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Psy280: Psy280: PerceptionPerception

Prof. AndersonProf. Anderson

Department of PsychologyDepartment of Psychology

Chemical sensesChemical senses

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Chemical senses: Chemical senses: Your are what you eat Your are what you eat

(smell)(smell) What’s it good for?What’s it good for? Chemical composition of our surroundingsChemical composition of our surroundings

Olfaction (i.e., smell)Olfaction (i.e., smell) Distal/remote sensingDistal/remote sensing Small concentrations of airborne substancesSmall concentrations of airborne substances

Gustation (i.e., taste)Gustation (i.e., taste) Proximal/immediate sensingProximal/immediate sensing Check if appropriate to enter your bodyCheck if appropriate to enter your body Last sense to useLast sense to use

If it looks like and it smells like, it probably is itIf it looks like and it smells like, it probably is it

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Comparative tasteComparative taste Not all organisms “taste” with a Not all organisms “taste” with a

tonguetongue Moth antennae

Fly “feet”

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In good and bad tasteIn good and bad taste Useful for the bodyUseful for the body

Tend to taste goodTend to taste good Potentially harmfulPotentially harmful

Tend to taste badTend to taste bad Tend to taste bitterTend to taste bitter

Not always the case: Not always the case: Influence of cultureInfluence of culture The burn of capsaicinThe burn of capsaicin BitternessBitterness

Compare with visionCompare with vision All dangerous things All dangerous things

ugly?ugly? All ugly things All ugly things

dangerous?dangerous?

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Taste in infancyTaste in infancy

Neonatal “liking” Neonatal “liking” responsesresponses

SweetSweet Lip smackingLip smacking SmilesSmilesBitterBitter GrimaceGrimace Lip retractionLip retraction Nose wrinkleNose wrinkle

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Anatomy of taste: Anatomy of taste: PapillaePapillae

FiliformFiliform Cone shapedCone shaped All over the tongueAll over the tongue Give rough appearanceGive rough appearance

FungiformFungiform Mushroom shapedMushroom shaped Tip & sidesTip & sides

FoliateFoliate Folds at sidesFolds at sides

CircumvallateCircumvallate Flat moundsFlat mounds At backAt back

Other taste receptorsOther taste receptors PalatePalate LarynxLarynx

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Anatomy of taste: The Anatomy of taste: The budbud

All papillae contain All papillae contain taste buds except the taste buds except the filiformfiliform Thus, centre of tongue is Thus, centre of tongue is

“taste-blind”“taste-blind” Taste budsTaste buds

Multiple taste cellsMultiple taste cells Create taste poreCreate taste pore

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Taste sensory Taste sensory transductiontransduction

Different taste cell Different taste cell types for different types for different tastestastes Specificity at receptor Specificity at receptor

levellevel SaltSalt

NaClNaCl Na+ entry into cellNa+ entry into cell DepolarizationDepolarization

SourSour H+ ions block H+ ions block

channelschannels

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Taste pathwayTaste pathway Electrical signals carried by Electrical signals carried by

3 pathways3 pathways Chorda tympaniChorda tympani

Front & sideFront & side Glosso-pharyngealGlosso-pharyngeal

BackBack VagusVagus

Mouth & larynx Mouth & larynx NST (brainstem)NST (brainstem) Gustatory thalamusGustatory thalamus Primary taste areasPrimary taste areas

Insular/opercular cortexInsular/opercular cortex Secondary taste areasSecondary taste areas

Orbitofrontal cortexOrbitofrontal cortex

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Insular cortex and Insular cortex and disgustdisgust

Disgust = “bad Disgust = “bad taste”taste”

Anterior insular Anterior insular cortex is primary cortex is primary taste areataste area

Viewing disgust Viewing disgust faces increase faces increase activationactivation

Lesions impair Lesions impair recognition of recognition of disgustdisgust

Disgust vs fear

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Taste experienceTaste experience What tastes do we taste?What tastes do we taste? 4 (maybe 5) basic tastes4 (maybe 5) basic tastes

Sweet (Sucrose), bitter (quinine), sour (HCl), Sweet (Sucrose), bitter (quinine), sour (HCl), salty (NaCl)salty (NaCl)

And … umami (MSG)And … umami (MSG) All taste experience can be described in All taste experience can be described in

terms of their combinationsterms of their combinations Some substances are primarily 1 tasteSome substances are primarily 1 taste

Sodium chloride: SaltySodium chloride: Salty Quinine: BitterQuinine: Bitter

Some are combinationsSome are combinations Sodium nitrate: salty, sour, & bitterSodium nitrate: salty, sour, & bitter

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Neural code for taste: Neural code for taste: SpecificitySpecificity

Different taste receptors carry different dimensions of taste?Different taste receptors carry different dimensions of taste? Salt receptors related to saltiness?Salt receptors related to saltiness? Block receptors (amiloride)—> impair salt perceptionBlock receptors (amiloride)—> impair salt perception Leaves other sensations intactLeaves other sensations intact

Parallel between receptor morphology and tasteParallel between receptor morphology and taste E.g., circumvallate (back) = bitter?E.g., circumvallate (back) = bitter? Foliate (side) =sour?Foliate (side) =sour?

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Neural code for taste: Neural code for taste: SpecificitySpecificity

4 different types 4 different types of fibers in of fibers in chorda tympanichorda tympani

Activation of Activation of specific fiber specific fiber tracts tracts responsible for responsible for taste sensationstaste sensations E.g. “sweet”, E.g. “sweet”,

“bitter” neurons“bitter” neurons

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Problem with taste Problem with taste specificity codingspecificity coding

Taste neurons response are a combination Taste neurons response are a combination of quality (e.g. bitter) and intensityof quality (e.g. bitter) and intensity

E.g., same magnitude of response in E.g., same magnitude of response in “bitter” neuron“bitter” neuron A high concentration of sucroseA high concentration of sucrose low concentration of quininelow concentration of quinine

Similar to colour visionSimilar to colour vision Neurons response a result of wavelength and Neurons response a result of wavelength and

intensityintensity Need 2 or more receptors to resolve ambiguityNeed 2 or more receptors to resolve ambiguity

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Neural code for taste: Neural code for taste: Distributed codingDistributed coding

Across fiber patternsAcross fiber patterns Emphasize degree of Emphasize degree of

overlap between fibersoverlap between fibers Idea: More overlap—> Idea: More overlap—>

greater taste similaritygreater taste similarity Relative to ammonium Relative to ammonium

chloride (NHchloride (NH44Cl)Cl) NaCl more distinct than NaCl more distinct than

KClKCl Correlation between Correlation between

taste and across fiber taste and across fiber patternpattern

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Tastes differTastes differ Taste is dynamicTaste is dynamic

Depends upon internal state: HungerDepends upon internal state: Hunger Adaptation/Sensory-specific satiety (SSS)Adaptation/Sensory-specific satiety (SSS)

PeripheralPeripheral Chewing, smelling induces SSSChewing, smelling induces SSS Sweet desserts follow savory mealsSweet desserts follow savory meals

AlliesthesiaAlliesthesia CentralCentral Changed pleasantness that is not sensory basedChanged pleasantness that is not sensory based Decreased pleasantness of sucrose when tubed into stomachDecreased pleasantness of sucrose when tubed into stomach Animals change diet based on nutritional needsAnimals change diet based on nutritional needs

Individual differencesIndividual differences Experience: cultureExperience: culture Genetics: tasters and nontastersGenetics: tasters and nontasters

saccharin (bitter or tasteless)saccharin (bitter or tasteless)

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Flavor = Taste+smellFlavor = Taste+smell Eating chocolate with a Eating chocolate with a

stuffed nosestuffed nose Where’s the flavor?Where’s the flavor?

Taste Identification is Taste Identification is impaired without smellimpaired without smell

What we call taste is What we call taste is really an interaction really an interaction between our chemical between our chemical sensessenses

Locate taste as occurring Locate taste as occurring in the mouthin the mouth Taste nerves carry Taste nerves carry

somatosensory/texture info somatosensory/texture info as wellas well

Like visual capture

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Distal chemical sensing: Distal chemical sensing: OlfactionOlfaction

For many mammals it is For many mammals it is the most important the most important sensesense IdentificationIdentification

Smell “face”Smell “face” localizationlocalization

We are vision/hearing We are vision/hearing dominate mammalsdominate mammals Under-appreciate/under-Under-appreciate/under-

use our sense of smelluse our sense of smell

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Olfactory epitheliumOlfactory epithelium

Olfactory mucosaOlfactory mucosa Mucus!Mucus! High in nasal cavityHigh in nasal cavity Site of transductionSite of transduction Contains olfactory Contains olfactory

receptor neurons receptor neurons (ORN)(ORN)

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Nose hair: Olfactory ciliaNose hair: Olfactory cilia ORN have ciliaORN have cilia Cilia contain Cilia contain

olfactory receptor olfactory receptor proteinsproteins Similar to visual Similar to visual

pigmentpigment TransductionTransduction

Odorants bind to Odorants bind to ORsORs

Change shape of Change shape of proteinprotein

Ion flow across ORIon flow across OR ElectricityElectricity

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Smell blindSmell blind

Olfactory nerve passes through Olfactory nerve passes through cribriform plate (skull) to reach OBcribriform plate (skull) to reach OB

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Smell antennae: Olfactory Smell antennae: Olfactory bulbsbulbs

An outcropping of An outcropping of the brainthe brain

Its like a snail in Its like a snail in your brain!your brain!

Electrical Electrical responses in cilia responses in cilia passed through passed through olfactory nerve to olfactory nerve to OBOB

Chemotaxis

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How many receptor types How many receptor types are there?are there?

1000 different kinds of olfactory receptors 1000 different kinds of olfactory receptors (OR)(OR)

10 million OR neurons10 million OR neurons 10,000 of each type of OR10,000 of each type of OR Each OR neuron has only one type of receptorEach OR neuron has only one type of receptor 1000 neuronal chemical detectors1000 neuronal chemical detectors

Compare to visions 4 receptor types (3 Compare to visions 4 receptor types (3 cones, 1 rod)cones, 1 rod)

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Mapping onto the bulbMapping onto the bulb Similar ORN axons go to similar Similar ORN axons go to similar

portions of the bulbportions of the bulb Glomeruli (1000-2000)Glomeruli (1000-2000) Inputs mainly from 1 ORNInputs mainly from 1 ORN Thus, each glomerulus responds to Thus, each glomerulus responds to

similar compoundssimilar compounds Like orientation columns in visual cortexLike orientation columns in visual cortex

Glomeruli codingGlomeruli coding Similar structure, not smellSimilar structure, not smell Odotope mapsOdotope maps

Mapping of similar chemical featuresMapping of similar chemical features

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Distributed coding of Distributed coding of smellsmell Olfactory code is a Olfactory code is a

complex patterncomplex pattern Overlap across 1000 ORN Overlap across 1000 ORN

types represents smell types represents smell qualityquality

Number of receptors Number of receptors would suggest specificity would suggest specificity codingcoding

Millions of colours can be Millions of colours can be perceived with 3 conesperceived with 3 cones

How many odors?How many odors?

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Experience and Experience and identification of odorsidentification of odors

Can tell the difference between Can tell the difference between 10,000 odors10,000 odors

Distributed coding suggests much Distributed coding suggests much greater numbergreater number

Poor at identificationPoor at identification Vision dominatesVision dominates Get better with experienceGet better with experience

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Of mice and menOf mice and men Rats up to 50 times more sensitive to odors Rats up to 50 times more sensitive to odors

than humansthan humans Dogs can be 10,000 times more sensitiveDogs can be 10,000 times more sensitive

Yet olfactory receptors equally sensitiveYet olfactory receptors equally sensitive 1 molecule can stimulate an olfactory receptor1 molecule can stimulate an olfactory receptor

Can’t get more sensitive than that!Can’t get more sensitive than that! Many more receptors (1 billion compared to 10 Many more receptors (1 billion compared to 10

million)million) Decreases # of molecules needed for neural responseDecreases # of molecules needed for neural response

ExpertiseExpertise Wine tasters don’t get more sensitive w/ their noseWine tasters don’t get more sensitive w/ their nose Better at retrieving labels from memoryBetter at retrieving labels from memory

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Rebuilding your neural Rebuilding your neural nose: Olfactory nose: Olfactory neurogenesisneurogenesis

Mucosa is exposedMucosa is exposed Not safely protected like photoreceptors or Not safely protected like photoreceptors or

auditory ciliaauditory cilia Unlike vision/audition receptors Unlike vision/audition receptors

regenerateregenerate Every 5-7 weeksEvery 5-7 weeks Axons have to find way to bulbAxons have to find way to bulb

Create new synapsesCreate new synapses Constant rebuilding olfactory systemConstant rebuilding olfactory system

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What special about What special about neural transmission in neural transmission in

olfaction?olfaction? Unlike other senses, short distance to brainUnlike other senses, short distance to brain Vision/audition have many synapses between Vision/audition have many synapses between

retina and brainretina and brain Central destinations of olfactory Central destinations of olfactory

information from bulbinformation from bulb Primary olfactory cortex (piriform cortex)Primary olfactory cortex (piriform cortex) Secondary olfactory cortex (orbitofrontal cortex)Secondary olfactory cortex (orbitofrontal cortex) AmygdalaAmygdala

Unlike other senses, no mandatory thalamic Unlike other senses, no mandatory thalamic relayrelay

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What’s the neural code for What’s the neural code for smell?smell? How does the brain know what of hundreds of How does the brain know what of hundreds of

chemicals are entering the nose?chemicals are entering the nose? Don’t really knowDon’t really know Odor qualityOdor quality

Related to physical/chemical properties?Related to physical/chemical properties? e.g., structure of moleculee.g., structure of molecule Odotopes in olfactory bulb (OB)Odotopes in olfactory bulb (OB)

Similarly structured molecules smell the same?Similarly structured molecules smell the same? Not necessarilyNot necessarily

Differently structured molecules smell different?Differently structured molecules smell different? Not necessarilyNot necessarily

Thus, not easy to relate smell with physicochemical Thus, not easy to relate smell with physicochemical properties of stimulus or OB mapsproperties of stimulus or OB maps

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The hedonic primacy of The hedonic primacy of olfactionolfaction

Sensory and emotional experienceSensory and emotional experience Not the same for vision/auditionNot the same for vision/audition

Seeing and feeling more distinctSeeing and feeling more distinct More intertwined in the chemical sensesMore intertwined in the chemical senses

Why?Why? Orbitofrontal cortexOrbitofrontal cortex

Plays dual rolePlays dual role Critical for emotionalCritical for emotional experienceexperience Secondary sensory Secondary sensory cortex for olfactioncortex for olfaction

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What makes a bad smell What makes a bad smell smell bad?smell bad?

Amygdala/Amygdala/piriform = piriform = intensityintensity

Medial Medial OFC = OFC = goodgood

Lateral Lateral OFC = badOFC = bad

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The smell of attractionThe smell of attraction Attraction and symmetryAttraction and symmetry

Symmetry associated with Symmetry associated with immune system health, healthy developmentimmune system health, healthy development Pleasant odorPleasant odor

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Does the world smell Does the world smell different to each nostril?different to each nostril?

Nostrils are different sizesNostrils are different sizes Alternate every few hours Alternate every few hours

which is bigger!which is bigger! Airflow in each nostril differsAirflow in each nostril differs

Odorants attachment to Odorants attachment to mucosa depends on airflowmucosa depends on airflow Some better at low vs high Some better at low vs high

and vice versa and vice versa Provides two olfactory Provides two olfactory

images of the worldimages of the world Result: better olfactory acuity Result: better olfactory acuity

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Smell constancy:Smell constancy:Little and big sniffsLittle and big sniffs

Intensity and concentration constancyIntensity and concentration constancy Do big sniffs make for more intense smells? NoDo big sniffs make for more intense smells? No Sniff activity in piriform Sniff activity in piriform

cortexcortex Magnitude estimation for odor strength equal

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Olfactory subliminal Olfactory subliminal perception: Pheromonesperception: Pheromones

Odorless airborne Odorless airborne chemicals can powerfully chemicals can powerfully influence behaviorinfluence behavior Sexual behaviourSexual behaviour MoodMood Menstrual synchronizationMenstrual synchronization Bruce effect: Aborted fetusBruce effect: Aborted fetus

Accessory olfactory Accessory olfactory systemsystem Vomeronasal organ (VNO)Vomeronasal organ (VNO) Not sure if functional in Not sure if functional in

humanshumans

Like Like extrageniculostriate extrageniculostriate visual pathwayvisual pathway

Nonconscious visionNonconscious vision

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ESPESP

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Extrasensory perception: Extrasensory perception: ESPESP

The feeling of presences, being, or energy without The feeling of presences, being, or energy without use of the 5 basic sensesuse of the 5 basic senses

The problem with ESP is that it is “extrasensory”The problem with ESP is that it is “extrasensory” Sensory systems are the receivers of Sensory systems are the receivers of

environmental stimulationenvironmental stimulation Without a receiver there is no perceptionWithout a receiver there is no perception

Tree falls in a forestTree falls in a forest Subliminal is sensory (e.g., visual, olfactory, Subliminal is sensory (e.g., visual, olfactory,

auditory), but nonconsciousauditory), but nonconscious Below subjective threshold for perceptionBelow subjective threshold for perception Brain can discriminate thingsto which we don’t have Brain can discriminate thingsto which we don’t have

conscious accessconscious access E.g., amygdala and “unseen” fearE.g., amygdala and “unseen” fear

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Why is it possible?Why is it possible? What have we learned?What have we learned?

All about conscious perceptionAll about conscious perception Guides our own investigationsGuides our own investigations

Colour, motion, depth, pitch, smell, taste, etc.Colour, motion, depth, pitch, smell, taste, etc. Bias in what “phenomena” we investigateBias in what “phenomena” we investigate

ESP might represent sensory systems that ESP might represent sensory systems that are functional but unknownare functional but unknown Don’t represent conscious information processingDon’t represent conscious information processing

E.g. discovery of new photoreceptor that regulates E.g. discovery of new photoreceptor that regulates circadian rhythms circadian rhythms

Electromagnetic waves outside the visual Electromagnetic waves outside the visual spectrumspectrum

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Experiments on ESP: Experiments on ESP: Ganzfeld researchGanzfeld research

senderattempts to ‘psychically’ send target to receiver

receiverreports imagery

trees... buildings...clouds...

All “sensory” information reducedAll “sensory” information reduced Receiver in sound proof chamber with ping pong balls on eyes, earphones w/ white noiseReceiver in sound proof chamber with ping pong balls on eyes, earphones w/ white noise Reduce external sensory “noise” to enhance sensitivity to weak signalReduce external sensory “noise” to enhance sensitivity to weak signal Progressive relaxation: Decrease internal somatic noiseProgressive relaxation: Decrease internal somatic noise

Target randomly chosen

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At end of session…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: Experiments on ESP: Ganzfeld researchGanzfeld research

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ResultsResults 1974-19971974-1997

50+ studies from 15 different labs 50+ studies from 15 different labs Hit rate = 33.2%, significantly different from Hit rate = 33.2%, significantly different from

chance (25%)chance (25%) Dynamic targets better than static (37% vs 27%)Dynamic targets better than static (37% vs 27%) Higher rates when a friend versus stranger is the Higher rates when a friend versus stranger is the

sender (44% vs 26%)sender (44% vs 26%) 50% hit rate for “artistic” students (n=20)50% hit rate for “artistic” students (n=20)

Julliard studentsJulliard students

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ProblemsProblems Experimenter needs to be blind to targetExperimenter needs to be blind to target Sensory “leakage”Sensory “leakage”

Sensory cues from use of same targetSensory cues from use of same target The file drawer problemThe file drawer problem

How many studies not showing effect unreported?How many studies not showing effect unreported?

What are the limits of this perception?What are the limits of this perception? Send over telephone wire?Send over telephone wire?

Reading other mindsReading other minds Would be difficult to home in on one signalWould be difficult to home in on one signal Potentially insulting too!Potentially insulting too!

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MagnetoreceptionMagnetoreception Diverse animals can use the earth’s magnetic field as Diverse animals can use the earth’s magnetic field as

orientation cueorientation cue North/south axis, and local magnetic fieldsNorth/south axis, and local magnetic fields

Magnetic map senseMagnetic map sense Like having an internal GPSLike having an internal GPS Homing pigeons, spiny lobstersHoming pigeons, spiny lobsters

Placed in novel locationPlaced in novel location Don’t monitor outward journeyDon’t monitor outward journey Can navigate backCan navigate back

Know very little about the physiological mechanismsKnow very little about the physiological mechanisms No obvious receptorsNo obvious receptors

Accessory structures usual focus sensory stimuli on sensory surfaceAccessory structures usual focus sensory stimuli on sensory surface Lenses: visionLenses: vision Outer ear: auditionOuter ear: audition

Biomaterials don’t affect magnetic field linesBiomaterials don’t affect magnetic field lines

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THE ENDTHE END