Sensation

https://www.youtube.com/watch?v=unWnZvXJH2o

Module 09

Let’s see if you labeled correctly:

Let’s take in our surroundings:

• What do you see?– What shapes are around you? What colors?

• What sounds are you listening to?• What can you feel?

– Is your clothing comfortable, what about your chair?

• What do you taste?• Are there any odors?

• This awareness of the world around you is called sensation.

Sensation

• The process by which our sensory systems (eyes, ears, and other sensory organs) and nervous system receive stimuli from the environment

• Bottom-up processing:– Information processing that focuses on the raw

material entering through the eyes, ears, and other organs of sensation

Perception

• The process of organizing and interpreting sensory information

• Top-Down Processing:– Information processing that focuses on

expectations and experiences in interpreting incoming sensory information

Sensation and Perception• Do you see some marks that look the same as

others, but are meant to be interpreted differently?– Sensation brings image from paper to your brain, a bottom-up

process of gathering environmental info through the senses.– Perception involves knowing what to make of the individual

marks in the sentence. This top-down interpretation relies on your experiences with, and expectations about, language.

Thresholds:an edge or a boundary

What are absolute thresholds

and difference thresholds,

and how do they differ?

Absolute & Difference Threshold• Absolute threshold:

– The minimum stimulation needed to detect a particular stimulus.

– Ex: Dimmest star in the sky would be right at the absolute threshold for vision.

• What about for taste/hearing?

• Difference threshold – Aka: just noticeable difference– Minimum difference that a person can

detect b/t 2 stimuli.– The smallest detectable change in a stimulus.

• When does sound become too loud or when is something too tight?

Sensory Adaptation

How does sensory adaptation make your life easier?

• When we filter out the non-changing aspects of our environment.– If a stimulus is constant and unchanging, eventually a

person may fail to respond to it.– Diminished sensitivity as a result of constant stimulation.

– EX: getting into a swimming pool that seems rather chilly

• What happens at first? After a while?

– EX: ever look for your sunglasses and realize they are on your head?

Selective AttentionHow does selective attention relate to effective study skills?

• Focusing conscious awareness on a particular stimulus to the exclusion of others– You can’t pay attention to every single little

thing at once!

• The ability to focus on one stimulus at a time– Ever blocked out sound to help you study/sleep?

• Allows a person to function in a world filled with many stimuli

So… what do you see?

• You can attend to one view or the other:– Old or young

woman

• You can earn learn to switch back and forth.

• You cannot see both images at once.

The Visual System: The Nature of Light

What is light?

Module 9: Sensation

Electromagnetic Energy

• Light enters the eye as waves of electromagnetic energy.

• An energy spectrum that includes X-rays, radar, and radio waves .– A small portion of the spectrum includes

light visible to the human eye

The Electromagnetic Spectrum

• Light is a form of electromagnetic energy. This energy travels in waves, ranging from short gamma rays to long radio waves. The human eye can detect only a small portion of these waves, the visible spectrum, as light.

1st characteristic of waves: Hue

• The color of light as determined by the wavelength of the light energy– What color is this power point slide?

• Includes: red, orange, yellow, green, blue, indigo and violet (ROY G BIV)

• The eye can detect 7 million separate hues

Wavelength

2nd characteristic of waves: Amplitude

• The brightness of light as determined by height of the wave

• The taller the wave, the brighter the color– Thus greater

amplitude stronger hue.

The Visual System: The Structure of the

Visual System

What are the major parts of the visual system, and what roles do these parts

play in our ability to see?

Module 9: Sensation

Cornea• Light first strikes the cornea!

• The clear bulge on the front of the eyeball

• Begins to focus the light by bending it toward a central focal point

• Protects the eye

Iris• Colored part

• A ring of muscle tissue that forms the colored portion of the eye

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

Pupil• The adjustable opening in

the center of the eye that controls the amount of light entering the eye (surrounded by the iris)– In bright conditions the iris

expands, making the pupil smaller.

– In dark conditions the iris contracts, making the pupil larger.

• Ex: wake up in middle of night go to the bathroom, turn on light and watch your pupil shrink in the mirror.– Restricting light b/c it’s too bright for you.

Lens• A transparent structure behind the pupil

• Focuses the image on the back of the eye (retina)

• Muscles that change the thickness of the lens change how the light is bent thereby focusing the image

• Lens not letting you focus?– Get contacts/glasses

Nearsightedness & Farsightedness• With normal vision, the lens

changes in thickness to cause the light rays from a viewed object to converge at the retina.– The result is a clear focused

image.

• In a nearsighted person’s eye, the lens causes light rays from distant objects to converge in front of the retina, which blurs the image.

• If a person is farsighted, the lends causes light rays from close objects to converge behind the retina.

• Corrective lenses, help the eye’s own lens focus the image correctly.

Retina

• All other structures (cornea, pupil, iris, lens) direct traffic – move visual info to retina!

• Important processing center at the back of the eyeball

• Light-sensitive surface with cells that convert light energy to nerve impulses

• Made up of three layers of cells

– Receptor cells

– Bipolar cells

– Ganglion cells

Retina layer: Receptor Cells

• Deepest layer of retina.

• Can change light energy into nerve impulses that the brain can interpret.– Without this, the brain would be completely

isolated from information in the outside world.

• Two different types: – Rods and cones

• Visual receptor cells located in the retina.

• Different in appearance and function.

Comparing and Contrasting:Rods Cones

• Can only detect black and white.

• Have a lower absolute threshold.

• Respond to less light than do cones.

• Under dim light, only rods respond and you see the worlds in shades of gray.

• Less of them.• Can detect sharp images

and color.• Need more light.• Many cones are

clustered in the fovea, where your vision is best.

Fovea• The central focal point of the retina

• The spot where vision is best (most detailed)

Two remaining layers of the retina:

• Bipolar Cells:– Middle layer of retina.– Gather information from the rods and cones and pass

it on to the ganglion cells

• Ganglion Cells:– Top layer of retina.– Receive info from bipolar cells and transmit it through

their axons, which together form the optic nerve.

Visual Processing in the Retina

Optic NerveThe nerve that carries visual info. from the eye to the occipital lobes of the brain.

Parts of the Eye – Blind Spot (check page 166 in your book)

• The point at which the optic nerve travels through the retina to exit the eye.

• The lack of receptor rods and cones at this point creates a small blind spot.

The Visual System: Color Vision

What are the two theories of color vision? Which one offers the best explanation of how

we see colors?

Module 9: Sensation

#1:Trichromatic (three-color) Theory

• Theory of color vision that says cones are “tuned” to be sensitive to red, green and blue light– All the colors we see are a combination of

these three colors.

• Based on work of Helmholtz and Young

• Similar to the design of a color TV

• Subtractive Color Mixing– When mixing colored paints,

each new color SUBTRACTS (soaks up) another wavelength.

– Red, blue, and yellow combine to make black paint.

• Additive Color Mixing– When mixing colored lights,

each new color ADDS another wavelength.

– Red, green, and blue combine to make white light.

Color Deficient Vision

• People who lack one of the three types of cones– Usually the red or green receptors are

missing

• Usually referred to as color blindness

• In inherited and found more in males

• Sometimes people don’t even know the problem exists.

#2: Opponent-Process Theory of Color

• Ewald Hering’s theory that says color is processed in opponent pairs of color:

– Red-green, yellow-blue, black-white

• Light that stimulated one half of the pair inhibits the other half

• Explains the afterimage effect

Afterimage Effect:Stare at the white dot in the middle w/o blinking

So…what do you see?

Really great video to watch (45 min)

http://www.dailymotion.com/video/xq1p3e_national-geographic-test-your-brain-episode-1-pay-attention_shortfilms

Hearing: The Nature of Sound

What is sound??

Sound Pitch

• Sound, like light, comes in waves– Sound is vibration

• Features of sound include:

– Pitch

– Hertz

– decibels

• A sound’s highness or lowness

• Dependent on the frequency of the sound wave

• Is measured as hertz (Hz)

Hertz (Hz) Decibel (dB)

• Determines pitch

• A measure of the number of sound wave peaks per second; measures “frequency”

• Human hearing goes from 20 Hz to 20,000 Hz

• Determines loudness

• A measure of the height of the sound wave– Sometimes called

amplitude

• Named after Alexander Graham Bell.

Hearing: The Structure of the

Auditory System

What are the major components of the auditory system?

What is the function of each?

Module 9: Sensation

Parts of the Ear – Sound WavesAuditory Canal

• The opening through which sound waves travel as they move into the ear for processing

• Ends at the tympanic membrane (eardrum)

Tympanic Membrane (eardrum)

• The tissue barrier that transfers sound vibration from the air to the tine bones of the middle ear

• Can be damaged by objects in the ear or exceptionally loud noises

Parts of the Ear – Tympanic Membrane

Ossicles• Three tiny

bones that transfer sound waves from the eardrum to the cochlea

• Hammer, anvil and stirrup

Cochlea• A hearing

organ where sound waves are changed into neural impulses

• The major organ of hearing

• Filled with fluid

• snail shaped body tube

Oval Window

• The point on the surface of the cochlea which receives the sound vibration from the ossicles

• As the oval window vibrates, the fluid in the cochlea vibrates.

Parts of the Ear – Oval Window

Hair Cells• The receptor cells for hearing in the cochlea that

change sound vibrations into neural impulses

• Similar to the rods and cones within the eye

Auditory Nerve• The nerve that carries sound info. from the ears to the temporal lobes of the brain

Semicircular Canals

• Organs in the inner ear used in sensing body orientation and balance (vestibular sense)

• Relies on fluid in the canals– Spinning in circles disrupts the fluid.

Parts of the Ear – Semicircular Canals

Divisions of the Ear

• Ear’s structure can be divided into:

• The outer ear• The middle

ear• The inner ear

Hearing: Localization of SoundHow do you identify where a sound is coming from?

• Locating where sound is originating from

• Done through two cues:

– Which ear hears the sound first?

– Which ear hears the louder sound?

Other Senses: #1: Taste

• Taste is a chemical sense.

• Receptor cells are located primarily on the tongue and in the mouth.

• Four different tastes:

– Salty, sweet, sour and bitter

• Damaged taste receptor cells are replaced within a few days.

Supertasters Nontasters

• People with an abundance of taste receptors

• Approximately 25% of the population

• People with a minimum of taste receptors

• Taste with less intensity than the rest of the population

• Approximately 25% of the population

#2: Smell

• Smell is a chemical sense.

• Olfactory cells in the upper nasal passages detect molecules in the air.– Taste and smell interact to produce flavor.

• Olfactory Cells– The chemical receptor cells for smell

– Located in the nasal passages

Smell

Smell

#3: Touch

• Touch receptors are on the skin

• Four basic skin senses are

– Pain, warmth, cold, and pressure

• All skin sensations are a combination of these four basic senses

Gate-control Theory of Pain

• Pain messages travel on one set of nerve fibers containing pain gates.– The gates are open when pain is felt.

• Other sensory messages go through another set of fibers.

• The nonpain fibers can close the pain gates to stop the sense of pain.

Other Senses: Body Senses

Kinesthetic Sense Vestibular Sense• The system for sensing

the position and movement of individual body parts

• Relies on receptor cells from the muscles and joints

• One’s leg “falling asleep” is a disruption of the kinesthetic sense

• The system for sensing body orientation and balance

• Relies on fluid in the semicircular canals of the inner ear

• Spinning in circles disrupts the fluid.