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Chapter 2

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University of Toronto Scarborough
Konstantine Zakzanis

Kharthika Mohanachandran PSYC31H3S WINTER 2012 Zakzanis – Lecture 2/Chapter 2 Notes CHAPTER 2: BASIC CONCEPTS EXAMINING THE BRAIN. - Neurological examinations includes extensive study of brain’s chief product  behaviour - Neurologist studies person’s strength, efficiency, reactivity, and appropriateness of their responses to commands, questions, discrete stimulation of particular neural subsystems, and challenges to specific muscle groups and motor patterns - Neurologist also examines body structures, looking for such evidence of brain dysfunction as welling of retina/atrophied muscles due to insufficient neural stimulation - Scanning techniques began in mid 1970s  imaging has become critical for diagnosis - STRUCTURAL NEUROIMAGING -  Both reconstruct different densities and constituents of internal structures into clinically useful shadow pictures of the intracranial anatomy o COMPUTERIZED TOMOGRAPHY (CT)  first technology sensitive to soft tissue; can see fractures o MAGNETIC RESONANCE IMAGING (MRI)water molecules that have different magnetic properties when in different tissue environments; can localize and identify lesions, atrophy (shrinkage); can look at smaller structures that can’t be viewed on CT  Can show quantified data  brain mapping - NPA  another way to study brain via behavioural product o Involves intensive study of behaviour by means of interviews and standardized scaled tests and questionnaires that provide precise and sensitive indices of behaviour o Takes brain fxn as its point of departure o Findings are interpreted within clinical context of patient’s presentation and other observations - Direct observation is impossible, but goals are set out for this to happen - Newer techniques rely on INDIRECT, typically non-invasive methods  also used by cognitive neuroscientists and NP’ists to examine correlates of behaviour in both patient and healthy populations - Earliest instrument used to measure brain function and still used are ELECTROPHYSIOLOGICAL o Includes EEG, electrodermal activity, and evoked & event-related potential (EP, ERP) o EEG’s have been used to study cognition  i.e. high frequency  associated with attentional activity o Magnetoencephalography (MEG)  cousin of EEG; records magnets rather than electrical fields); therefore, better depths and sensitivity than EEG becoming more commonplace o Electrodermal activity  skin conductance/galvanic skin response  Reflects ANS fxning  emotional responses  Has recognition in absence of conscious perception o ER/ERPs –demonstrate hemispheric specializations; processing speed and efficiency - FUNCTIONAL NEUROIMAGING/ FUNCTIONAL BRAIN IMAGING - o Explore both normal brain functioning and nature of specific brain disorders  Regional cerebral blood flow (rCBF) – one of the older brain imaging tech  reflects brain’s metabolic activity indirectly via magnitude changes of blood flow in different brain regions  inexpensive  Positron Emission Tomography (PET) Kharthika Mohanachandran PSYC31H3S WINTER 2012 Zakzanis – Lecture 2/Chapter 2 Notes  Visualizes brain metabolism directly as glucose radioisotopes emit decay signals  quantity indicates level of brain activity in a given area  Gives valuable info about fxn’ing of diseased brains but also an impt tool for understanding normal brain activity  LIMITATION: reliance on radioisotopes that must be generated in a nearby cyclotron and have only a short half-life; expensive  Single photon emission computed tomography (SPECT)  Similar to PET but CHEAPER  Involves a contrast agent readily available  Helpful in identifying seizure onset  LIMITATION: doesn’t have necessary temporary and spatial resolution for use in activation studies in cognition; limited clinical application b/c most studies report group findings rather than individuals  Functional magnetic resonance imaging (fMRI)  Motor and language mapping  Popular method for investigating traditional psychological processes such as time perception, semantic processing, emotional processing, response inhibition, face recognition, somatosensory processing, sexual arousal, etc.  Affects NP greatly, as well as cognitive neuroscience * BOTH STRUCTURAL AND FXN’L NEUROIMAGING TECHNIQUES LACK INFORMATION ON BEHAVIOUR!* - Invasive techniques such as the WADA TEST and electrical cortical stimulation mapping to minimize surgical risk to these functions identifies cerebral language and memory dominance in neurosurgery o These procedures significantly reduced cognitive morbidity following epilepsy surgery, but have also greatly enhanced knowledge of brain-behaviour relationships o Ie. Atypical language representation  alters expected pattern of NP’l findings even in absence of large cerebral pathology o Generalization by these techniques is limited b/c of atypical fxning of these patients’ diseased or damaged brain  limitation; also b/c affords only a limited range of assessable behaviour due to restrictions of patient responses/short duration of medication effects “BRAIN DAMAGE” AND “ORGANICITY” NEUROPSYCHOLOGY 1.0 - 1930s and 40s and well into 50s  “brain damage” or brain dysfxn as a unitary phenomenon - LH language fxns - Much work on brain damaged patients  based on the assumption that organicity was characterized by one central & therefore universal behavioural defect - Teuber  believed that this heuristic formulation was true - Many efforts to try proving this, but it couldn’t be validated b/c no one behavioural phenomenon could be found that was shared by all brain injured persons but by no one else o The one-dimensional approach to NP NEUROPSYCHOLOGY 2.0 th - Next evolutionary stage; existed until last quarter of 20 century o “brain damage” still as a unitary phenomenon but given measurable extension  not on/off, but can vary along a single dimension Kharthika Mohanachandran PSYC31H3S WINTER 2012 Zakzanis – Lecture 2/Chapter 2 Notes o Provided by Karl Lashley his Law of Mass Action and Principle of Equipotentiality  knew that even in rats, i.e. visual discrimination, was compromised by lesions involving well-defined cortical areas of the brain  in addition to Lashley, L.F. Chapman & Wolff  concluded that sheer extent of cortical loss played a greater role in determining the amount of cognitive impairment than the site of lesion o “Brain damage” / “organicity”  took on a one-dimensionality and lack of specificity similar to that of the concept “sick”  Neither had etiological implications  Neither implies presence or absence of any symptom or sign  Neither predicted anything based on either term  Brain damage as a measurable condition that remains a vigorous concept, reflected in may test and battery indices, rations, and quotients that purport to represent some quantity or relative degree of neurobiological impairment o Behavioural repercussions of brain damage vary by nature, extent, location, duration of the lesion; with age, sex, physical condition and psychosocial background and status of the patient; with individual neuroanatomical and physiological differences  impt you have normative data o When dealing with individual patients, concept of brain damage only becomes meaningful in terms of specific behavioural dysfunctions and their implications regarding underlying brain pathology - The pressure that changed CNP was NEW TECHNOLOGY (i.e. imaging) NEUROPSYCHOLOGY 3.0 - Latest stage - CT & MRI changed referrals for NPA - No need to test for “organicity” when it can be determined medically - NP’ists called to “characterize” cognitive impairment via o Breadth (global vs. Attentional) o Severity (very poor to excellent attentional abilities) o consistency with diagnosis o veracity (forensics) truthfulness of a person’s responses; are they malingering/exaggerating their responses particularly in a forensic setting o By knowing individual PROFILES, we can make a diagnosis DIMENSIONS OF BEHAVIOUR - Behaviour is conceptualized into 3 functional systems o 1. Cognition: information-handling aspect of behaviour  Have received the most attention  Partly b/c they are readily conceptualized, measured, and correlated with neuroanatomically identifiable systems  Partly b/c cognitive defects of brain injured patients can figure in their symptomology  Partly b/c structured nature of most medical and psych’l examinations doesn’t provide much opportunity for subtle emotional and control deficits to become evident o 2. Emotionality: concerns feelings and motivation o 3. Executive Functions: how behaviour is expressed/controlled  How cognition and emotionality come together Kharthika Mohanachandran PSYC31H3S WINTER 2012 Zakzanis – Lecture 2/Chapter 2 Notes - Disruptive effects of most brain lesions, regardless of size or location, usually involve all three systems - Greek philosophers  first to conceive of a tripartite division of behaviour o Postulated that different principles of the “soul” governed that rational, appetitive, and animating aspects of behaviour – inferred organization of behaviour Cognitive Functions. - Not directly observed; are inferred from behaviour - 4 major classes of cognitive functions  all have their analogues in computer operations of input, storage processing, and output o 1. Receptive Functions  Involve abilities to select, acquire, classify, and integrate info  Sensory Reception.  Perception. o 2. Memory and Learning  Information storage  i.e. A.R. Damasio, H. Damasio, and Tranel – describe memory (info storage and retrieval) components of visual recognition o 3. Thinking  Mental organization and reorganization of information  i.e. A.R. Damasio, H. Damasio, and Tranel also call attention of role that thinking (concept formation) plays in the seemingly simple act of identifying a visual stimulus by name o 4. Expressive Functions  Means via information is communicated or acted upon - Each of these 4 are distinct classes of behaviours but they all work in close, interdependent concert  all are bound together –different facets of the same activity o Use practical applications and theory-making benefit from our ability to differentiate various components of behaviour (both memory and thinking) - Attentional functions differ from functional groups listed above b/c they underlie/maintain the activity of the cognitive functions  attn’l fxns serve as command operations calling one or more cognitive fxns into play  classified thus as mental activity variables - Cognitive activity –originally associated with a single fxn, intelligence o Has now become clear that behaviour measured by “intelligence” tests involves specific cognitive and executive fxns o IQ = a derived score used in many test batteries designed to measure a hypothesized general ability, intelligence  b/c of multiplicity of cognitive fxns assessed in these batteries, IQ scores are NOT useful in describing cognitive test performances;  In NPA, IQ =unreliable indices of neuropathic deterioration  IQ may obscure selective defects in specific tests  IQ scores are meaningless; often misleading CLASSES OF COGNITIVE FUNCTIONS. - Studies of blindsight (perception w/o awareness) or covert face recognition in prosopagnosia indicate how perception and awareness each depend upon intercellular networks where info is transferred in both parallel and serial processing networks - Receptive Functions.  Entry of info into central processing system proceeds from sensory stimulation (i.e. sensation, through perception  concerns integration of sensory impressions into psychologically meaningful data into memory) Kharthika Mohanachandran PSYC31H3S WINTER 2012 Zakzanis – Lecture 2/Chapter 2 Notes o Ie. Light on retina involves a visual sensation  Components of sensation can be splintered into even smaller receptive units  Nobel Prize – Hubel & Weisel  neurons in visual cortex are arranged in columns that respond to stimuli presented at specific locations and at specific orientations  Sensory Reception.  Involves arousal process triggers central registering, analyzing, encoding and integrating activities  Sensations are rarely experienced alone & perception depends on attentional factors greatly  Most sensory data enter NB’l systems as perceptions already endowed with previously learned meanings  NPA focuses on the 5 senses: sight, hearing, touch, taste, & smell  Berthoz (2000)  other senses i.e. movement, space, balance & effort  Perception and the agnosias  i.e. perception involves encoding impulses transmitted by the aroused retina into a pattern of hues, shades, and intensitites recognized as a daffodil in bloom  Involves active processing of continuous torrent of sensations o As well as their inhibition or filtering from consciousness o Comprises of many successive stages  1 processing sequence  Involves simplest physical or sensory characterstics: o Color o Shape o Tone  Serve as foundations for more complex, “higher” levels of semantic and visuoconceptual processing that integrate sensor stimuli with one another & organism’s past experiences o Corticol distribution and complexity of perceptual activities make them highly vulnerable to brain injury o Perceptual defects by brain injury can occur through loss of primary sensory input such as vision or smell and also through impairment of specific integrative processes  Sensation and perception have its own functional integrity  Perceptual activities include awareness, recognition, discrimination, patterning, and orientation  Impairment to perceptual integration  disorders of recognition, the agnosias = NO KNOWLEDGE o Teuber’s definition: “a normal percept stripped of its meanings” o True agnosia: whole perceptual field; right or left –no knowledge o vs. Unilateral imperception: patient unaware of sensations or events on only one side  i.e. propagnosia Kharthika Mohanachandran PSYC31H3S WINTER 2012 Zakzanis – Lecture 2/Chapter 2 Notes  a visual agnosia  2 diff forms: o 1) inability to recognize familiar faces o 2) inability to recognize unfamiliar faces  Usually does NOT occur together  Can occur with or without intact abilities to recognize associated characteristics o Ie. Facial expressions, age, sex  thus subcategories o E. Goldberg  divided agnosias into two main categories  1. Associative agnosias – breakdown in one or more aspects of patient`s information store or “generic” knowledge  2. Apperceptive agnosias – due to higher level perceptual disturbances MEMORY. - Memory is a cortical network, an array of connective links formed by experience b/w neurons of the neocortex –Joaquin M. Fuster, 1995 - Central to all cognitive fxns; memory, learning, and intentional access to this knowledge store - NP’ists are very good at measuring memory - Via studying amnesic and degenerative disorder patients, memory can be divided into TWO long-term storage and retrieval systems o 1. Declarative (Explicit) Memory.  Deals with facts and events; available to consciousness  Mayes divides declarative memory into:  Semantic memory – facts  Episodic – autobiographic memory o 2. Nondeclarative (Implicit) Memory.  “nonconscious”  Mayes divides nondeclarative memory into:  Item-specific implicit memory (ISIM)  Procedural implicit memory o Mayes therefore had four long-term storage systems PLUS 1 for short-term  Working memory (short-term memory)  supported by neuroimaging studies - July 25, 2002  Tulving had counted 134 different named types of memory Declarative (EXPLICIT) Memory. - This refers to remembering information, objects and events - What patients refer to when thinking they have memory problems - The “memory” of common parlance - Always involves awareness - Demitrack et al. (1992)  explicit memory involves a conscious and intentional recollection process Stages of Memory Processing - 3 kinds of memory are distinguishable; 2 are stages of short-term storage - Short-term memory is also essential for consolidation process The stages. 1. Registration (Sensory) Memory. a. Holds large amounts of incoming information briefly (for seconds) in sensory store b. A selecting and recording process where perceptions enter memory system (not strictly a memory or perception fxn) Kharthika Mohanachandran PSYC31H3S WINTER 2012 Zakzanis – Lecture 2/Chapter 2 Notes c. Involves programming of acquired sensory response patterns in recording and memorizing center of the brain d. Early stage processing via sensory modality can be seen by either: i. Iconic memory  visual image lasting for 200 msec ii. Echoic memory  auditory replay lasting up to 2000 msec e. Affective, set (perceptual and response predisposition), and attn-focusing components of perception play an integral role in this stage f. Info being processed is either done as short-term memory or it quickly decays 2. 2A. Immediate memory a. First stage of short-term memory (STM) storage b. Temporarily holds info retained from registration process c. STM may be equated to simple immediate span of attn d. Serves as a limited capacity store where info transfers to a more permanent store  as a limited capacity retrieval system e. Handles about 7 bits of info at a time, give or take 2  restricted holding capacity imposes severe limitations on amount of info we’re able to perceive, process, and remember (G.A. Miller) f. Of sufficient duration to enable a person to respond to ongoing events when more enduring forms of memory have been lost g. Last about 30 seconds to several minutes h. Hypothesized that working memory consists of two subsystems i. Phonological loop –processes language ii. Visuospatial sketch pad –for visuospatial data iii. Fxn of working memory: to hold info in mid, to internalize info, and to use that info to guide behaviour without the aid of or in absence of reliable external cues
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