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, 3 rd 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 smell if given a choice Not so fast…
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 Women4.4 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)
If odors are so important, why don’t we know it?
Odor Effects Without Detection 1983 & 1985Kirk-Smith et al.WarwickBehavior & self-report 1988 & 1990Lorig & Schwartz Yale EEG 1991 & 1993Lorig et al. W&LERP & Behavior 1998 & 2000 Kline & Schwartz ArizonaEEG & self-report 1999Sobel, et al. BerkeleyfMRI 2001McClintock et al.ChicagoPET 2002Walla et al.ViennaMEG 2004Jacquot, et al.Franche-ComteSkin conductance 2005Lundstrom & Olsson UppsalaSelf-report 2005Holland et al.RadboudBehavior 2009 Zucco et al. Padua, IT Behavior 2010 Li et. al. Northwestern fMRI & self-report 2010 Sela & Sobel Wiseman fMRI & self-report and others Lorig, 2012 Chemosensory Perception Year Investigators University Dependent Var.
Odor and Health Is olfaction related to health? Sure! Just what you’d expect… Aging Allergies Sinusitis Nasal polyps Smoking VOC exposure Head Trauma
Odor and Health And many you wouldn’t… Parkinson’s Disease Multiple Sclerosis Anorexia nervosa Diabetes Down syndrome HIV Epilepsy (temporal lobe) Schizophrenia (including 1 st degree relatives) Autism Alzheimer’s Disease (Serby, 1985)
Olfaction and Alzheimer’s Olfactory loss precedes cognitive impairment but 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