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Chapter 2

PSYC31 - Clinical Neuropsychology Ch. 2

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Pare, Dwayne

PSYC31 – Chapter 2: Basic Concepts Examining the Brain  Historically, the clinical approach to the study of brain functions involved the neurological examination, which includes study of the brain’s chief product- behavior  Neuropsychological assessment is another method of examining the brain by studying its behavioral product, but in far more detail than what is covered in the mental status portion of a neurological exam  Neuropsychological assessment relies on many of the same things as psychological assessment and involves the intensive study of behavior by means of interviews and standardized test and questionnaires  Neuropsychological assessment is a means of measuring in a quantitative, standardized fashion the most complex aspects of human behavior  In a broad sense, a behavioral study can be considered neuropsychological so long as the questions that prompted it ultimately lead relate to brain function Laboratory Techniques for Assessing Brain Function  Earliest instruments for studying the brain function that remain in use are electrophysiological  These include EEG, EP, ERP, and electrodermal activity  EEG frequency and patterns are affected by many brain diseases and have been used to study aspects of normal cognition o EEG is especially useful in diagnosing seizure disorders and sleep disturbances and for monitoring depth of anesthesia  EP and ERPs can be used to identify hemispheric specialization and assess processing speed and efficiency  MEG records magnetic fields and has been used to examine brain functions in patients and healthy volunteers o Has higher resolution than EEG o Can more precisely identify the source of epileptic discharges in patients with a seizure disorder o This technique is not entered into regular clinical usage o EEG and MEG are not good with spatial resolution  Electrodermal activity reflects autonomic nervous system functioning and provides a sensitive and robust measure of emotional responses and feelings  One of the older functional brain imaging techniques, regional cerebral blood flow (rCBF) reflects the magnitude of blood flow in different brain regions o Inexpensive means for visualizing and recording brain function  CT and MRI techniques reconstruct different densities and constituents of internal brain structures into clinically useful 3D pictures of the intracranial anatomy  Higher magnet strengths for MRI have allowed more fine-grained visualization of neural structure  A CT might be best suited for acute head injury when skull fracture and/or bleeding are suspected, whereas MRI might be the study of choice in the chronic stages of head injury, when the clinician is especially concerned about white matter integrity  PET visualizes brain metabolism directly as glucose radioisotopes emit decay signals, their quantity indicating the level of brain activity in a given area o PET contributes valuable info about the functioning of diseased brains o PET applications are limited by their dependence on radioisotopes that have a short half-life and must be generated in a nearby cyclotron o An important application for PET is in the diagnosis if neurodegenerative diseases (Alzheimer’s and frontotemporal dementia)  SPECT is similar to PET but less expensive and involves a contrast agent that is readily available  Comparison of interictal and ictal SPECT scans in epilepsy surgery candidates has been valuable for identifying the site of seizure onset  fMRI is a technique that capitalizes on the neural phenomenon that increasing neuronal activity requires more oxygen o amount of oxygen delivered by blood flow actually tends to exceed demand, creating a ratio of oxygenated to deoxygenated blood known as the BOLD signal which can be precisely and accurately measured and quantified o fMRI has a great degree of spatial resolution permitting visualization of brain areas that are activated during various cognitive tasks o it is widely available, noninvasive and doesn’t require a medical context for its application o popular method for examining all types of psychological processes o it has suffered from being used and abused by investigators whose knowledge of the brain and of historical brain-behavior relationship studies is woefully inadequate  the need to identify cerebral language and memory dominance in neurosurgery candidates led to the development of techniques such as Wada test and electrical cortical stimulation mapping o these procedures are invasive and afford only a limited range of assessable behavior due to the restrictions on patient response in an operating theater and the short duration of medication effects o patients undergoing such techniques typically have diseased of damaged brains which could have prompted reorganization of function Neuropsychology’s Conceptual Evolution  in the early 1900s clinicians treated brain damage or brain dysfunction as if it were a unitary phenomenon (organicity)  much of the work with brain damaged patients continued to be based on the assumption that organicity was characterized by one central and therefore universal behavioral defect  no one behavioral phenomenon could be found that was shared by all brain injured persons  Luria led neuropsychology’s evolution in 20 century believed that the use of symptoms made evident by neuropsychological assessment to infer local brain damage was the essence of neuropsychology  Luria’s focus was on qualitative analysis: the value of careful qualitative neuropsychological analysis of cognitive and behavioral systems included some psychometric instruments in his examinations  He emphasized the importance o breaking down complex mental and behavioral functions into component parts  He pointed out that higher mental functions represent complex functional systems based on jointly working zones of the brain cortex  The concept of “brain damage” has no etiological or pathological implications nor can predictions or prescriptions be based on such a diagnostic conclusion  The presence of “brain damage” has been clinically established and often verified radiologically before the patient even gets to the neuropsychologist  The site and extent of a lesion or the diagnosis of a neurobehavioral disease are not in themselves necessarily predictive of the cognitive and behavioral repercussions of the known condition  Although “brain damage” may be useful as a general concept that includes a broad range of behavioral disorders, when dealing with individual patients, the concept of “brain damage” only becomes meaningful in terms of specific behavioral dysfunctions and their implications regarding underlying brain pathology and real-world functioning  Neuropsychological assessment helps to determine what are the ramifications of the known brain injury or evident brain disorder Concerning Terminology  Many earlier terms for specific neuropsychological phenomena have not been supplanted or fallen into disuse so that even now one can find 2 or more expressions for the same or similar observations Dimensions of Behavior  Behavior may be conceptualized in 3 functional systems o Cognition (information handling aspect of behavior) o Emotionality (concerns feelings and motivation) o Executive functions (how behavior is expressed)  Each of them can be treated separately even though they are interconnected  In neuropsychology, the cognitive functions have received more attention than emotionality and executive function maybe because in brain injured patients, cognitive defects are more prominent  The nature of most medical and neuropsychological assessment doesn’t provide much opportunity for emotional and control deficits (limitation for neuropsychological examinations)  The disruptive effects of most brain lesions, regardless of size or location, usually involve all 3 systems  Behavior problems may also become more acute as secondary reactions to the specific problems created by the brain injury further involve each system Cognitive Functions  4 major classes of cognitive functions o Receptive functions o Memory and learning o Thinking o Expressive functions  Within each class of cognitive functions, a division may be made between verbal and nonverbal functions  The identification of discrete functions within each class of cognitive functions varies with the perspective and techniques of the investigator  Attentional functions differ from the functional groups listed in that they underlie and maintain the activity of the cognitive functions o Attentional functions serve somewhat as command operations, calling into play one or more cognitive functions o For this reason they are classified as mental activity variables Neuropsychology and the Concept of Intelligence: Brain Function Is Too Complex To Be Communicated in a Single Score  Cognitive activity used to come under the rubric of intelligence in the early days and was attribute to a single function  From a neuropsychological POV: intelligence is a tendency for cerebral regions subserving different intellectual functions to be proportionately developed in any one individual  Some neuropsychologists have attempted to identify the neural correlates of general intelligence (Spearman’s g)  Some studies suggest a relationship between specific neural sectors and concept of intelligence  Statistically significant associations were found between g and a circumscribed network in frontal and parietal cortex  The neural correlates of g were highly coextensive with those associated with full scale IQ scores  General intelligence draws on connections between regions that integrate verbal, visuospatial, working memory and executive processes  One of neuropsychology’s earliest finding was that the summation scores (IQ scores) on standard intelligence tests to not bear a predictably direct relationship to the size of brain lesions  In cognitively intact adults singular experiences plus specialization of interests and activities contribute to intraindividual differences  Socialization, cultural differences, personal expectations, educational limitations etc are some factors that magnify intraindividual differences  Spearman’s g cannot account for multiple intelligences and fails to incorporate emotional abilities and social intelligence  When considering the role of frontal lobes in human intellect, it is important to distinguish between intelligence as a global capacity to engage in adaptive, goal-directed behavior and intelligence as defined by performance on standard psychometric instruments  Even though frontal cortices constitute necessary anatomical substrate for human intelligence as a global capacity, extensive frontal lobe damage may have little or no impact on abilities measured by intelligence tests  Composite IQ scores are often good predictors of academic performance  Performance on intelligence tests is highly correlated with school achievement  In neuropsychological assessment , IQ scores are notoriously unreliable indices of neuropathic deterioration  IQ scores may obscure selective deficits in specific test  Composite scores (IQ scores) have no place in neuropsychological assessment  Many patients with dementing disorders, brain injuries, or brain diseases, whose mental abilities have deteriorate to the point that they cannot continue to work , will still perform well on the WIS batteries to be denied SSDI o The SSDI requires a drop in 15 points in the IQ score from premorbid levels o The SSDI may refuse to benefit cognitively disabled persons simply on the grounds that their IQ score is too high, even when assessment reveals a pattern of disparate levels of functioning that preclude the patient from earning a living Classes of Cognitive Functions Receptive Functions  Entry of info into the central processing systems proceeds from sensory stimulation (sensation through perception) which involves the integration of sensory impressions into psychologically meaningful data and thence into memory  Sensory reception o Arousal process that triggers central registration leading to analysis, encoding, and integrative activities o Perception of sensations also depends on attentional factors o From the 5 traits, sight and hearing have received the most attention  Perception and the Agnosias o Perception involves active processing of continuous torrent of sensations as well as their inhibition or filtering from consciousness o Simplest physical or sensory characteristics come first in the processing sequence and serve as foundations for the more complex higher levels of processing o The extensive cortical distribution and complexity of perceptual activities make highly vulnerable to brain injury o Perceptual defects resulting from brain injury can occur through loss of primary sensory input and through impairment of specific integrative processes o The perceptual functions include activities such as awareness, recognition, discrimination, patterning, and orientation o Impairments in perceptual integration appear as disorders of recognition (agnosia) o Agnosia = normal percept stripped of its meaning; lack of knowledge denotes an impairment of recognition o 6 different kinds of visual agnosias, 3 distinctive auditory agnosias o Distinction between associative and apperceptive agnosia refers to a basic difference in the mechanism underlying the recognition disorder o Associative agnosia is failure of recognition that results from defective retrieval of knowledge pertinent to a given stimulus (problem is centered on memory) o Apperceptive agnosia is disturbance of the integration of otherwise normally perceived components of a stimulus (problem is centered on perception) Memory  Different memory systems o HM had anterograde amnesia (couldn’t learn new info or recall ongoing events) o Memory functions in terms of 2 long-term storage and retrieval systems  Declarative system (explicit memory) deals with facts and events and it available to consciousness  Sematic (fact memory)  Episodic (autobiographic memory)  Nondeclarative system (implicit system) deals with consciousness  Item-specific implicit memory  Procedural memory  Declarative (explicit) Memory o This kind of memory that patients may be referring to when complaining of memory problems, that teachers address for most education activities and that is the memory of common parlance o It has been described as the mental capacity of retaining and reviving impressions or of recalling previous experiences o Always requires awareness  Stages of memory processing o For clinical purposes a 3 stage declarative memory provides a suitable framework for conceptualizing and understanding dysfunctional memory 1. Registration (sensory memory) holds large amounts of incoming info briefly. Info being registered is further processed as short-term memory or it quickly decays 2. Immediate memory is the first stage of short-term memory storage and temporarily holds info retained from the registration process. Short-term memory may be equated with simple immediate span of attention. Immediate memory is a limited capacity store from which info is transferred to a more permanent store. It typically lasts from about 30 seconds up to several minutes. Immediate memory is usually conceptualized as a unitary process and it may oper
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