Contemporary Neuroimaging and Methods in Adult Neuropsychology

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Table of Contents

Abstract
Introduction
Brain imaging and electrophysiological testing
Structured vs. unstructured assessment procedures
Conclusion
References

Abstract

Neuropsychology is the applied science of brain-behavior relationships. The aim of this essay is to review in brief neuroimaging, and electrophysiological testing, besides reviewing structured and unstructured approaches in interviewing neuropsychiatric patients.

Introduction

Neuropsychology is the applied science of brain-behavior relationships; therefore, a neuropsychologist should have a working knowledge of physiology, psychology, and neurology to be able to assess, diagnose, and treat patients. Neuropsychology uses methods that assess specific anatomical locations and collections of functional systems (D’Amato and Hartlage, 2008).

Brain imaging and electrophysiological testing

Brain imaging techniques produce images for brain structure or functional activity and include many methods. Computerized axial tomography (CT scanning) images are produced by exposure to low levels of radiation passing through the head at different angles, thus, it produces slice by slice images of the brain or other CNS structures. Each image is analyzed by a computer to generate an effective compound X-ray image. Besides exposure to radiation, CT images do not effectively show the contrast in different tissues’ density, which can be enhanced by injecting a contrast medium. Thus, CT produces structural images pointing to structural brain changes useful in locating lesions but do not provide measures for functional activity (Stirling, 2002).

Magnetic resonance imaging (MRI) is more recent than CT scanning. The basic principle is exposing the hydrogen atoms present in the target organ (like the brain) to radio waves in a strong magnetic field. Minute magnetic fields resulting from spinning hydrogen atoms are measured and computer-processed to generate successive slice by slice images (in coronal, sagittal, or horizontal planes). Because the hydrogen atoms’ density varies in different brain tissues, MRI images are of higher resolution compared to CT images, with the second advantage of no exposure to radiation. Functional MRI measures brain structure and function, with the underpinning principle is active neurons need higher levels of oxygenated hemoglobin. Thus, the scanner detects the different magnetic fields resulting from different proportions of oxygenated hemoglobin in active and inactive neurons. This technique has proved efficacy in recognizing functional changes when patients undertake tests for working memory (Stirling, 2002).

Positron emission tomography (PET) uses the principle that active neurons use glucose more than inactive ones. Thus, shortly before the test, radioactively labeled glucose is injected (a radioactive marker), which can be of many depending on the half-life period or the affinity of the target tissue. The PET scanner measures gamma rays resulting from decay, thus assessing activity. PET provides color-coded images of patients’ brains as they undertake assignments, therefore it assesses functional brain activity. Other imaging techniques are regional cerebral blood flow and single-photon emission computerized tomography, which are variants of PET (Stirling, 2002).

Electrophysiological brain assessment includes EEG and recording evoked potentials, where EEG measures the pattern of the brain’s electrical activity as an ongoing brain activity. Although EEG provides a direct record of brain activity, analysis and interpretation of the record are difficult whether recorded in alert aroused state or in the awakened but relaxed state. Evoked potentials measure which parts of the cerebral cortex are mostly used in various sensory or mental tasks (real-time EEG study). Thus, both techniques assess the functional activity of the brain. Evoked potentials provide better assessment of phenomena of psychological significance especially if the stimulus event and task are simple (Beaumont, 2008).

Structured vs. unstructured assessment procedures

Neuropsychological methods of assessment and testing can be either structured (inflexible) where all patients are subjected to a standard battery of tests. Alternatively the unstructured method (flexible) method can be used where the test design depends on the problem for referral or the patient’s symptoms (D’Amato and Hartlage, 2008). However, in this case, certain conditions must be looked for, which include what test to examine a specific function, test sensitivity, reliability, and validity, and effect of variables like age, gender, and education of the test response (Therapeutic and technology assessment subcommittee-American Academy of Neurology, 1994).

Of the structured assessment procedures Halstead- Reitan Neuropsychology Test Battery incorporates a range of tests covering the essential elements of psychological abilities. It produces information from the component of intelligence, language abilities, perceptual, psychomotor, memory, learning, and thinking abilities. It depends on using cut-off scores to separate patient’s performance because of brain damage from normal. Luria- Nebraska Neuropsychology Test whose components are motor function, rhythmic and pitch skills, tactile, visual, receptive and expressive speech functions. Components include reading and writing skills, and intellectual processes. Scoring is made through formal protocols and it has the advantages of being less time-consuming and linking to patients’ problems at a clinical level (Groth-Marnat, 2003).

In the unstructured approach, the examiner needs to be attentive to the content (what the patient says) and the process (how the patient talks or behaves during examination). In collecting patient initial data the clinician uses an unstructured or semi-structured approach where it provides flexibility and centers on the individuality of the patient. A major disadvantage of unstructured approach is examiners may be influenced by their preferred theories, personal or cultural biases (Groth-Monart, 2003). There are three inherent disadvantages of unstructured approach, which are low reliability, low validity, and lack of standardization in both content and process (US merit Systems Protection Board, 2003).

Conclusion

Irrespective of structure approach, a neuropsychiatric patient interview needs to assess patient’s strengths, adjustment level, nature and history of the disorder, diagnosis and personal and family history of relevance.

References

Beaumont, J. G. (2008). Introduction to Neuropsychology (2^nd edition). New York: The Guilford Press.

D’Amato, R. C., and Hartlage, L. C. (2008). Essentials of Neuropsychological Assessment (2^nd edition). New York: Springer.

Groth-Marnat, G. (2003). Handbook of Psychological assessment (4^th edition). New Jersey. John Wiley &Sons Inc.

Stirling, J. (2002). Introducing Neuropsychology. East Sussex. Psychology Press-Taylor Francis Group.

Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology (1994). Assessment: Neuropsychological testing of adults. Considerations for neurologists. Neurology, 47, 592-599.

U. S. Merit Systems Protection Board. (2003). The federal selection interview: Unrealized potential. Washington, DC: Office of Policy and Evaluation.

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