A Little Nasal Knowledge:

Tyler S. Lorig, Ph.D.

WASHINGTON AND LEE UNIVERSITY

The Scienceof Scent

What smells?

A molecule of vanillin - grey spheres are carbon, red - oxygen, white - hydrogen

Richard Axel Linda Buck2006

Rhinencephalon or Limbic System

The Rhinencephalon Defines the Brain of

Mammals•Territoriality

•Hunt/forage/food intake

•Maternal Behavior

•Infant Attachment

•Sexual Selection

•Hormone Regulation

“From a clinical point of view, the importance of the olfactory system is slight, just as the sense of smell is of relatively minor importance in the normal life of civilized man.”

A. Brodal, Neurological Anatomy,

3rd

What about Humans?

So...olfaction is vestigial in humans

•We almost never notice odors

•When we notice, we can’t identify

•Noses are funny

•Much of odor perception is a nuisance

•98% of undergrads would loose smellif given a choice

Not so fast…

Your Brain and Jelly Beans

or SKITTLEs

Smells, Tastes and Flavors

Sweet salty, bitter, sour, Umami…EVERYTHING ELSE is an odor

You

Mate

Offspring

Love it!

Hates it!

????????

it

1000 Receptor Types ….only 330 expressed in humans

U.S. Consumer Market 2001 : Source Kline & Co.

From Gilbert and Firestein, Nature Neuroscience 2003

Fine Fragrances for Men and Women 4.4 billion

Toiletries (soap, deodorant, bath) 6.6 billion

Hair care products 6.1 billion

Laundry products 6.1 billion

Home fragrances 2.3 billion

Functional Fragrances

Total Market 25.5 billion

Currently more than 40 billion (Kline)

$1,691 per ounce

1 oz $13,860.00

“Kyara”

National Geographic (1986)

The New Speed Dating?

(Associated Press, 2012)

Yes: Pheromone Parties

If odors are so important, why don’t we know it?

Odor Effects Without Detection

1983 & 1985 Kirk-Smith et al. Warwick Behavior & self-report1988 & 1990 Lorig & Schwartz Yale EEG1991 & 1993 Lorig et al. W&L ERP & Behavior1998 & 2000 Kline & Schwartz Arizona EEG & self-report1999 Sobel, et al. Berkeley fMRI2001 McClintock et al. Chicago PET2002 Walla et al. Vienna MEG2004 Jacquot, et al. Franche-Comte Skin conductance2005 Lundstrom & Olsson Uppsala Self-report2005 Holland et al. Radboud Behavior2009 Zucco et al. Padua, IT Behavior2010 Li et. al. Northwestern fMRI & self-report2010 Sela & Sobel Wiseman fMRI & self-reportand others

Lorig, 2012 Chemosensory Perception

Year Investigators University Dependent Var.

Odor and HealthIs olfaction related to health?Sure! Just what you’d expect…

AgingAllergiesSinusitisNasal polypsSmokingVOC exposureHead Trauma

Odor and Health

And many you wouldn’t…

Parkinson’s DiseaseMultiple SclerosisAnorexia nervosaDiabetesDown syndromeHIVEpilepsy (temporal lobe)Schizophrenia (including 1st degree relatives)AutismAlzheimer’s Disease (Serby, 1985)

Olfaction and Alzheimer’s

Olfactory loss precedes cognitive impairmentbut variability and loss due to aging makes prediction hard

“Olfactory (bulb) tau pathology showed highly significant correlation with neuritic Braak staging in the brain, while both scores showed significant but low correlation with age.” Attems & Jellinger 2006

Perceptual and effects are related to ApoE4 and appear to be sensory rather than cognitive pathology

Course of AD

Olfactory Tau

Detectable olfactory loss

ApoE 4?

Cognitive Impairment