1 / 46

Psy280: Perception

Psy280: Perception. Prof. Anderson Department of Psychology Chemical senses. Chemical senses: Your are what you eat (smell). What’s it good for? Chemical composition of our surroundings Olfaction (i.e., smell) Distal/remote sensing Small concentrations of airborne substances

owena
Télécharger la présentation

Psy280: Perception

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. Psy280: Perception Prof. Anderson Department of Psychology Chemical senses

  2. Chemical senses: Your are what you eat (smell) • What’s it good for? • Chemical composition of our surroundings • Olfaction (i.e., smell) • Distal/remote sensing • Small concentrations of airborne substances • Gustation (i.e., taste) • Proximal/immediate sensing • Check if appropriate to enter your body • Last sense to use • If it looks like and it smells like, it probably is it

  3. Comparative taste • Not all organisms “taste” with a tongue Moth antennae Fly “feet”

  4. In good and bad taste • Useful for the body • Tend to taste good • Potentially harmful • Tend to taste bad • Tend to taste bitter • Not always the case: Influence of culture • The burn of capsaicin • Bitterness • Compare with vision • All dangerous things ugly? • All ugly things dangerous?

  5. Taste in infancy Neonatal “liking” responses Sweet • Lip smacking • Smiles Bitter • Grimace • Lip retraction • Nose wrinkle

  6. Anatomy of taste: Papillae • Filiform • Cone shaped • All over the tongue • Give rough appearance • Fungiform • Mushroom shaped • Tip & sides • Foliate • Folds at sides • Circumvallate • Flat mounds • At back • Other taste receptors • Palate • Larynx

  7. Anatomy of taste: The bud • All papillae contain taste buds except the filiform • Thus, centre of tongue is “taste-blind” • Taste buds • Multiple taste cells • Create taste pore

  8. Taste sensory transduction • Different taste cell types for different tastes • Specificity at receptor level • Salt • NaCl • Na+ entry into cell • Depolarization • Sour • H+ ions block channels

  9. Taste pathway • Electrical signals carried by 3 pathways • Chorda tympani • Front & side • Glosso-pharyngeal • Back • Vagus • Mouth & larynx • NST (brainstem) • Gustatory thalamus • Primary taste areas • Insular/opercular cortex • Secondary taste areas • Orbitofrontal cortex

  10. Insular cortex and disgust • Disgust = “bad taste” • Anterior insular cortex is primary taste area • Viewing disgust faces increase activation • Lesions impair recognition of disgust Disgust vs fear

  11. Taste experience • What tastes do we taste? • 4 (maybe 5) basic tastes • Sweet (Sucrose), bitter (quinine), sour (HCl), salty (NaCl) • And … umami (MSG) • All taste experience can be described in terms of their combinations • Some substances are primarily 1 taste • Sodium chloride: Salty • Quinine: Bitter • Some are combinations • Sodium nitrate: salty, sour, & bitter

  12. Neural code for taste: Specificity • Different taste receptors carry different dimensions of taste? • Salt receptors related to saltiness? • Block receptors (amiloride)—> impair salt perception • Leaves other sensations intact • Parallel between receptor morphology and taste • E.g., circumvallate (back) = bitter? • Foliate (side) =sour?

  13. Neural code for taste: Specificity • 4 different types of fibers in chorda tympani • Activation of specific fiber tracts responsible for taste sensations • E.g. “sweet”, “bitter” neurons

  14. Problem with taste specificity coding • Taste neurons response are a combination of quality (e.g. bitter) and intensity • E.g., same magnitude of response in “bitter” neuron • A high concentration of sucrose • low concentration of quinine • Similar to colour vision • Neurons response a result of wavelength and intensity • Need 2 or more receptors to resolve ambiguity

  15. Neural code for taste: Distributed coding • Across fiber patterns • Emphasize degree of overlap between fibers • Idea: More overlap—> greater taste similarity • Relative to ammonium chloride (NH4Cl) • NaCl more distinct than KCl • Correlation between taste and across fiber pattern

  16. Tastes differ • Taste is dynamic • Depends upon internal state: Hunger • Adaptation/Sensory-specific satiety (SSS) • Peripheral • Chewing, smelling induces SSS • Sweet desserts follow savory meals • Alliesthesia • Central • Changed pleasantness that is not sensory based • Decreased pleasantness of sucrose when tubed into stomach • Animals change diet based on nutritional needs • Individual differences • Experience: culture • Genetics: tasters and nontasters • saccharin (bitter or tasteless)

  17. Flavor = Taste+smell • Eating chocolate with a stuffed nose • Where’s the flavor? • Taste Identification is impaired without smell • What we call taste is really an interaction between our chemical senses • Locate taste as occurring in the mouth • Taste nerves carry somatosensory/texture info as well Like visual capture

  18. Distal chemical sensing: Olfaction • For many mammals it is the most important sense • Identification • Smell “face” • localization • We are vision/hearing dominate mammals • Under-appreciate/under-use our sense of smell

  19. Olfactory epithelium • Olfactory mucosa • Mucus! • High in nasal cavity • Site of transduction • Contains olfactory receptor neurons (ORN)

  20. Nose hair: Olfactory cilia • ORN have cilia • Cilia contain olfactory receptor proteins • Similar to visual pigment • Transduction • Odorants bind to ORs • Change shape of protein • Ion flow across OR • Electricity

  21. Smell blind • Olfactory nerve passes through cribriform plate (skull) to reach OB

  22. Smell antennae: Olfactory bulbs • An outcropping of the brain • Its like a snail in your brain! • Electrical responses in cilia passed through olfactory nerve to OB Chemotaxis

  23. How many receptor types are there? • 1000 different kinds of olfactory receptors (OR) • 10 million OR neurons • 10,000 of each type of OR • Each OR neuron has only one type of receptor • 1000 neuronal chemical detectors • Compare to visions 4 receptor types (3 cones, 1 rod)

  24. Mapping onto the bulb • Similar ORN axons go to similar portions of the bulb • Glomeruli (1000-2000) • Inputs mainly from 1 ORN • Thus, each glomerulus responds to similar compounds • Like orientation columns in visual cortex • Glomeruli coding • Similar structure, not smell • Odotope maps • Mapping of similar chemical features

  25. Distributed coding of smell • Olfactory code is a complex pattern • Overlap across 1000 ORN types represents smell quality • Number of receptors would suggest specificity coding • Millions of colours can be perceived with 3 cones • How many odors?

  26. Experience and identification of odors • Can tell the difference between 10,000 odors • Distributed coding suggests much greater number • Poor at identification • Vision dominates • Get better with experience

  27. Of mice and men • Rats up to 50 times more sensitive to odors than humans • Dogs can be 10,000 times more sensitive • Yet olfactory receptors equally sensitive • 1 molecule can stimulate an olfactory receptor • Can’t get more sensitive than that! • Many more receptors (1 billion compared to 10 million) • Decreases # of molecules needed for neural response • Expertise • Wine tasters don’t get more sensitive w/ their nose • Better at retrieving labels from memory

  28. Rebuilding your neural nose: Olfactory neurogenesis • Mucosa is exposed • Not safely protected like photoreceptors or auditory cilia • Unlike vision/audition receptors regenerate • Every 5-7 weeks • Axons have to find way to bulb • Create new synapses • Constant rebuilding olfactory system

  29. What special about neural transmission in olfaction? • Unlike other senses, short distance to brain • Vision/audition have many synapses between retina and brain • Central destinations of olfactory information from bulb • Primary olfactory cortex (piriform cortex) • Secondary olfactory cortex (orbitofrontal cortex) • Amygdala • Unlike other senses, no mandatory thalamic relay

  30. What’s the neural code for smell? • How does the brain know what of hundreds of chemicals are entering the nose? • Don’t really know • Odor quality • Related to physical/chemical properties? • e.g., structure of molecule • Odotopes in olfactory bulb (OB) • Similarly structured molecules smell the same? • Not necessarily • Differently structured molecules smell different? • Not necessarily • Thus, not easy to relate smell with physicochemical properties of stimulus or OB maps

  31. The hedonic primacy of olfaction • Sensory and emotional experience • Not the same for vision/audition • Seeing and feeling more distinct • More intertwined in the chemical senses • Why? • Orbitofrontal cortex • Plays dual role • Critical for emotional experience • Secondary sensory cortex for olfaction

  32. What makes a bad smell smell bad? • Amygdala/piriform = intensity • Medial OFC = good • Lateral OFC = bad

  33. The smell of attraction • Attraction and symmetry • Symmetry associated with • immune system health, healthy development • Pleasant odor

  34. Does the world smell different to each nostril? • Nostrils are different sizes • Alternate every few hours which is bigger! • Airflow in each nostril differs • Odorants attachment to mucosa depends on airflow • Some better at low vs high and vice versa • Provides two olfactory images of the world • Result: better olfactory acuity

  35. Smell constancy:Little and big sniffs • Intensity and concentration constancy • Do big sniffs make for more intense smells? No • Sniff activity in piriform cortex Magnitude estimation for odor strength equal

  36. Olfactory subliminal perception: Pheromones • Odorless airborne chemicals can powerfully influence behavior • Sexual behaviour • Mood • Menstrual synchronization • Bruce effect: Aborted fetus • Accessory olfactory system • Vomeronasal organ (VNO) • Not sure if functional in humans • Like extrageniculostriate visual pathway • Nonconscious vision

  37. ESP

  38. Extrasensory perception: ESP • The feeling of presences, being, or energy without use of the 5 basic senses • The problem with ESP is that it is “extrasensory” • Sensory systems are the receivers of environmental stimulation • Without a receiver there is no perception • Tree falls in a forest • Subliminal is sensory (e.g., visual, olfactory, auditory), but nonconscious • Below subjective threshold for perception • Brain can discriminate thingsto which we don’t have conscious access • E.g., amygdala and “unseen” fear

  39. Why is it possible? • What have we learned? • All about conscious perception • Guides our own investigations • Colour, motion, depth, pitch, smell, taste, etc. • Bias in what “phenomena” we investigate • ESP might represent sensory systems that are functional but unknown • Don’t represent conscious information processing • E.g. discovery of new photoreceptor that regulates circadian rhythms • Electromagnetic waves outside the visual spectrum

  40. trees... buildings... clouds... sender receiver attempts to ‘psychically’ send target to receiver reports imagery Experiments on ESP: Ganzfeld research Target randomly chosen • All “sensory” information reduced • Receiver in sound proof chamber with ping pong balls on eyes, earphones w/ white noise • Reduce external sensory “noise” to enhance sensitivity to weak signal • Progressive relaxation: Decrease internal somatic noise

  41. At end of session… • Receiver shown 4 pictures (3 decoys plus target) • Must rate each picture in terms of matching imagery • 25% chance of rating target picture highest Experiments on ESP: Ganzfeld research

  42. Results • 1974-1997 • 50+ studies from 15 different labs • Hit rate = 33.2%, significantly different from chance (25%) • Dynamic targets better than static (37% vs 27%) • Higher rates when a friend versus stranger is the sender (44% vs 26%) • 50% hit rate for “artistic” students (n=20) • Julliard students

  43. Problems • Experimenter needs to be blind to target • Sensory “leakage” • Sensory cues from use of same target • The file drawer problem • How many studies not showing effect unreported? • What are the limits of this perception? • Send over telephone wire? • Reading other minds • Would be difficult to home in on one signal • Potentially insulting too!

  44. Magnetoreception • Diverse animals can use the earth’s magnetic field as orientation cue • North/south axis, and local magnetic fields • Magnetic map sense • Like having an internal GPS • Homing pigeons, spiny lobsters • Placed in novel location • Don’t monitor outward journey • Can navigate back • Know very little about the physiological mechanisms • No obvious receptors • Accessory structures usual focus sensory stimuli on sensory surface • Lenses: vision • Outer ear: audition • Biomaterials don’t affect magnetic field lines

  45. THE END

More Related