement
Oder quantity and categorization

, o Plato: Pleasant vs Unpleasant
 Not always the same for humans
o Smell is not analitycal  It’s abstract and synthetic
Wine aroma wheel
o Inner cirkels  more general
o Outer cirkels  more detailed
Measuring olfactory function
o Sniffing sticks
 Identification  name of identify odors
 Discrimination  how well distinguish/tell odors apart
 Detection threshold  when does somebody detect the smell
o Olfactometer
 Controlled and fast
o Normative values
 For objective testing
 Clinical diagnoses for examble
- Odor sensitivity
o Individuals have different sensitivity for selected smells
o Thresholds differ per smell
 In concentrations ppm/ppb/ppt ranges
o Mostly it’s not necessary to know the amount of the odor
 More important to detect a type of odor
- Odor discrimination
o Differ in structural  possible to distinguish
 More structurally similar odors are difficult to distinguish
- Sense of smell
o Influenced by:
 Age
Getting older  less sense of smell
 Sex
Women better than men
 Smoking
 By smoking  less sense of smell
 Quitting  reversible effect
 Genetics
Genes influence
 Size of the nose
 Bulb volume is correlated with odor identification ability
 Nasal volume is correlated with odor detection ability
Sniffing and smelling
o Intensity of molecules into the nose  influences the sense of smell
o Sniff duration is more important than sniff strength
o Magnitude