PSY 201 Midterm Study Guide Chapters 4&5
PSY 201 Midterm Study Guide Chapters 4&5 PSY 201
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Chapter 4 Terms to Know: • Locked-in syndrome: when the body and most of the facial muscles are paralyzed but consciousness remains and the ability to perform certain eye movements is preserved • Consciousness: One's subjective experience of the world, resulting from brain activity • Attention: conscious awareness • Selective listening experiment: The participant receives different auditory messages in each ear, but is required to repeat only one Cannot report content of the unattended input Cannot report oddities (ex. repeated word) in unattended input Can report change in pitch or disappearance in unattended input ‣ suggests low-level sensory processing is completed Can report the occurrence of subject's own name in the unattended input ‣ suggests some amount of semantic processing (meaning) is completed • Cocktail party phenomenon: being able to focus one's auditory attention on a particular stimulus while ﬁltering out a range of other stimuli • Shadowing: when a participant wears headphones that delivers one message to one ear and a different message to the other. He/she is asked to attend to one of the two messages and "shadow" it by repeating aloud • Donald Broadbent & ﬁlter theory: humans process information with limited capacity and select information to be processed early • Overt vs. covert attention Overt attention: directing attention by moving the eyes/head/body Covert attention: directing attention without moving the eyes/head/body ‣ covert=hidden from view; secret ‣ looking at something, but attention is directed elsewhere ‣ Spotlight (searchlight) metaphor of attention • Change blindness: failure to notice large changes in the environment, when there is no sudden transient in the image to draw our attention to the change demonstrates that we don't fully process all of the rich details in the scenes we experience • Subliminal perception: The processing of information by sensory ystems without conscious awareness • Freudian slip: when one is speaking, and accidentally inserts a word on one's subconscious mind in place of another word • Left hemispatial neglect: Damage to the right parietal lobe lobe causes left hemispatial neglect, in which the patient has difﬁculty directing attention to the left half of space • Attention & the right parietal lobe • Localization of function (modularity): different regions of visual cortex processes different aspects of the visual image • Binocular rivalry: Different images are shown to the two eyes Typically, perception will not be a mix of the two, but will spontaneously ﬂip from one intact image to the other Neuronal activity in the FFA and PPA reﬂect the contents of perceptual awareness. Also true for other visual areas • Persistent vegetative state: When one is induced into a coma as part of a medical treatment and remains in that unconscious state for more than a month vegetative state: no consciousness, occasional random movements, startles at loud noises, eyes wince at bright light or when startled, no communication, random crying or smiling • Minimally conscious state: between vegetative state and full consciousness partially conscious, reaches for objects and may grab them, sometimes responds to commands with blinking or body movement, tracks moving objects with eyes, occasionally forms intelligible sounds or gestures, sometimes smiles at jokes or cries when sad • Global workspace model: consciousness arises as a function of which brain circuits are active • Split-brain: When the corpus callosum is severed • Corpus callosum: The thick band of myelinated axons that connects the two cerebral hemispheres • Callosotomy: (surgical severing of the corpus callosum) performed in a few patients with life- threatening seizures in order to isolate abnormal neural ﬁring to one hemisphere • Confabulate: a memory disorder that causes people to have inaccurate memories • Interpreter: The left hemisphere’s tendency to construct a world that makes sense is called the interpreter • Circadian rhythms: Biological patterns that occur at regular intervals as a function of time of day • Zeitgeber: a stimulus (like the morning sun) that acts to reset the biological clock without the zeitgeber, human circadian rhythm has a cycle of approx. 25 hrs. duration • Suprachiasmatic nucleus: information about light detected by the eyes are sent here • Pineal gland: secretes hormones • Stages of sleep Wakefulness ‣ Beta, alpha rhythms Stage 1: when you drift off into sleep ‣ Theta rhythm ‣ Can be easily aroused Stage 2: "really asleep" ‣ Theta rhythm, sleep spindles (occasional bursts of activity), K-complexes (large waves) ‣ less sensitive to external stimulation Stages 3 & 4: slow-wave sleep ‣ Delta rhythm ‣ Very hard to wake when in this stage of sleep REM sleep: paradoxical sleep ‣ Marked by rapid eye movements, dreaming, and paralysis of motor systems ‣ Beta rhythm ‣ REM-related paralysis • Insomnia: A sleep disorder characterized by an inability to sleep • Narcolepsy: A sleep disorder in which people experience excessive sleepiness during normal waking hours, sometimes going limp and collapsing • Cataplexy: complete loss of muscle tone during the awake state, related to a hyperexcitability of the neurons of the nucleus magnocellularis • REM behavior disorder: opposite of narcolepsy • Somnambulism: sleepwalking most common in children • Theories for why we sleep Restorative theory: sleep provides a chance for the brain and body to repair the wear and tear that occurs while we're awake ‣ prolonged mental activity causes increased sleep that night ‣ high levels of growth hormones released during sleep facilitates repair of damaged tissues ‣ sleep strengthens immune system Circadian rhythm theory: sleep allows for a period of downtime that protects the animal ‣ conserves energy during the night in which it would be difﬁcult to replace the calories spent foraging;hunting for food (ex. hibernation) ‣ quiet period makes it easier to remain undetected by predators Learning: Sleep allows for a period of memory consolidation and clean-up • Dreams REM vs. non-REM dreams ‣ REM deams • Associated with a narrative storyline • Often bizarre/illogical, but accepted unquestioningly • Perceptions and actions within the dream are associated with activation in associated brain areas • Motoneurons are inhibited so that the dream is not acted out (REM-related paralysis, except for eye movements) ‣ non-REM dreams • Less of a narrative component • Often a simple "feeling" or emotion • non-REM dreams associated with somnambolism (sleep-walking); cannot occur during REM sleep because during REM sleep, the body is paralyzed night terrors: dreams associated with abstract feelings of intense dread/fear (NOT nightmares) Theories on the meaning of dreams ‣ Freudian Theory: dreams reﬂect unconscious conﬂicts within the mind of the dreamer, in a symbolic form disguised to avoid direct confrontation with the conﬂict • No evidence for this ‣ Action-Synthesis Theory: dreams reﬂect the brain's (left hemisphere interpreter's?) attempt to create a narrative to explain the random ﬁring of neurons that occurs during the dream, with the deactivation seen in the frontal lobe contributing to the illogical nature of the dream ‣ Evolved Threat-Rehearsal Theory: dreams provide a virtual simulation of threatening or unusual circumstances so that strategies for coping can be tested and rehearsed for when instances occur in the real world • Hypnosis: A social interaction during which a person, responding to suggestions, experiences changes in memory, perception, and/or voluntary action Posthypnotic suggestion: A suggestion made to a hypnotized person that speciﬁes an action to be performed after awakening from the hypnotized state Sociocognitive theory: hypnotized people behave as they expect hypnotized people to behave, even if those expectations are faulty Neodissociation theory: acknowledges the importance of social context to hypnosis, but views the hypnotic state as an altered state Hypnotic analgesia: a form of pain reduction • Meditation: A mental procedure that focuses attention of an external object or on a sense of awareness Concentrative meditation: you focus your attention on one speciﬁc thing ‣ Mantra Mindfulness meditation: letting your thoughts ﬂow freely, paying attention to them but trying not to react to them • Runner’s high: one minute they are in pain, and the next they are euphoric and feeling a glorious release of energy • Religious ecstasy: religions ceremonies decrease awareness of the external world and create feelings of euphoria • Flow: a particular kind of experience that is so engrossing and enjoyable • Psychoactive drugs: mind-altering substances that change the brain's neurochemistry by activating neurotransmitter systems • Stimulants: drugs that increase behavioral and mental activity • Depressants: reduce behavioral and mental activity by depressing the central nervous system • Opiates: (narcotics) help relieve pain • Hallucinogens: produce alterations in cognition, mood, and perception • Dopamine: located in brainstem involved in: motor control ‣ pathway damaged in Parkinson's disease • causes tremors • can eventually cause cognitive deffects • symptoms of Parkinson's can be relieved with L-DOPA (precursor molecule) deep brain electrical stimulation feelings of pleasure, reinforcement & reward ‣ pathway stimulated by pleasure associated with food, sex, money, addictive drugs ‣ reuptake blocked by cocaine, amphetamine (stimulants, such as methamphetamine), and methylphenidate (Ritalin) • Amphetamines and methamphetamine Amphetamines are stimulants that increase dopamine in the synapse Methamphetamine breaks down into amphetamine into the body • Cocaine: a stimulant that results in a wave of consciousness • Alcohol: activates GABA receptors (GABA is the primary inhibitory neurotransmitter in the brain) • Marijuana: can have effects of a stimulant, depressant, or hallucinogen THC Cannabinoid receptors • MDMA (ecstasy or Molly): produces an energizing effect similar to that of stimulants serotonin ‣ involved in regulation of mood, eating, sleep, dreaming, pain ‣ most recognized for regulating mood review also the Chapter 3 material on MDMA ‣ MDMA produces an energizing effect similar to that of stimulants, but it also causes slight hallucinations • Addiction: Drug use that remains compulsive despite its negative consequences Tolerance: a person needs to consume more of a particular substance to achieve the same subjective effect Withdrawal: feelings of anxiety, tension and cravings for the addictive substance Questions to Consider: 1. What is the difference between the contents of consciousness and the levels of consciousness? A. The levels of consciousness depend on conclusions about content. Examples of contents of consciousness include “the taste of coffee,” “feelings of pain,” or “the experience of redness,” and examples of levels of consciousness are coma, the vegetative state, and the minimally conscious state. 2. What are the beneﬁts and costs of attention? A. Attention involves being able to focus selectively on some things and avoid focusing on others. It can be beneﬁcial to focus on something, but while you're focusing on one thing, you avoid attention of something else which may potentially be costly. 3. In a selective listening experiment, much of the unattended stream of information cannot be reported, which might be taken to imply that it is not processed by the brain. List two ﬁndings that suggest, to the contrary, that this unattended information IS being partially processed by the brain. A. The participant can report change in pitch or disappearance in unattended input (suggests low-level sensory processing is completed) and can report the occurrence of subject's own name in the unattended input (suggests some amount of semantic processing [meaning] is completed). 4. Describe how damage to the right parietal lobe affects attention, using the results from line cancellation and line bisection tasks as examples? A. Damage to the right parietal lobe can cause left hemispatial neglect, characterized by a lack of awareness of the space opposite the damaged brain region (so damage to the right parietal lobe affects the space of the left space of the patient). When asked to bisect a line (through the center), patients with damage to the right parietal lobe tend to cut the line towards the right side since they are not aware of the left side of the line. Another test is the line cancellation test where short lines are scattered throughout a page and patients are asked to cross through all the lines of the page. Patients with left hemispatial neglect will ignore all the lines on the left side of the page. 5. How does change blindness demonstrate that we attend to much less information in the world than we subjectively believe? A. Change blindness demonstrates that we attend to much less information in the world because we fail to notice the big changes that occur around us. 6. Is there a single area of the brain responsible for consciousness? A. No. Consciousness is associated with a distributed neural system: there is no single area where it all comes together. 7. Does the activation in the PPA and FFA reﬂect more the images that are shown to the eyes during binocular rivalry, or the conscious awareness of what is seen? A. That activity in the FFA and PPA reﬂects what is perceived (the conscious awareness of what is seen) rather than the retinal stimulus (the images that are shown to the eyes). 8. How can fMRI be used to assess whether someone thought to be in a persistent vegetative state is capable of the levels consciousness required to understand simple commands? A. A brain-injured patient in a minimally conscious state was asked to imagine either playing tennis, or walking through the rooms of her house. The fMRI measured brain activity and the brain activation reﬂected the same differences in these tasks as those seen in healthy patients. 9. Why can’t split-brain patients verbally report what they see in the left visual ﬁeld, but can easily ﬁnd the named object with the left hand? A. The right hemisphere controls the left side of a person's body, and has enhanced spatial abilities, making the patient able to ﬁnd the object with their left hand. However, the left hemisphere controls language, and since the brain is split and the patient is using the right side of the brain to see what is in the left visual ﬁeld, they cannot verbally report what they see. 10. How do the confabulations of split-brain patients lead to the theory of the left hemisphere interpreter? A. The left hemisphere’s tendency to construct a world that makes sense. Confabulations occur when a person presents false information and defends their thoughts even though people contradict them. (See picture below for example) 11. How has the Stroop task been use to demonstrate that posthypnotic suggestions can actually alter brain function? A. The Stroop effect states that naming the color of a word when the color and word is congruent is easier and quicker than when it is incongruent (Congruent - RED BLUE GREEN YELLOW; Incongruent - RED BLUE GREEN YELLOW). It demonstrates interference in the reaction time of a task. With posthypnotic suggestions, reaction times were faster (especially with the incongruent words). 12. What are some of the effects of sleep deprivation? A. A long period of sleep deprivation causes mood problems and decreases cognitive performance. People who suffer from chronic sleep deprivation may experience attention lapses and reduced short-term memory. 13. How do the sleep cycles change throughout the night? A. There are different stages of sleep. Wakefulness, stage 1 (when you ﬁrst drift off into sleep; can be easily aroused), stage 2 ("really asleep", less sensitive to external stimulation), stages 3&4 (slow-wave sleep; very hard to wake up when in this stage), and REM sleep (paradoxical sleep, marked by rapid eye movements, dreaming, and a paralysis of motor systems) 14. What prevents us from acting out our dreams? A. Usually, narrative dreams happen in REM-sleep and in this stage, your motor systems are paralyzed so you are unable to move. 15. Last night, I dreamt that I arrived to give my lecture wearing nothing but my underwear. Use the Freudian, action-synthesis and evolved threat-rehearsal theories to speculate on the meaning of my dream. A. Freudian theory (dreams reﬂect unconscious conﬂicts within the mind of the dreamer): the dreamer may be afraid to show up to the lecture wearing nothing but underwear; Action-Synthesis Theory (dreams reﬂect the brain's attempt to create a narrative to explain random ﬁring of neurons that occurs during the dream): it may just be an illogical dream to explain the random ﬁring of neurons; Evolved Threat-Rehearsal Theory (dreams provide a virtual simulation of threatening or unusual circumstances): this dream may have occurred so just in case this does happen, the dreamer has a strategy to cope because it has been tested and rehearsed for in the dream. 16. What is some of the evidence that the strength of an addiction is not simply determined by the drug taken, but is also affected by the environmental context of the drug user? A. Children imitate the behavior of role models, especially those they admire or with whom they identify. For children whose parents smoke, the modeling of the behavior may be continuous through early childhood and elementary school. When parents smoke, their children tend to have positive attitudes about smoking and to begin smoking early. Also, people whos peers smoke are more likely to smoke to ﬁt in. Question #10: Chapter 5 Terms to Know: • Synesthesia: causes one sensory response to automatically trigger another sense simultaneously • Sensation: initial coding of information from the senses ex. Loud noise, yellow blur, fast motion, wind in face, exhaust smell • Perception: brain's interpretation of those messages ex. Taxi blaring its horn as it narrowly misses you (representation of what happened) • Sensory stimuli: Gathering of information from the environment (sensory stimuli) • Mental representation: Transformation into a virtual world in the mind (mental representation) • Sensory transduction: Process of converting energy (information) in the environment into energy (information) in the nervous system; accomplished by specialized neurons (sensory receptors) • Sensory receptors: specialized neurons that helps with sensory transduction • Sensory coding: Translation of physical properties of stimulus into patterns of neural activity (action potentials) • Doctrine of speciﬁc nerve energies vs. Rate law Doctrine of speciﬁc nerve energies suggests that tones of different pitch will be represented by the ﬁring of action potentials in different auditory neurons The rate law suggests that the intensity (loudness) of a sound will be represented by the number of action potentials in an auditory neuron will ﬁre in a given period of time. • Absolute threshold: Smallest amount of energy needed to detect a stimulus • Subthreshold (subliminal) stimuli: a stimulus too weak to evoke a response • Difference threshold: Smallest detectable difference (the just noticeable difference, jnd) between two stimuli Weber’s law: The jnd is proportional to the magnitude of the original stimulus (ex. larger stimulus leads to larger jnd) • Signal detection theory: A theory of perception based on the idea that the detection of a stimulus requires a judgment--it is not an all-or-nothing process Hits: when a signal is presented and the participant detects it Misses: if the participant fails to detect the signal False alarms: if the participant "detects" a signal that was not presented Correct rejections: If the signal is not presented and the participant doesn't detect it Response bias: participant's tendency to report detecting a signal in an ambiguous trial • Kinesthesis: moving body awareness • Audition: hearing; the sense of sound perception Sound wave: a pattern of changes in air pressure during a period of time; it produces the percept of a sound ‣ Frequency: determines pitch; higher frequency=higher in pitch (how fast the wave is moving) ‣ amplitude: determines loudness; higher amplitude=louder sound (how "tall" the wave is) Eardrum & ossicles ‣ eardrum: A thin membrane that marks the beginning of the middle ear; sound waves cause it to vibrate ‣ ossicles: three bones in the ear known as the hammer, anvil, stirrup that transfers the eardrum's vibrations The basilar membrane is located in the center of the cochlea; Movement of the basilar membrane stimulates hair cells to send information to the auditory nerve Cochlear implants: a small electronic device that can help provide the sene of sound to a person who has a severe hearing impairment Primary auditory cortex: Auditory neurons in the thalamus extend their axons to this cortex in the temporal lobe Temporal vs. place coding ‣ Temporal coding: mechanism for encoding low-frequency auditory stimuli in which the ﬁring rates of cochlear hair cells match the frequency of the sound wave ‣ Place coding: mechanism for encoding high-frequency auditory stimuli in which the frequency of the sound wave is enclosed by the location of the hair cells along the basilar membrane • Vestibular sense: Perception of balance determined by receptors in the inner ear • Somatosensation: Perception of sensory stimuli coming from the skin that involves senses of touch, temperature, body position, and pain Tactile stimulation: Anything that makes contact with our skin provides tactile stimulation. This stimulation gives rise to the experience of touch. Pain: a warning system that stops you from continuing activities that may harm you ‣ Two kinds of nerve ﬁbers identiﬁed for pain: • Fast ﬁbers: for sharp, immediate pain • Slow ﬁbers: for chronic, dull, steady pain Gate control theory of pain: we experience pain when pain receptors are activated and a neural "gate" in the spinal cord allows the signals through to the brain. Pain signals are transmitted by small-diameter nerves. The ﬁbers can be blocked at the spinal cord by the ﬁring of larger sensory nerve ﬁbers. Sensory nerve ﬁbers can "close a gate" and prevent/ reduce the perception of pain • Olfaction: The sense of smell Olfactory epithelium: A thin layer of tissue, within the nasal cavity, that contains the receptors for smell Olfactory bulb: The brain center for smell, located below the frontal lobes • Gustation: The sense of taste Taste buds: sensory organs in the mouth that contain the receptors for taste Salty, sweet, bitter, sour, umami (Japanese for "savory" or "yummy") supertasters: when you have more taste buds/papillae than average • Vision Eye ‣ Cornea: the eye's thick transparent outer layer that focuses the incoming light ‣ Pupil: dark circle at the center of the eye. It's a small opening in front of the lens. Contracting or dilating the pupil determines how much light enters the eye ‣ iris: a circular muscle, determines the eye color and controls the pupil's size ‣ Lens: where incoming light enters ‣ accommodation: A process where the muscles behind the iris change the shape of the lens. They ﬂatten it to focus on distant objects and thicken it to focus on closer objects ‣ Retina: The thin inner surface of the back of teh eyeball; it contracts the sensory receptors that transduce light into neural signals Rods & cones ‣ Rods • 120 million (more rods than cones) • Has a high sensitivity to dim light • No sensitivity to color • Low sensitivity to ﬁne detail • Primarily located in periphery ‣ Cones • 6 million • Low sensitivity to dim light • Sensitivity to color • High sensitivity to ﬁnd detail • Primary location in the fovea Photopigment (Rhodopsin): protein molecules that become unstable and split apart when exposed to light ‣ Opsin & retinal • Opsin: the protein part of visual photo pigments. • The other part is a vitamin A sub-product considered to be retinal ‣ Isomerization: the structural arrangement of a molecule without any change in its atoms Ganglion cells: the ﬁrst neurons in the visual pathway with axons Fovea: Area in the center of the retina with high density of cones, and overlying cell layers pulled aside, to provide high-resolution images of the central part of the visual scene Optic nerve: The axons (that ganglion sells their signals along from inside the eye to the thalamus) gathered into a bundle Blind spot: Area of retina in which the ganglion cell axons depart the eye along the optic nerve, crowding out any photoreceptors. Electromagnetic spectrum: the range of wavelengths or frequencies over which electromagnetic radiation extends Hue, brightness & saturation: color is categorized along these 3 dimenisons ‣ hue: consists of the distinctive characteristics that place a particular color in the spectrum (a color's greenness or orangeness). Determined by the light's dominant wavelength when it reaches the eye ‣ brightness: the color's perceived intensity. Determined by the total amount of light reaching the eye ‣ saturation: purity of the color. Varies according to the mixture of wavelengths in a stimulus Trichromatic theory: color vision results from activity in three different types of cones ‣ S-, M- and L-cones: the three cones in the trichromatic theory (respond to small, medium, and large wavelengths respectively) Opponent process theory: ‣ Retinal ganglion cells are either: • excited by green/inhibited by red • excited by red/inhibited by green • excited by blue/inhibited by yellow • excited by yellow/inhibited by blue • excited by white/inhibited by black • excited by black/inhibited by white ‣ Opponent colors: • red & green • blue & yellow • black & white Optic chiasm: At the optic chiasm, half of the axons in the optic nerves cross. Lateral geniculate nucleus of the thalamus: At the optic chiasm, half of the axons in the optic nerves cross. Primary visual cortex is located in the occipital lobe What (ventral) vs. Where (dorsal) streams ‣ Ventral stream: lower stream; specialized for the perception and recognition of objects, such as determining their colors and shapes ‣ Dorsal stream: upper stream; specialized for spatial perception--determining where an object is and relating it to other objects in a scene ‣ patient D.F. suffered bilateral damage along the ventral stream of visual processing. The effect was visual form agnosia: she is able to control her actions with respect to objects, but cannot describe or recognize these objects verbally. Gestalt principles ‣ Principles of proximity, similarity, continuity • proximity: The closer two ﬁgures are to each other, the more likely we are to group them and see them as part of the same object • Similarity: we tend to group ﬁgures according to how closely they resemble each other (in shape, color, orientation) • continuity: we tend to group together edges or contours that have the same orientation • (good continuation), closure: we tend to complete ﬁgures that have gaps Figure & ground ‣ Reversible images (ambiguous ﬁgures): ex. you can see a picture of the three vases or two faces, but not at the same time Bottom-up vs. top-down processing ‣ Bottom-up processing: Hierarchical sensory processing that relies only on information available in the sensory input (Perception based on the physical features of the stimulus) ‣ Top-down processing: Hierarchical sensory processing that relies on prior knowledge of the properties of the objects or events to be detected (How knowledge, expectations, or past experiences shape the interpretation of sensory information) ‣ Sometimes, the brain's assumptions of how the world works can be misleading. Face perception ‣ Prosopagnosia: deﬁcit in the ability to recognize faces, but not in the ability to recognize other objects ‣ Fusiform gyrus: in the right hemisphere, may be specialized for perceiving faces Monocular (pictorial) depth cues ‣ Occlusion (Interposition): If one object partially hides another from view, the object that is blocked is seeing as being further away. • Only provides information on relative (not absolute) depth ‣ Relative Height: Objects that are closer to the horizon in the visual ﬁeld appear further away ‣ Cast Shadows: If source of light is known, the location of a shadow can provide further information of an object's location in depth ‣ 3-D Shape from Shading: Highlights and shadows are cast on an object in a way that is consistent with... • the object's shape in depth, and • the known (or assumed) sources of light ‣ Relative Size: If two objects are the same size, the one whose image takes up less of the visual ﬁeld (smaller) will appear to be further away. ‣ Familiar Size: If the actual size of an object is known, its distance can be judged by the size of its visual image--a more distant object will have a smaller image. ‣ Atmospheric (Aerial) Perspective: Distant objects look less sharp than nearby objects due to the greater amount of dust, water vapor, and pollution we have to look through to see the more distant object ‣ Linear perspective: Lines that are actually parallel will converge in the image as distance increases ‣ Texture gradient: Elements that are equally spaced will appear to be packed closer and closer together as distance increases Oculomotor depth cues are based on our ability to sense the position of our eyes and the tension in our eye muscles ‣ Convergence: eyes must "converge" to see nearby objects ‣ Accommodation: lens changes shape to focus the image Movement-produced depth cues are created by movement of the observer or by movement of the objects in the environment ‣ Motion parallax: Nearby objects move across the visual image faster than more distant ones ‣ Structure from Motion: you can see a structure based on movement of parts Binocular depth cues uses the fact that our left and right eyes receive slightly different images because they are observing the scene from slightly different positions ‣ Binocular disparity: the difference in the images of the two eyes, caused by the eyes' slightly different locations in space ‣ Stereopsis: the impression of depth that is derived from disparity Ponzo illusion & Ames room Color blindness ‣ Trichromatopia: typical color vision, with three functional cones ‣ Dichromatopia: Atypical color vision, caused by a genetic mutation that prevents the formation of one cone type • Protanopia: defective L-cones (red end of the spectrum); ~1% of men, .02% of women) • Deuteranopia: defective M-cones; ~1% of men, .02% of women • Tritanopia: defective S-cones; ~.001% of men, .03% of women ‣ Monochromatopia: Atypical color vision, caused by a genetic mutation that prevents formation of two or three of the cone types; ~.00001% of men and women • Although you might have one functional cone, you have nothing to compare it to ‣ Anomalous color vision: Atypical color vision, caused by a genetic mutation that alters (but does not eliminate) the function of one or more cone types; ~6% of men, .4% of women ‣ Tetrachromatopia: Atypical color vision, caused by a genetic mutation that effectively causes a fourth cone type to develop (thought to occur in ~1% of women; see 100x more colors than typical) Questions to Consider: 1. How does sensation differ from perception? A. Sensation is the detection of stimuli while perception is the processing of that stimuli. 2. What are the types of energy detected by the different sensory systems? How are these energies transduced by sensory receptors in the different sensory systems? A. VISION: Stimuli--light waves; Receptors--Light-sensitive rods and cones in the retina of the eye; Pathways to the brain--Optic nerve B. HEARING: Stimuli--Sound waves; Receptors--Pressure-sensitive hair cells in the cochlea of inner ear; Pathways to the brain--Auditory nerve C. TASTE: Stimuli--Molescules dissolved in ﬂuid on the tongue; Receptors--Cells in taste buds on the tongue; Pathways to the brain--Portions of facial, glossopharyngeal, and vagus nerves D. SMELL: Stimuli--Molecules dissolved in ﬂuid on the membranes in the nose; Receptors-- Sensitive ends of olfactory mucous neurons in the mucous membranes; Pathways to the brain--Olfactory nerve E. TOUCH: Stimuli--Pressure on the skin; Receptors--Sensitive ends of touch neurons in skin; Pathways to the brain--Cranial nerves for touch above the neck, spinal nerves for touch elsewhere 3. How are the physical properties of a stimulus coded into neural activity (review the rate law and doctrine of speciﬁc nerve energies from Chapter 3). A. Doctrine of speciﬁc nerve energies states that the nature of perception is deﬁned by the pathway over which the sensory information is carried and the origin of the sensation is not important. The rate law states that the strength of a stimuli is determined by the ﬁring rate of the nerve impulses. Physical properties of a stimulus is coded by the pathway which the stimulus takes and the ﬁring rate of it. 4. Is the jnd for 100 pounds greater or smaller than for 50 pounds? A. Greater. According to Weber's Law, the jnd is proportional to the magnitude of the original stimulus (ex. larger stimulus leads to larger jnd). 5. “Taste” is not only experienced by the mouth. What other senses contribute? A. Smell also contributes to taste. 6. What sequence of events occurs in the rods and cones to transduce light into neural energy? A. Light ﬁrst passes through the cornea. It focuses the incoming light which then enters the lens. Then, the light is bent farther inward and focused to form an image on the retina where the rods and cones are located. From there, the rods and cones send information to a second layer of cells called bipolar cells which pass the light onto the next set of cells (ganglion cells). The axons of the ganglion cells make up the optic nerve which sends information to the thalamus in our brain. 7. How do the rods and cones differ in terms of number, sensitivities to dim light, color, ﬁne detail, and location in the retina? Why is a star at twilight visible when you see it in your visual periphery, but disappears when you look right at it? A. Rods a. 120 million b. High sensitivity to dim light c. No sensitivity to color d. Low sensitivity to ﬁne detail e. Primarily located in periphery B. Cones a. 6 million b. Low sensitivity to dim light c. Sensitivity to color d. High sensitivity to ﬁne detail e. Primary location in the fovea C. You are able to see a star in your periphery but not when you look right at it because rods have high sensitivity to dim light and is able to pick up light in the periphery, versus looking right at the source, the cones are unable to respond to the light. 8. How do the color dimensions of hue, brightness and saturation correspond to the physical characteristics of light (wavelength, amplitude and purity)? A. Hue is determined by the light's dominant wavelength when it reaches the eye. Brightness is determined by the amplitude. Saturation is the purity of a color and varies according to the mixture of wavelengths in a stimulus. 9. Describe why we can perceive any color in the rainbow, even though we only have three different cone types? How do the relative activations of the three cone types differ when we see something green versus something blue? How about something magenta, which contains light from both the blue and red ends of the spectrum? A. The cones combine so we can perceive all the colors in the rainbow. 10. Why is there a red afterimage after something green is removed from the visual ﬁeld after prolonged viewing? How can the afterimage of blue be yellow when there are no cones that speciﬁcally respond to yellow light? A. According to the opponent processing theory, ganglion cells create the perception that red and green are opposing colors. There may not be cones that respond speciﬁcally to yellow light, but a cell can get excitatory input from both red and green cones to make a yellow receptor. 11. What happens in the optic chiasm that causes things in the left visual ﬁeld to be processed ﬁrst by visual areas in the right hemisphere, and vice versa? A. Optic nerves partially cross. The crossing over of optic nerve ﬁbers at the optic chiasm allows the visual cortex to receive the same hemispheric visual ﬁeld from both eyes. 12. What do the impairments and abilities of Patient D.F. tell us about how visual cortex is organized? A. Patient D.F. suffered bilateral damage along the ventral stream of visual processing. The effect was visual form agnosia: she is able to control her actions with respect to objects, but cannot describe or recognize these objects verbally. Her dorsal stream of visual processing was left in tact. They concluded that the ventral stream was for perception and recognition of objects. The dorsal stream was for spatial perception and determining where an object is related to other objects in a scene. 13. How do bottom-up and top-down processing combine to yield our perception of the world? A. Bottom-up processing occurs when data is relayed from one level of mental processing to the next, always moving to a higher level of processing (sensory) while top-down processing goes from higher to "earlier" levels in processing (knowledge and expectation). We are constantly learning and processing new things (bottom-up) and using that information again (top-down). 14. Be able to look at a picture and describe some of the pictorial depth cues that are present. 15. Why do distorted depth cues sometimes lead to illusions of size (e.g., the Ponzo illusion)? A. We use depth cues to determine size and sometimes, we misperceive. In the ponzo illusion, a ﬂat surface can give the illusion of depth using linear perspective, and two lines that are the same length can look different because we perceive higher objects closer to the horizon and more toward the tip of the converging lines as farther away, so it looks a lot larger (See picture below) 16. Why does rubbing the skin near an injury help reduce the pain? A. The nerve ﬁbers that are identiﬁed for pain can be blocked at the spinal cord by the ﬁring of larger sensory nerve ﬁbers. If you rub the skin near an injury, it is ﬁring larger nerve ﬁbers and can reduce the perception of pain. 17. People with only one functional eye have altered depth perception. Why is their depth perception diminished, and why is it not eliminated altogether? A. There are two types of depth cues; binocular and monocular depth cues. People with only one functional eye will not be able to use their binocular depth cues, resulting in altered depth perception, but they are able to use monocular depth cues since they are available to each eye alone. Question #15
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