AP Psychology SENSATION Chapter 4 (Bernstein), pages 106-149 Introducing Your Senses • You have been told you have to give up one of your senses. 1. which one would you choose NOT to have? 2. Why would you choose this sense and not one of the others? 3. Describe the physiological processes/physical structures that would be affected by your lack of this sense. Introducing Your Senses 1. VISUAL DOMINANCE: we are very reliant on our sense of vision and “give priority” to information that comes through that sense. 2. INTERACTION OF TASTE AND SMELL: by giving up smell, you are also giving up much of the flavor of food. In addition, you will no longer be able to use smell to detect danger (e.g., smelling smoke). 3. INCREASED SENSITIVITY: if you lose one sense, the other senses do NOT become more sensitive (e.g., you cannot develop more rods and cones). Rather you do attend more to the other sensory cues and would notice things that you might not otherwise. Introducing Your Senses Physiological Processes/ Physical Structures 1. VISION--lack of rods or cones or damage to the cornea, lens, retina, the optic nerve, the occipital lobe or thalamus 2. HEARING--damage to the tympanic membrane, the mealleus, incus, or stapes (conduction deafness), the basilar membrane, the auditory nerve (nerve deafness), or the temporal lobe or thalamus 3. SMELL--damage to olfactory neurons or the olfactory bulb 4. TASTE--damage to the taste buds or papillae and the thalamus 5. TOUCH--difficulty surviving; wouldn’t be able to swallow or feel pain (which is important!). There could be damage to the skin’s sensory neurons, the spinal cord, and the thalamus 6. KINESTHESIA--damage to receptors in the muscles and joints that send information to the spinal cord and the thalamus 7. VESTIBULAR--no sense of balance or the positions of one’s head in space; could have damage to the vestibular sacs in the inner ear or cerebellum; if problem exists with the vestibular-ocular reflexes produced by the eye muscles, there could be damage to the vestibular sense WHAT ARE OUR SENSES? 1. A SENSE is as system that translates information from outside the nervous system into neural activity. 2. Messages from the senses...SENSATIONS 3. Sensation v. Perception (the process of giving meaning to sensation, Ch. 5) • difficult to distinguish because interpretation of sensations begins in sense organs and continues into the brain 4. Some General Info • stream of info from different senses can interact (e.g., ____________________ ) • experience can change the sensations we receive (e.g., ____________________ ) • “reality” differs from person to person (e.g., ____________________ ) 5. Our senses gather information about the world by detecting various forms of ENERGY (e.g., light, heat, sound, physical pressure). 6. Humans depend primarily on VISION, HEARING, and the SKIN SENSES. SENSORY SYSTEMS •Steps in Sensation 1.ACCESSORY STRUCTURES modify/change environmental energy before “detected” by the sensory system itself (ex. the outer ear is an accessory structure that collects sound). 2.TRANSDUCTION converts environmental energy into neural activity (much like translating English into another language). •SENSORY RECEPTORS specialized cells that detect energy forms •Sensory receptors respond best to changes in environmental energy •ADAPTATION is a process in which responsiveness to an unchanging stimulus decreases over time. 3.Sensory 4.for nerves carry output from receptors to CNS (spinal cord and brain) all senses except smell, info goes first to thalamus which relays it to appropriate sensory area of the cerebral cortex for complex processing SENSORY SYSTEMS • The Problem of Coding • CODING is the translation of a stimulus’ physical properties into a pattern of neural activity that specifically identifies those properties • DOCTRINE OF SPECIFIC NERVE ENERGIES states that stimulation of a particular sensory nerve provides codes for that one sense, no matter how the stimulation takes place (ex. gently pressing eyeball produces optic nerve activity and little spots of light) • In other words... We have sensory systems which allow us to take in information from the outside world and make “sense” of it in our inside world (the brain). • SOUND is a repetitive fluctuation in the pressure of a medium, HEARING such as air. • Vibrations of an object produce the fluctuations in pressure that create sound. • A wave is a repetitive variation in pressure that spreads out in three dimensions. • Physical Characteristics of Sound • Sound is represented graphically by waveforms (2-D) which have three characteristics: • AMPLITUDE or intensity is the difference in air pressure from baseline to peak • WAVELENGTH is the distance from one peak to the next • FREQUENCY is the number of complete waveforms, or cycles that pass by a given point in space every second. One cycle per second is 1 hertz (Hz). • Frequency and wavelength are related; the longer the wavelength, the lower the frequency (and vice versa) • Most sounds are mixtures of many frequencies and amplitudes, but HEARING • Psychological Dimensions of Sound • Physical characteristics of sound waves produce the psychological dimensions of sound. • LOUDNESS determined by amplitude of the sound wave; waves with greater amplitude produce sensations of louder sounds. • Loudness is described in units called decibels, dB. Zero dB is the minmal detectable sound for normal hearing. • PITCH is how “low” or “high” a tone sounds. High frequency waves are senses as high-pitched sounds. • Humans can hear sounds from about 20 Hz to 20,000 Hz. • TIMBRE is sound’s quality. Consists of complex wave patterns that enables you to differentiate sounds. PARTS OF THE EAR • Outer Ear... CHANNELS the sound (pinna, auditory canal, tympanic membrane/eardrum) • Middle Ear... AMPLIFIES the sound (hammer/malleus, anvil/incus, stirrup/stapes) • Inner Ear... TRANSDUCES the sound (cochlea, basilar membrane, hair cells/cilia, auditory nerve) HEARING • Focusing the Sound: THE HUMAN EAR YOUR TASKS • GROUP 1 Describe the roles of the cochlea, basilar membrane, hair cells, and auditory nerve in the process of AUDITORY TRANSDUCTION. Include a description of the types of deafness. • GROUP 2 Describe how information is relayed to the primary auditory cortex and how the cortex codes the frequency and location of sounds. • GROUP 3 Describe the process of coding auditory information. Discuss the relationship between PLACE THEORY and FREQUENCY-MATCHING THEORY (VOLLEY THEORY) on frequency coding. PLACE THEORY v. FREQUENCY-MATCHING THEORY Place Theory pitch is signaled/identified according to the locations of vibrations along the basilar membrane pitch determined by the places where the membrane vibrates and activates hair cells of the organ of Corti certain frequencies are too low to cause vibrations along the basilar membrane (explained by frequencymatching theory) Frequency-Matching Theory a neuron responds (or fires) to frequencies up to 500 Hz used to explain how we hear deep, low frequencies pitch of sound determined by neuron (or group of neurons) firing patterns neurons have a maximum firing frequency which falls within the range of frequencies we can hear; volley theory attempts to explain this by stating groups of neurons cooperate to code these higher-frequency sounds (still higher frequencies explained by place theory) TEST YOUR MAD SKILLS! VISION • LIGHT • a form of energy known as electromagnetic radiation • most invisible to the human eye • VISIBLE LIGHT • electromagnetic radiation with a wavelength from approx. 400 nanometers (one-billionth of a meter) to about 750 nanometers • does not need a medium to pass through (such as air or water...or molasses) • has properties of both waves and particles (light rays and light waves both correct terminology) • sensations of light dependent upon two physical dimensions: • LIGHT INTENSITY how much energy the light contains; determines brightness • LIGHT WAVELENGTH determines color you sense; different wavelengths produce sensations of different colors (ROYGBIV) VISION • o c u s i n g t h e L i g h t : T H E H U M A N E Y E VISION • Converting Light into Images (VISUAL • PHOTORECEPTORS the specialized cells in the retina that convert light into neural activity • PHOTOPIGMENTS chemicals in photoreceptors that respond to light TRANSDUCTION) • light strikes photoreceptors • photoreceptors break apart and chemical reaction begins • cell’s membrane polarity changes and signal sent to the brain • in dim conditions photoreceptors make extra photopigment to detect little light • DARK ADAPTATION the increasing ability to see in the dark over time (after half hour, sensitivity increases 10,000 fold) VISION• • RODS & CONES RODS and CONES the two types of photoreceptors in the retina that differ in shape, composition, and response to light • Approx. 120 million rods and 6-7 million cones • Cones provide the basis for color vision • Cones use one of three varieties of iodosin photopigments, each sensitive to different light wavelengths • Rods use the photopigment rhodopsin, making them more sensitive to light than cones; rods cannot discriminate color • Most cones concentrated in fovea allowing detailed vision, or ACUITY • Variations in density of cones in the fovea account for differences in visual acuity • Rods are located in the periphery of the retina, not in the fovea QuickTime™ and a Sorenson Video 3 decompressor are needed to see this picture. VISION • RODS & CONES • INTERACTIONS IN THE RETINA • • Rods and cones connect to bipolar cells and then to ganglion cells. • When amounts of light reaching any two photoreceptors differ, the photoreceptor receiving more light inhibits the output to the brain from the photoreceptor receiving less light, making it seem like there is less light at that cell than there is. • LATERAL INHIBITION is made possible by interneurons which make sideways connections between photoreceptors and exaggerate the amount of light reaching them. This exaggeration allows clearer vision. • Each ganglion cell can relay info to the brain only about its own RECEPTIVE FIELD, the part of the retina and the corresponding part of the visual world to which that cell responds • These receptive fields create complex combinations that give us optimum detection of light variations such as edges and small spots of light or dark. By enhancing the sensation of important features, the retina gives us an “improved” version of the visual world. • The OPTIC DISK is located where the optic nerve leaves the eye. It contains no rods or cones and creates a BLIND SPOT or void in the visual field. This is unnoticed because the other eye compensates for it. Axons of the the ganglion cells form the optic nerve which extends out of the eye and into the brain. “The Island of the Colorblind” from the BBC series THE MIND TRAVELER with Dr. Oliver Sacks Click HERE to begin program. REPRES ENTATI ONS VISION• • Once the optic nerve leaves each eyeball, the bundle of fibers meet at the OPTIC CHIASM in the brain. Here they cross to the opposite side of the brain. The fibers from the inside half of each eye cross over. The outside half of each eye do not. This brings all visual info from the left half of the visual world to the right hemisphere of the brain • VISION • VISU AL PATH WAY S& REP RESE NTAT IONS From the optic chiasm, info is sent to the region of the thalamus called the LATERAL GENICULATE NUCLEUS (LGN) where neurons then relay the visual input to the PRIMARY VISUAL CORTEX for complex processing. • FEATURE DETECTORS specialized neurons in the LGN that respond to different aspects of an image such as size, shape, and angle • PARALLEL PROCESSING refers to how the brain processes multiple sources of info at once. It’s still debated as to where all this processing takes place and may involve several regions of the brain, not just the visual cortex. VISION • SEEING COLOR • PERCEPTION OF COLOR • How we perceive color depends on three characteristics of light waves: HUE, SATURATION, and BRIGHTNESS. • HUE refers to the color people psychologically experience. It is determined by wavelength. Short wavelengths produce bluish colors. Long wavelength produce reddish colors. Medium wavelengths produce orange, green, yellow colors. • SATURATION refers to color purity. Purity depends on the complexity of light wave. (ex. red comprised of a single wave; pink comprised of a combination of red and white light) • BRIGHTNESS refers to the intensity of the light wave as determined by the amplitude, or height, of a wave (tall wave/great amplitude would be a very bright color; low wave/low amplitude would be a dull color) • SEEING COLOR • COLOR MIXING • Colors are based on the dominant wavelength present. How colors are mixed determines which color people perceive. • SUBTRACTIVE COLOR MIXING VISION • occurs by mixing different paint colors • like other physical objects, paints reflect certain wavelengths and absorb all others • combining all paint colors will result in black • ADDITIVE COLOR MIXING • the effects of the wavelengths from each light are added together • mixing two lights of equal intensity results in a color midpoint on a line between the two starting colors on a color wheel • VISION TRICHROMATI C THEORY OF COLOR VISION (YoungHelmholz Theory) • the eye has three types of receptors, each sensitive to a specific wavelength • blue-sensitive cone short wavelengths • green-sensitive cone medium wavelengths • red-sensitive cone wavelengths • colors other than blue, green, and red triggers combination of cones which produces other colors (ex. purple results from triggering blue and red-sensitive cones at the same time) • COLOR BLINDNESS can be explained by the trichromatic theory • people with who are born long • VISION • OPPONENTPROCESS THEORY OF COLOR VISION (Ewald Hering) • the color-sensitive components of the eye are grouped into three pairs: red-green, blue-yellow, and black-white • each element signals one color or the other but never both • this theory explains AFTERIMAGES when an image is perceived even though the stimulus has been removed (ex. staring at a yellow dot then looking away and seeing a blue dot...the afterimage) • according to Hering, different colors are produced through combinations of the pairs being activated at the same time (ex. purple results from VISION • SYNESTHESIA • involves more unusual mixing of senses that improve the experience of a sensation • “feeling” color or sounds as touches; “tasting” shapes; sensing colors when hearing certain sounds • possibly from connections between neighboring sensory areas of the brain VISION EXPERIMENTS Neuroscience for Kids: VISION EXPERIMENTS Neuroscience for Kids: COLOR VISION THE CHEMICAL SENSES: SMELL & • OLFACTION (click HERE before continuing) • • • Olfaction (or Smell) detects chemicals that are airborne, or volatile • olfactory receptors on dendrites of specialized neurons in the moist lining of the nose (mucous membrane) • odor molecules bind to receptors causing depolarization of dendrites’ membrane and causes changes in the firing rates of neurons • a single odor molecule can cause a change in the membrane potential of an olfactory neuron but normal odor detection requires about 50 molecules • • olfactory neurons live only about 2 months and are repeatedly replaced • • IMPORTANCE TO RESEARCH • how smells are coded in combinations of receptors may help researches develop “electronic noses” that may have an application in national security and medical diagnosis TASTE accessory structures include nose, mouth, and upper part of throat odor molecules reach receptors through nose or through opening in the palate at back of mouth humans have approx. 1,000 different olfactory receptors (1-2% of genes) allowing us to discriminate tens of thousands of different odors understanding how olfactory neurons generate may someday be helpful in treating brain damage BACK THE CHEMICAL SENSES: SMELL & TASTE • More on OLFACTION • • the only sense that bypasses the thalamus • olfactory bulb’s connection to the amygdala may account for relationship between smell and emotional experiences (losing the sense of smell sometimes indicates brain diseases that disrupt memory and emotion) • mechanism of olfaction similar across species but not sensitivity (humans have approx. 9 million olfactory neurons; dogs have about 225 million) • no agreement on basic smells • BUT WAIT! THERE’S MORE! olfactory axons extend directly into the brain to the olfactory bulb and then sent to various brain regions for further processing THE CHEMICAL SENSES: SMELL & TASTE • PHEROMONES • Dogs and many other species have an accessory olfactory system that detects these chemicals that when released by one animal and detected by another can shape the second animal’s behavior and/or physiology • in mammals, pheromones can be nonvolatile chemicals that animals lick and pass into an olfactory organ called the vomeronasal organ • role of pheromones in humans less clear • the human vomeronasal organ is capable of responding to certain hormonal substances and can influence certain hormonal secretions • not everyone has a vomeronasal organ • odorants that cannot be consciously detected have been shown to influence mood and can alter parts of the brain that not directly involved in olfaction • a possible human gene for pheromone receptors has been found • pheromones capable of producing physiological changes in humans related to reproduction but no solid evidence for a human (or even a primate) sexual attractant pheromone • associations between certain odors and emotional experiences that enhance sexual attraction is LEARNED • individual mammals, including humans, have distinct “odor type” determined by immune cells and other inherited physiological factors THE CHEMICAL SENSES: SMELL & TASTE • GUSTATION • Gustation (or Taste) is the chemical sense system in the mouth • receptors for taste are in taste buds grouped together as papillae in mouth and throat • humans have about 10,000 taste buds (mostly on tongue, also on roof of mouth and back of throat) • human taste system detects only a few elementary sensations (sweet, sour, bitter, salty) • research has identified two other tastes • umami enhances other tastes and is produced by monosodium glutamate (MSG) and certain other proteins • astringent produced by tannins such as those found in teas • different tastes transduced into neural activity in different ways • sweetness and bitterness signaled when chemicals fit into specific receptor sites • sour and salty act through direct effects on the ion channels in membranes of taste cells • salty also enhances taste of food by suppressing bitterness • “supertasters”--about 25% of population has thousands of taste buds whereas “nontasters” have only hundreds THE CHEMICAL SENSES: SMELL & TASTE • SMELL, TASTE, and FLAVOR • smell and taste act as two components of one system...FLAVOR • most of what makes food taste good comes from odors detected by the olfactory system • ANOSMIA is inability to distinguish smells and also interrupts ability to determine flavor even when the gustation system is in working order • olfactory and gustatory pathways converge in the ORBITOFRONTAL CORTEX where neurons also respond to the sight and texture of food • responses of neurons in this “flavor cortex” also influenced by hunger and satiety (fullness) • tastes and odor prompt strong emotional responses • reactions to bitter and sweet flavors appear to be inborn • few other innate flavor preferences as most are LEARNED • taste and flavor perception as well as motivation to consume certain flavors is affected by nutritional needs (ex. desire for salty drink or food after exercise) • flavor also affected by texture and temperature THE SOMATIC SENSES • • • also known as the body senses or somatosensory systems located throughout the body rather than in specific, localized organs include the following: 1. skin senses of touch, temperature, and pain 2. kinesthesia--the sense that tells the brain where the parts of the body are with respect to each other 3. vestibular system/proprioceptive senses--tells the brain about the position and movement of the head THE SOMATIC SENSES •TOUCH AND TEMPERATURE •Stimulus and Receptors for Touch •energy detected by the sense of touch is physical pressure on tissue (usually skin) •skin covers approx. 2 yards of surface and weights more than 20 lbs •hairs on skin bend and deform the skin just beneath them •nerve endings in the skin act as receptors that transduce pressure into neural activity are in, or just below, the skin •exact process of transduction in the skin is still unknown •humans not just passive responders; touch is an active sense used to get specific information •high density of touch receptors in fingertips •some blind people can read 200 words of Braille per minute THE SOMATIC SENSES •TOUCH AND TEMPERATURE •Adaptation of Touch Receptors •constant input leads to adaptation resulting in reduced response to constant stimulation •somatosensory system responds best to change in touch •neurons fire rapidly when stimulus first sensed •then most neurons slowly return to baseline while only a few fire giving a sense of a constant stimulation •Coding and Representation of Touch Information •sense of touch codes info about two aspects of an object in contact with the skin •INTENSITY of stimulus (weight or heaviness) coded by both the firing rate of and number of neurons stimulated •LOCATION coded by the location of neurons responding to touch; input from left side of body goes to right side of brain, and vice versa THE SOMATIC SENSES •TOUCH AND TEMPERATURE •Temperature •touch and temperature seem to be separate senses; difference not always clear •some sensory neurons of skin respond to change in temperature but not to simple contact •“warm fibers” increase firing rate when temperature is between 95-115 degrees F •temperatures above 115 cause pain and stimulate different fibers •“cold fibers” respond to broad range of cool temperatures •many fibers responding to temperature also respond to touch causing sensations of temperature and touch/pressure to interact •warm and cold objects can “feel” up to 250% heavier than body-temperature objects •touching an object made up of alternating warm and cold spots gives sensation of intense heat •people having frostbite feel burning sensation THE SOMATIC SENSES • PAIN AS AN INFORMATION SENSE • pain receptors are free nerve endings that extend from spinal cord to skin and muscles (no dendrites) • when stimulated, these sensory neurons cause the release of various neurotransmitters including substance P, a neurotransmitter that activates a “gate” in the spinal cord that either lets pain impulses travel to the brain or blocks their progress (Gate-Control Theory of Ronald Melzack and Patrick Wall) • input from other skin senses (touch, temperature) may “take over” pathways that pain impulses would have used (ex. rubbing area around a wound; cold/hot pack on a injury) • two types of nerve fibers carry pain signals to spinal cord where they are sent to the thalamus and then relayed to somatosensory cortex, frontal lobe, and limbic system (for emotional elements of pain) • A-delta fibers carry sharp pain and are myelinated to carry inputs quickly • C fibers carry chronic, dull aches and burning sensations • • each signals different brain areas different pain neurons cause release of different neurotransmitters (allowing for the THE SOMATIC SENSES • EMOTIONAL ASPECT OF PAIN • all senses can have an emotional component, most of which are learned • • pain is more direct • necessary for our survival by allowing us to pull or away or stop doing something that could cause us injury • cognition affects our emotional response to pain • understanding the nature of pain makes it less aversive although just as intense • pain-reducing strategies such as distracting thoughts also affects emotional responses to pain specific pathways carry an emotional component of the painful stimulus to areas of the hindbrain and reticular formation (in the limbic system) as well as other areas via the thalamus THE SOMATIC SENSES • NATURAL ANALGESICS • the brain can close the “gate” by sending signals back down the spinal cord resulting in analgesia, the absence of pain sensation in the presence of a normally painful stimulus • at least three chemicals released by the body during stress play a role in the brain’s ability to block pain signals: serotonin, endorphins, and endocannabinoids • • endorphins act as pain killers at many levels • are also released by the adrenal and pituitary glands as pain-relieving hormones • “range of use” includes reducing labor pains during late pregnancy to allowing severely injured athletes and soldiers to continue to perform with no apparent pain • once crisis has passed, the release of another neurotransmitter reactivate pain sensitivity counteracting endorphins’ analgesic effects in the spinal cord, they block the synapses of fibers that carry pain signals THE SOMATIC SENSES • PROPRIOCEPTION & EQUILIBRIOCEPTION • The proprioceptive senses and the sense of balance provide information about the position of the body and what each part of the body is doing THE SOMATIC SENSES • EQUILIBRIOCEPTION • Vestibular Sense • • often thought of as the “sense of balance” • two vestibular sacs and three semicircular canals in the inner ear are the organs for this sense • vestibular sacs filled with fluid and contain small crystals called otoliths that rest on hair endings • semicircular canals are fluid-filled and arc-shaped tubes with tiny hairs extending into fluid • as head moves, otoliths shift in sacs and fluid moves in the canals stimulating hair endings • neurons activated and travel with the auditory nerve, signaling the brain about the amount and direction of head movement • vestibular system has neural connections to: cerebellum (coordinate body movements), autonomic nervous system (affect digestion), eye muscles (fix eyes on a point in space if head is moving...vestibular-ocular reflexes) • dizziness occurs when the fluids in the vestibular system are not level tells brain about the position of the head in space and about its general movements THE SOMATIC SENSES • PROPRIOCEPTION • Kinesthesia • the sense that tells you where parts of your body are with respect to each other • guide all our movements because the brain, with practice, will automatically make them simple and fluid • primary source of kinesthetic information comes from special receptors (proprioceptors) in joints and muscles • transduced info goes to spinal cord to thalamus to cerebellum and somatosensory cortex for smooth coordination of movements • NOTE: kinesthesia often distinguished from proprioception due to proprioception’s reliance on balance (kinesthesia is unaffected by sense of balance and deals only with motion) Enhancing proprioceptive quality & adaptation: • The following exercises and body systems have an effect on proprioceptive awareness. • Movement for movement's sake in any variety of movement patterns and ranges of motion with different tensions/loads (i.e., dancing, tai chi, yoga). • Traditional cardio, strength and flexibility conditioning. • Balance conditioning, eyes open and closed. • Rotational movements (not just linear and lateral). • Visual acuity: Use vision to adjust movements when recovering balance. Instead of focusing downward, look ahead to realign the head and neck. • Auditory system: The inner ear registers head and body movement like a built-in level. To function properly, the head and neck must be situated over a balanced spine. • Rhythm: Heart beat, breathing patterns and even walking are rhythmic by nature. Have clients strive to feel rhythm during sports and as they work out. • Stance: Movements should be initiated from an "athletic stance" (ankles, knees and hips slightly flexed) and an upright posture. Stance is also referred to as the clients' "base of support," or the distance created between their feet. • Weight transfer: Bodies are especially sensitive to weight changes that take place with stance or postural shifts. Clients will feel weight transfer from the feet upward. • Constant motion: Have clients get a feel for constant, dynamic movements (versus static positions) as they try the drills mentioned in this article. • FROM: FITNESS MANAGEMENT MAGAZINE--A PUBLICATION • FITNESS/HEALTH/ATHLETIC CLUBS AND FACILITIES DIRECTED TO