The significance of sensory motor functions as indicators of brain dysfunction in children

Size: px

Start display at page:

Download "The significance of sensory motor functions as indicators of brain dysfunction in children"

Reynard Francis
5 years ago
Views:

Archives of Clinical Neuropsychology 18 (2003) 11 18 The significance of sensory motor functions as indicators of brain dysfunction in children Abstract Ralph M.

1 Archives of Clinical Neuropsychology 18 (2003) The significance of sensory motor functions as indicators of brain dysfunction in children Abstract Ralph M. Reitan, Deborah Wolfson Reitan Neuropsychology Laboratory, P.O. Box 66080, Tucson, AZ , USA Accepted 7 August 2001 Sensory perceptual and motor functions are closely dependent on the integrity of the brain and nervous system. Standardized tests have been developed to assess these functions, but such tests are not routinely used to evaluate children who are suspected of having a neuropsychological basis for their difficulties. Higher-level functions (such as verbal and academic abilities, executive functioning, etc.) are obviously important in producing successful performances, but the brain and nervous system correlates of these abilities are less well defined than the correlates for sensory motor abilities. Our contention is that tests from these two general areas (higher-level and lower-level aspects of brain functioning) can be used effectively in a complementary manner to evaluate individual children. The first step in this process is to evaluate formal sensory motor tests and to assess their validity as a brief preliminary examination used to differentiate between brain-damaged and control children. The results of this study demonstrated striking differences between the groups and indicated that sensory motor testing might serve very effectively, when used in conjunction with higher-level tests, to identify those children whose higher-level impairment is due to brain impairment rather than a lack of environmental opportunities or advantages National Academy of Neuropsychology. Published by Elsevier Science Ltd. All rights reserved. Keywords: Brain damage; Sensory perceptual functions; Motor functions; Higher-level functions; Lower-level functions Presented at the Reitan Society (Tucson Chapter) on May 9, Corresponding author. Tel.: ; fax: address: reitanlabs@aol.com (R.M. Reitan) /02/$ see front matter 2002 National Academy of Neuropsychology. PII: S (01)

2 12 R.M. Reitan, D. Wolfson / Archives of Clinical Neuropsychology 18 (2003) Introduction Sensorimotor functions have been studied for many years, with the earlier studies focusing on abilities among normal or mentally ill persons (King, 1954). However, systematic evaluation of the dependence of these abilities on the integrity of the brain and the use of such measures in the clinical evaluation of individual subjects required the development of formal neuropsychological tests that were administered and scored according to specified procedures (Halstead, 1947; Reitan, 1959). Even in such clinically oriented approaches to the neuropsychology of brain functions, though, sensorimotor tests have not generally occupied positions of central interest. Neuropsychological studies of impairment resulting from brain damage, in both children and adults, have generally focused on higher-level aspects of brain functions (intellectual and cognitive abilities), although lower-level brain functions (sensory perceptual and motor skills) obviously are of significance in subserving adaptive abilities, and when studied, have been found to be sensitive indicators of brain damage (Reitan & Wolfson, 1992). Several aspects of sensory perceptual and motor skills recommend their importance as indicators of brain status and their potential significance in complementing measurements of higher-level abilities in clinical evaluation of the individual child: 1. Lower-level brain functions relate closely to input or sensory functions (especially vision, hearing, and touch); these input avenues, in turn, are integrally dependent upon well-defined tracts, pathways, and nuclei which relate evidence of dysfunction directly to the biological status of the brain. 2. The anatomical organization of motor functions, stemming from relatively well-defined areas within the cerebral cortex and extending through pathways and nuclei to effector organs (muscles and glands), is also directly related to the biological status of the nervous system. 3. Interindividual variations in the adequacy of sensory perceptual and motor functions may be the result of deficits in receptor and transmission mechanisms. Standardized tests have been developed which principally reflect cerebral limitations of sensory motor functions and permit discounting of limitations due to peripheral aspects of nervous system dysfunction (Reitan & Wolfson, 1992). 4. Lateralized deficits of both sensory perceptual and motor functions, as a result of differential involvement of the two cerebral hemispheres, provide an opportunity to relate deficits to impaired brain functions of the individual person through the use of intraindividual (as opposed to interindividual) comparisons, thus largely avoiding the problem of variability that occurs in any large group of nonbrain-damaged persons and the problem of differentiating poor performances due to brain damage from poor performances due to normal variability. 5. Lateralized deficits also provide an opportunity for identifying a differential degree of involvement of the two cerebral hemispheres, depending on which side of the body is principally impaired. 6. The close dependence of sensory motor functions on the biological status of the nervous system permits measured deficits to be related to brain impairment, as contrasted with the

3 R.M. Reitan, D. Wolfson / Archives of Clinical Neuropsychology 18 (2003) much greater dependence of higher-level brain functions on environmental opportunities, educational advantages, and so forth. 7. Although brain-related deficits in sensory motor functions are probably not as closely related to real-life adaptive abilities, academic success, and so forth, as higher-level brain functions (attention, verbal skills, executive functions, etc.), they are, nevertheless, clearly important in the sense that realistic and accurate contact with the external environment, through input avenues to the brain, is necessary in all aspects of behavior. Motor abilities, as mechanisms for implementing responses directed by the brain, are also necessary for expression of intelligent and adaptive behavior. These points are well established, inasmuch as theories of brain behavior relationships historically have routinely stressed the integration of sensory motor and higher-level brain functions (see Reitan & Wolfson, 1992 for a review of neuropsychological theories). Although basic sensory perceptual and motor skills are often taken for granted, they may in fact serve a much more fundamental and pervasive role as integral and necessary elements of the full cycle of adaptive behavior than is generally appreciated. It is not necessary to argue in support of the importance of higher-level neuropsychological functions, but two points should be emphasized: 1. Higher-level neuropsychological functions are less closely related to specific anatomical or structural aspects of the nervous system than are lower-level neuropsychological functions, and, in certain areas, are strongly dependent upon environmental influences and opportunities for their development. 2. The close relationship of lower-level functions to the biological status of the brain renders their measurement of great value in supplementing a neuropsychological (brain-related) interpretation of higher-level deficits. Rather than being in a position only to speculate whether an impairment of higher-level functions is due to brain damage, findings of corresponding and correlated lower-level deficits may answer the question unequivocally. The above considerations prompted us to undertake the present study of the usefulness of sensory perceptual deficits and motor dysfunctions in differentiating the performances of a group of children with heterogeneous conditions of brain damage and a group of nonbraindamaged children. 2. Method 2.1. Participants Two groups, one composed of control children and the other composed of brain-damaged children, were compared on sensory perceptual and motor tests. A major advantage of using these groups in an initial study is that they help to establish a framework within which additional groups that might have impairment of brain functions (such as children with learning or academic deficiencies) can be evaluated.

4 14 R.M. Reitan, D. Wolfson / Archives of Clinical Neuropsychology 18 (2003) Each of the groups was composed of 20 subjects. The control group consisted of 11 girls and 9 boys who were functioning normally. Eleven of these children attended an urban school and 9 attended a small-town school. They were all volunteers, and parental approval was obtained with the only explanation that some behavioral tests would be given for research purposes. Nine of the children were given a neurological examination by a neurologist and no evidence of past or present brain damage or disease was found. None of the remaining 11 children upon questioning reported any illness or injury that may have compromised brain functions. Children in the group had a mean age of years (S.D. = 0.94) and had completed a mean of 6.05 grades in school (S.D. = 0.89). All of the children in the second group had evidence of brain disease or damage, and all of them were referred for evaluation because of their neurological (medical) conditions rather than primarily for an assessment of academic problems. Each of these children had a definite neurological diagnosis. The diagnoses included the following: generalized epileptic seizures, 5; traumatic brain injury, 5; complex partial epileptic seizures, 3; encephalitis, 2; posterior fossa lesion, 2; subarachnoid hemorrhage, 1; left frontal glioma, 1; and heredito-degenerative brain disease, 1. This group had a mean age of years (S.D. = 1.47) and had completed a mean of 4.95 grades in school (S.D. = 1.82). The groups were composed so that they would be comparable in age (t ratio =.13; P <.90), but they were not selected for educational progress. Some of the brain-impaired children had not been consistently promoted from one grade to the next, although 14 of them had made normal progress. Two of the brain-impaired children were receiving special educational assistance. The number of grades completed was significantly less for the brain-damaged group than for the control group (t ratio = 2.39; P<.03). Of course, it is hardly surprising that brain disease/damage is reflected in academic aptitude and progress Dependent variables The tests administered to each child included a number of sensory perceptual and motor tests that are included as part of the Halstead Reitan Neuropsychological Test Battery for Older Children. These tests have been described in detail, with complete instructions for administration and scoring (Reitan & Wolfson, 1992), and have been extensively tested for their clinical applicability. The tests will be described only briefly here, with a statement of the purpose of the test and the method of administration and scoring. The sensory perceptual tests selected for this study focused principally on tactile perception because the tactile modality is probably less influenced by environmental influences and training than either vision or hearing. The first test, Bilateral Simultaneous Sensory Stimulation, requires the subject to register and report incoming sensory stimuli. The examiner lightly touches either the subject s left hand, right hand, or both hands simultaneously in a prescribed sequence, and the subject responds by indicating whether the stimulus was perceived on the left hand, right hand, or both hands. The critical error occurs when the child reports only one hand being touched when both hands were touched. Brain-damaged persons often correctly report a stimulus when given only to one side of the body (activation of only the contralateral cerebral hemisphere), but when both sides of the brain are activated simultaneously with bilateral stimulation, the less functional cerebral hemisphere is not able to register the incoming

5 R.M. Reitan, D. Wolfson / Archives of Clinical Neuropsychology 18 (2003) signal. Thus, the stimulus to one hand, across from the more impaired side of the brain, is not reported. This type of error rarely occurs among nonbrain-damaged children. The same general procedure is used with auditory and visual stimuli. It is clear that Bilateral Simultaneous Sensory Stimulation depends upon the ability to perceive and report simple sensory stimuli when delivered simultaneously to both sides of the body. This task is hardly ever difficult for persons with normal brain status. The second sensory perceptual test requires the subject to identify without the use of vision which finger has been lightly touched by the examiner. When necessary to ensure accuracy in reporting (as contrasted with a failure in perception), practice is given with the eyes open. Five trials, administered in random sequence, are given to each finger, resulting in a total of 20 trials for each hand. The score for each hand is the number of errors in the 20 trials. The final sensory perceptual test involves perception of numbers written on the distal finger-pads of each hand. The stimuli are prescribed numbers which were selected through experimentation to avoid confusion in reporting. Each finger receives a stimulus four times (for a total of 20 trials). The score is the total number of errors for each hand. The motor tests used in this study measured finger tapping speed for each hand, using a specific apparatus and a standardized procedure for administration and scoring (see Reitan & Wolfson, 1992). Five 10-s trials were given to each hand and the score was the mean of five trials. Our purpose in selecting this test was to measure a primary or basic aspect of motor functioning rather than a skilled task that might be more influenced by training or environmental factors. The information given above is not sufficient to permit valid administration of these tests, but was presented to provide a brief description of the tests used in this study and the scoring procedures. Precise procedures have been developed for each test in order to achieve valid results for the individual child (Reitan & Wolfson, 1992), which go well beyond the space limitations of this paper. The tests selected for this study have an additional advantage over and beyond providing information about how well each child performed. They also produce scores that identify the side of the body on which the error, or diminished performance, occurred. This information in turn correlates with the underlying anatomical and physiological substrate for the defective performances, with the general rule being one of contralaterality (the impaired side of the body is across from the damaged cerebral hemisphere). Experimental data among normals suggest that hand, eye, or ear preference has little effect on sensory perceptual results using these tests. However, hand preference has a distinct effect on finger tapping speed, with the preferred hand usually achieving a greater speed Data processing The first step was to transform rawscores on each test for each participant into Neuropsychological Deficit Scale (NDS) scores. The advantages of performing this transformation were twofold: (1) to place each score on a standard scale so that scores would be comparable among tests, and (2) to permit ready interpretation of the brain-related significance of each score. Achievement of these purposes was possible because the NDS score is a direct transformation of raw scores into NDS scores of 0, 1, 2, and 3, and these scores cover a range from excellent

6 16 R.M. Reitan, D. Wolfson / Archives of Clinical Neuropsychology 18 (2003) d from by guest on 01 October 2018

7 R.M. Reitan, D. Wolfson / Archives of Clinical Neuropsychology 18 (2003) scores and normal scores (NDS scores of 0 and 1) to mild to moderate impairment (NDS score of 2) and definite and severe impairment (NDS score of 3) (Reitan & Wolfson, 1992). In addition, differences in raw scores on each test for the two sides of the body were also converted to NDS scores that represent the same scale from 0 to 3. This latter transformation provides an intraindividual indicator, comparing the adequacy with which each side of the brain subserves each test for the individual subject, as a complement to how well the subject performs in accordance with normative standards. This latter NDS score has a special advantage inasmuch as it relates closely to the known anatomy of the sensory and motor systems with regard to the contralaterality of brain-effector and brain-receptor relationships. The test data permitted scoring of a number of variables for each child in the study and statistical analyses as well were based on NDS scores for each variable (adequacy of performance and right left differences); a total NDS score for the sensory perceptual tests; a total NDS score for the motor tests; and an overall sensorimotor NDS score. The groups were compared on means for each of these scores using t tests. 3. Results The results of this study, summarized in Table 1, indicate that (1) the brain-damaged group had lower means (poorer scores) on every variable, (2) the mean differences were statistically significant in every instance except for two variables based on intraindividual differences in performances on the two sides of the body, and (3) striking intergroup differences were present on many of the variables. The findings strongly support the validity of the adequacy of sensory motor functions as a basis for reliably identifying deficits in brain-damaged as compared with nonbrain-damaged children. The NDS was originally devised in a conservative manner, attempting to avoid overestimating the abilities of normal children and/or underestimating the abilities of brain-impaired children (Reitan & Wolfson, 1992). The results shown in Table 1 bear out this conservative approach. Mean values for the controls were consistently in the normal range (below 1), and on the motor (finger tapping) measure, were consistently in the range of excellent performances as reflected by the NDS score range of 0, 1, 2, and 3. This result may be due to the fact that all control children in the present study were functioning normally, whereas in the original determination of NDS ranges, there were a number of clinical referrals who had a variety of problems even though they had no evidence of brain damage. 4. Discussion The results of this study support the potential for conjoint and complementary use of sensorimotor (lower-level) brain functions and intellectual and cognitive (higher-level) brain functions in clinical evaluation of the individual child. While higher-level brain functions would appear to be more closely related to complex adaptive abilities than lower-level brain functions (although both obviously are important), it must be remembered that lower-level brain functions are more closely correlated with the structure and physiological functioning of the neurosensory

8 18 R.M. Reitan, D. Wolfson / Archives of Clinical Neuropsychology 18 (2003) and neuromuscular systems, and that deficits may therefore be more readily attributed to biological disorders rather than to environmental influences such as socioeconomic status, educational advantages, and the opportunities for ability development. Clinical experience in our laboratory over the years, using both lower-level and higher-level measures of brain functions in evaluation of each child, has clearly shown that a brain-related basis for academic deficiencies and behavioral disorders is much more readily identified when both levels of brain function are assessed and there is an opportunity to integrate lower-level and higher-level brain functions in the individual case. The results of this study prompted an informal examination of the relationship of tests of lower-level and higher-level brain functions for a number of individual children, recognizing that brain-damaged children would generally show evidence of impairment in both areas and that controls would generally perform adequately in both areas. While these expectations appear to have been confirmed, the informal examinations also suggested hypotheses for further study. Certain children showed disparities between lower-level and higher-level scores. Children with impaired lower-level scores (consistent with brain dysfunction) but fairly adequate higher-level scores usually were children whose deficits had been recognized early and who had received the benefits of vigorous intervention, special tutoring, etc. Children with adequate lower-level scores (consistent with normal brain functions) but impairment of higher-level scores often had failed to receive adequate stimulation and training through environmental experiences and educational opportunities. These observations suggest that intraindividual comparisons of scores on measures of lower-level and higher-level brain functions may provide significant insights about the individual child, although more research and clinical observation are obviously necessary. The results of this study are also relevant to the need for development of a short preliminary battery to identify children with brain-related limitations of adaptive abilities. Neuropsychological capabilities of children are routinely called upon in school performances, and it is important to understand the bases for limitations in academic aptitude and progress when they occur. The striking sensitivity of sensorimotor abilities to the status of the brain suggests that the tests used in this study, which generally require only min to administer, could readily be coupled with existing validated tests of higher-level brain functions to form a preliminary test battery that could identify children whose problems stem from disorders of brain function. References Halstead, W. C. (1947). Brain and intelligence: A quantitative study of the frontal lobes. Chicago: University of Chicago Press. King, H. E. (1954). Psychomotor aspects of mental disease. An experimental study. Cambridge: Harvard University Press. Reitan, R. M. (1959). The effects of brain lesions on adaptive abilities in human beings. Tucson, AZ: Neuropsychology Press. Reitan, R.M., & Wolfson, D. (1992). Neuropsychological evaluation of older children. Tucson, AZ: Neuropsychology Press.

Psychological Tests that Examine Brain Functioning

Psychological Tests that Examine Brain Functioning Psychology 372 Physiological Psychology Steven E. Meier, Ph.D. Listen to the audio lecture while viewing these slides or view the video presentation available