Neuropsychology is the study of brain-behavior relationships through objective, scientific methods. The main goal in neuropsychology is to understand how the brain produces and controls behavior and mental processes, including emotions, cognition, and consciousness. This goal is met by studying both healthy and damaged brain systems using objective measures to link biological and behavioral domains.
The goal of clinical neuropsychology is to study how cognitive skills such as memory, language, and attention change an individual’s life as a result of brain injury, disease, or developmental process. The ultimate objective is the clinical application of that knowledge to human problems. Neuropsychological tests and methods are used to compare an individual’s behavior to that of individuals with known brain dysfunction and to a normal control population. Psychologists draw inferences from the test data regarding what type of brain dysfunction may be present. From this point, realistic expectations for adjustment, remediation, and rehabilitation of behavior are made.
Neuropsychology is the fastest-growing subspecialty in psychology. Prior to 1975, neuropsychology was not considered a separate subspecialty, and was often part of clinical psychology, biopsychology, or neuroscience. Between 1975 and 1990, there was an increase in the clinical uses of neuropsychological information beyond the research laboratory, with an emphasis on creating test batteries that could be used to guide diagnosis and intervention with neurology patients. During this era, three professional organizations were founded (the International Neuropsychological Society, the National Academy of Neuropsychology, and Division 40 of the American Psychological Association, or APA), and several academic journals representing the discipline were established. In the years since 1990, neuropsychology has enjoyed increased acceptance in health care and forensic areas, but the economic changes (e.g., decreased reimbursement) that have affected health care in general also have affected clinical neuropsychology.
This article outlines the main uses of neuropsychological assessment, and discusses the debate regarding the use of fixed versus flexible batteries. A typical neuropsychological evaluation is described. Tests are suggested to measure functioning in a variety of domains. Finally, the future of neuropsychology is addressed.
Uses of Neuropsychological Assessment
Neuropsychological assessment is used for many purposes. Patients may be referred by a neurologists or general practitioner for an assessment as part of a diagnostic workup (e.g., for dementia) or to establish a baseline following an injury or illness. Neuropsychologists may be asked to complete an assessment for the purpose of evaluating competency or independence, or to make a recommendation about a patient returning to work or school.
School personnel may refer students to determine if a learning disorder or other developmental disorder exists, to specify subtype and prognosis of the disorder, and to recommend academic accommodations. Assessment may also be used to provide recommendations for psychosocial or family interventions. Information from the evaluation may help family members accept the patient’s limitations and consider changes in the environment to accommodate any deficits.
Finally, neuropsychological assessment may be used to evaluate change over time. This information may be used to determine the course of changes and the prognosis for future functioning in cases involving traumatic brain injury or a progressive disease (e.g., certain dementias). Also, treatment efficacy (e.g., effect of medications or rehabilitation efforts) can be evaluated with repeated assessments.
Fixed Versus Flexible Batteries
One controversial issue in neuropsychology is the use of fixed versus flexible test batteries. The most commonly used fixed battery of tests is the Halstead-Reitan Neuropsychological Battery (HRB). The HRB is a group of psychological tests that, taken together, are used by neuropsychologists to distinguish patients considered to have brain damage from patients with no known history of disease. The HRB uses an index of impairment to predict the presence of brain damage in patients. Test norms exist for a normal control group and for patients with various types of brain damage. The HRB has stimulated a great deal of research in past years.
There are several advantages to using a fixed battery. Since a standard set of measures is used, the functioning of different patients can be compared. An evaluation is unlikely to overlook an important condition because all subjects are evaluated for all basic neuropsychological abilities. Fixed batteries are easy to teach, because the beginning student does not have to make decisions about test selection, and interpretation is objective and data driven. Finally, fixed batteries are useful for empirical studies and facilitate comparison across different research projects.
There are also disadvantages to fixed batteries. First, the purely empirical approach does not always lead to the most interpretable measures because it can be difficult to describe what the tests are measuring or to tie task performance to real-life situations. Fixed batteries tend to be unnecessarily long and tedious for some patients. This leads to noncompliance and discomfort, especially in older or more impaired patients. These batteries can be difficult to justify economically, which forces the use of technicians. Then the neuropsychologist loses the opportunity to directly observe the patient’s behavior during the assessment.
Another approach is the use of a flexible battery (also referred to as the process or hypothesis approach). In this method, the neuropsychologist adapts each exam to the individual patient. Tests are selected based on hypotheses about the patient and available information, such as medical findings and history. Standard tests may be used, or tests may be altered to determine the nature of the deficit. Qualitative interpretations of test results and patient behavior play an important part in forming conclusions.
An advantage of the process approach is that it takes into account the individual nature of the patient’s deficits, and adapts the exam to obtain more precise measurements of a cognitive ability. The exam can reduce assessment time by focusing on the most important areas and ignoring those that are not relevant for the patient’s prognosis. Finally, the process approach emphasizes the way in which the patient fails or succeeds in a particular cognitive task. For example, if a patient is unable to answer a factual question, the process approach allows further investigation beyond the standardized test. The difficulty could be caused by an impairment of speech comprehension, expressive aphasia, or poor factual knowledge. By allowing the patient to answer in a different form (e.g., multiple choice), the neuropsychologist obtains information that would have been missed using a purely standardized approach.
One disadvantage of the process approach is that the exam may selectively confirm an opinion because its content emphasizes what the neuropsychologist thinks is important. A deficit may be missed because an area was not considered relevant. This affects prognosis and rehabilitation since they rely on the brain functioning as a whole. Second, using tests that are not standardized for a clinical population can cause problems. Subjective interpretation of what a score might mean may be completely wrong. A test that measures one thing in a normal population may measure something different in a neuropsychological population. Finally, the process approach is more difficult to teach because few rules and procedures exist. Judgments made by the neuropsychologist often depend on extensive clinical experience, so the exam must be conducted by the neuropsychologist rather than a technician. This places limits on the time of the neuropsychologist.
A majority of neuropsychologists combine the fixed and process approaches in the form of a modified battery. They integrate data from a variety of sources (tests, medical findings, and developmental history), while taking into account the injury or disease process, personality, and other moderating variables that may affect test performance.
Typical Neuropsychology Evaluation
History and Behavioral Observation
A neuropsychological evaluation begins with taking a history of the patient beginning with demographic information, reason for referral, and the patient’s chief complaint. Family history should include the state of health or the cause of death of parents, brothers, and sisters; history of familial diseases such as hypertension, stroke, or cancer; and history of cognitive or emotional disorders in the family. Social history should include use of drugs and alcohol, and reactions to life situations of stress and conflict.
A medical history begins with prenatal development and assesses several areas. It is important to assess whether the patient was a premature baby, whether any complications occurred during or after delivery, and history of childhood diseases, developmental problems, major illnesses, accidents, head injuries, or loss of consciousness. Delays in the acquisition of motor, language, or intellectual skills are examined. When assessing for brain injury, details about the accident are gathered (e.g., when it occurred, loss of consciousness, hospitalization, and occurrence of posttraumatic amnesia).
An educational history is taken, including highest grade level achieved, academic performance, and general attitude toward education. Patients are asked if they ever received any special tutoring, were placed in any special classes, ever failed or had to repeat a grade, or had difficulties with any particular subjects. Vocational history should include the type of jobs held, the frequency of job changes, and any recent occupational problems.
Handedness is determined since it is an indicator of cerebral dominance, which can affect responses to neuropsychological assessments. It is usually sufficient to ask the patient which hand is dominant, but it may be necessary to obtain responses on a lateral dominance exam. Most of the population is right-handed, indicating left hemisphere dominance, but less than half of those who are left-handed are left hemisphere dominant.
Behavioral observations should go beyond physical description and include general appearance, personal hygiene, and noticeable physical defects (e.g., vision, hearing, and gait). In addition, it is important to be sensitive to other aspects of behavior including speech (speech difficulties, flow, appropriateness, and affect), posture, facial expression, eye contact, tics, and any unusual behaviors or involuntary movements.
General intellectual Functioning
Intellectual functions for adults are most frequently measured with the Wechsler Adult Intelligence Scale—Third Edition (WAIS-III). The WAIS-III consists of 14 subtests that are combined into three IQ scores and four index scores. Although the WAIS-III was not developed to be a neuropsychological instrument, several scores are helpful in forming hypotheses about a patient’s presenting problem. The reliability and validity of all of the Wechsler scales have been well documented.
The Verbal Comprehension Index (VCI) is made up of three subtests: Vocabulary (vocabulary knowledge), Similarities (semantic information and abstract thinking), and Information (factual knowledge). Performance on the VCI is influenced by educational history; it requires understanding words, drawing conceptual similarities, and knowledge of social situations. The Perceptual Organization Index (POI) is a measure of nonverbal abilities and novel problem solving. The POI comprises three subscales: Picture Completion (visual processing and attention to detail), Block Design (visual-motor ability, spatial processing, and problem solving), and Matrix Reasoning (visual processing and abstract reasoning skills in a multiple choice task). The POI assesses ability to examine a problem, use visuomotor and visuospatial skills, create solutions, and then test them.
The Working Memory Index (WMI) consists of the three subtests: Arithmetic (arithmetic abilities and working memory), Digit Span (encoding and verbal short-term memory in Digits Forward and working memory in Digits Backward), and Letter-Number Sequencing (working memory). Working memory is an executive function that is essential for cognitive flexibility and planning ability, as well as learning and self-monitoring. Working memory is an active process and is not the same as short-term memory, which is often viewed as a passive process. Finally, the Processing Speed Index (PSI) includes two subtests, Digit Symbol-Coding (visuomotor coordination and response speed) and Symbol Search (visual processing). The PSI assesses skills in focusing attention and quickly scanning and discriminating between visual information.
Two WAIS-III subtests are not used in computing any index scores, but they are used to calculate IQ scores and they provide information that is useful in neuropsychological assessment. The Picture Arrangement subtest measures visual processing and sequential thinking. The Comprehension subtest measures social knowledge and practical reasoning. Finally, Object Assembly is a completely optional subtest. Matrix Reasoning, which replaced Object Assembly in determining Performance IQ in the WAIS-III provides a purer measurement of perceptual organization because it does not measure speed of performance.
Attention implies alertness to the world and can be broadly defined as the ability to attend to a stimulus. Four processes must be assessed when diagnosing attention-related disorders.
Encoding is the capacity to briefly hold information in mind while performing some cognitive operation on it. Encoding involves the sequential registration and recall of information, and is related to listening comprehension. Encoding is typically measured by the WAIS-III Arithmetic and Digit Span (Digits Forward) subtests. Other tests used to measure encoding include the first trial of a list learning test, such as the California Verbal Learning Test, 2nd Edition (CVLT-II), discussed below in Learning and Memory. The interference trials of the CVLT-II can also be used as a measure of encoding. Other narrative tests for encoding include sentence repetition or story recall tests (e.g., the Wechsler Memory Scale—Third Edition [WMS-III] Logical Memory subtest).
Sustained attention is the capacity to stay on task for an appreciable interval, respond quickly to designated targets, and inhibit responses to nontargets. Inhibition is central to the concept of sustaining attention because attending to a stimulus implies inhibiting a response to other stimuli. Sustained attention is typically measured with a continuous performance test presented on a computer or other mechanical device, such as the Gordon Diagnostic System or the Connors’ Continuous Performance Test II (CPT II).
Shift is the capacity to shift attentional focus in response to changing information. The Wisconsin Card Sort Technique (WCST), a good measure of abstract reasoning, concept generation, and perseverative responding, is the best measure of the ability to shift attention. The WCST requires patients to sort cards into categories according to color, form (shape), and number, using changing feedback from the examiner. Patients who have difficulty shifting will continue using the same category instead of using feedback to adjust their behavior.
The final component of attention is focus/execute, which is the capacity to concentrate attentional resources on a specific task (focus), screen out distracting stimuli, and respond appropriately and quickly (execute). Focus/execute is typically measured by tests such as the WAIS-III Coding and Symbol Search sub-tests, the Color-Word and Trail-Making subtests of the Delis-Kaplan Executive Function System (D-KEFS), and the Stroop Color and Word Test. These tests require persons to quickly make perceptual discriminations and a verbal or motor response.
Language functions comprise several cognitive abilities, including comprehension, speech, reading, writing, and spelling. Patients may experience a variety of language difficulties. Dysarthria is a disorder of articulation that can result in slurring or mumbling. Dysprosody is an interruption of speech melody caused slowing and monotone voice. Apraxia is the inability to carry out movements of the face and speech apparatus. Aphasia is a language disturbance characterized by errors of grammar and word choice. Alexia is a reading inability that occurs either as a loss of reading ability in a previously literate person or as dyslexia, a developmental learning disorder. Finally, agraphia is an acquired disturbance in writing.
The first step in language assessment is to observe the patient’s spontaneous speech in response to general questions during the intake interview. Behaviors observed include articulation problems, syntax errors, word-finding pauses, or any other marked change in speech production. Expressive language deficits are usually indicated by word retrieval difficulty or problems with word fluency. These are assessed using a picture naming test (e.g., Boston Naming Test) or a verbal fluency measure such as the D-KEFS Verbal Fluency (described under Executive Functioning Skills below). The Wechlser Individual Achievement Test—Second Edition (WIAT-II) Oral Expression subtest and the D-KEFS Proverbs subtest may also be useful in assessing a patient’s expressive language abilities.
A second language area to assess is auditory comprehension or receptive language. Many language disorders cause impairment in this area. To measure auditory comprehension, a patient may be asked to respond to pointing commands (e.g., point to a chair) or yes-no questions, or given the WIAT-II Listening Comprehension subtest. The Token Test provides a more structured measure of receptive language. This test uses a series of tokens in various sizes, shapes, and colors arranged in front of the patient, who is asked to respond to a series of commands of increasing length (e.g., “Put the green circle on the red square”).
Both oral word reading and reading comprehension are measured, using tests such as the Word Reading, Pseudoword Decoding, and Reading Comprehension subtests of the WIAT-II, the Reading Decoding sub-test of the Wide Range Achievement Test 4 (WRAT4), or the Nelson-Denny Reading Test. These reading skills are supported by different neuropsychological functions and must be assessed separately. Inability to decode words is typically a phonological problem, while reading comprehension is influenced by several factors, such as attention and working memory. Spelling and written expression can be assessed by the
WRAT4 or WIAT-II Spelling subtests and the WIAT-II Written Expression subtest. Usually math skills are assessed with other academic skills, using the WRAT4 Math Computation, or WIAT-II Numerical Operations and Math Reasoning subtests.
Executive Functioning Skills
Executive functioning involves several complex cognitive skills mediated by the frontal lobes, including planning, sequencing, inhibition, flexibility, organization, reasoning, and problem solving. Working memory allows the individual to maintain internal representations in order to guide behavior, and as such, is an important part of self-control. Difficulties in executive function are associated with several conditions (e.g., attention deficit/hyperactivity disorder, or ADHD).
Planning involves complex problem solving to achieve a goal. Planning is most often assessed with a tower test, such as the Tower of London or the D-KEFS Tower Test. These tests require the rearrangement of colored balls or disks on pegs to match a model, using rules that define acceptable moves. Maze tracing tasks provide an alternative measure of planning.
Response inhibition is the ability to delay a response or to not respond to nontarget stimuli. Many neuropsychological tests use a measure of rule violations to assess response inhibition. For example, on a tower test, rule violations occur when the patient uses two hands to solve the item, after being told that this is not an acceptable move. Errors on a Stroop color-word interference trial also indicate difficulties with response inhibition, when patients are unable to refrain reading the word when they are only to name the ink color. Finally, most continuous performance tests include a measure of the number of times an individual responds to nontarget stimuli, indicating a problem with response inhibition.
Working memory is viewed as an executive function skill that allows an individual to hold information in mind while performing an operation on it. It is measured using the WAIS-III Digit Span (Digits Backward), Arithmetic, and Letter-Number Sequencing subtests. Another useful test for measuring working memory is Auditory Consonant Trigrams (ACT), which requires the patient to hold three consonants in mind while counting out loud backward from a given number by threes for intervals varying from 0 to 36 seconds.
Concept formation and reasoning tasks can be thought of as measures of abstract thinking, problem solving, and organization. Several subtests on the WAIS-III measure this component of executive functioning, including Comprehension, Similarities, and Matrix Reasoning. Other measures of concept formation and reasoning include the Wisconsin Card Sorting Test and the D-KEFS Sorting and Twenty Questions subtests.
Finally, verbal fluency can be considered both an executive function skill and a language component. Verbal fluency involves auditory attention, working memory, word production, mental processing speed, and vocabulary storage. It is typically measured with a test such as the Controlled Oral Word Association test (COWA) or the D-KEFS Verbal Fluency test. There are two parts to these tasks. The first measures letter (phonemic) fluency. The patient is instructed to generate words beginning with a given letter (e.g., F, A, S) in a limited time period. Letter fluency relies on working memory to facilitate word retrieval and keep track of recent responses. In category (semantic) fluency, the patient is asked to name as many items in a category (e.g., animals) as possible in a limited time period. Typically category fluency is easier for patients to perform than letter fluency, since information is stored in categories within long-term memory.
Learning and Memory
A common initial complaint of neuropsychological dysfunction is memory problems. Learning and memory are assessed using a variety of methods, depending on the type of memory being measured. The WAIS-III Digit Span (Digits Forward) subtest is one measure of immediate recall (encoding), while Digits Backward is a measure of working memory. The WAIS-III Information subtest is sometimes considered as an indicator of long-term memory, but is dependent on the individual’s academic history.
New learning typically is assessed using a list learning exercise, such as the California Verbal Learning Test, 2nd Edition (CVLT-II) or the Rey Auditory Verbal Learning Test (RAVLT). In the CVLT-II, the examiner reads aloud a list that contains 16 common words, each of which belongs to one of four categories (fruits or spices). The patient is then asked to recall as many of these items as possible. The examiner records how many items the patient is able to recall over several repeated trials, and whether or not category information is being used. Next, an interference list is administered. Immediately after the recall of the interference list, the patient is asked to recall the trial list again. Finally, after a longer delay of about 20 minutes, the examiner asks the client to recall the trial list a final time. The RAVLT follows a similar pattern, although there are no categories on the lists that are administered, which may make it a slightly more difficult test.
The CVLT-II and the RAVLT are particularly useful because they contain a recognition trial following the final recall trial. It is important to differentiate a patient’s ability to voluntarily recall information from his or her ability to recognize it as something he or she previously heard. A difference between recall and recognition of list items allows the examiner to determine if the information was learned and stored, learned and forgotten, or never learned.
Story recall (e.g., WMS-III Logical Memory) is another method of assessing verbal learning and memory that allows the individual to use context clues to aid recall. Visual memory can be assessed using the WMS-III Faces subtest or other tests included in the visual-perceptual exam.
Visual Perception, Constructional Ability, and Sensory-Motor Abilities
A neuropsychological assessment should include an evaluation of visual perception and constructional abilities, both right hemisphere functions, and sensory and motor abilities. Visual perception consists of two independent process, visuoperceptual ability and visuospatial ability. Visuoperceptual deficits can take several forms, including visual agnosia (deficits in object and facial recognition) and form or pattern discrimination problems. Object recognition is commonly measured using an object naming test (e.g., the Boston Naming Test). Pattern discrimination is measured using the WAIS-III Matrix Reasoning and Symbol Search subtests. Facial discrimination can be measured by WMS-III Faces test.
Visuospatial deficits include visual neglect, problems with visuospatial judgment (position and orientation of objects), and topographic disorientation (difficulties on navigational tasks). Visual neglect can be measured using cancellation tests (e.g., D-KEFS Visual Scanning) or drawing tests, such as asking the patient to draw a clock, house, or flower. Visuospatial judgment can be assessed with a drawing test, or with the use of a line orientation test (e.g., Benton Judgment of Line Orientation). Finally, the patient’s behavior is observed for any difficulties with navigation (e.g., getting lost in familiar surroundings).
Constructional ability is the capacity to draw or assemble an object from memory or by copying a model. Deficits in this domain cause patients to have difficulties integrating parts into a whole. These deficits are typically measured with a copying task (e.g., Rey Complex Figure Test) or a block assembly task (e.g., WAIS-III Block Design subtest).
Sensory and motor abilities are assessed because results can provide information about lateralized cortical problems. Sensory tasks measure the ability to perceive tactile input, and are measured by finger discrimination tasks. Motor speed and control are measured by finger-tapping tasks. Motor programming (e.g., planning, implementing, and automating new motor routines) is measured by imitating hand positions. Fine motor skills include visual motor precision and dexterity, and are measured by finger-tapping or maze-tracing tasks. Finally, motor strength is measured using a hand dynamometer.
Mood and Personality
As a final domain, mood and personality are assessed to determine any evidence of thought, anxiety, or other mood disorder. The presence of psychiatric symptoms can affect scores on neuropsychological measures. Tests used to screen for symptoms include the Beck Depression Inventory, the Minnesota Multiphasic Personality Inventory-2 (MMPI-2), and various behavioral rating scales.
Interpretation and Report Writing
The final step in the evaluation involves the interpretation of the results and preparation of a report. The report is used to inform the referral source and others about the patient, and to provide guidelines that may be used in treatment and remediation. It is good practice to avoid using technical or ambiguous terms, to be objective, to include relevant history but not inappropriate details, and to support all conclusions. All tests and procedures used are described, and performance on all tests is reported, not just scores that suggest some form of impairment. Finally, specific recommendations for the patient that are realistic and based on resources and services that are available are included.
Neuropsychology is likely to continue growing as a psychological subspecialty, particularly as advances in neuroscience continue to occur. Although most states do not offer specific licensure in neuropsychology, this may change in the future. Currently the only credential available to demonstrate competence is board certification or diplomate status achieved through peer review and examination. Several professional organizations have developed specific guidelines for training in neuropsychology. Minimum criteria for a clinical neuropsychologist now include a doctoral degree in psychology from an accredited university, an internship in a clinically relevant area, state licensure, and two years of specialty training in neuropsychology.
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