psychology 210 lecture 4 kevin r smith. vision sensory system –the eye –exactly what we sense...
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Psychology 210Psychology 210
Lecture 4Lecture 4
Kevin R SmithKevin R Smith
VisionVision
Sensory SystemSensory System– The eyeThe eye– Exactly what we sense from our environmentExactly what we sense from our environment
Perceptual SystemPerceptual System– The brainThe brain– How we put together what we sense into a How we put together what we sense into a
visual picturevisual picture
The brain constructs our The brain constructs our environmentenvironment
Multiple experiences of an item Multiple experiences of an item lead to different interpretationslead to different interpretations
The Visual Sensory SystemThe Visual Sensory SystemLight is made of wavesLight is made of waves
WavelengthWavelength– Different colors have different wavelengthsDifferent colors have different wavelengths
AmplitudeAmplitude– Different amplitudes lead to differences in brightnessDifferent amplitudes lead to differences in brightness
Visible spectrumVisible spectrum– 400nm to 750nm400nm to 750nm– ROY G BIVROY G BIV– Short wavelengths are near blue and violetShort wavelengths are near blue and violet– Long wavelengths are near red and orangeLong wavelengths are near red and orange
Properties of Light and WavesProperties of Light and WavesThe color of an object is The color of an object is determined by its abilities determined by its abilities across two dimensionsacross two dimensions– AbsorptionAbsorption– ReflectionReflection
Colors that are reflected Colors that are reflected are the colors that we seeare the colors that we see– A red sweater is red A red sweater is red
because it reflects because it reflects wavelengths that we wavelengths that we perceive as redperceive as red
Other wavelengths would Other wavelengths would be absorbed and NOT be absorbed and NOT visible as a color for this visible as a color for this sweatersweater
Properties of Light and WavesProperties of Light and Waves
Black is a color that Black is a color that absorbs all other absorbs all other colorscolors– ie. It is the absence of ie. It is the absence of
reflected colorreflected color
White is a color that White is a color that reflects all other colorsreflects all other colors– ie. It is the presence of ie. It is the presence of
all colorsall colorsprismsprisms
White object
Properties of Light and WavesProperties of Light and Waves
RefractionRefraction– The change of The change of
direction of the wavesdirection of the wavesOccurs in waterOccurs in water
Different substances Different substances refract light refract light differentlydifferently
The eyeThe eyeScleraSclera– Outer covering that Outer covering that
protects the eye and protects the eye and gives it shapegives it shape
CorneaCornea– Protective covering for the Protective covering for the
eyeeye– Begins to bend the light Begins to bend the light
waves and focus themwaves and focus them
Aqueous humorAqueous humor– Fluid filled area behind the Fluid filled area behind the
corneacornea– Provides nutrients to the Provides nutrients to the
cornea and lenscornea and lens
Parts of the eyeParts of the eyePupilPupil– Area in the center of the eyeArea in the center of the eye– Controls the amount of light that entersControls the amount of light that enters– IrisIris
The muscle that controls the widening or narrowing of the pupilThe muscle that controls the widening or narrowing of the pupil
LensLens– Bend to focus light onto the retinaBend to focus light onto the retina– AccommodationAccommodation
The process of the bending of the lens to properly focus the image on our The process of the bending of the lens to properly focus the image on our retinaretina
Vitreous humorVitreous humor– Gives the eye its shapeGives the eye its shape– Does not regenerateDoes not regenerate
The vitreous humor your born with is what you still haveThe vitreous humor your born with is what you still have– FloatersFloaters
Debris that gathers in the vitreous humor and casts shadows onto the retinaDebris that gathers in the vitreous humor and casts shadows onto the retina
RetinaRetina
Translates light waves into an electrical signal our brain Translates light waves into an electrical signal our brain can processcan processConcaveConcave– Object on retina is translated upside-downObject on retina is translated upside-down
PhotoreceptorsPhotoreceptors– Rods and conesRods and cones
Optic Disk/ Optic NerveOptic Disk/ Optic Nerve– Area in the retina where nerves and blood vessels exit the eyeArea in the retina where nerves and blood vessels exit the eye– Forms a blind spotForms a blind spot
FoveaFovea– Area in center of retinaArea in center of retina
Layers of the RetinaLayers of the RetinaFour main types of Four main types of visual processing visual processing neuronsneurons– Ganglion cell layerGanglion cell layer– Amacrine and Amacrine and
bipolar cell layerbipolar cell layer– Horizontal cellsHorizontal cells
Visual Sensory Visual Sensory NeuronsNeurons– PhotoreceptorsPhotoreceptors
RodsRodsConesCones
Rods and ConesRods and Cones
Where a sensory signal Where a sensory signal (light waves) gets (light waves) gets changed into electrical changed into electrical energyenergy– Process called Process called
transductiontransduction
RodsRods– Sensitive to black and Sensitive to black and
whitewhite– Most of them in peripheryMost of them in periphery
ConesCones– Sensitive to colorSensitive to color– Most of them in foveaMost of them in fovea
RodsRods
Contain rhodopsinContain rhodopsin
120 million in a 120 million in a human eyehuman eye
Responsible for Responsible for night vision night vision
Very sensitive to Very sensitive to lightlight
Very poor clarityVery poor clarity
ConesCones
6 million in the 6 million in the human eyehuman eye
Responsible for Responsible for vision in bright vision in bright lightlight
Excellent clarityExcellent clarity
3 different types 3 different types with different with different pigmentspigments
ConesCones
Three different typesThree different types– Blue, shortBlue, short– Green, mediumGreen, medium– Red, longRed, long
Horizontal CellsHorizontal CellsIntegrate Integrate information from information from the the photoreceptorsphotoreceptors
Transfer that Transfer that information to information to bipolar cellsbipolar cells
Bipolar cellsBipolar cells
Receive input from Receive input from horizontal cells and horizontal cells and photoreceptorsphotoreceptors
Transmit information Transmit information to amacrine cellsto amacrine cells
Contain receptive Contain receptive fieldsfields– Antagonistic center-Antagonistic center-
surround organizationsurround organizationphotoreceptors
Horizontal cellsBipolar cells
Amacrine Cells
Amacrine CellsAmacrine Cells
Respond to changes Respond to changes in the visual in the visual environmentenvironment
Connect bipolar cells, Connect bipolar cells, ganglion cells, and ganglion cells, and other amacrine cellsother amacrine cells
Ganglion cellsGanglion cells
Receive input from bipolar and amacrine Receive input from bipolar and amacrine cellscells
Same center-surround receptive fields Same center-surround receptive fields found in bipolar cellsfound in bipolar cells
On-center bipolar fields connect to on-On-center bipolar fields connect to on-center ganglion cellscenter ganglion cells
Off-center bipolar fields connect to off-Off-center bipolar fields connect to off-center ganglion cellscenter ganglion cells
What do receptive fields do?What do receptive fields do?
On-center and off-center fields provide for On-center and off-center fields provide for greater acuitygreater acuity
Large unchanged surfaces don’t activate Large unchanged surfaces don’t activate the neurons as well as changing surfaces the neurons as well as changing surfaces with lines, cracks, and endswith lines, cracks, and ends