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

marie.hicks@rccd.edu

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

2

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

3

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

4

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

7

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

Blind spot

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

9

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

11

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

12

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

17

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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SYNESTHESIA

When numbers have personality and letters have taste

4m

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PROSOPAGNOSIA

I don ’ t know who you are…

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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Preview for Thursday

Person Swap

Ames Room

5m

2m

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