The Visual SystemThe Visual System

The Awareness TestThe Awareness Test

Just for funJust for fun, let’s test your , let’s test your awareness of your surroundings…awareness of your surroundings…

How do we see? How do we see? No light? No sight!No light? No sight!

light enters the eye as waves light enters the eye as waves of electromagnetic energy of electromagnetic energy

length of the wave determines length of the wave determines a light’s colora light’s color

the height of the wave the height of the wave (amplitude) determines (amplitude) determines brightness brightness

Structure of the Structure of the Visual SystemVisual System

Optic Nerve (1)Optic Nerve (1)nerve that carries visual information from nerve that carries visual information from

the eye to the occipital lobes of the brainthe eye to the occipital lobes of the brain

Blind Spot (2) Blind Spot (2) where the optic nerve exits the eyewhere the optic nerve exits the eye no rods and cones at this point, so there is a no rods and cones at this point, so there is a

small blind spot in vision (pg. 166)small blind spot in vision (pg. 166)

Retina (3)Retina (3)

has cells that has cells that convert light convert light energy to nerve energy to nerve impulsesimpulses

made up of three made up of three layers of cells:layers of cells: Receptor cellsReceptor cells Bipolar cellsBipolar cells Ganglion cellsGanglion cells

Receptor CellsReceptor Cells

sight - change light into neural impulses sight - change light into neural impulses the brain can understandthe brain can understand

visual system has two types of receptor visual system has two types of receptor cells – rods and conescells – rods and cones

RodsRods

only detect only detect black, , white, , and shades ofand shades of graygray

ConesCones

detect detect sharpsharp images images and and ccoolloorr

cluster at the foveacluster at the fovea

Bipolar CellsBipolar Cells

middle layer middle layer of retinaof retina

gather gather information information from rods & from rods & cones and pass cones and pass it on to the it on to the ganglion cellsganglion cells

Ganglion CellsGanglion Cells axons of axons of

ganglion cells ganglion cells form the optic form the optic nervenerve

blind spot is blind spot is created where created where optic nerve optic nerve exits the eye exits the eye ((page 166page 166))

Cornea (4)Cornea (4)

outside layer on outside layer on the front of the the front of the eyeballeyeball

two tasks:two tasks:focuses light by focuses light by

bending it bending it toward a central toward a central focal pointfocal point

protects the eyeprotects the eye

Pupil (5)Pupil (5)

opening in center opening in center of eyeof eye

controls amount controls amount of light entering of light entering the eye the eye (surrounded by (surrounded by the iris)the iris)

Iris (6)Iris (6)

colored portion of colored portion of the eyethe eye

regulates the size regulates the size of the pupil by of the pupil by changing its size - changing its size - allowing more or allowing more or less light to enter less light to enter the eyethe eye

Lens (7)Lens (7)

focuses the image focuses the image on the back of the on the back of the eye (eye (retinaretina))

muscles that change muscles that change the thickness of the the thickness of the lens change how the lens change how the light is bent thereby light is bent thereby focusing the imagefocusing the image

FoveaFoveacentral focal point of the retinacentral focal point of the retinaspot where vision is best (most detailed)spot where vision is best (most detailed)

Color Vision TheoriesColor Vision Theories

Trichromatic (three-color) TheoryTrichromatic (three-color) Theory

cones are “tuned” to be cones are “tuned” to be sensitive to red, green sensitive to red, green & blue wavelengths of & blue wavelengths of lightlight

all the colors we see all the colors we see are a combination of are a combination of these three colorsthese three colors

Color Deficient VisionColor Deficient Vision

people who lack one people who lack one of the three types of of the three types of conescones

usually the red or usually the red or green receptors are green receptors are missingmissing

inherited & found inherited & found more in malesmore in males

Opponent-Process Theory of ColorOpponent-Process Theory of Color

color-processing neurons oppose one color-processing neurons oppose one another:another: red – greenred – green yellow – blueyellow – blue black – whiteblack – white

light that stimulated one half of the pair light that stimulated one half of the pair inhibits the other halfinhibits the other half

HearingHearing

SoundSound

sound comes in sound comes in waves that are waves that are produced by produced by vibrationvibration

The Structure of the The Structure of the Auditory SystemAuditory System

Auditory Canal (6)Auditory Canal (6)

opening where opening where sound waves enter sound waves enter the ear for the ear for processingprocessing

Tympanic Membrane/Eardrum (7)Tympanic Membrane/Eardrum (7)

transfers sound transfers sound vibration from vibration from the air to the the air to the ossiclesossicles

Tympanic Membrane (w/ tear)Tympanic Membrane (w/ tear)

OssiclesOssicles

three tiny bones three tiny bones that transfer that transfer sound waves sound waves from the eardrum from the eardrum to the cochleato the cochlea

hammer (5) hammer (5) anvil (4) anvil (4) stirrup (3) stirrup (3)

Ossicles – Hammer, Anvil, StirrupOssicles – Hammer, Anvil, Stirrup

Oval WindowOval Window

receives sound receives sound vibration from vibration from the ossiclesthe ossicles

vibrates the fluid vibrates the fluid in the cochleain the cochlea

Cochlea (2)Cochlea (2)

where sound where sound waves are waves are changed into changed into neural impulsesneural impulses

filled with fluidfilled with fluid

CochleaCochlea

Hair CellsHair Cells receptor cells in the cochlea that change sound receptor cells in the cochlea that change sound

vibrations into neural impulsesvibrations into neural impulses

Hair CellsHair Cells

Semicircular CanalsSemicircular Canals

used in sensing used in sensing body orientation body orientation and balance and balance (vestibular sense)(vestibular sense)

relies on fluid in relies on fluid in the canalsthe canals

Auditory Nerve (1)Auditory Nerve (1)

formed by fibers formed by fibers at the base of at the base of each hair celleach hair cell

nerve that carries nerve that carries sound from the sound from the ears to the ears to the temporal lobestemporal lobes

How can we tell the difference How can we tell the difference between different sounds?between different sounds?

3 Theories:3 Theories:place theoryplace theoryvolley theoryvolley theory frequency theoryfrequency theory

Place Theory of HearingPlace Theory of Hearing

different types of sound waves vibrate different types of sound waves vibrate different locations/places on the cochleadifferent locations/places on the cochlea

high sounds vibrate one area, low sounds high sounds vibrate one area, low sounds anotheranother

problem: very low sounds cause entire problem: very low sounds cause entire cochlea to vibratecochlea to vibrate

Frequency Theory of HearingFrequency Theory of Hearing

frequency with which the cochlea is frequency with which the cochlea is vibrated tells us what sound we hearvibrated tells us what sound we hear

problem: cannot explain how we tell the problem: cannot explain how we tell the difference between high-pitched sounds difference between high-pitched sounds (neurons can only fire so fast)(neurons can only fire so fast)

Volley Theory of HearingVolley Theory of Hearing

sensory neurons in the cochlea (the hair sensory neurons in the cochlea (the hair cells) fire in groups, as volleyscells) fire in groups, as volleys

pattern of firing allows us to tell the pattern of firing allows us to tell the

difference between sounds difference between sounds

SensationSensation

SensationSensation

awarenessawareness of the of the worldworld

process where our process where our sensory systems & sensory systems & nervous system nervous system receive stimuli from receive stimuli from the environmentthe environment

PerceptionPerception

interpretationinterpretation of of sensory informationsensory information

process of process of organizing & organizing & interpreting sensory interpreting sensory informationinformation

Two ways we process information:Two ways we process information:

1.1. bottom-up processingbottom-up processing analyze the raw material entering through analyze the raw material entering through

the eyes, ears, etc.the eyes, ears, etc.

2.2. top-down processingtop-down processing focus on expectations & experiences in focus on expectations & experiences in

interpreting sensory information interpreting sensory information

Interpret this Sensory Information…Interpret this Sensory Information…

I’m going to Fl --- for spring break.I’m going to Fl --- for spring break. ““Daylight savings time ends tomorrow, and so Daylight savings time ends tomorrow, and so

people should remember to change their …”people should remember to change their …” “ ”“ ”

Perception in ActionPerception in Action

How do you interpret this sensory information?

Top-down or Bottom-up? ExampleTop-down or Bottom-up? Example(don’t write this )(don’t write this )

Identify an unknown object based Identify an unknown object based on elements of sensation:on elements of sensation:red spherered spherecool, hard surfacecool, hard surfacefits comfortably in your handfits comfortably in your handpleasant aromapleasant aromasatisfying crunch when bittensatisfying crunch when bitten tastes both sweet and tarttastes both sweet and tart

Analysis of this data leads to the Analysis of this data leads to the perception that the unknown perception that the unknown object is an _________________.object is an _________________.

Top-down or Bottom-up? ExampleTop-down or Bottom-up? Example(don’t write this either)(don’t write this either)

Would the descriptions below be Would the descriptions below be processed top-down or bottom-processed top-down or bottom-up? Explain.up? Explain. red spherered sphere cool, hard surfacecool, hard surface fits comfortably in your handfits comfortably in your hand pleasant aromapleasant aroma satisfying crunch when bittensatisfying crunch when bitten tastes both sweet and tarttastes both sweet and tart

What types of sensations would What types of sensations would you experience when eating the you experience when eating the food pictured to the right? food pictured to the right?

IllusionsIllusions

Module 10: PerceptionModule 10: Perception

IllusionsIllusions

misinterpreting sensory stimulimisinterpreting sensory stimuli

help researchers understand how sensation help researchers understand how sensation and perception normally worksand perception normally works

Müller-Lyer IllusionMüller-Lyer Illusion

Müller-Lyer IllusionMüller-Lyer Illusion

Most people think segment AB equals BC. In reality AB is much longer than BC.

Theory: we have learned to interpret arrowheads at the ends of a line as an indication of distance

Müller-Lyer IllusionMüller-Lyer Illusion

Müller-Lyer IllusionMüller-Lyer Illusion

Müller-Lyer IllusionMüller-Lyer Illusion

Ames Room PhotosAmes Room Photos

explain the photos at the top of page 200explain the photos at the top of page 200

video Segment: “Ames Room Illusion video Segment: “Ames Room Illusion Explained”Explained”

Ames Room Illusion: Secret Ames Room Illusion: Secret RevealedRevealed