Chapter 6 - Sensation Notes
Chapter 6 - Sensation Notes PSY 151
Popular in Intro to Psychology
Popular in Psychlogy
This 13 page Class Notes was uploaded by Patrece Savino on Tuesday February 9, 2016. The Class Notes belongs to PSY 151 at Wake Forest University taught by Dr. Schrillo in Winter 2016. Since its upload, it has received 88 views. For similar materials see Intro to Psychology in Psychlogy at Wake Forest University.
Reviews for Chapter 6 - Sensation Notes
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 02/09/16
Chapter 6 – Sensation Sensory Processing (receptors – outside of the system) Sensation – the detection of simple properties of stimuli such as brightness, color, warmth, and sweetness o ex. Seeing the color blue Perception – the recognition of objects (animate and inanimate), their locations, their movements, and their backgrounds o ex. Recognizing the blue sky Transduction o Only sense receptors in brain are ones that detect local conditions like temperature & salt concentration in the blood supply o Sense organs detect stimuli such as light, sound, taste, odor, or touch Information about stimuli transmitted to brain through neural impulses (action potentials in the sensory nerves) o Transduction – the process by which the sense organs convert energy from environmental events into neural activity; each sense organ responds to a particular form of energy given off by environmental stimulus and translates that energy to neural firing so that the brain can respond o Receptor cells – specialized sensory neurons that release chemical neurotransmitters that stimulate other neurons, thus altering the rate of firing of their axons Sensory Coding o Anatomical Coding Johannes Muller formulated doctrine of specific nerve energies Sensory organs in the body send their information to the brain through different nerves Brain has no direct info about physical energy on a given sense organ anatomical coding allows brain to interpret location and type of sensory stimulus according to which incoming nerve fibers are active Sensory coding for body’s surface is anatomical o Temporal Coding Temporal coding – coding of sensory information in terms of time Rate (pattern) – by firing at a faster or slower rate according to the intensity of a stimulus, an axon communicates quantitative information to the brain o Ex. Skin sends touch/temperature/vibration/pain/stretch by certain frequencies that reflect intensity/type of touch Signals produced by a particular set of neurons (an anatomical code) tell where the body is being touched and the rate at which these neurons fire (a temporal code) tells how intense that touch is Psychophysics o Psychophysics – the systematic study of the relation between the physical characteristics of stimuli and the psychological responses (or perceptions) they produce o The Principle of the JustNoticeable Difference Ernst Weber defined the justnoticeable difference as the smallest difference between two similar stimuli that can be distinguished (aka difference threshold) Ex. Magnitude of weights being lifted Logarithmic pattern Weber fraction – the ratio between a justnoticeable difference and the magnitude of a stimulus; reasonably constant over the middle range of most stimulus intensities o Signaldetection Theory Threshold – the thin line between not perceiving and perceiving Difference threshold – the minimum detectable difference between two stimuli Absolute threshold – the minimum intensity of a stimulus that can be detected discriminated from no stimulus at all Bias with thresholds when subjects know that they are being tested signaldetection theory Signaldetection theory is an alternative method of measuring sensitivity to changes in physical stimuli that takes into account random changes in the nervous system Every stimulus event requires discrimination between a signal (the stimulus) and a noise (the combination of background stimuli and random activity of the nervous system) Takes into account our willingness to report detecting a signal (response bias) o Ex. Flash of light followed by tone Vision Light o Light consists of radiant energy similar to radio waves o Wavelength – the distance between adjacent waves of radiant energy in vision most closely associated with the perceptual dimension of hue Wavelength of visible light is relatively short (380760 nm) All other wavelengths are not visible to human eyes Entire range of wavelengths known as the electromagnetic spectrum The Eye & Its Functions o Eyes are housed in a bony socket and covered by the eyelid to keep out dust and dirt o Eyelids edged by eyelashes that keep foreign matter out of open eyes o Eyebrows prevent sweat on the forehead from dripping into eyes o Reflex mechanisms further protect the eye ex. Sudden approaches of object toward face result in eyelid closure and withdrawal of the head Cornea Sclera Iris Lens Retina Photoreceptors Optic Bipolar Cells Ganglion Cell Disk Transparen The Pigmented Lies Located on the More than 130 a a neuron in a neuron in t tissue tough muscle of beneat inner surface of million circular the retina the retina covering outer the eye h the the back of the embedded in structur the front of layer of iris eye the retina e the eye the located eye; at the the exit “white point ” of the from the eye retina of the axons of the ganglio n cells that form the optic nerve Admits Coats controls Causes image is upside Specialized all receives Receives light the eye the size of images down and flipped neurons that axons information information the pupil to be horizontally; transduce light leave from the from which focuse brain into neural the eye photoreceptors photoreceptors constricts d on compensates activity at this and passes it by means of in bright the point on to the bipolar cells, light and retina Accommodation Information and join ganglion cells, and from dilates in : changes in from the optic from which which axons dim light photoreceptors nerve, axons proceed proceed thickness of the lens of the eye is transmitted to which through the through the that focuses neurons that connect optic nerves to optic nerves to images of near or send axons s to the the brain the brain distant objects on toward the brain the retina (ciliary optic disk muscles) Performs sensory functions of the eye Contains rods and cones o nearsighted – eye is too long, image is out of focus need a concave lens to correct the focus o farsighted – eyes are too short need a convex lens to correct the focus o rods – function mainly in dim light; very sensitive to light but insensitive to differences between colors o cones – function when level of illumination is bright enough to see things clearly; responsible for color vision o fovea – small pit in the back of the retina approximately 1mm in diameter, contains only cones; responsible for most acute and detailed vision Transduction of Light by Photoreceptors o A molecule derived from vitamin A is the central ingredient in the transduction of the energy of light into neural activity o In the absence of light, this molecule attaches to a protein form a photopigment o Photopigment – a complex molecule found in photoreceptors; when struck by light, it splits apart and stimulates the membrane of the photoreceptor in which it resides Four kinds of photopigments (one for rods, 3 for cones) Rhodopsin – the photopigment contained by rods; pink Once photopigments split they become bleached Bleached photopigments = decreased sensitivity to light Adaptation to Light and Dark o Dark adaptation – the process by which the eye becomes capable of distinguishing dimly illuminated objects after going from a bright region to a dark one High levels of illumination strike the retina rate of regeneration of rhodopsin falls behind the rate of the bleaching process, so the rods are not very sensitive If you enter a dark room after being in the sunlight there are too few intact rhodopsin molecules in your eyes to respond immediately to dim light In the light you’re using cones (photopic vision) enter darkness, color goes away; use rods (scotopic vision) and it takes time for this adjustment Eye Movements o 3 types of movements: saccadic movements – the rapid movement of eyes that is used in scanning a visual scene, as opposed to the smooth pursuit movements used to follow a moving object; abrupt shifts in gaze from one point to another – eyes jump around from point to point to point about 5 jumps/second ex. Reading a line of text in a book vergence (conjugate) movements – the cooperative movement of the eyes, which ensures that the image of an object falls on identical portions of both retinas ex. Holding a finger in front of your face and bringing it closer = vergence toward nose pursuit movements – the movement of the eyes to maintain an image upon the fovea ex. Fixing gaze on a moving car Color Vision (Cones) o Light: wavelengths between 380760 mm Perceptual Dimension Physical Dimension Physical Characteristics Hue Wavelength Length of oscillation of light radiation Brightness Intensity Amount of energy of light radiation Saturation Purity Intensity of dominant wavelength relative to total light energy o The Dimensions of Color Hue – perceptual dimension of color determined by wavelength; the effect of a particular hue is caused by the mixture of lights of various wavelengths Brightness – a perceptual dimension of color determined by intensity or degree of radiant energy emitted by a visual stimulus Color of maximum brightness = vibrant; minimum = black Saturation – a perceptual dimension of color determined by purity of a color; fully saturated color consists of only one wavelength o Additive Color Mixing When two wavelengths of light are present, we see an intermediate color rather than the two components Additive color mixing – the addition of two or more lights of different wavelengths seen together as a light of an intermediate wavelength Mixing two beams of light of different wavelengths always yields a lighter color o Color Coding in the Retina Trichromatic theory – the theory that color vision is accomplished by three types of photodetectors, each of which is maximally sensitive to a different wavelength (hue) of light Thomas Young Sensitive to three colors: “pure” blue, green, and red Other psychologists later said that we perceive yellow as pure too Opponent Process – the representation of colors by the rate of firing of two types of neurons: red/green and yellow/blue Yellow/blue ganglion cells are excited by yellow light and inhibited by blue light changes the rate of firing o Negative Afterimages Negative afterimage – the image seen after a portion of the retina is exposed to an intense visual stimulus; a negative afterimage consists of colors complementary to those of the physical stimulus Ex. Staring at an image for a long time then shifting gaze to a blank wall You see the opposite colors that your retina dictates (ex. Pg 167) o Defects in Color Vision Protanopia – a form of hereditary anomalous color vision; caused by defective “red” cones in the retina red cones filled with green photopigment Deuteranopia – a form of hereditary anomalous color vision; caused by defective “green” cones in the retina green cones filled with red photopigment Trianopia – a form of hereditary anomalous color vision; caused by lack of “blue” cones in the retina lack of blue cones Audition Sound o Hertz – primary measure of the frequency of vibration of sound waves; cycles per second human ear perceives vibrations from 3020,000 Hz can vary in intensity (amplitude) and frequency variations produce changes in our perception of a sound’s loudness and it’s pitch more intense vibrations produce louder sound more rapid vibrations produce higher pitch o Timbre – a perceptual dimension of sound that corresponds to its complexity The Ear and Its Functions o Pinna – fleshcovered cartilage attached to the side of the head (what people generally refer to as the “ear”); helps funnel sound waves through the ear canal and toward the middle and inner ear o Eardrum – thin, flexible membrane that vibrates back and forth in response to sound waves and passes these vibrations on to the receptor cells in the inner ear Attached to the first set of 3 middleear bones called the ossicles o Ossicle – one of the three bones in the middle ear (the hammer, the anvil, and the stirrup) that transmit acoustical vibrations from the eardrum to the membrane behind the oval window of the cochlea These bones act together in lever fashion to transmit the vibrations of the eardrum to the fluidfilled structure of the inner ear o Cochlea – the bony structure that contains the auditory receptor cells Filled with a liquid Bony chamber (vestibule) is attached to the cochlea and contains two openings, the oval window and the round window Oval window – an opening in the bone surrounding the cochlea; the stirrup presses against a membrane behind the oval window and transmits sound vibrations into the fluid within the cochlea Divided into three chambers by two membranes: Basilar membrane – contains the auditory receptor cells; vibrates as the footplate of the stirrup presses back and forth against the membrane behind the oval window and pressure changes in the fluid above the basilar membrane o Varies in its width and flexibility along its length different frequencies of sound cause different parts of the basilar membrane to vibrate o Higher frequency sounds cause end near oval window to vibrate; medium frequency sounds cause the middle to vibrate; and low frequency sounds cause the tip to vibrate o Round window – an opening in the bone surrounding the cochlea; movements of the membrane behind this opening permit vibrations to be transmitted through the oval window into the cochlea when the basilar membrane flexes down, the displacement of the fluid causes the membrane behind the round window to bulge out fenestration o sounds are detected by special neurons known as auditory hair cells located on the basilar membrane o auditory hair cells – transduce mechanical energy caused by the movement of the basilar membrane into neural activity; posses hairlike protrusions called cilia the ends of the cilia are embedded in the tectorial membrane o tectorial membrane – a fairly rigid shelf that hangs over the basilar membrane like a balcony; serves as a shelf against which the cilia of the auditory hair cells move when sound waves cause the basilar membrane to vibrate, the cilia are stretched and the pull on the cilia of the auditory hair cells is translated into neural activity mechanical force on cilia cell ion channels open in membrane of cilia positive ions can enter release of a neurotransmitter that causes a message to be sent through the auditory nerve to the brain Detecting and Localizing Sounds in the Environment o Pitch and Loudness Cochlear implant – devices that are used to restore hearing in people with deafness caused by damage to the hair cells; external part of cochlear implant consists of a microphone and electronic signal processor Evidence that the basilar membrane uses a place code to detect pitch Restores a person’s ability to understand speech Frequencies about 200 Hz (high) are hard to perceive Frequencies lower than 200 Hz cause the tip of the basilar membrane to vibrate in synchrony with the sound waves Neurons that are stimulated by hair cells located there are able to fire in synchrony with these vibrations at the same frequency as the sound brain counts these vibrations and detects lower frequency sounds (ex. of temporal (rate) coding) o Timbre Fundamental frequency – the lowest, and usually most intense, frequency of a complex sound; most often perceived as the sound’s basic pitch Waveform consists of a series of sine waves that includes the fundamental frequency and many overtones Overtones – integer multiples of the fundamental frequency; a component of a complex tone; one of a series of tones whose frequency is a multiple of the fundamental frequency Different portions of the basilar membrane respond to different overtones o Perception of Environmental Sounds Pattern recognition – the auditory system must recognize that particular patterns of constantly changing activity received from the hair cells on the basilar membrane belong to different sources, and few patterns are simple mixtures of fixed frequencies Lewis et al. (2004) Study pg. 173 Played sounds forward then backward and backward was impossible to recognize o Locating the Source of a Sound If a source of a sound is on your right and produces a high frequency sound, your right ear will receive more intense stimulation than your left ear will; the brain uses this difference to calculate the location of the source of the sound Differences in arrival time of sound pressure waves at each eardrum If a sound is located on one side of your head, one eardrum will be pushed in and the other pushed out Axons in the right and left auditory nerves will fire at different times; the brain detects this disparity and so perceives the location of the sound at one side or the other The brain can detect differences in firing times of a fraction of a millisecond and the easiest auditory stimuli to locate are those that produce brief clicks which cause brief bursts of neural activity The Chemical Senses chemosenses – taste and smell Gustation – the sense of taste o Different from flavor which includes odor and texture o Taste Receptors and the Sensory Pathway Taste reception begins with the tongue – creases and bumps Papillae – a small bump on the tongue that contains a group of taste buds Taste bud – a small organ containing receptor cells shaped like the segments of an orange o have hairlike projections called microvilli that protrude through the pore of the taste bud into the saliva that coats the tongue and fills the trenches of the papillae o receptor cells form synapses with dendrites of neurons that send axons to the brain through three different cranial nerves o The Five Qualities of Taste Sourness, sweetness, bitterness, saltiness, and umami Umami – Japanese word for “good taste;” refers to the taste of monosodium glutamate, a substance that is often used as a flavor enhancer in Asian cuisine umami receptor detects the presence of gultamate, an amino acid found in proteins; provides the ability to taste proteins Olfaction – the sense of smell o Anatomy of the Olfactory System Olfactory mucosa – the mucus membrane lining the top of the nasal sinuses; contains the receptors and cilia of the olfactory receptors Receptor cells have axons that pass through small holes in the bone above the olfactory mucosa and form synapses with neurons in the olfactory bulbs Olfactory bulbs – stalklike structures located at the base of the brain that contain neural circuits that perform the first analysis of olfactory information Interaction between the odor molecule and receptor cell is similar to interaction between neurotransmitter and postsynaptic receptor on a neuron When an odor molecule fits a receptor molecule located on the cilia of the receptor cell, the cell becomes excited Olfactory information is not sent to the thalamus and relayed to a specialized region of the cerebral cortex but instead it is sent directly to several regions of the limbic system (particularly the amygdala and limbic cortex of the frontal lobe) o The Dimensions of Odor Olfactory system contains several hundred different receptor molecules located in the membrane of the cilia of the receptor cells Humans can recognize up to 10,000 odors We can use a relatively small number of receptors to detect many different odorants a particular odorant binds to more than one receptor Because a given glomerulus receives information from only one type of receptor, different odorants produce different patterns of activity in different glomeruli Still not known which molecules stimulate which receptors Araneda, Kini, and Firestein (2000) The Somatosenses somatosenses – bodily sensations; sensitivity to such stimuli as touch, pain, and temperature The Skin Senses o The entire surface of human body is innervated (supplied with nerves) by the dendrites of neurons that transmite somatosensory information to the brain Cranial nerves convey information from the face and rest of the front portion of the head Spinal nerves convey information from the rest of the body’s surface Most common type of skin sensory receptor is the free nerve ending which infiltrate the middle layers of both smooth and hairy skin and surround the hair follicles in hairy skin Largest of specialized skin receptors is the Pacinian corpuscle which is visible to the naked eye and very sensitive to touch When they are moved their axons fire a brief burst of impulses Provides information about vibration o Touch and Pressure Touch is sensation of very light contact of an object with the skin and pressure is produced by more forceful contact The ability to localize precisely the part of the body being touched varies across the surface of the body Most sensitive regions are lips and fingertips Most common measure of tactile discrimination (the ability to tell touches apart) is the twopoint discrimination threshold A researcher touches a person with one or both legs of a caliper and asks the person to say whether the sensation is coming from one or two points o Temperature We know of 6 mammalian thermoreceptors sensitive to ranges of temperatures One is found in the anterior of the hypothalamus (region of brain responsible for measuring and maintaining body temperature) o Pain At least 3 types of pain receptors (nociceptors) High threshold mechanoreceptors are free nerve endings that respond to intense pressure (ex. a strike or a pinch) Second type of free nerve ending responds to the extremes of heat, acids, and presence of capsaicin (the active ingredient in chile peppers) Another type of nociceptor are sensitive to ATP (a chemical that serves as an energy source in all cells of the body) o ATP is released when the blood supply to a region of the body is disrupted or when a muscle is damaged o These nociceptors may be partly responsible for the pain caused by angina, migraine, damage to muscles, and some kinds of cancer Opiates (ex. morphine) Produce analgesia (a reduction in pain) by stimulating opioid receptors on neurons in the brain; these neurons block the transmission of pain information Tranquilizers (ex. diazepam [valium]) Depress neural systems that are responsible for the emotional reaction to pain but do not diminish the intensity of pain People feel pain but it doesn’t bother them Pain/fear of pain is one of the most effective motivators of human behavior Phantom limb – sensations that appear to originate in a limb that has been amputated Melzack, Ramachandran, and Hirstein The Internal Senses o Sensory receptors located in our internal organs, bones, and joins, and muscles convey painful, neutral, and pleasurable sensory information o Muscles contain special sensory receptors One class located at the junction between muscles and tendons that connect them to the bones provides information about the amount of force the muscle is exerting Another stretchdetection system called the muscle spindles inform the brain about changes in the muscle length The Vestibular Senses o “sense of balance” o vestibular apparatus – located in the inner ear; provides additional sensory input that helps us remain upright o semicircular canals – three liquid filled organs in the inner ear oriented at right angles from one another that detect changes in the rotation of the head rotation of the head causes motion of liquid, which stimulates the receptor cells located in the canals o vestibular sacs – one of two sets of receptor organs in each inner ear that detects changes in the tilt of the head; contains crystals of calcium carbonate that are embedded in a gelatinlike substance attached to the receptive hair cells in one sac, the receptive tissue is on the wall and in the other it is on the floor head tilts weight of calcium carbonate crystals shifts produces different forces on the cilia of the hair cells change the activity of the hair cells information is transmitted to the brain help us maintain an upright head position
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'