Psych Exam 2 Notes PDF

LECTURE 11 BRAIN ORGANIZATION: The Historic Brain and “Animal Spirits”: Galen (130-200 AD) - “Animal spirits” produced by heart, flow through ventricles and stored for movement and sensation - Ventricles were the instrument of the soul - Brain tissue was the seat of intellec...

LECTURE 11 BRAIN ORGANIZATION: The Historic Brain and “Animal Spirits”: Galen (130-200 AD) - “Animal spirits” produced by heart, flow through ventricles and stored for movement and sensation - Ventricles were the instrument of the soul - Brain tissue was the seat of intellect (animal spirits flowed into the brain with the nerves) Rene Descartes (1596-1650) - Reflexes - sensory stimulation caused valves in ventricles to release animal spirits into hollow nerves which caused movements - Voluntary behavior - required interaction with the soul via the pineal gland Cerebral cortex and Phrenology: Phrenology - Franz Joseph Gall (1758-1828) - Cortex is functionally specialized - Function is correlated with size - Bumps on skull due to well developed cortical areas - Correlations between traits and bump patterns reveal how cortex is organized - Phrenology had the right theory but the wrong methods - Bumps on head NOT a good predictor of cognitive abilities - Mid 1800s - looked at relationship between focal brain damage and cognition Cerebral hemisphere: - Brain is specialized into 2 hemispheres that - Control the opposite sides of the body (contralateral control) - Are connected by the corpus callosum (composed of white matter tracts that contain myelinated axons) - Are functionally symmetrical (motor cortex and sensory cortex) - Have specialized abilities Cerebral cortex (from the greek word “bark”: - Outer covering of 2 brain hemispheres - Has 20-23 billion neurons with >100 connections  - Controls complex aspects of perception, emotion, movement and thought Cerebral Lobes: - Occipital (seeing) - Visual information (visual cortex) - Parietal (sensing) - Info about body senses (sensory cortex) - Temporal (hearing/speaking) - Hearing (auditory cortex) - Language (Wernicke's area) - Memory - Frontal (doing) - Planning, judgement, memory, reasoning, abstract thinking, movement (motor cortex) Sensory (somatosensory) cortex: - In front end of parietal lobe - Topographical representation of the body - Larger areas of the sensory cortex devoted to more sensitive body areas - Helps you feel touch and where your body is in space (proprioception) - Remember homunculus (sensory system’s view of your body) Motor Cortex: - In back of frontal lobe next to parietal lobe - Topographical representation of the body - Larger areas of motor cortex devoted to body areas requiring precise control Basal Ganglia - directs intentional movement: - Receives input from cerebral cortex - Sends output to motor centers in brainstem - Striatum involves control of posture and movement - Responsible for habits Limbic System: - Hypothalamus, hippocampus and amygdala - Motivation, emotion, learning and memory - Hippocampus - creates new memories and integrates them into a network of knowledge - integral for creating memories about specific events Episodic Memory - specific past events: - Conscious recollection and contextual information - Happiest moment of my life - What happened at a certain memorable location - Automatically captures info - Hippocampus doesn't need to be driven by intentions to store information - Stored memories are protected from inference - Stores highly similar episodes and these memories do not interfere with each other Emotion and its adaptivity: Emotion - the affective aspect of consciousness, visceral aspects of a physiological response Adaptive benefits - fight or flight response, more efficient decision-making, better social interaction - Emotion can be maladaptive (anger, substance abuse) Amygdala: - On tip of each side of the hippocampus - Central role in emotional processes (fear and aggression specifically) - Plays significant role in the formation of emotional memories - Attaches significance to events associated with fear, punishment or reward - Amygdala works with hippocampus to enhance recall of emotionally salient events The brainstem - life sustaining functions: Pons - sleep, respiration, swallowing, bladder function, hearing, equilibrium, taste, eye movement, facial expressions, facial sensation, and posture Medulla - controls heartbeat and breathing Reticular formation - sleep, wakefulness, and levels of arousal LECTURE 12 SUBCORTICAL STRUCTURES AND HORMONES: Ventricles in the Brain - Ventricles contain CSF to cushion the brain and spinal cord - Things that can go wrong with the ventricles: - Hydrocephalus, headaches, head enlargement, learning disability,  short-term memory loss, motion and visual problems Pineal Gland - “Seat of the soul”: - Descartes called the pineal gland the “seat of the soul” - Only structure in brain that isn’t split in half - “Entrance to the 3rd eye” - Actual function: secrete melatonin to regulate circadian rhythms Limbic system structures and functions: - Amygdala = threat/emotions - Hippocampus = memory - Hypothalamus = 4 Fs (helps maintain homeostasis) - Fight - Flight - Feeding - Sexual activity The Bodys Radio: Hormones vs. Neurons: Hormones - Slow moving - Travel through blood - Target broad areas - Have a longer effect Neurons - Electrochemical action potentials - Messages are fast-acting - Localized - short-lived The endocrine System: - A communication system that influences thoughts and behaviors - Consists of: - Pineal gland - Thyroid gland  - Parathyroid gland - Adrenal glands - Gonads - Hypothalamus - Pituitary gland - Thymus - Pancreas Endocrine system and the CNS: - Hormone release controlled by the hypothalamus and pituitary - Based on the neural activation, the hypothalamus secretes a releasing factor - Ex: GHRH (growth hormone releasing hormone) - This causes the pituitary to release a specific hormone - Ex: GH (growth hormone) released from anterior pituitary - Hormone travels to endocrine sites throughout the body - Ex: GH goes into blood and acts on many systems to promote growth The pituitary Gland - “master gland of endocrine system”: - Receives hormone signals from the hypothalamus - Sends hormone signals to other glands to control stress, digestive activities and reproductive activities - Anterior pituitary produces hormones - Produces GH. ACTH, TSH, FSH, LH and prolactin - Posterior pituitary stores hormones produced by the hypothalamus - ADH (antidiuretic hormone/vasopressin) and oxytocin HPA Axis: Hypothalamic-pituitary-adrenal axis - Regulates your stress response (fight/flight) - Negative feedback (output reduces upstream effects) LCTURE 13: CHANGING THE BRAIN: Neuroplasticity in response to damage: - Brain plasticity (neuroplasticity) - changes in neural pathways and synapses due to changes in behavior, environment, neural processes, thinking, emotions and changes as a result of injury - Brain has amazing amount of neuroplasticity  - Can lose entire parts of your brain and still maintain function with few deficits Examples Neuroplastciitys: - Example: Parkinson’s disease - Neurodegenerative disorder - Loss of dopamine cells in the substantia nigra (between midbrain and diencephalon) - Profound disturbances in movement - Cognitive deficits - Symptoms aren’t readily apparent until 60-80% of these cells are already gone Savantism: - Island of ability contrasts with general disability - Surprisingly limited in rage - Calendar calculating, Charles and George Finn - Could say what day of the week it was given a date even hundreds of years ago - Music - Perfect pitch, multiple instruments, can reproduce music after hearing them once - Math - Can do extremely complicated math problems very quickly in their head - Art - Produce intricate art with more precision than typical artistic abilities - Mechanical - Construct and repair complex mechanisms without training - Mnemonism - Can remember and recall unusually long lists of data/information Mnemonism: Kim Peak (1951-2009): - Overall IQ = 87 - developmental disorder - Limited abstract/conceptual thinking - Can commit any fact to memory, reads 2 pages at a time (one with each eye) in 8-10 seconds and retains 95% of information - Music recall - Had cranium Bifidum, Macrocephaly, Cerebellar/left hemisphere abnormalities and a missing Corpus Callosum Biological Basis of Savantism: - No one biological theory can account for all types of savant - Paradoxical Functional Facilitation - research that focuses on unexpected changes to  the nervous system - Looks at how damage leads to an increase in performance Why aren’t we all geniuses? - Evolutionary Cognitive Trade-Offs - May be increased evolutionary fitness benefits to not everyone being a genius - Underlying biological constraints (female pelvic size and bipedal locomotion) may have an effect - All about the U-shaped curve Enviormental influences of Brain Plasticity: Benefits of an Enriched Environment - You begin life with MORE neurons than you will have as an adult - “If you use it you will grow” - Enriched environments associated with thicker cerebral cortex, larger cortical neurons, more ACh, more synapses per neuron, thicker synapses and increased learning ability Deprived Enviorments - Bucharest Earlt intervention project: Nikolae Ceaucescu’s 1966 decree: - Goal = increase population - Result = child abandonment and institutionalization - 1989: 170k children in state institutions - Randomized controlled trial of foster care as an intervention for abandoned children placed in institutions Institutionalization leads to: - Social problems and trouble with attachment - Externalizing problems - inattention/hyperactivity - IQ and cognitive deficits - “Autism-like” syndrome - Growth stunting BEIP Study Design: - Independent Variables: Institutionalized, Foster Care, Non-Institutionalized - Dependent Variables: IQ, Brain Volume, Psychiatric Evaluations  - Measured at: 30, 42, 54 months, and again at 8 yrs. Critical Periods for Certian functions: - ADHD symptoms are not significantly reduced in those placed in foster care at ANY age - Institutionalization results in disrupted cortical development and reduced thickness in many cortical areas - These reductions in thickness explain elevated ADHD symptoms in institutionalized children - Results suggest that foster care has a lasting impact on the brain and cognitive development Ritalin Methylphenidate (MPH): - Originally used to treat ADHD - Psychostimulant related to amphetamine and cocaine - Lower doses improve cognitive performance and reduce locomotor activity, even in healthy (non-ADHD) individuals Modafinil: - Development to treat sleep disorders like narcolepsy - Psychostimulant related to amphetamine and cocaine - Alters many neurotransmitters - Results in extreme alertness/focus - Currently in use by surgeons, military/NASA, wall street workers Beta Blockers: - Developed to treat heart conditions - Wide usage by athletes, musicians, actors - considered a performance-enhancing drug - Tamps down the adrenergic system - Not a true cognitive enhancer by can improve performance in high-stress situations - Not as selective as other cognitive enhancers - many side effects Caffeine: - Hard to study due to lack of naive control subjects and withdrawal effects - Improve incidental (unconscious process of memorizing information) but not intentional learning (conscious effort to memorize information) - Slight improvement to working memory LECTURE 14: REWARD AND MOTIVATION Motivation/ motivational drive: Motivation - the drives (wants and needs) that guide behavior Motivational Drive - psychological state that motivates the satisfaction of needs Examples of Motivational Drives: - Hunger - Sex - Thirst - sleep Qualities of Motivational Drives: - Energizing - active behaviors (make you do something) - Directive - guide behaviors towards satisfying specific goals or needs - Persistent - maintain a behavior until you achieve your goal or need - Strength - motives must be strong enough to make you do something Theories of Motivation: 1. Drive Reduction Theory - drives (hunger, thirst, sexual frustration) motivate us to minimize negative feelings and seek pleasure a. Drives motivate us to meet goals that increase our survival and reproduction b. We’re motivated to maintain homeostasis through these drives c. 2. Incentive Theories - there are internal drives and external objects and goals that motivate behavior a. Intrinsic Motivation - motivated by internal goals i. Example: you want to do well in this course to master the material because you’re genuinely interested in it b. Extrinsic Motivation - motivated by external goals i. Example: you want to do well in this course to get an A so grad schools see it Drive reduction theory: - DW - developed intense salt craving and when taken off high-salt diet in the hospital, he died 3 days later - shows how body creates these drives for survival - His adrenal glands (regulate salt) were deficient which was why he craved salt so  much - Hunger - when hungry we’re motivated to eat - If we eat too much our brain will make us not be hungry for a while - Arousal - controls the strength of our drives - Yerkes-Dodson law - performance on tasks increases with arousal up to a certain level until arousal gets too high and then performance decreases - Arousal can shift depending on time of day - Substances (caffeine) and complexity of tasks affects arousal Conflicting drives: - Drives can conflict - Some drives generate an approach to something (food, objects) - Other drives generate avoidance (rude people, scary animals) - Avoidance-Approach Gradient - If you are near feared goal the avoidance is stronger than approach - If you are far from feared goal then approach is stronger than avoidance - Example of feared goal = an attractive person - Scared of rejection so avoid when close - Avoidance gradient is steeper than the approach gradient Incentive Theory: Incentives - internal drives and external objects and goals that motivate behavior a. Intrinsic Motivation - motivated by internal goals b. Extrinsic Motivation - motivated by external goals - People are motivated to satisfy needs for competence and personal control - Rewards undermine people’s feelings that they are choosing to do something for themselves - Primary needs take precedence over secondary needs (Maslow’s Hierarchy of Needs) Reward: 3 Main Components 1. Wanting - the desire to obtain a reward a. Dopamine is responsible for the “wanting” component of reward 2. Liking - feeling of pleasure that occurs when a reward is received a. Endorphins are responsible for “liking” b. Drugs that block endorphins decrease perceived enjoyment of food and other rewards  3. Reinforcement - effects the reward have on promoting behavior a. Thought of as learning b. Animals learn that certain cues signal the availability of a reward and encourage the animal to look for that reward Reward pathways in the brain: dopamine: Reward pathways in the brain - Ventral tegmental area (VTA) - produces dopamine - Nucleus Accumbens (NAcc) - receives dopamine from the VTA, processes reward - Prefrontal cortex (PFC) - links rewards to actions Reward and addiction: - Cocaine, amphetamine, opium, heroin (and other drugs) - exert their effects through actions on the brain reward systems - Reinforce learning between cues in the environment and the feelings and behaviors of liking and/or wanting the drug - Other examples of addiction - Social media - brain releases dopamine when we talk about ourselves - A new TikTok video every scroll encourages us to keep going - Gambling - rewards are unpredictable so we get the dopamine release every time which motivates us to keep gambling (uses variable ratio reinforcement schedule) What motivates eating: - Hypothalamus - crucial brain area involved in eating - Regulates hunger and satiety signals - Hormones - communicate with the hypothalamus to influence eating - Insulin - regulates hunger and eating through its actions in the brain - Insulin decreases blood glucose and suppresses appetite and therefore food intake - Ghrelin - triggers hunger (ghrelin sounds like gremlin - gremlin is hungry) - Leptin - regulates fat - Stored in fat cells, mice that lack this gene become obese - Research found that who are obese and not lacking leptin are resistant to the effects of leptin When eating signals go awry: - Anorexia - by the time of treatment, people with anorexia have extremely low  leptin levels compared to age and BMI matched controls - With treatment and weight gain there is a disproportionate rise in leptin levels What other things motivate eating? - Sight and smell - Flavor - Variety LECTURE 15 SLEEP AND EMOTION: Sleep basics: - We study sleep using an electroencephalogram (EEG) - 1 Hz = 1 cycle/sec Sleep stages: Stage I - lighter sleep, easily woken, EEG wavelengths are lower frequency than wakefulness but still high Stage II - deeper than Stage I, appearance of sleep spindles and K complexes (implicated in memory consolidation), occurs after ~15-20 mins of Stage I Stage III and IV - together form SWS (slow wave sleep), importance for muscle repair, enter Stage III after ~1hr of sleep, alternate between III and IV for ~1hr REM sleep (paradoxical sleep) - energetically expensive (especially compared to other stages - hence the paradox), synapses activated, prevents degradation, strengthens memories, muscles lose tone, sleep paralysis occurs, hallucinations (dreams set in) Why is REM sleep special: REM = rapid eye movement - Makes up ~25% of total sleep - EEG output looks like you’re awake (beta waves) - Nervous system is aroused (HR, breathing) - Time for dreaming - Very important for learning (synapses activated) Dreaming: - Occurs during both NREM and REM (most often in REM) - Often forget dreams (~70% that are remembered have negative content)  - Major Dream Theories - Psychoanalytic Theory - dreams are an important opportunity to work through feelings and drives that aren’t consciously expressed - Information Processing Theory - dreams are an opportunity to process and consolidate information from the previous day - Threat Simulation Theory - brain gets practic handling threatening situations Three major theories of why we need sleep: 1. Preservation and Protection Theory a. sleep evolved as a survival mechanism to conserve energy and protect animals from harm during times when they are most vulnerable. 2. Body-Restoration Theory a. sleep helps the body recover and repair itself, with processes like muscle growth, tissue repair, and protein synthesis occurring primarily during deep sleep. 3. Brain Maintenance Theory of REM Sleep a. REM sleep serves to stimulate neural circuits, promoting brain health and potentially aiding in memory consolidation and learning. Central Brain regions involved in sleep: - Hypothalamus - controls the onset of sleep - Hippocampus - a memory region active during dreaming - Amygdala - an emotion center active during dreaming - Thalamus - prevents sensory signals from reaching the cortex - Reticular formation - regulates the transition between sleep and wakefulness - Pons - helps initiate REM sleep Sleep and the brain: - Suprachiasmatic Nucleus (SCN) - Rhythm generating neurons - Circadian rhythms - Pineal gland - Melatonin Circadian rhythms: - Biological rhythms/biological clock - Circadian = “about a day” - Cycles every 24 hours - Caused by light  - Yawning theory - cooling the brain, empathy Dual process theory - process s and c: Process S (homeostatic Sleep drive) - Steadily increases during waking hours - Negatively associated with alertness and vigilance - ↑ Process S = ↓ Alertness/vigilance - Subjectively feel grouchy - Drops immediately and dramatically with sleep onset - reduces “sleepiness” - Unclear the physiological mechanisms - certain hormones seem important Process C (Circadian drive for arousal) - Numerous physiological/biological cycles - Cortisol (day), growth hormone (night), body temperature (day) - Peaks and troughs throughout the day - Synchronized by the suprachiasmatic nucleus - Particularly sensitive to light, but other cues are involved Controlling sleep-wakefulness: - Caffeine/alcohol - Melatonin - Work - Exercise - Light - Naps - Sleep hygiene - Practices habits that create an environment, both internal and external, that is conducive to restful sleep Imporance of sleep: - Restorative physically and mentally - Crucial for learning and memory - BAD long term effects of disordered sleep (increased risk of hypertension, diabetes, obesity, depression, heart attack and stroke) - Important for regulating emotions (lack of sleep causes an increase in negative moods like anger, frustration, irritability and sadness) What happens if we don’t sleep?  - Randy Gardner - record holder for sleep deprivation (11 days and 25 mins) - Experienced mood swings, hallucinations, paranoia - Memory and attention lapses - Slurred speech and trouble reading and watching TV, trouble using hands after 3 days Lecture 16 smell, taste, and pain perception: General sensory process Physical stimulus → pysciolucal response → sensory experience Physical stimulus = matter of energy influencing the body Physiological response = chemical/ electrical activity within the body Sensory experience = subjective sensation (psychological experience) Senses: 5 Classic Senses: Touch, Sight, Sound, Smell, Tase Other senses: proprioception, vestibular/gravity, tension/stretch, chemoreceptors, time Types of Touch Senses: pressure, temperature, pain, itch - Some sensations are combinations: wet = cold + pressure - Tickle - lightly stoke touch receptor - Itch - lightly stroke pain receptor - Searing hot - you’re cold and you go in something warm (ex: hot tub) Sensor mapping: fingertip, front/back of hand, forearm, back, cheek - what are the differences? - Think of homunculus (ex: fingertips and front of hand have more sensory receptors than back of hand and forearm) - Sensory neurons have some kind of ending that connects to the outside world - senses something mechanical, send to interneuron - SAME mnemonic - Sensory Afferent (to CNS), Motor Efferent (to muscles/glands) Taste sensations: 6 tastes: Sweet, sour, bitter, salty, umami (savory), fat Why do we have these sensations? - Sweet = calories = energy - Fat = energy - Sour = protect from toxic acids, spoiled foods, unripe - Umami = taste of protein to grow and repair tissue - Bitter = is the food poisonous or safe? - Salty = sodium is essential to physiological processes Physiology of Tasting - Dissolving all food into solution (saliva) → taste receptors all chiming in and organize into taste buds - Lock and key → taste buds sense particular flavors - Taste maps are myths → all 6 tastes can be sensed by receptors all over the tongue The Gustator pathway: - Human mouth contains ~5,000-10,000 taste buds evenly distributed over the tongue - Each taste bug includes 50-100 taste receptor cells Gustatory Pathway 1. Taste buds 2. Facial Nerve + Glossopharyngeal nerve 3. Medulla oblongata 4. Thalamus 5. Gustatory Cortex Smell (olfaction): - Airborne odor molecules are inhaled through the nose - Olfactory receptor cells in the nasal cavity are stimulated - Receptor cell stimulation converted to neural signals and go to olfactory bulb - Smell and taste are very closely related - Rodents and bears have much larger olfactory bulbs than humans - rodents/bears need smell more for survival - Sense of smell diminishes over time (old people use more perfume/cologne) Olfactory Neural Pathway: - Olfactory neurons are the ONLY neurons that directly link to the outside world  - Dendrite is directly underneath mucus - Connect the temporal lobe part of neural pathway involved in conscious recognition of smells - Olfaction is the only sense that does NOT go through the thalamus - Amygdala and hippocampus are closely associated regions (this is why smells are easily linked with memories and emotions) Pain: Pain = unpleasant sensory or emotional experience, warns us about actual or potential tissue damage - If you’re born without pain, you will not live more than 5 years usually - C fibers - transmit longer lasting, duller pain - A-delta fibers - fast acting, transmit sharp pain - Delta airlines - fast planes - Nociceptors - pain receptors Gate Control Theory - Why we hold/rub a wound - Spinal cord contains neurological gate that blocks pain signals via larger fibers → allows pain signals to pass to the brain through small nerve fibers Biopsychosocial Approach to Pain - Biological, social-cultural and psychological influences to how we experience pain - Biological influences - activity in spinal cord’s large and small fibers, brain’s interpretation of CNS activity - Social-cultural influences - presence of others, empathy for others pain, cultural expectations - Psychological influences - attention to pain, learning based on experience, expectations LECTURE 17 hearing and psychophsyics: Audition - the sense or act of hearing: Properties of Sound Waves: Frequency - corresponds to our perception of pitch - Length of the sound wave Amplitude - corresponds to our perception of loudness - Height of the sound wave Complexity - corresponds to our perception of timbre (tone quality) - Perceived as sound quality or resonance The ear: - Outer Ear - sound waves are collected - Middle Ear - sound waves are amplified - Inner Ear - sound waves are transduced into coded neural messages Structures of the Ear: - Pinna - visible outer ear, helps pinpoint and locate sound - Auditory Canal - where sound travels to reach the eardrum - Cochlea - a coiled, bony, fluid-filled tube through which sound waves are transduced into nerve impulses - Auditory Nerve - converged nerve cell fibers, sends messages to the thalamus and auditory cortex in the temporal lobe - Semicircular Canals - fluid-filled tubes that help you keep your balance by detecting head rotation - Oval Window - separates inner ear from middle ear - Ossicles - 3 small bones (malleus, incus, stapes) in the middle ear that transmit and amplify sound vibrations - Malleus = “hammer” , Incus = “anvil”, Stapes = “stirrup” Cochlea: - In the cochlea, as distance from the stapes increases, pitch decreases (lower amplitude) Sound - aging, pitch and tinnitus: - Cochlea loses hair cells as you age → decreased sensitivity to higher pitches - Hair cells cannot be replaced - Mosquito noise - used to drive teens from loitering spots (heard by babies and animals but only bothers ages 12-20yrs, not detected by older people) - Tinnitus - constant ringing in ears, caused by damage to the hair cells in the inner ear (caused by aging, loud noises, infections, etc) Localizing Sound Sources - ears on either side of head gives us stereophonic hearing - Timing method - which ear is stimulated first, best with low frequency sounds - Volume method - which ear is stimulated most vigorously, best with high frequency sounds Cochlear implant: Deafness - disruptions in cochlea - Cochlear impact stimulates auditory nerve - Listens for vibrations, turns them into electrical signals and sends those down electrode array that stimulates auditory nerve which sends signal to brain Leacture 18: Vision (part 1): Vision: - Transforms light energy into neural signals - Represents objects in the environment in terms of shape, size, color, and location Light Energy - Hue = the color experienced - Wavelength = distance from one peak to the other - Intensity = determined by the wave’s amplitude The electromaganic spectrum: - Violet has SHORTEST wavelength - Red has LONGEST wavelength Know the parts of the human eye Rods and Cones: - Rods (sense light/dark) - Function in dim light - Detect black and white vision - NOT colors - Necessary for peripheral and twilight vision - Cones (sense colors) - Near center of retina (fovea) - Function in bright light/daylight - Detect fine detail - Enable color perception - Red cones (60%) - Green cones (30%) - Blue cones (10%) Vision in other creatures: Mantis Shrimp - 12 color-receptive cones - +4 UV receptive cones - Can covertly signal (send signals to communicate) to each other for mating - Improves image quality in water - Polarized vision cuts glare - Can move eyes independently of each other Jumping Spider - Have 6 eyeballs, 2 for depth, 4 for movement Nonhuman Primate - Half of females are trichromatic, males are all dichromatic - Why? Evolutionary pressure - different foraging strategies - Trichromatic females forage for berries - need to see when they’re ripe - Dichromatic primates devote more of vision to see prey (hues of browns) Trichromatic theory of vision: - Hermann von Helmholtz - first scientific theory of color vision - 3 types of cones sensitive to different wavelengths of light determine how we perceive color - Combining the wavelengths of red, blue and green - Explains red-green colorblindness Opponent process theory: - Explains colored image that occurs when initial stimulus is gone - 4 basic colors divided into 2 sets: red-green and blue-yellow - Each color opposes the other Focusing vision: - Normal vision - nearby and faraway objects focused on the retina - Nearsighted - faraway objects focused in front of the retina - Farsighted - nearby objects focused behind retina - Accommodation - the lens changes shape to focus near or far objects on the retina - Corrective lenses change the focal point The visual pathway:  - Objects in the right visual field stimulate left half of retinas - Objects in the left visual field stimulate right half of retinas - Axons of ganglion cells form the optic nerve - Retina routes visual information over the optic chiasm (cross-over) to visual area in the thalamus (LGN - lateral geniculate nucleus) LEACTURE 19: Vision (part ii) visual illusions: Evolution of vision: - Vision did not evolve to provide us with a truthful representation of our physical environment but rather evolved to provide us with a useful representation of our physical environment - Seeing vs perceiving - You see before you perceive (image goes through several layers or processing) Light Spectrum - We see a very small part of the light spectrum (only visible light) - Would be too energetically expensive to see the whole spectrum - Bees see UV spectrum - much different than humans - Cats have duller, wider peripheral vision but blurry on sides (bc cats are nocturnal and this type of vision is most useful for them at night) Brain filters out information: - Brain filters out our nose so we do not see it when we are looking around Blind Spot - Spot where the optic nerve exits the eye - No photoreceptors here - creates a blind spot - Whatever information falls in front of the optic nerve doesn’t reach the brain Brain Fills in information: - The brain fills in peripheral vision by inferring information that isn’t directly given - The brain automatically fills in the blind spot by extrapolating surrounding information Top- down vs. bottom up visual perception: Bottom-up processing - uses basic physical characteristics of visual elements (ex: line, edge, shape, color) to group them into a unified whole Top-down processing - in addition to physical characteristics, also uses prior knowledge, context or expectation to interpret complex stimuli Gestalt grouping principles: Set of grouping principles based on the Gestalt theory that the human brain will attempt to simplify complex images by organizing multiple elements into a whole 1. Closure* 2. Common fate 3. Continuation* 4. Similarity* 5. Figure ground* 6. Proximity* 7. Symmetry Illusions: - Hidden (redacted) illusion - Images hidden within other images - Spinning dancer illusion - Dancer can be perceived as moving left or right - Ebbinghaus illusion - Second circle appears larger due to the smaller circles surrounding it even though both orange circles are the same size Deptch perception - ability to see things in 3d to judge distance: - We use monocular or binocular cues to gather information about a given stimulus regarding depth Monocular Depth Cues - depth cues that only need to be perceived with one eye - Occlusion - Relative size - Linear perspective - Texture gradient - Motion parallax Binocular Depth Cues - need to be perceived using both eyes Binocular depth cues: Binocular Disparity - caused by the distance between two eyes, provides each eye with a slightly different image  - Brain compared difference between retinal images to gauge distance Convergence - provides the brain cues about an object’s distance through feedback from eye muscles Represenational illusions - making sense of reality: Physiological vs Cognitive Illusions - Illusions are misrepresentations of reality Physiological Illusions - due to the biology of the eye - Blind spots, afterimage hazes, color reversals, false movements, seeing things further away as smaller (not a representation of reality - not actually smaller) Cognitive Illusions - take advantage of our preconceived representations of reality - Our brain uses cues about how we believe things should be (perceived depth, shadows, and checker boards) - makes us think we see something different from what is really there What vs where pathways: Dorsal “Where” Pathway - tells us spatial location of object, where information is coming from - NOT fooled by illusion Ventral “What’ Pathway - perceptions add up and tells us the final information about what something actually is - fooled by illusion Visual perception: - Object Recognition - easily recognizable across viewpoint and configurations - Object Classification - how would you describe something and its features? - Ex: what makes a chair a chair? - Specialization: Faces - the human (and seemingly primate) brain has specialized systems for face recognition - The Fusiform Face Area (FFA) recognizes faces - Face pareidolia - we perceive faces in random patterns that don’t actually have facial features - The Thatcher Effect - it becomes more difficult to detect local feature changes in an upside-down face despite identical changes being obvious in an upright face - The specialized face systems in our social brain has evolved in a specific way - Our brain fills in the gaps, problems aren’t apparent until our brain decides  something isn’t there Where problems dorsal pathway: Damage to Dorsal Stream - Optic Ataxia - can recognize objects but cannot use information to guide actions, difficulty reaching for objects and incorrect hand orientation - Associative Agnosia - can perceive integrated whole but cannot link to knowledge - Can copy objects but don’t know what it is - “I can see it, i just don’t know what it is” KEY TAKEAWAY: Reality is subjective - Perception is a construction of reality - When image is perceived in the cortex we add layers to it: biases, memories, conscious experience (everyone is different!) - Very different from the actual object