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Distinguish between Sensation versus perception
Psychology 1: General Psychology J. Marie Hicks, Ph.D. Adjunct Psychology Instructor marie.hicks@rccd.edu
Module 5
Sensation
1
INTRODUCTION
J. Marie Hicks, M.A. Doctoral Candidate UCR
Office hours available by arranged appointment
Access to Blackboard is through Open Campus
You will need to have internet access, check your email frequently, and attend class
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THREE DEFINITONS
Eyes, ears, nose, skin, and tongue
Transduction is the process by which a sensory organ changes or transforms physical energy into electrical signals, which become neural impulses
Adaptation
Sensation versus perception
Perceptions
Eyes, ears, nose, skin, and tongue are complex, miniaturized, living sense organs that automatically gather information about your environment
Transduction
Process in which a sense organ changes, or transforms, physical energy into electrical signals that become neural impulses, which may be sent to the brain for processing
Adaptation
The decreasing response of the sense organs as they’re exposed to a continuous level of stimulation
Sensation versus perception
Relatively meaningless bits of information that result when the brain processes electrical signals that come from the sense organs
Perceptions
Meaningful sensory experiences that result after the brain combines hundreds of sensations
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EYE: VISION
Stimulus: light waves – stimuli for vision
Invisible (too short)
Visible (just right)
Invisible (too long)
Stimulus: light waves
Invisible (too short)
gamma rays, x-rays, ultraviolet rays
Visible (just right)
particular segment of electromagnetic energy that we can see because these waves are the right length to stimulate receptors in the eye
Invisible (too long)
radar, FM, TV, shortwave, AM
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EYE: VISION
Structure and function
Eyes perform two separate processes
Process called transduction
Vision: seven steps
image reversed
light waves
cornea
pupil
iris
lens
retina
Structure and function
Eyes perform two separate processes
first: gather and focus light into precise area in the back of eye
second: area absorbs and transforms light waves into electrical impulses
Process called transduction
Structure and function
Vision: seven steps
image reversed
light waves
cornea
pupil
iris
lens
retina
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EYE: VISION
Structure and function
Image reversed
Light waves
Cornea
Pupil
Iris
Lens
Retina
Image reversed
in the back of the eye, objects appear upside down, somehow the brain turns the objects right side up
Light waves
light waves are changed from broad beams to narrow, focused ones
Cornea
rounded, transparent covering over the front of your eye
Pupil
round opening at the front of the eye that allows light waves to pass into the eye’s interior
Iris
circular muscle that surrounds the pupil and controls the amount of light entering the eye
Lens
transparent, oval structure whose curved surface bends and focuses light waves into an even narrower beam
Retina
located at the very back of the eyeball; a thin film that contains cells that are extremely sensitive to light
light-sensitive cells, called photoreceptors, begin the process of transduction by absorbing light waves
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EYE: VISION
Retina
Three layers of cells
Rods – Rhodopsin
Periphery of retina
Better for movement
Highly light sensitive/dim light
Black white gray
Corner of eye
Cones – Opsins
Fovea of retina
Fine detail
Need bright light
Color vision
Central visual field
Retina
Three layers of cells
back layer contains two kinds of photoreceptors that begin the process of transduction
change light waves into electrical signals
Then feed forward to bipolar cells, then ganglion cells, then become optic nerve and feed out through the blind spot in back of the eye
rod located primarily in the periphery
cone located primarily in the center of the retina called the fovea
Rods – greatest density 10-20 degrees from fovea
Photoreceptor that contain a single chemical, called rhodopsin
Activated by small amounts of light
Very light sensitive
Allow us to see in dim light
See only black, white, and shades of gray
Cones – center back of eye around blind spot (optic nerve exit)
Photoreceptors that contain three chemicals called opsins
Activated in bright light
Allow us to see color
Cones are wired individually to neighboring cells
Allow us to see fine detail
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EYE: VISION
Visual pathways: eye to brain
Optic nerve
Optic chiasm
Lateral Geniculate Nucleus
(LGN) in thalamus
Primary visual cortex
Visual association areas
Visual pathways: eye to brain
Optic nerve
impulses flow through the optic nerve as it exits from the back of the eye
the exit point is the “blind spot”
the optic nerves partially cross and pass through the thalamus, through the LGN
The optic nerves from both eyes meet and cross at the optic chiasm,[13] [14] at the base of the hypothalamus of the brain. At this point the information coming from both eyes is combined and then splits according to the visual field.
The corresponding halves of the field of view (right and left) are sent to the left and right halves of the brain, respectively, to be processed. That is, the right side of primary visual cortex deals with the left half of the field of view from both eyes, and similarly for the left brain.[11] A small region in the center of the field of view is processed redundantly by both halves of the brain.
The lateral geniculate nucleus (LGN) is a sensory relay nucleus in the thalamus of the brain.
the thalamus relays impulses to the back of the occipital lobe in the right and left hemisphere
Visual pathways: eye to brain
Primary visual cortex
back of the occipital lobes is where primary visual cortex transforms nerve impulses into simple visual sensations
Visual association areas
primary visual cortex sends simple visual sensations to neighboring association areas
damage to the visual association area = visual agnosia: difficulty in assembling simple visual sensations into more complex, meaningful images
8
EYE: VISION
Visual pathways: eye to brain
Optic nerve
impulses flow through the optic nerve as it exits from the back of the eye
the exit point is the “blind spot”
the optic nerves partially cross and pass through the thalamus, through the LGN
The optic nerves from both eyes meet and cross at the optic chiasm,[13] [14] at the base of the hypothalamus of the brain. At this point the information coming from both eyes is combined and then splits according to the visual field.
The corresponding halves of the field of view (right and left) are sent to the left and right halves of the brain, respectively, to be processed. That is, the right side of primary visual cortex deals with the left half of the field of view from both eyes, and similarly for the left brain.[11] A small region in the center of the field of view is processed redundantly by both halves of the brain.
The lateral geniculate nucleus (LGN) is a sensory relay nucleus in the thalamus of the brain.
the thalamus relays impulses to the back of the occipital lobe in the right and left hemisphere
Visual pathways: eye to brain
Primary visual cortex
back of the occipital lobes is where primary visual cortex transforms nerve impulses into simple visual sensations
Visual association areas
primary visual cortex sends simple visual sensations to neighboring association areas
damage to the visual association area = visual agnosia: difficulty in assembling simple visual sensations into more complex, meaningful images
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EYE: VISION
Making colors from wavelengths
Sunlight
White light
light waves
Shorter wavelengths
Violet/blue/green
Longer wavelengths
Yellow/orange/red
An apple
Red reflected
Making colors from wavelengths
Sunlight is called white light because it contains all the light waves
White light passes through a prism; separates light waves that vary in length
Visual system transforms light waves of various lengths into millions of different colors
Shorter wavelengths of violet, blue, green
Longer wavelengths of yellow, orange, and red
An apple is seen as red because reflection of longer light waves that brain interprets as red
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EYE: VISION
Color vision
Trichromatic theory
Three types of cones in the retina
three opsins – blue, green, red (primary colors)
Opponent-process theory
Afterimage
visual sensation
red-green and blue-yellow
Two types of ganglion cells in retina…
when excited… one color & when inhibited… the other
Trichromatic theory
three different kinds of cones in the retina
each cone contains one of the three different light-sensitive chemicals, called opsins
each of the three opsins is most responsive to wavelengths that correspond to each of the three primary colors
blue, green, red
all colors can be mixed from these primary colors
Opponent-process theory
Afterimage
visual sensation that continues after the original stimulus is removed
ganglion cells in retina and cells in thalamus respond to two pairs of colors: red-green and blue-yellow
when excited, respond to one color of the pair
when inhibited, respond to complementary pair
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EYE: VISION
Color blindness
Monochromatic
Dichromatic
Inability to distinguish two or more shades in the color spectrum
Monochromatic
total color blindness; black and white
result of only rods and one kind of functioning cone
Dichromatic
inherited genetic defect; mostly in males
trouble distinguishing red from green
two kinds of cones
see mostly shades of green
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EAR: AUDITION
Stimulus: Sound waves – stimuli for hearing (audition)
Amplitude
Loudness
Frequency
Pitch
Stimulus
Sound waves
stimuli for hearing (audition)
ripples of different sizes; sound waves travel through space with varying heights and frequency
Loudness
Amplitude
distance from the bottom to the top of a sound wave; height
Subjective experience of a sound’s intensity
Brain calculates loudness from specific physical energy (amplitude of sound waves)
Pitch
Frequency
number of sound waves occurring within a second; speed
Subjective experience of a sound being high or low
Brain calculates from specific physical stimuli
Speed or frequency of sound waves
Measured in cycles (how many sound waves in a second)
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Measuring sound waves
Decibel
Threshold
EAR: AUDITION
Measuring sound waves
Decibel: unit to measure loudness
Threshold for hearing
0 decibels (no sound)
140 decibels (pain and permanent hearing loss)
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Structure
Outer ear
consists of three structures
external ear
auditory canal
tympanic membrane
EAR: AUDITION
Structure
Outer ear
consists of three structures
external ear
oval-shaped structure that protrudes from the side of the head
function
pick up sound waves and then send them down the auditory canal
auditory canal
long tube that funnels sound waves down its length so that the waves strike the tympanic membrane (ear drum)
tympanic membrane
taut, thin structure commonly called the eardrum
sound waves strike the tympanic membrane and cause it to vibrate
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Middle ear
bony cavity, membranes, ossicles
Ossicles
MALLEUS (hammer)
INCUS (anvil)
STAPES (stirrup)
Inner ear
cochlea
vestibular system
EAR: AUDITION
Middle ear
bony cavity sealed at each end by membranes that are connected by three tiny bones called ossicles
hammer, anvil, and stirrup
hammer is attached to the back of the tympanic membrane
anvil receives vibrations from the hammer
stirrup makes the connection to the oval window (end membrane)
Inner ear
contains two structures sealed by bone
cochlea: involved in hearing
vestibular system: involved in balance
Cochlea
Bony coiled exterior that resembles a snail’s shell
Contains receptors for hearing
Function is transduction
Transforms vibrations into nerve impulses sent to the brain for processing into auditory information
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Auditory brain areas
Two-step process occurs after the nerve impulses reach the brain
Primary auditory cortex
Auditory association area
Auditory cues
Direction of sound
Calculating pitch
frequency theory
place theory
Calculating loudness
EAR: AUDITION
Auditory brain areas
Sensations and perceptions: Two-step process occurs after the nerve impulses reach the brain
Primary auditory cortex
Top edge of temporal lobe, transforms nerve impulses into basic auditory sensations
Auditory association area
Combines meaningless auditory sensations into perceptions (meaningful melodies, songs, words, or sentences)
Auditory cues
Direction of sound
determined by brain; calculates slight difference in time it takes sound waves to reach the two ears
Calculating pitch
frequency theory
applies only to low-pitched sounds, rate that nerve impulses reach the brain determines how low a sound’s pitch is
place theory
brain determines medium-to-higher-pitched sounds from the place on the basilar membrane where maximum vibration occurs
Calculating loudness
brain calculates loudness primarily from the frequency or rate of how fast or how slow nerve impulses arrive from the auditory nerve
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VESTIBULAR SYSTEM: BALANCE
Position and balance
Vestibular system –
semicircular canals
Function of vestibular system
Issues with vestibular system
Motion sickness (sensory mismatch between information from the vestibular system)
Symptoms
Meniere’s disease (malfunction of the semicircular canals of the vestibular system)
Symptoms
Vertigo (malfunction of the semicircular canals of the vestibular system)
Symptoms
Position and balance
Vestibular system is located above the cochlea in the inner ear, Includes semicircular canals: Bony arches set at different angles
Each semicircular canal is filled with fluid that moves in response to movements of your head.
Canals have hair cells that respond to the fluid movement
Function of vestibular system
Includes sensing the position of the head, keeping the head upright, and maintaining balance
Motion sickness (sensory mismatch between information from the vestibular system)
symptoms: feelings of discomfort, nausea, and dizziness in a moving vehicle – head bouncing, but distant objects look fairly steady
Meniere’s disease (malfunction of the semicircular canals of the vestibular system)
symptoms: dizziness, nausea, vomiting, spinning, and piercing buzzing sounds
Vertigo (malfunction of the semicircular canals of the vestibular system)
symptoms: dizziness and nausea
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CHEMICAL SENSES
Taste – Chemical sense
Tongue
Surface of the tongue
Taste buds
Tongue: Five basic tastes
sweet
salty
sour
bitter
umami: meaty-cheesy taste
Taste
Chemical sense because the stimuli are various chemicals
Tongue
Surface of the tongue
Taste buds
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CHEMICAL SENSES
Surface of the tongue
Chemicals to Molecules to taste buds
Taste buds – Receptors for taste
Flavor
Combination of taste and smell
Surface of the tongue
Chemicals, which are the stimuli for taste, break down into molecules
Molecules mix with saliva and run into narrow trenches on the surface of the tongue. Molecules then stimulate the taste buds
Taste buds
Shaped like miniature onions
Receptors for taste
Chemicals dissolved in saliva activate taste buds produce nerve impulses that reach areas of the brain’s parietal lobe
Brain transforms impulses into sensations of taste
Flavor
Combination of taste and smell – Onion / Apple / Potato
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CHEMICAL SENSES
Smell, or olfaction
Direct to olfactory bulb
No routing or “middle man”
Steps
stimulus
olfactory cells
sensation and memories
functions of olfaction
Stimulus
we smell volatile substances. Volatile substances are released molecules in the air at room temperature
examples: skunk spray, perfumes, warm brownies; not glass or steel
Olfactory cells
receptors for smell located in a one-inch-square patch of tissue in the uppermost part of the nasal passages
olfactory cells are covered in mucus that dissolves volatile molecules and stimulates the cells
the cells trigger nerve impulses that travel to the brain, which interprets the impulses as different smells
Sensations and memories
nerve impulses travel to the olfactory bulb
nerve impulses are relayed to the primary olfactory cortex, cortex transforms nerve impulses into olfactory sensations
we can identify as many as 10,000 different odors
we stop smelling our deodorants or perfumes because of decreased responding (adaptation)
Functions of olfaction
one function: to intensify the taste of food
second function: to warn of potentially dangerous foods
third function: to elicit strong memories; emotional feelings
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TOUCH
Touch
Includes pressure, temperature, and pain
Receptors for the sense of touch
Skin
Hair receptors
Free nerve endings
Pacinian corpuscle
Touch
Includes pressure, temperature, and pain
Beneath the outer layer of skin are a half-dozen miniature sensors that are receptors for the sense of touch
change mechanical pressure or temperature variations into nerve impulses that are sent to the brain for processing
Skin
Outermost layer: Thin film of dead cells containing no receptors
Just below are first receptors, which look like groups of thread-like extensions
Middle and fatty layer: Variety of receptors with different shapes and functions. Some are hair receptors.
Hair receptors
Free nerve endings wrapped around the base of each hair follicle
Hair follicles fire with a burst of activity when first bent
If hair remains bent for a period of time, the receptors will cease firing
Sensory adaptation. Example: wearing a watch
Free nerve endings
Near bottom of the outer layer of skin. Have nothing protecting or surrounding them
Pacinian corpuscle
In fatty layer of skin: Largest touch sensor. Highly sensitive to touch
Responds to vibration and adapts very quickly
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TOUCH
Brain areas
Somatosensory cortex
Homunculus
Somatosensory cortex
Located in the parietal lobe
Transforms nerve impulses into sensations of touch, temperature, and pain
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4m
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PROSOPAGNOSIA
5m
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PAIN
What causes pain?
What is Pain?
Pain results from many different stimuli
How does the mind stop pain?
Gate control theory of pain – Lamaze?
Pain: unpleasant sensory and emotional experience that may result from tissue damage, one’s thoughts or beliefs, or environmental stressors
Pain results from many different stimuli
How does the mind stop pain?
Gate control theory of pain
Nonpainful nerve impulses compete with pain impulses in trying to reach the brain and creates a bottleneck or neutral gate
Shifting attention or rubbing an injured area decreases the passage of painful impulses. Result: pain is dulled
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PAIN
What causes pain? What causes it to stop?
Endorphins
Dread
Acupuncture
Endorphins
Chemicals produced by the brain and secreted in response to injury or severe physical or psychological stress
Pain-reducing properties of endorphins are similar to those of morphine
Brain produces endorphins in situations that evoke great fear, anxiety, stress, or bodily injury as well as intense aerobic activity
Dread
Connected to pain centers in brain
Not the act itself that people fear. Time waiting before event causes dread
Acupuncture
Trained practitioners insert thin needles into various points on the body’s surface and then manually twirl or electrically stimulate the needles. After 10 to 20 minutes of stimulation, patients often report a reduction in various kinds of pain
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5m
2m
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