1 / 49

Olfaction 2

Olfaction 2. PSY 295 – Sensation & Perception Christopher DiMattina , PhD. Olfaction and vision. Olfaction and vision. Many analogies between olfaction and vision Last time we talked about the olfactory epithelium “Retina of the nose”. ORNs and photoreceptors.

liona
Download Presentation

Olfaction 2

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Olfaction 2 PSY 295 – Sensation & Perception Christopher DiMattina, PhD

  2. PSY 295 - Grinnell College - Fall 2012

  3. Olfaction and vision PSY 295 - Grinnell College - Fall 2012

  4. Olfaction and vision • Many analogies between olfaction and vision • Last time we talked about the olfactory epithelium • “Retina of the nose” PSY 295 - Grinnell College - Fall 2012

  5. ORNs and photoreceptors • Different ORNs express different receptor proteins which bind different odorants (~400 in humans) • Three kinds of cones are maximally sensitive to different wavelengths PSY 295 - Grinnell College - Fall 2012

  6. Synthesis and analysis • Odors are perceived as unitary wholes – no ‘bacon’ molecule • However, people can be trained to detect components • Mostly synthetic (like color mixing) but can also be analytic PSY 295 - Grinnell College - Fall 2012

  7. Binocular Rivalry • In vision, presenting different stimuli to the two eyes results in bi-stable percept • Alternately see either a face or a house, but not both at once PSY 295 - Grinnell College - Fall 2012

  8. Binaral rivalry • Two smells presented into nose at once • Alternately perceive one of the two smells PSY 295 - Grinnell College - Fall 2012

  9. Zhou & Chen (2009) • Marker scent in one nostril, rose scent in other nostril • Same stimulus on each trial, perception alternates PSY 295 - Grinnell College - Fall 2012

  10. Zhou & Chen (2009) PSY 295 - Grinnell College - Fall 2012

  11. Visual stimuli influence smell • Binocular rivalry experiment – picture of rose and marker • Smell ambiguous mixture scent • When visually perceiving rose/marker, smell rose/marker PSY 295 - Grinnell College - Fall 2012

  12. Imagery • Brain imaging of humans during visual imagery shows activation of same areas involved in visual perception • Similar results do not hold for olfactory imagery PSY 295 - Grinnell College - Fall 2012

  13. We are visual creatures • Perhaps rats dream of smells or can imagine smells better? PSY 295 - Grinnell College - Fall 2012

  14. Center-surround organization • Inhibitory interactions between glomeruli create center-surround organization – “nearby” odors inhibit each other PSY 295 - Grinnell College - Fall 2012

  15. Olfactory Psychophysics PSY 295 - Grinnell College - Fall 2012

  16. We are sensitive to odorants • Can detect extremely small concentrations • Human ORNs can be excited by 1 molecule • Have fewer ORNs than other animals which are much more sensitive (i.e. dogs) PSY 295 - Grinnell College - Fall 2012

  17. Commonsense thresholds PSY 295 - Grinnell College - Fall 2012

  18. Declines with age • Number of ORNs regenerated is less than number that die • About 50% of population is effectively anosmic after 85 • Taste and trigeminal systems do not decline as much, which is why elderly like salty and spicy foods PSY 295 - Grinnell College - Fall 2012

  19. Odor recognition memory • Excellent retention of odor memories compared to visual memories • Does not require verbal labels PSY 295 - Grinnell College - Fall 2012

  20. Olfaction and language • Olfactory processing localized to right hemisphere • Language localized to left hemisphere • Olfactory information not integrated with thalamus • May explain lack of verbal labels for smells PSY 295 - Grinnell College - Fall 2012

  21. Adaptation • We adapt rapidly to smells • One cause is G-protein coupled receptor internalization following odorant binding PSY 295 - Grinnell College - Fall 2012

  22. Adaptation • Beneficial to be most sensitive to new smells and insensitive to constant smells • Especially useful if you live on a cow farm PSY 295 - Grinnell College - Fall 2012

  23. Cross-adaptation • Smelling odors similar to a given odorant can cause ORN adaptation (at perfume store) • Why does this make sense in terms of how ORNs work? PSY 295 - Grinnell College - Fall 2012

  24. Both central and peripheral adaptation • Adaptation plays role in olfactory rivalry • Both peripheral and central effects PSY 295 - Grinnell College - Fall 2012

  25. Zhou and Chen (2009) • Present adapting odor to one nostril • Test either that nostril or opposite nostril • See cross adaptation – cannot be due to receptor effects PSY 295 - Grinnell College - Fall 2012

  26. Olfactory Hedonics PSY 295 - Grinnell College - Fall 2012

  27. What smells good and bad? PSY 295 - Grinnell College - Fall 2012

  28. Familiar odors smell better • Subjects tested with both familiar and unfamiliar odors • Gave ratings of pleasantness, familiarity, complexity to each • People prefer familiar odors, less complex odors PSY 295 - Grinnell College - Fall 2012

  29. Intensity PSY 295 - Grinnell College - Fall 2012

  30. Cross-cultural variability • The Japanese find the smell of cheese disgusting • Westerners find smell of some Japanese foods disgusting PSY 295 - Grinnell College - Fall 2012

  31. Nature or nurture? • Infants have very different odor preferences than adults • Sometimes do not find feces disgusting • Cross-cultural variability • Some cultures use cow dung in their hair • Associative learning PSY 295 - Grinnell College - Fall 2012

  32. Learned taste aversion • We can learn an aversion to certain flavors when it has been paired with sickness • Maybe you have aversions for food or kinds of alcohol which made you sick • For a while in college I found vodka disgusting after getting sick PSY 295 - Grinnell College - Fall 2012

  33. Generalist and specialist species • Species with simpler ecology do have innate smell aversions (predators) • It makes sense for species like ours which live in a variety of habitats to be able to learn associatively which smells predict trouble PSY 295 - Grinnell College - Fall 2012

  34. Orbitofrontal cortex • Olfactory pathway projects to orbitofrontal cortex • Responsible for determining ‘value’ of stimuli PSY 295 - Grinnell College - Fall 2012

  35. Devaluation of rewards • Rats trained to associate visual conditioned stimulus with food pellets in a cup • After they learned this, the food was devalued by pairing it with injections of LiCL (induce nausea) • Normal rats stopped going to the de-valued food, OFC lesion rats did not PSY 295 - Grinnell College - Fall 2012

  36. Neural codes for expected rewards • Rats had to sniff an odor port which gave one of two odors predicting either a good reward (sucrose solution) or bad reward (quinine solution) • During learning, neurons in OFC respond differently to smells predicting sucrose and quinine solutions PSY 295 - Grinnell College - Fall 2012

  37. Odor hedonics caveats • All people find painful odors aversive • Different people express different receptors, so some people may lack receptors for unpleasant odors (can’t smell compounds in sweat) PSY 295 - Grinnell College - Fall 2012

  38. Associations differ across cultures • Americans rate wintergreen as pleasant (i.e. mints, gum, candy, etc…) • In Britain it was used to flavor medicines, so has unpleasant associations PSY 295 - Grinnell College - Fall 2012

  39. Olfaction, memory and emotion PSY 295 - Grinnell College - Fall 2012

  40. Are odors the best cue to memory? • Smells bring back memories • But are they really more reliable than memories evoked by other stimuli? PSY 295 - Grinnell College - Fall 2012

  41. Experiment – Herz (1998) • People could recall memories evoked by any cue just as well • Olfactory memories had the richest emotional content PSY 295 - Grinnell College - Fall 2012

  42. Aromatherapy • Can induce positive emotions with odors • Only works however if an odor has positive associations PSY 295 - Grinnell College - Fall 2012

  43. Neuroanatomical relationships • Orbitofrontal cortex receives projections from primary olfactory and gustatory cortex • Responsible for conscious olfactory perception and assigning hedonic value to stimuli PSY 295 - Grinnell College - Fall 2012

  44. Emotions and olfaction are analogous • Either like or dislike, approach or avoid PSY 295 - Grinnell College - Fall 2012

  45. Pheromones PSY 295 - Grinnell College - Fall 2012

  46. Vomeronasal organ • Some animals have another smell organ which detects compounds of higher molecular weight (pheromones) • Projects to accessory olfactory bulb PSY 295 - Grinnell College - Fall 2012

  47. Pheromones • Used for social communication in a variety of species • Ants and social insects • When a bee stings us, cue from stinger invites other bees to attack us! PSY 295 - Grinnell College - Fall 2012

  48. Pheromones provide sexual cues in animals • Male monkey will ignore female in heat if nose blocked • Female pig needs to be exposed to male pig pheromones to mate PSY 295 - Grinnell College - Fall 2012

  49. Humans pheromones are controversial • We do not have a vomeronasal organ or accessory olfactory system • Evidence however for some chemical signaling, mostly in a sexual context PSY 295 - Grinnell College - Fall 2012

More Related