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Sensation and Perception Sensation • The process by which our sensory systems (eyes, ears, and other sensory organs) and nervous system receive stimuli from the environment Sensation • Input comes from the five senses: –Visual (Eyes) –Audio (Ears) –Cutaneous/Tactile (Touch) –Olfaction (Smell) (Nose) –Gustation (Taste) (Tongue) Receptor Cells • Each of the five senses is specifically coded to only take in one type of stimulus, whether is be light waves, sound waves, smell, taste, or touch. Perception • The process of organizing and interpreting sensory information • How we recognize, interpret, and organize our sensations Bottom-Up Processing • Information processing that focuses on the raw material entering through the eyes, ears, and other organs of sensation • This is the sensation part of awareness Top-Down Processing • Information processing that focuses on expectations and experiences in interpreting incoming sensory information • This is the perception part of your awareness Top Down Processing can lead to errors! do you see the tiger? (top down) do you see the hidden tiger? (bottom up) do you see the mountains? (top down) do you see the face? (bottom up) Module 9: Sensation Thresholds Absolute Threshold • A threshold is an edge or a boundary • For sensations, it is the point where you either sense a stimulus or don’t Technically, its “The minimum stimulus that a person can detect 50% of the time” Absolute Detection Threshold • The minimum intensity of energy required to produce sensation in a receptor cell • Taste: 1 gram of table salt in 500 liters of water Smell: 1 drop of perfume diffused throughout a three room apartment • Touch: The wing of a bee falling on your cheek from a height of 1 centimeter • Hearing: The tick of a watch from 6 meters away • Vision: A candle flame on a clear night, 30 miles away • One testable way to determine the thresholds for various people is through SIGNAL DETECTION • Incremental changes in sound, taste, etc. are made to test for reactions in people. Tone tests (hearing) are an example. Signal Detection Results • Hit – signal present and sensed • Miss – signal present but not sensed • False Alarm – signal absent, but sensed • Correct Rejection – signal absent, and not sensed • IE. Frog eye’s have receptor cells that fire only in response to small, dark, moving objects. Theoretically, a frog would starve to death while knee-deep in motionless flies. Remember………… …ABSOLUTE means we either see it, smell it, taste it….or we don’t! Difference Threshold • The minimum difference that a person can detect between two stimuli 50% of the time • Also called just noticeable difference • (JND) Hey! someone Is it just must me or have did suddenly turned on get another a little brighter light! in here?! Ernst Weber and Weber’s Law • The greater the magnitude of the stimulus, the larger the difference must be in order to be noticed – IE. If you are carrying 20 lbs. and add 5 lbs., it’s noticeable. If you are carrying 100 pounds and add 5 pounds, it may not be noticeable. You need to add 10 lbs. to 100 pounds to make it noticeable. Sensory Adaptation • When exposed to a stimuli over a period of time there will be a diminished sensitivity to it • If a stimulus is constant and unchanging, eventually a person may fail to respond to it Example of Sensory Adaptation • A hot tub – after a certain period of time no longer seems as hot Let’s see how good your senses are! TAKE THE AWARENESS TEST ON THE NEXT SLIDE! Selective Attention • Focusing conscious awareness on a particular stimulus (sense) to the exclusion of others Selective Attention Example • Walking down the hallway – all 5 senses are firing. What grabs your attention? Selective hearing • Do you think it exists? Selective Attention • Focusing conscious awareness on a particular stimulus to the exclusion of others • The ability to focus on one stimulus at a time • Allows a person to function in a world filled with many stimuli Module 9: Sensation The Visual System: The Nature of Light Module 9: Sensation The Visual System: The Structure of the Visual System 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 Parts of the Eye – Cornea Iris • A ring of muscle tissue that forms the colored portion of the eye; creates a hole in the center of the iris (pupil) • Regulates the size of the pupil by changing its size--allowing more or less light to enter the eye Parts of the Eye - Iris 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. Parts of the Eye - Pupil 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 • Glasses or contacts correct problems in the lens’ ability to focus. Parts of the Eye - Lens Nearsighted - Myopia Farsighted - Hyperopia Retina • Light-sensitive surface with cells that convert light energy to nerve impulses • At the back of the eyeball Parts of the Eye - Retina Receptor Cells • These cells are present in every sensory system to change (transduce) some other form of energy into neural impulses. • In sight they change light into neural impulses the brain can understand. • Visual system has two types of receptor cells – rods and cones • Visual receptor cells located in the retina • Can only detect black and white • Respond to less light than do cones Rods • Visual receptor cells located in the retina • Can detect sharp images and color • Need more light than the rods • Many cones are clustered in the fovea. Cones Fovea • The central focal point of the retina • The spot where vision is best (most detailed) Parts of the Eye - Fovea Visual Processing in the Retina Visual Processing in the Retina Visual Processing in the Retina Visual Processing in the Retina Optic Nerve • The nerve that carries visual information from the eye to the occipital lobes of the brain Parts of the Eye – Optic Nerve • The point at which the optic nerve travels through the retina to exit the eye Blind Spot • There are no rods and cones at this point, so there is a small blind spot in vision. Parts of the Eye – Blind Spot Retinal Implant Module 9: Sensation The Visual System: Color Vision Color Vision • There are two theories of color vision: –Trichromatic Theory –Opponent-Process Theory Can you see what is in the middle? Trichromatic Theory Young-Helmholtz Theory • Cones are pre-set to be sensitive to RED, GREEN, and BLUE. All of the colors that we see are combinations of those three colors. 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 Red-Green Color Blindness Opponent-Process Theory • Sensory receptors in the retina come in pairs: –Red/Green –Yellow/Blue –Black/White •Only one side is “on” at a time Opponent Process Theory ON” “OFF” red green green red blue yellow yellow blue black white white black Afterimage Effect Opponent-Process Theory • If one sensor is stimulated, the other is inhibited • If one sensor is overstimulated, and fatigues, the paired sensor will be activated, causing an afterimage Module 9: Sensation Hearing: The Nature of Sound Sound • Sound, like light, comes in waves • Sound is vibration • Features of sound include: –Pitch –Hertz –decibels Pitch • A sound’s highness or lowness in tone • Dependent on the frequency of the sound wave – the more “waves per second” the higher the frequency or pitch • Is measured as hertz (Hz) Hertz (Hz) • A measure of the number of sound wave peaks per second; measures “frequency” • Determines the pitch of the sound • Human hearing goes from 20 Hz to 20,000 Hz Low Pitch • Wave peaks are far apart Human hearing goes from 20 Hz to 20,000 Hz although some ears (and speakers) are better than others High Pitch • As pitch increases, so do the number of waves Remember - Human hearing goes from 20 Hz to 20,000 Hz note: a kilohertz is 1,000 hertz so 20 kilohertz equals 20,000 hertz Decibel (dB) • A measure of the height of the sound wave • Determines the loudness of the sound • Sometimes called amplitude Module 9: Sensation Hearing: The Structure of the Auditory System PINNA Also called the auricle. The visible part of the outer ear. • It collects sound and directs it into the outer ear canal. Parts of the Ear – Auditory Canal Auditory Canal • The opening through which sound waves travel as they move into the ear for processing • Ends at the eardrum THE MIDDLE EAR Eardrum • Also called the tympanic membrane. A thin membrane that vibrates when sound waves reach it. • it transfers sound vibration from the air to the tiny 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 – Fun fact: the stirrup is the smallest bone in the human body – only .25 cm Parts of the Ear - Ossicles 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 • The Ossicles amplify the vibration of the eardrum Cochlea • A hearing organ where sound waves are changed into neural impulses (transduction) • The major organ of hearing • Filled with fluid; a snail shaped body tube Parts of the Ear - Cochlea Hair Cells • The receptor cells for hearing in the cochlea that change sound vibrations into neural impulses • Transduction! Movement of the fluid causes the hair cells to move which causes TRANSDUCTION! Parts of the Ear - Hair Cells Auditory Nerve • The nerve that carries sound information from the ears to the temporal lobes of the brain Parts of the Ear – Auditory Nerve 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 Divisions of the Ear Divisions of the Ear Divisions of the Ear Parts of the Ear • Sound waves to Outer Ear• Ear Canal, Eardrum (waves bounce on membrane) • Middle Ear- hammer, anvil, stirrup • Small bones vibrated by waves • Oval Window (membrane vibrates) • Inner Ear- sound waves ripples fluid in cochlea and activates hair cells Problems with hearing • Conduction deafness (middle ear damage) • Nerve deafness (hair cell or auditory nerve damage) How do we hear? Place Theorydifferent frequencies in sound waves cause vibrations at different places in the cochlea Low Frequencies High Frequencies Frequency Theory- different frequency of the sound wave vibrates the inner ear at a different rate Module 9: Sensation Hearing: Sound Localization Localization of Sound • Locating where sound is originating from • Done through two cues: –Which ear hears the sound first? –Which ear hears the louder sound? Localization of Sound EUSTACHIAN TUBE • A tube that connects the middle ear to the back of the nose; it equalizes the pressure between the middle ear and the air outside. When you "pop" your ears as you change altitude (going up a mountain or in an airplane), you are equalizing the air pressure in your middle ear. Problems with hearing • Conduction deafness (middle ear damage) • Nerve deafness (hair cell or auditory nerve damage) • Cochlear Implant Module 9: Sensation Other Senses: Taste (Gustation) Taste • Taste is a chemical sense. • The receptor cells for taste are the taste buds. Taste • Taste is a chemical sense. • The little bumps on our tongues are actually called papillae • Inside some of these papillae are clumps of taste cells. • These clumps of cells are actually the taste buds. • On average, adults have about 7,500 taste buds. • These receptor cells are located in the tongue and in the mouth. • When food dissolves on these receptors, TRANSDUCTION occurs • Damaged taste receptor cells are replaced within a few days to 2 weeks Taste • Taste Sensations –sweet –sour –salty –bitter - umami (savory-msg) Supertasters • People with an abundance of taste receptors • Approximately 25% of the population Nontasters • People with a minimum of taste receptors • Taste with less intensity than the rest of the population • Approximately 25% of the population Module 9: Sensation Other Senses: Smell • Smell is a chemical sense. • Olfactory receptors/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 Smell Other Senses: Touch Touch • Touch receptors are on the skin • Four basic skin senses are – Pain – warmth – cold – pressure • All skin sensations are a combination of these four basic senses Sensitivity of Diff body to pain Most Sensitive • Back of knees • Neck region • Bend of elbow Least Sensitive • Tip of the Nose • Sole of foot • Ball of thumb • 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 non-pain fibers can close the pain gates to stop the sense of pain. Suppressing Pain (this is a link…in case its not working….) 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 non-pain fibers can close the pain gates to stop the sense of pain. Module 9: Sensation Other Senses: Body Senses Kinesthetic 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 Vestibular 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. Parts of the Ear – Semicircular Canals The End