Presentation on theme: "PSYC 330: Perception THE CHEMICAL SENSES. The Chemical Senses Smell and Taste – Olfaction and gustation Odors – Volatile molecules Tastes – Soluble molecules."— Presentation transcript:
The Chemical Senses Smell and Taste – Olfaction and gustation Odors – Volatile molecules Tastes – Soluble molecules – Trigeminal system “tactile” sensation of some smells and taste – temperature
Comparisons with other senses Evolutionarily Old Slow Regenerative Ipsilateral Not well understood
The Stimulus Odorants – aromatic Volatile (airborne) Small Hydrophobic Shape-pattern theory - lock and key fit - chemical structure Vibration theory - atomic vibration Data? Most consistent with SHAPE - specific anosmia (inability to smell ONE thing) - stereoisomers (same atoms arranged in new shape)
Olfactory System - Hardware Purpose of nose is to prepare air for breathing Internal shape of nose directs odorants upward towards olfactory system (turbinates) Olfactory cleft - location Olfactory epithelium - surface basal cells (“stem” cells for OFS) olfactory sensory neurons dendrites have cilia with receptors supporting cells Cribriform plate – separates nose from brain Olfactory bulb – lays along surface of brain; includes glomeruli (organized by odor NOT by location)
Transduction and Early Processing Odorant binds to receptor AP sent along olfactory sensory neuron Travel thru cribriform plate (olfactory nerve) into olfactory bulb Synapse at glomeruli sorted by TYPE of receptor, not location Mitral cells…. Climb on the gypsy wagon…..
An interesting aside…. Craft (2011) Transnasal insulin therapy for Alzheimer’s patients
Coding Smells Buck and Axel (1991) – Genetic code for 1,000 types of olfactory receptors – Similarity across mammal species BUT Not all expressed (pseudogenes) Dogs express 80% (20% pseudogenes) Humans express 30-40% Differences relate to smell sensitivity (not number of odors perceived)
Pattern Theory Shape of odorant molecule is important Odorant-Receptor fit – Pattern of odorant compounds fitting into various receptor types different pattern in glomeruli activation unique smells Evidence – Specific anosmias – Stereoisomers
Adaptation Adaptation defined – Receptor-level adaptation Receptor recycling Cross adaptation – Olfactory habituation Dalton (2002) long term receptor changes “cognitive” habituation
Hedonics Particularly important as it relates to taste Learned Durian fruit... its odor is best described as pig-shit, turpentine and onions, garnished with a gym sock. Richard Sterling
Olfactory Memories and Emotions Olfactory cortex (orbitofrontal cortex) Limbic system (amygdala) Limbic system (hippocampus) Accuracy? Memories with strong emotional content
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