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chapter14and15.pdf
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Sensation and Perception
Chapters 14 & 15: Olfaction and Gustation
Most images © 2014 Worth Publishing. Most images from Yantis (2014)
Lecture Outline
• Odorants • Odor detection &
identification • Olfactory impairments • Olfactory adaptation • Olfactory system
– Turbinates – Olfactory epithelium – ORNs – Olfactory nerve – Cribiform plate – Olfactory bulb / glomeruli – Neural code – Pathways to the brain
• Odors, emotion and memory • Pheromones • Gustation
– Basic tastes – Flavor – Taste buds – Papillae – TRCs – receptor and
presynaptic – Encoding taste – Taste and flavor in the brain – Individual differences – Taste modification
http://en.wikipedia.org/wiki/File:Lemon.jpg
http://en.wikipedia.org/wiki/File:PeanutButter.jpg
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Odorants
• Olfaction – sense of smell
• Odorants – molecules that the olfactory system can process when they are at a sufficiently high concentration – Mostly C, H, O, N, S
– Smell ≠ molecule
– Smell = vibration?
– Notes http://www.ted.com/talks/luca_turin _on_the_science_of_scent
Odor Detection
• Concentration
• Olfactometer
• Higher concentrations of odorants ≈ intensity
• Detection threshold
Odor Identification
• Identification threshold
• Poor at naming odorants
– Top-down / contextual information greatly helps
– Experience / practice / training helps too
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Olfactory Impairments
• Identification increases until late teens; decreases in the 60s • Women consistently better than men • Smoking decreases ability to identify odorants. Recovery
increases with time since cessation of smoking • Anosmia – inability to smell (particular odorants or
everything)
Olfactory Adaptation
• Adaptation – exposure to one odorant decreases sensitivity to that odorant across time
• Cross-adaptation – exposure to one odorant decreases the sensitivity to other, similar odorants
Olfactory System
• Turbinates
• Olfactory epithelium
• Olfactory receptor neurons
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Olfactory Transduction
• Cilia of ORNs • Olfactory nerve • Cribiform plate • Olfactory bulb / glomeruli
Olfactory Adaptation
• ORN
• Piriform cortex
Olfactory Neural Code
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Olfactory Bulb Activity / Code
Representing Odors in the Brain
• Piriform cortex – Anterior
– Posterior
• Amygdala → hypothalamus
• Entorhinal cortex → hippocampus
• All three project to the orbitofrontal cortex
Odors, Emotion and Memory
• Odor pleasantness
– Context
– Learned
• Memory
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Pheromones
• Pheromones
• Vomeronasal organ (VNO)
• Pheromones in humans
– Underarm secretions of women tend to cause the menstrual cycles of women to synchronize
– Sniffing tears produced by women watching a sad film reduced the sexual attractiveness of photos of women
– Women who sniff androstadienone (found in male sweat) report elevated mood and sexual arousal
– Men who sniff t-shirts of women who were ovulating had higher testosterone levels and reported the odor as more pleasant.
Gustation / Taste
• Tastant
• Sweet – sugars (carbon, hydrogen and oxygen)
• Salty – + and – ions
• Umami – amino acids
• Bitter – often indicates toxicity
• Sour – acids
• Hedonics
Flavor
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Effect of Temperature on Taste
Trigeminal Sense
• Irritants – chili peppers, menthol, carbonation, cinnamom, ethanol
Anatomical Basis of Taste
• Taste buds
• Papillae
– Filiform
– Fungiform
– Foliate
– Circum- vallate
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Taste Receptor Cells
• Taste receptor cells (TRC)
– Receptor – sweet, umami, bitter
– Presynaptic – salty, sour
Encoding Taste
• Labeled-line model
• Across-fiber pattern model
Taste and Flavor in the Brain
• Facial (CN VII)
• Glossopharngeal (CN IX)
• Vagus (CN X)
• Nucleus of the solitary tract in the medulla
• Thalamus (ventral posterior medial)
• Primary gustatory cortex (anterior insular, frontal operculum)
• Orbitofrontal cortex (flavor), amygdala (emotion), hypothalamus (hunger)
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Individual Differences
• Non-tasters vs tasters
• Supertaster
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Taste Modification
• Taste modifiers
– Gymnema sylvestre
– Synsepalum dulcificum (miracle fruit)
– Eriodictyon californicum (yerba santa)
http://en.wikipedia.org/wiki/File:Eriodictyon-californicum.jpg
