Welcome to Psyc 102 Sensation

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Welcome toPsyc 102Sensation Perception

• Prof. Stuart Anstis

Lindsay Lewis
Shai Azoulai
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FAQ Admission to this course

• WE teach the course
• ADMISSIONS admit!
• Go to UG Advisors, Ground floor Mandler
• Ask for Betty Gunderson tell her your story.

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About the course

• How to reach us? Email is good
• Speak to us after class
• (NOT before class! NOT during Break!)
• 3 hours/week (Be on time)
• COFFEE BREAKS (Mind if we cut in?)
• 1 min stretch breaks when equipment or instructor
  breaks down
• Demonstrations, Student volunteers
• USE the Web Page! webct.ucsd.edu

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The Harvard course

• Slides, videos, handouts
• Compiled by Patrick Cavanagh, Harvard U.
• Textbook Peter Gray, Psychology. 4th edn
• Web page

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Contacting us

• You can see us during OFFICE HOURS, listed on the
  Syllabus on the Web page
• Office hours Wednesday Noon Lunch, The Grove
• Questions about Psychology SA or TAs
• Questions about Tests Grades ask the TAs -
  not SA !
• When you see us around the campus,
• SAY HELLO ac as sl

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And now,Here is Lindsay to talk about the tests
And Shai to talk about the course Web Page
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Questions?

• About psychology?
• Ask Stuart, Shai or Lindsay.
• About TESTS? Or Web page?
• Ask Shai or Lindsay --
• NOT the Professor!

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Psy102 Syllabus
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Sensation Perception - Redundant? No

• Sensation - is the process of changing external
  stimuli into internal (neural) messages -
• is the study of the sensory organs and how they
  perform sensory transduction
• Perception - is the interpretation of those
  messages -
• the study of how the brain interprets sensations,
  giving them order and meaning

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Why should we care?

• We live in our heads external world gets in
  our heads only through our senses
• stored sensations memory use of stored
  sensations learning
• Perception allows us to examine how our own
  brains work - is the gateway to neuroscience
• Practical applications

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What are we going to study

• Exteroception (the external world)
• 5 Senses Stimuli
• Sight Light-waves Far
• Hearing Sound-waves Far
• Touch Physical pressure Near
• Taste Chemical Near
• Smell Chemical Medium

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• Proprioception (your own body)
• Balance organs
• Join muscle receptors - wheres your body
• Skin sensors - warm, cold, pain,

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Which senses are most important?

• Differs by animal -
• Humans?
• Ask them
• Look at amount of brain that is devoted to each
  sense
• optic nerve 1 million fibers, auditory nerve
  30,000 (3 of optic nerve)
• 1/3 to 1/2 of the brain is devoted to vision,
  with the remaining (1/2 -2/3) devoted to
  everything else

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Naïve realism -

• we experience the world they way we do because
  that is the way it isis false
• Proof
• the same physical stimulus can have different
  interpretations (either to different people or to
  the same person over time).

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Expectation
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Half the audience shut their eyes, please.
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Main themes to keep in mind

• Perception is an active process!
• Constantly interpreting the world
• Constantly searching for meaning

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Main themes to keep in mind

• Perception is an active process!
• Constantly making sense of the world
• The design of the system is amazingly elegant
• Extremely efficient
• Extremely compact
• Extremely effortless

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How good are our senses?

• Namely,
• How sensitive?
• Can we distinguish small differences?
• Compare ourselves to ideal observer?
• We use THRESHOLDS.

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THRESHOLD

• The weakest stimulus you can just detect
• Or discriminate
• LOW threshold HIGH sensitivity
• Examples
• Detection
• Faintest light you can just see
• Faintest sound you can just hear

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THRESHOLDS (continued)

• Discrimination
• (bad in politics good in sensation)
• Just noticeable difference (JND) between 2
• Light intensities 2
• Colors A few nm
• Sound frequencies (pitch) 0.3
• POSITIONS ON SKIN Where on body?

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Our senses are IDEALLY SENSITIVE !

• VISION
• One retinal rod can see one quantum
• Drop the chalk
• HEARING
• Almost hear jostling of air molecules on eardrum

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How many senses are there? Hmm

• EXTEROCEPTION (whats out there
• Seeing
• Hearing
• Smell
• Taste
• PROPRIOCEPTION (own body)
• Skin senses
• Muscle senses
• Balance organs

• Distance (Early warning)
• Distance
• Chemical (gas/vapour)
• Chemical (liquid)

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Each of the five senses activates a separate area
of the cerebral cortex. This brain is a computer
reconstruction based on fMRI data. Locations of
the primary sensory areas are shown in color.
Most activity takes place within hidden folds of
the brain.
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Touch

• Stimuli Mechanical pressure
• Receptors A number of different types of
  receptors in the skin

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Demo
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Active vs. Passive touch

• When investigating an object with touch we
  actively move our hands over itagain perception
  is an active process
• Demo

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Combining active passive touch

• Turning the Coin
• Aristotles Illusion (one Nose or Two?)
• The Dead Hand Illusion

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How do we know where our limbs are in space?--
Demo.

• You combine signals from
• joint receptors
• cutaneous receptors (responding to the stretching
  of skin)
• muscle spindles

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Homunculi sensory motor
Fig 5.11
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Somatosensory Cortex
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Homunculus statue
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• Each of the color-coded areas in this combined
  MRI/MEG image of the brain responds to the touch
  of a different finger of the right hand.

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Neural Plasticity- Amputee studies

• Amputated area no longer receiving input
• After a while the neighboring regions start take
  over the area
• is it new connections or unmasking of old
  connections?
• Research by V. S. RAMACHANDRAN, Psychology Dept,
  UCSD
• Video 51PhantomLimb.rm

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Hand on face / phantom limb
Sensory homunculus
New representation of missing hand on face
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Where are you inside your head?

• Point a finger -- aim with dominant eye
• Writing on skin of forehead or back

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Writing on skin

• On forehead -- face forward, look outwards
• On back -- stand behind yourself, face forward
• So, Face forward.

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Which way is up?

• Factors people may use
• Otoliths
• Visual cues (polarized objects)
• Feet down (astronauts)
• Body pressure

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Balance

• Vision
• Pressure
• Inner ear (vestibular system)
• 3 semi-circular canals (on each side)
• Rotary acceleration
• 2 organs with Otoliths
• Passive tilt (gravity)
• Linear acceleration

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Balance organs

• Semicircular canals
• 3 on each side
• Rotation

• Otoliths
• One on each side
• Gravity (tilt)
• Linear acceleration

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Semi- Circular canals
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Semi- Circular canals
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Fluid-filled Semicircular canals respond to
rotation (NOT linear acceleration nor gravity)
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Semi-circular only fire during acceleration and
deceleration

• So if you spin CW at constant speed
• initially fire CW
• then fire no motion
• when stop fire CCW

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Otoliths
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Otoliths

• Respond to linear acceleration and/or passive
  tilt.
• Can be fooled
• Star Tour ride at Disney

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Damaged labyrinths Cant read town clock while
walking (eye movements cant compensate for head
movements)
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Otoliths vs Vision for balance - David Lees
movable room
Video
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Ian Howards tumbling room

• Small room with a chair you are strapped into.
• He can move you in the room
• He can move the room around you
• He can move both you and the room
• He can vary the appearance of the room

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Ian Howard
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Vection- Polarized objects vs. No polarized
objects

• Your chair stays fixed. The room rotates head
  over feet. Do you feel as if you flipped over?
• Plain room - few
• Room set as a kitchen with many polarized
  objects- 90

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Why do people get motion sick?

• Conflicting motion signals from different senses
• Evolutionary basis - poisons often produce
  conflicting sensations
• Money Cheung 83 -Dogs w/o vestibular organs
  dont get sick from poison
• Active vs passive movement

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Why dont dancers get dizzy?

• Spotting technique
• Practice seems to reduce dizziness
• Self selection

Thank you.
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Smell Taste

• Stuart Anstis
• Psych 102, Winter 2002

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• Linda Buck (right) sniffs an odorant used to
  study the sense of smell. She and Richard Axel
  (left) discovered what appear to be the
  long-sought odorant receptor proteins.

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Smell (olfaction) Taste (gustation)

• Both are chemical senses
• In humans considered minor senses
• not so for other animals
• Do have good survival value in humans
• people very sensitive to smell of smoke
• taste aversion- we avoid certain tastes/smells

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Olfaction emotion

• In animals pheromones are important in sexual
  attraction and mating

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Thank you.
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How about in humans?

• no good evidence for pheromone detection in
  humans
• BUT.

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But

• Humans can tell gender by scent
• babies can tell the scent of their own mother
• Everyone has a different scent (except twins)
• Smells emitted by women can effect the menstrual
  cycle of other women (McClintock)

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Even so...Smell is big business

• Perfume industry, car sales, home sales, etc.
• Why,
• maybe because the (main) olfactory bulb still has
  connections to the limbic system - emotion and
  memory

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How do we identify different smells?

• Does a given receptor fire only for some
  preferred smell?
• No. The same cell will fire for many very
  different types of odorants
• Many different cells fire for the same odorant
• We now think that it the general pattern of
  activity across the olfactory bulb indicates the
  particular smell.

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What is the physical property of the molecule
that makes it smell the way it does.

• Shape of the molecule - seems not
• similar shaped molecules have very different
  smells
• We just dont know!

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Taste and Flavor

• Flavor comprises taste (output from the taste
  receptors) and other factors
• temperature
• texture
• appearance
• etc

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Taste buds

• Each taste bud has a number of (50) taste
  receptors
• receptor cells contact nerve cells of cranial
  nerves

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Saccharin Indole

• LOW Sweet
• HIGH Metallic

• LOW Flowery
• HIGH Dog poo

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Thank you.
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What do the free nerve endings do?

• Common chemical sense - Respond to high
  concentrations of molecules- the feeling of
  smells (like menthol feels cool).

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Olfaction

• Stimulus must give off vapors (gas molecules)
  that are soluble in fat.
• molecules travel to the nasal cavity (through
  the nose or back of the mouth)
• In nasal cavity 3 bones make separate baffles
  where the air is warmed humidified and purified
  (by tiny hairs)

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How sensitive is olfaction

• In humans it is pretty good, but varies with the
  scent
• in some cases can smell 1 part per 50 billion
• In dogs is much more sensitive than that
• we have 10 million receptors Dogs 200 million

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How does the olfactory system code strength of
smell?

• More firing stronger smell
• although sometimes changing the amount of smell
  molecule available can change its smell
• Example INDOLE
• Dilute flowery
• Concentrated Dog Poo

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Weird stuff about olfactory receptor cells

• They are real neurons where transduction
  occurs.
• Their axons end in the CNSyet they die about
  every 60 daysand new ones form!
• We are still not sure exactly how the
  transduction occurs.

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Coding taste

• Locations only true at low concentrations, at
  high concentrations a bitter substance will still
  excite receptors in the sweet area of tongue
• Again like smell, is thought to be the pattern of
  activity across a number of cells that gives the
  overall taste.

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Pain Temperature

• Both detected by free nerve endings
• subset for pain, subset for hot and subset for
  cold
• hot and cold do not overlap
• cold also responds to very hotso an isolated
  very hot stimulus may seem cold!

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Skin temperature sense adapts

• Put Left hand in COLD water
• Warm feels HOT

• Put right hand in HOT water
• Warm feels COLD

Put both hands in WARM water