Midterm One Review.docx

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Giampaolo Moraglia

Midterm One Introduction to Sensory Mechanisms Sensation, Consciousness, and Mind  Sensory processes require active exploration o Use conscious and unconscious processes  Sensory inputs enter the conscious-thought-mind (black box) o Sensory inputs = tactile, auditory, visual, etc  With time, build sensory input and create memories which develops “me”  Mind is the center of consciousness that generates thoughts, feelings, ideas, and perceptions, and stores knowledge and memories Doubling of Consciousness  Inputs processes at different speeds even though seem simultaneous o Brain processes audition faster than vision  If disconnect between sensory modalities, have doubling of consciousness  Déjà vu = one modality says happening now and another says happening in past, when it is actually happening for first time o Strange feeling  “the present has occurred in the past”  Jamais vu = feeling that happening for first time, even though already happened o Strange feeling  “unfamiliar about a familiar situation” o More rare  Both these phenomena can occur in normal by are commonly associated with temporal lobe epilepsy  Role of temporal lobe (temporal cortex)  disconnect between causes doubling of consciousness o Connects auditory, visual, olfactory, vestibular, spatial, and touch sensations o Associates with emotions (through amygdala) o Forms contextual memories (through hippocampus) Sensory Deprivation Syndrome  Develops following prolonged deprivation of sensory inputs  Ex. post incarceration syndrome o Incarceration = confinement  Some of features: hallucinations, poor social skills, drug abuse, personality disorders ‘Self’, Phantom and Neglect  Phantom limb syndrome: develops most often following traumatic amputation (no time to mentally prepare) o Ex. car accident where hand crushed and goes unconscious, then wakes up with no hand  The limb (amputated) “co-exists” as normal (ie. is there with rest of body)  The limb has “telescoped/shrunk” (ex. fingers at shoulder)  The limb exists close to another body part that was not related earlier (ex. fingers attached to face and when stimulate face, feel stimulating hand)  Neurons from hand move and get input from face because close to face area in brain  The limb (amputated) is “paralyzed” (more agony therefore have to use behaviour therapy to realize not there  The limb (amputated) is “painful”  many behavioural interventions required  No drugs will work because limb doesn’t exist  Ex. thought fingers pressing into palm therefore put normal hand in box with mirror and amputated limb in other box  get to clasp and unclasp hand to relieve pain  Unilateral neglect (or hemineglect): when the part of “self” does not belong to me o Accompanying damage to the right parietal lobe o Left half of body does not belong to “me” (ie. neglect existing limb) o Left side of space doesn’t exist o If damage to left parietal lobe, they do not develop hemineglect o Differs from hemi-anesthesia because no sensations to one side (sensory problem) whereas hemineglect is an attention problem Sensation, Perception and Cognition  Sensation  perception  cognition  Sensation: basic experience (unelaborated) or awareness as stimuli fall on sensory system  not categorized o Ex. “I feel something” or “I hear some sound”  Perception: a conscious (elaborated) sensory experience  is recognized o Ex. “I feel something smooth” or “I hear a voice”  Cognition: placing an object into a category o An outcome of perception, reasoning, learning, and memory o Ex. “This is an apple” or “This is my friend’s voice”  Processing times: input  experiencing a stimulus at the basic level (sensation) and held in sensory memory for about 0.25 seconds  filtering inputs (perception) and held in short term memory for about 0.5 minutes  further filtering, representing, clustering, binding, recalling (cognition) and held in long term memory/permanent memory for future use o May take several minutes to learn the first time Bottom-Up and Top-Down Processing  Bottom-up processing is recognizing based on analysis of details in the incoming information o There is not much prior “knowledge” of the object o Ex. studying the details of the picture before recognizing the picture as “rat” or “man”  Top-down processing is recognizing based on prior “knowledge” of the object o Ex. recognizing an object as “rat” or “man” after having seen picture of “rat” or “man”  Ambiguous pictures: we tend to see what we have previously seen upon being shown an ambiguous image (ie. top-down) The Man who Mistook His Wife for a Hat  How do you explain Mr. P’s behaviour? o While talking to Dr. Sacks he would look at his ears, nose, lips, etc as though they were strange objects o When asked to identify gloves he described them as series of pouches, meant to save money etc. but not as “gloves” o He talk to parking meters and fire hydrants as though they were school kids o When asked to point to his shoes he pointed to his feet o He could not recognize any of his pupils by face, but only by their voice o Could describe the geometry of a flower but could not recognize it  When he was asked to smell, he knew it was a rose (ie. olfaction intact) o While eating, dressing, or even painting, he had to hum a tune or sing a song related to it to accomplish it  Doesn’t understand when has finished any task o When shown a desert scene he saw a river in it, houses and gardens with people partying (while it only contained unbroken desert dunes) o Mistook his wife for a hat  Visual Form Agnosia – inability to recognize objects o Visual pathway and connection bad o Not using top-down processing properly o Can connect auditory inputs o Cannot recognize objects/shapes o Not analyzing as a whole, he isn’t connecting what he is seeing to what he is feeling (touch and visual) o Can perceive but not recognize objects (ie. perception intact, but recognition not) Agnosia Specific to Faces – Prosopagnosia  Inability to recognize faces  Patient is able to identify the individual objects that make up the face, but not the face as “Face”  However, most often they recognize it as “Face” but cannot recognize who it belongs to  Follows damage to the “face areas” of the temporal cortex (ie. fusiform face area) o FFA is located on the inferior surface of the temporal cortex o Looks like a spindle o Most on right side (left is still involved just not as much) Serial, Parallel Processing and Binding Problem  All senses except olfaction go through thalamus  How impulses are processed o Serial system (former model): information flows among the components and remains confined to that pathway o Parallel system (current model): information flows among the components but is not confined to that pathway  Not all steps needed  Can have retrograde connections  Binding problem/ principle: complex stimuli are perceived as individual whole not as combinations of independent sensations o The process by which binding occurs o Entire thing is one single whole sensation (binding all sensory inputs)  Binding problem is not the same as problem in binding o There is not deficit in binding, just how binding occurs  Perception (and cognition) is considered a binding success: all the pieces and aspects of an image are bound together at the same time, despite being processed by many different neurons in several cortical areas at different areas  Problem in binding when doubling of consciousness occurs (ie. déjà vu or jamais vu) Binding Failure  If an image is stabilized on the retina, the neurons would adapt  Images A and B: stabilized on the retina with an eye-tracking device o Fading/melting, fragmentation, breakdown and blackouts occur  Image C: more complex logical problem o Breakdown may follow a mosaic-pattern during a migraine or epileptic seizure o Only possible if there is top-down processing and a specific memory for the face  Complex image fragmentation follows Gestalt-like pattern o Images A-D: meaningful Gestalt fragments preserved during image breakdown o Image E: stabilized images of binocularly fused images of left and right eye show breakdown of the fused image and not the monocular form ruling out a peripheral process (receptor)  Used a stereoscope to show each eye sees a particular image  Together see a fused image  Shows higher processing The Perceptual Process  Sequence of processes that work together to determine our experiences of and reaction to stimuli in the environment  Process divided into 4 categories: stimulus (environmental stimulus  attended stimulus  stimulus on receptors)  electricity (transduction  transmission  processing)  experience and action (perception  recognition  action), and knowledge  Stimulus refers to what is out there in the environment, what we actually pay attention to, and what stimulates our receptors o Environmental stimulus: all of the things in out environment we can potentially perceive o Attended stimulus: the stimulus that a person is attending to at any given point in time  Changes from moment to moment as person shifts their attention o Stimulus on receptors: when person looks directly at stimulus which creates image of stimulus on retina (called a representation of the stimulus)  Electricity refers to the electrical signals that are created by the receptors and transmitted to the brain o Everything we perceive is based on electrical signals in our nervous system o Transduction: transformation of one form of energy into another form of energy  Occurs in nervous system when energy in environment is transformed into electrical energy  Ex. pattern of light on retina created by stimulus is transformed into electrical signals in thousands of visual receptors o Transmission: electrical signals activate other neurons, which in turn activate more neurons  Eventually these signals travel out of the eye and are transmitted to the brain o Processing: involves interactions between neurons  Signals that originate in receptors travel through maze of interconnected pathways between receptors and the brain and within the brain  In the nervous system, the original electrical representation on the stimulus that is created is transformed by processing into a new representation of the stimulus in the brain  Experience and action refers to our goal – to perceive, recognize, and react to stimuli o Backstage activity of transduction, transmission, and processing is transformed into things we aware of o Perception: conscious sensory experience  Occurs when electrical signals that represent the stimulus are transformed by brain into person’s experience of seeing stimulus o Recognition: our ability to place an object in a category that gives it meaning o Action: includes motor activities such as moving the head or eyes and locomoting through the environment  Action is an important outcome of perceptual process because of its importance for survival (ie. early in evolution of animals the major goal of visual processing was to help animal control navigation, catch prey, etc. not the see picture)  The fact that perception often leads to action means that perception is a continuously changing process  Knowledge refers to knowledge we bring to the perceptual situation o Can have its effect at many different points in the process o Bottom-up processing: incoming data provides starting point for perception  Essential for perception because the perceptual process usually begins with stimulation of receptors o As complexity of stimulus increase, role of top-down processing increases How to Approach the Study of Perception  Role of perceptual research is to understand each of the steps in the perceptual process that lead to perception, recognition, and action  Perception has been studied using two approaches: psychophysical approach and physiological approach  Psychophysical approach to perception involves measuring relationship between stimuli (physics) and perception (psycho)  Physiological approach to perception involves measuring relationship between stimulus and physiological processes and between physiological process and perception o Physiological processes are most often studied by measuring electrical responses in nervous system, but can also involve studying anatomy or chemical processes  Cognitive influences on perception: how the knowledge, memories, and expectations that a person brings to a situation influences their perception o Study by measuring how knowledge and other factors affect the relationship between stimuli and perception, stimuli and physiological processes, and physiological processes and perception Epistemology and Gestalt  Epistemology deals with the process of bringing the outside world to the inside mind  The Empiricist emphasizes that sensory information alone is not enough for a rich perceptional experience, it is driven by some prior knowledge o Infant’s world: “blooming, buzzing confusion” (ie. random and chaotic because there is lack of prior knowledge) o Baby’s world: “more structured” o Adult’s world: “orderly”  Structuralism: perceptions are sum of individual sensory elements  Empiricism: prior experience is vital (learning)  nurture  Apparent movement: illusion of movement between two stimuli that occurs when two stimuli that are in slightly different positions are flashed one after another with the correct timing o Actually no movement, just two stationary stimuli flashing on and off o Wondered how movement be caused by sensations since there was no stimulation in the space between the two stimuli, and therefore no sensation o Began the questioning of structuralist principles  Gestalt agrees with Empiricists that prior knowledge is important in perception however, innate abilities rather than learning is important  nature  In Gestalt, whole is different from sum of individual elements o Rejected idea that perception is built up of sensations, and proposed principles called laws of perceptual organization Gestalt Laws of Perceptual Organization  Perceptual organization involves the grouping of elements in an image to create larger objects  Pragnanz (good figure or simplicity): every stimulus pattern is seen in such a way that the resulting structure is as simple as possible o Central law of Gestalt psychology o Ex. in Olympic symbol see 5 rings, not a more complicated shape  Similarity: similar things appear to be grouped together o Ex. if see red and blue circles in alternating lines, think that there are columns of circles o Grouping also occurs for auditory stimuli  Good continuation: points that, when connected, result in straight or smooth curving lines are seen as belonging together, and the lines tend to be seen in such a way as to follow the smoothest path o Ex. Celtic knot is seen as interweaved pattern, not group of broken lines  Proximity: things that are near each other appear to be grouped together  Common region: elements that are within the same region of space appear to be grouped together o Common region overpowers proximity  Uniform connectedness: a connected region of visual properties, such as lightness, colour, texture, or motion, is perceived as a single unit  Synchrony: visual events that occur at the same time are perceived as belonging together  Common fate: things that are moving in the same direction appear to be grouped together o Common fate is like synchrony in that both principles are dynamic, but synchrony can occur without movement, and the elements don’t have to change in the same direction as they do in common fate  Meaningfulness or familiarity: things that form patterns that are familiar or meaningful are likely to become grouped together Perceptual Segregation: How Objects are separated from Background  Perceptual segregation: the perceptual separation of one object from another  The question of what causes perceptual segregation is often referred to as the problem of figure-ground segregation o When we see a separate object, it is usually seen as a figure that stands out from its background, which is called the ground  One way Gestalt psychologists studied the properties of figure and ground was by considering patterns like the reversible figure ground (ie. vase or face)  Properties of figure and ground: o Figure is more “thing like” and more memorable than the ground o Figure is seen as being in front of the ground o Ground is seen as unformed material and seems to extend behind the figure o The contour separating the figure from the ground appears to belong to the figure  border ownership  Factors which determine which area is figure: o Regions in the lower part of a display are more likely to be perceived as figure than regions in the upper part (no left- right preference) o Symmetrical areas, smaller areas, vertical-horizontal cross, and meaningful areas are more likely to be perceived as figure The Gestalt “Laws” as Heuristics  Reject the term law because the rules of perceptual organization don’t make strong enough predictions to qualify as laws  More accurately described as heuristics – rules of thumb that provide a best-guess solution to a problem  Algorithm: a procedure guaranteed to solve a problem (ex. procedure for addition) o In contrast, heuristic may not result in a correct solution every time, but they are faster  The fact that heuristics are usually faster than algorithms helps explain why the perceptual system is designed to operate in a way that sometimes produces errors Unimodal and Bimodal Binding  Unimodal binding: binding within a particular sensory modality (ie. vision, audition) o Unimodal visual binding tells us that this is “blue banana”, etc. o Binding failure  colour or object agnosia o If binding problem, go with shape not colour  Multimodal binding: binding between multiple sensory modalities (ie. vision + audition  audio-visual binding)  Multimodal integration and audiovisual simultaneity: to perceive the auditory and visual aspects of a physical event as occurring simultaneously o Although the time for processing sound is 30-50ms less compared to light stimulus, the brain recalibrates and makes adjustment o Speech perception is multimodal: visual and auditory inputs are bound o McGurk effect: sound perception is effected by both auditory and visual stimulations o Ventriloquist effect: mislocalizing sound source to a distant object  Clinical conditions associated with audiovisual binding failure are autism and schizophrenia o Schizophrenia is emerging as a major multisensory binding-failure disorder  Pulvinar: important thalamic nucleus required for binding o Largest thalamic nucleus in humans (almost 2/5) o Involved in feature binding:  Inter-hemispherical  Intercortical (association, sensory, motor)  Sensory cortex-amygdala (fear responses to threatening stimuli) o Clinical implications: drastically smaller volumes of pulvinar associated with schizophrenia and autism (lack of binding) Non-Nested and Nested Hierarchy  Non-nested hierarchy: ‘pyramidal’ structure the ‘top’ houses the conscious awareness, “Me” f o Each layer represents a different part so they are discrete o Clear distinction between higher and lower sensory processes o Each doll level still represents “Me”  Nested hierarchy: no clear distinction between the hierarchic system o “I” am represented at every level o Way of representing consciousness Attention and Perceptual Binding  Pre-attentive perception: prior to real attention o Identify the odd line (one red line or one horizontal line): the line pops out, no search required  Don’t require much attention  Feature integration, conjunctional perception, and binding problem o Identify the odd line (half lines horizontal and half vertical): must bind attention and colour together  Integrate features and conjunctional perception  Must use attentive serial search  Selective attention: focusing on specific objects  Divided attention: dividing attention to several objects at one time o Divided attention may be helpful in multi-tasking but could be risky  Attention and perception: attention is very important for perception o Stimulus that is not attended is not perceived, even if not in full view  intentional blindness  Ex. asked to count number of passes and miss gorilla in crowd  Normal (ie. all have) o People often have trouble detecting change even though its obvious when you know where to look  change blindness  Inattention and neglect: right side of body has attention from both right as well as left parietal lobes, but left side of body has attention only from right parietal lobe o Thus, lesion of right parietal lobe  neglect (left side) o And, lesion of left parietal lobe seldom  neglect (right side)  Due to right parietal lobe compensating for left lesion  Inattention and “pseudo neglect”: normally we are right brain dominant for spatial attention (attend to left space)  “pseudo neglect” for right side o Attention stronger on left because from both lobes, whereas right from only one lobe o Left ½ of image biases us more than right ½ therefore a line that is dark on left looks darker than a line with dark on right Attention and Perceiving the Environment  Why selective attention is necessary: to deal with the issue of overloading your brain with too much incoming stimuli, the visual system is designed is designed to select only a small part of this information to process and analyze o One of the mechanisms that help achieve this selection is the structure of the retina, which contains the all cone fovea  This area supports detail vision, so we much aim the fovea directly at objects we want to see clearly  How selective attention is achieved: eye movement – scanning a scene to aim the fovea at places we want to process more deeply o More to attention than eye movements (ie. can pay attention to things that are not directly in our line of vision or can look directly at something without paying attention) o There is a mental aspect of attention that occurs in addition to eye movements  Measuring eye movements: eye trackers determine the position of the eye by taking pictures of the eye and noting the position of a reference point o Fixations are places where the eye pauses to take in information about specific pats of the scene o The lines connecting the dots are eye movements called saccades o A person makes about 3 fixations per second  What determines how we scan a scene: looking behaviour depends on a number of factors, including characteristics of the scene and the knowledge and goals of the observer o Stimulus salience: refers to characteristics of the environment that stand out because of physical properties such as colour, brightness, contrast, or orientation  Areas with high stimulus salience are conspicuous  Capturing attention by stimulus salience is a bottom up process – it depends solely on the pattern of stimulation falling on the receptors  Saliency map takes into account colour, contrast, and orientation of an image o Knowledge about scenes: the knowledge we have about the things that are often found in certain types of scenes and what things are found together within a scene can help determine where we look o Nature of the observer’s task: when a person is carrying out a task, the demands of the task override factors such as stimulus saliency  Person fixates on few objects or areas that are irrelevant to the task and that eye movements and fixations were closely linked to the action the person was about to take o Learning from past experience: observers use learning about regularities in environment to determine when and where to look for something Perception Can Occur Without Focused Attention (Expt)  Observers looked at + on the fixation screen, then saw the central stimulus – an array of 5 letters – and were instructed keep looking at the centre of the array of letters  On some trials, all of the letters were the same and on others one of the letters was different from the other four  Letters followed immediately by the peripheral stimulus – either a picture of a face or a disc that was ½ green and ½ red, which was then masked  There were 3 conditions: o Central task condition: observer’s task is to indicate whether all of the letters are the same and the face or disc is not relevant o Peripheral task condition: observer’s task is to indicate whether a face flashed off the side is male or female, or if a disc flashed off to the side is red- green or green-red and the letters are not relevant o Dual task condition: observers are asked to do both  One result was that when observers only had to do one task at a time they performed well  In the dual task condition, performance on the faces was just as high as in the peripheral task condition which indicates that it is possible to take in information about faces even when attention is not focused on faces o Low percent of correct answers with disc o Faces are meaningful, and have a great deal of experience dealing with them o Also, we process faces as a whole, without having to perceive individual features o Makes it possible to categorize with out paying attention Does Attention Enhance Perception?  Effects of attention on information processing: in expt with precueing (ie. shown arrow indicating the side of the stimulus the target would appear), reaction times were much higher in valid trials rather than invalid trials (ie. higher when cue was correct direction) o Shows that information processing is more effective at the place where attention is directed o Enhancing effect of attention spreads throughout object (ex. if paying attention to one spot in rectangle, whole rectangle is given higher amount of attention)  Effects of attention on perception: observer views 2 stimuli and told to pay attention to one of them, then judge which one is brighter, with the goal being to determine whether the observer reports that the attended stimulus appears brighter when the 2 stimuli have the same intensity o New study used in order to reduce the possibility that bias could occur because of observers’ preconceptions that used grating stimuli with alternating light and dark bars  Interested in determining whether attention enhanced the perceived contrast between bars  Higher perceived contrast would mean there appeared to be an enhanced difference between light and dark bars  Instead of asking observers to judge contrast of stimuli, asked to indicate orientation of the grating that had higher contrast which reduced bias  Before gratings presented, a small dot flashed on left or right to shift attention  When there was a large difference in contrast between two gratinds, the attention capturing dot had no effect  When gratings identical, the one that had more attention appeared to have more contrast Attention and Experiencing a Coherent World  Function of attention to help create binding, which is the process by which features (ie. colour, form, motion) are combined to create our perception of a coherent object  Binding problem: the problem of how neural activity in many separated areas in the brain is combined to create our perception of a coherent object  Feature integration theory: describes the processing of an object as occurring in two stages o First stage is the preattentive (doesn’t depend on attention) where object broken down into features such as colour, location, orientation o Second stage is focused attention stage (depends on attention) where features are recombined, so we perceive object as whole  Process of binding linked to physiology in this stage because object causes activity in both what and where stream  Attention is glue that combines info from what and where streams and causes us to perceive all of features to be combined at a specific location o With multiple objects, we need to focus our attention on each object in turn o Illusory conjunctions: features associated with one object can be incorrectly associated with another object  Reason they occur is that stimuli presented rapidly, and the observer’s attention is distracted by focusing on something else o Visual search: look for an object among number of other objects  Conjunction searches good for studying binding because finding the target involves focusing attention at a specific location  Conjunction searches activate parietal lobe (where stream)  Physiological approach to bindings, the synchrony hypothesis, states that when neurons in different parts of the cortex are firing to the same object, the pattern of nerve impulses in these neurons will be synchronized with each other o Paying attention to particular object many increase synchrony among neurons representing object Attention Failure and Simultanagnosia  Cannot grasp the whole scene  Either fixes to one component of the scene (ie. in picture of pyramid, focuses on one block of pyramid) or cannot bind several components together  binding failure and simultanagnosia  Due to bilateral lesion of parietal lobe (Baliant’s syndrome)  caused by stroke Eye Movement and Selective Attention  Eye movements are very important for selective attention and perception  Saccades: swift, jerky scanning movements (ex. reading, viewing a room, viewing a picture)  In prosopagnosia, saccades while viewing a face are defective  Saccades are also defective in Baliant’s syndrome Blind sight  Ability to respond to visual stimulus without perceiving it consciously o Occurs following primary visual cortex damage (subconscious vision used)  Action blindsight (the most common): patients are able to accurately act upon blind field stimuli (ie. by pointing, grasping or cascading towards them)  Attention blindsight: they do not see but “sense” or “feel” something moving  Agnosopsia: cannot see, do not know what it is, but can discriminate form (ie. face) and wavelength (colours) above chance level o Ie. Can match colours, cannot name  Affective blindsight: face is particularly perceived as though “there may be something there” above chance level, especially when there is fearful expression in the face  Possible explanations: o Residual neurons in the damaged V1 may still be functioning  “degraded vision” o Direct pre-existing connections between brain-stem structures, LGN, pulvinar and extra striate cortex (circumventing V1)  “higher association areas” have direct connections to subcortical areas o Plasticity in the surviving neuron pathways  will not have blindsight few days after stroke, but will in few years because secondary connections strengthen due to plasticity o Rewiring of pre-existing brain-stem, LGN, pulvinar, and extrastriate cortical connections Cortical and Subcortical Organization of Sensory Processes  Areas: certain areas in the cortex have specific functions (ex. sensory cortex, motor cortex)  Columns: neurons with similar properties grouped
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