Journal of Clinical and Experimental Neuropsychology

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Electrophysiological evidence of lateralized disturbances in children with learning disabilities Audrey J. Mattson , Daniel E. Sheer & Jack M. Fletcher To cite this article: Audrey J. Mattson , Daniel E. Sheer & Jack M. Fletcher (1992) Electrophysiological evidence of lateralized disturbances in children with learning disabilities, Journal of Clinical and Experimental Neuropsychology, 14:5, 707-716, DOI: 10.1080/01688639208402857 To link to this article: http://dx.doi.org/10.1080/01688639208402857

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Journal of Clinical and Experimental Neuropsychology 1992, Vol. 14, NO. 5, pp. 707-716

0168-8634/92/1405-0707$3.00 8 Swets & Zeitlinger

Electrophysiological Evidence of Lateralized Disturbances in Children with Learning Disabilities* Audrey J. Mattson and Daniel E. Sheer University of Houston

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Jack M. Fletcher Department of Pediatrics University of Texas Medical School Houston

ABSTRACT This study used an electrophysiological measurement operation to investigate lateralized processing deficits associated with academic learning-disabilitysubtypes. Fast frequency EEG activity in the 36-44 hertz (Hz) band was recorded from reading-disabled (RLD), arithmeticdisabled (ALD), and nondisabled control children engaged in verbal and nonverbal cognitive tasks. The control group, but neither LD group, exhibited a task-dependent shift in lateralization of 40 Hz EEG the RLD subjects generated proportionately less left-hemisphere 40 Hz activity than control or ALD subjects during the verbal task and the ALD subjects generated proportionately less right-hemisphere activity than control or RLD subjects during the nonverbal task. These results indicate that laterized processing deficits are associated with different types of disabilities, and provide external validation of learningdisability classifications based on academic performance patterns.

A major area of emphasis in learning disability (LD) research concerns methods of classifying disabled learners into homogeneous subtypes (Fletcher & Satz, 1985; Fletcher & Morris, 1986; Rourke, 1985). Rourke and co-workers (Rourke, 1982; 1989; Rourke & Finlayson, 1978; Rourke & Strang, 1978; Strang & Rourke, 1985) have proposed that L D children can be classified based o n academic performance patterns. They conducted a series of studies in which a variety of neuropsychological tests were administered to LD children divided into three groups on the basis of scores from the Wide Range Achievement Test (WRAT; Jastak & Jastak, 1978) (0201s & Rourke, 1988; Rourke & Finlayson, 1978;

* This manuscript is dedicated to Dr. Daniel E. Sheer, who passed away on May 28,1991. Supported in part by NIMH Grant #MH40715, Electrophysiological Analysis of Learning Disabilities. We thank Ron Ridder for his assistance in recruiting and testing subjects. Correspondence should be sent to Audrey J. Mattson, Ph.D. at her current address: Department of Neurology, University of Minnesota, Box 295 UMHC, Minneapolis, MN 55455,USA. Accepted for publication: December 15, 1991.

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Rourke & Strang, 1978). Group 1 was composed of children who exhibited deficits in reading, spelling, and arithmetic; Children in Group 2 were relatively adept at arithmetic, but exhibited marked deficits in reading and spelling; and Children in Group 3 exhibited deficits only on the arithmetic subtest. On neuropsychological testing, children in Group 1 and Group 2 exhibited impaired performance on verbal measures believed to assess left-hemisphere processing systems (e.g.. psycholinguistic tests). In contrast, children with specific arithmetic disorders (Group 3), performed poorly on nonverbal tasks that are used to assess the functioning of right-hemisphere systems (e.g., visuoperceptual measures). The neuropsychological test patterns identifiedby Rourke (1982) and subsequent investigators (e.g., Fletcher, 1985) provide indirect evidence linking academic based LD subtypes with lateralized central nervous system dysfunction (Taylor & Fletcher, 1983). Additional data using different measurement techniques (i-e., not based on psychological test profiles) are also needed, however, to validate the existenceof lateralizedprocessing disturbances in children with various subtypes of learning disabilities. For example, Stelmack and Miles (1990) recorded visual event-related potentials (Ems) from reading-disabled (Group 2) and normal children during a priming / recognition memory task. Group differences were found in ERPs generated to unprimed words at laterally placed posterior electrodes. The pattern of results suggested left-hemisphere processing deficiencies in the reading-disabled group, thus supporting Rourke’s (1982) model. Electrophysiological techniques are well suited to the study of processing within the central nervous system because they are noninvasive and can be utilized while subjects engage in cognitive tasks. Another electrophysiological technique that has potential as a tool for investigating lateralized processing deficiencies associated with LD subtyps is 40 Hz EEG (Sheer, 1989; Sheer & Shock, 1986). Previous studies have demonstrated that fast frequency EEG activity in the 36-44 Hz band (40 Hz) is positively correlated with problem-solving abilities, learning, and attention (Loring & Sheer, 1984; Sheer, 1984: Spydell, Ford, & Sheer, 1979; Spydell & Sheer, 1982). In addition, these studies demonstrated that the lateralization of 40 Hz EEG activity in adults is normally task-dependent. When subjectsengage in verbal tasks, 40 Hz activity increases within the left hemisphere, whereas proportionally greater 40Hz EEG activity occurs over the right hemisphere during visual-spatial tasks. Forty Hz EEG activity reflects ‘focused arousal’, a state of localized cortical activity (Sheer, 1984; 1989). Sheer’s (1984) model for the control of attention proposed that five hierarchical and orthogonal processing modes exist that can be dissociated, on the one hand, by different brain circuitry, and on the other, by different sets of behavioral operations. According to the model, ‘focused arousal’ represents the interaction between facilitatory neural processing (i.e., phasic arousal generated within the midbrain reticular formation) and specific sensory inputs. Forty Hz EEG, reflecting a state of focused arousal, is generated when an individual concentrates on a specific mental task. Sheers’ concept of ‘focused

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arousal’ overlaps partially with other constructs of attention, such as sustained attention (Douglas, 1983), selective attention (Kinsbourne, 1973; Posner, 19881, and effortful processing (Hasher 8z Zacks, 1979). Sheer (1974,1976) and Auerbach (1981) investigated the generation of 4 0 Hz EEG activity in LD children and controls matched for age and IQ. These studies found that nondisabled controls exhibited significant increases in 40 Hz EEG activity when engaged in various cognitive tasks, but LD children did not. These findings indicate that the relationship, consistently found in normal adults and children between cognitive processing and 40 Hz EEG, does not occur in LD children. Speciffc LD subtypes, however, were not examined. The present study expands on Rourke’s (1982) earlier work by using 40 Hz EEG methodology to investigate whether children with academic subtypes of LD exhibit lateralized processing deficits. Forty Hz EEG activity was recorded bilaterally from children with arithmetic disabilities (ALD), reading disabilities (with or without additional problems in arithmetic) (RLD), and nondisabled control children while they engaged in verbal and nonverbal cognitive tasks. It was hypothesized that (a) a task-dependent shift in the lateralization of 40 Hz activity would occur in the control children, but not in either group of L D children; (b) during the verbal condition, RLD disabled children would generate proportionally less 40 Hz EEG activity in the left hemisphere than would ALD children or controls; and (c) during the nonverbal condition ALD children would generate proportionally less right hemisphere 40 Hz EEG activity than would either the RLD children or controls. METHOD Subjects Twenty-six right-handed subjects ranging in age from 9 to 15 years were tested. Children with a history of neurologic or emotional disturbance were excluded from the study. Parental consent and child assent were obtained. Subjects were not compensated for their participation. There were 8 subjects in the reading-disabled (RLD) group, 8 in the arithmeticdisabled (ALD) group, and 10 in the control group. The LD and control groups were comparable in age and gender (Table 1). Controls were recruited from the community and screened for inclusion in the study using the Wechsler Intelligence Scale for Children-Revised (WISC-R, Wechsler, 1974) and the Wide Range Achievement Test (WRAT, Jastak & Jastak. 1978). Criteria for inclusion in the study were a Full Scale IQ greater than 80, with either the Performance or Verbal IQ greater than 85, and scores above the 40th centile on WRAT reading and arithmetic subtests. The LD children had either a specific impairment in arithmetic or in reading, with or without additional problems with arithmetic. They were indentified by two clinical neuropsychologists on the basis of previous clinical evaluations that included the WISCR and M A T , or similar instruments (see Table 1). Full scale IQ requirements for LD subjects were the same as for controls. The ALD group corresponded with Rourke’s (1982) “Group 3”. That is. subjects obtained an Arithmetic score below the 35th centile and a Reading score above the 40th centile. The RLD group corresponded to a combination of Rourke’s (1982) “Group 1” and “Group 2”. That is, six RLD subjects obtained reading and arithmetic scores below the 35th centile (Group l), while two subjects were

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Table 1. Age, Gender, Intelligence. and Achievement Test Scores by Group. Controls n

Gender Male Female Age (Yr; Mo)

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M

Arithmetic Disabled'

Reading Disabled

10

8

8

8 2

6 2

0

12;4 SD (23) Wechsler Intelligence Scale for Children-Revisedb Full Scale IQ M 117.2 SD (15.7) Wide Range Achievement Test (centiles)b Reading M 88.3 SD (10.8) spelling M 72.7 SD (16.1) Arithmetic M 77.7 SD (15.7)

8

12;o (1;8)

11;3

95.5 (6.4)

104.1 (14.3)

62.3 (10.8)

14.1 (9.8)

44.3 (24.1)

13.6 (11.9)

13.1 (9.7)

23.4 (22.1)

(20)

An IQ score was not obtained for one subject, and achievement test scores were not obtained for two children in this group. Test scores for two reading-disabled subjects were obtained on comparable measures.

below the 35th centile in reading and above the 40th centile in arirhmetic (Group 2). The academic criteria were liberal compared to those previously used by Rourke (1982). However, the majority of LD children were significantly more impaired than the criteria suggest (see Table 1). The data contained in Table 1 includes test scores for all but two LD subjects. We did not receive Full Scale IQs. or a comparable score, for two ALD children, or achievement test scores for one of these subjects. This subject had been tested and placed into the group. However, the child's file was apparently misplaced and her test scores were not obtained. Apparatus and Materials A specially designed computer system was used to record and analyze 40 Hz EEG activity. This system, which has been described in detail elsewhere (Raghavan, Glover, & Sheer, 1986), contains high quality signal amplifiers and corrects for muscle activity (70 Hz activity) using an analysis of covariance algorithm. Trials with muscle activity above a set criterion (Lea,70 Hz power > 10,OOO as calculated by computer system from either active electrode) were excluded from analyses. A Bell and Howell Ring Master Auto Focus Sound Slide projector (model G99B) presented stimuli during EEG procedures. The unit was commercially designed to present synchronized audio and visual information. Internal circuits were modified to generate a 1-volt external signal pulse at lo00 Hz after receiving an internal electrical pulse pre-

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recorded on audio tape. The extemal pulse was an input to the EEG analyser system and initiated signal processing during each test trial.

Experimental Procedures Subject Preparation. Four gold-plated disc EEG electrodes (Grass #E5G) filled with electrode cream were secured to the subjects’ scalp. Prior to attachment, the sites were cleaned of dry skin and oils using a cotton swab and mild abrasive cleanser (omni prep). Electrode impedance measures were less than 3k ohms. Electrodes were placed according to the international electrode placement system (Jasper. 1958). Active electrodes were placed in the middle of the triangles formed by 01 P3 T5 on the left and 02 P4 T6 on the right, which is above the junction between parietal-temporal-occipital brain regions bilaterally. Both electrodes were referenced to Cz, and a common ground was secured to the center of the subjects’ forehead one inch below the hairline. Cz was used as a reference, rather than the earlobes, because it is freer of muscle artifact and still equal distance from the active electrodes. After attachment of the electrodes, subjects were seated in a recliner chair facing the rear view projection screen of the Bell and Howell slide projection system. The electrodes were then connected to the 40 Hz EEG computer analyser. Prior to beginning the test procedures, subjects were given an opportunity to ask questions. Testing Procedures. The verbal and nonverbal tasks utilized were adaptations of standard

neuropsychological tests. The verbal task was a modification of the sentence repetition test described by Baker and Leeland (1967) and Spreen and Benton (1969). Subjects listened to sentences presented on audio-tape. Each sentence was preceded by the warning, “Ready.” After each sentence was presented, a brief paused occurred. This was followed by a “beep.” After the “beep”, subjects had been instructed to repeat the sentence to the examiner. During the 14-s interval, from sentence presentation until just prior to the subject’s response, the 40 Hz EEG computer automatically recorded 40 Hz activity from each hemisphere. The nonverbal task was a modification of the Test of Face Recognition (Benton, Van Allen, Hamsher, & Levin, 1975). The nonverbal trials consisted of the following sequence. On the slide screen, directly in front of the subject, a face was projected for three seconds. Then three additional faces were projected one at a time. Following the last face a blank slide appeared on the screen. This was the subject’s cue to tell the examiner how many of the last three faces were of the same person as the first picture. The computer analyser automatically recorded 40 Hz activity from both hemispheres during the 14-s interval from presentation of the first face until just prior to the subject’s response. Each subject completed at least 16 trials of the verbal, sentence repetition, task and 16 trials of the nonverbal, facial recognition, task. The presentation of task mals alternated. Eight verbal trials were presented first. This was followed by 16 or 24 nonverbal trials. Then the final set of verbal trials was presented. Each verbal trial was unique. Facial recognition trials consisted of a set of eight items that were presented two or three times.

RESULTS The research hypotheses were tested using nonparametric statistics consisting of three within-subject and four between-subject comparisons. The within-subject analyses were conducted to determine whether each group exhibited a taskdependent shift in 40 Hz EEG activity. For each group, a Wilcoxon matched pairs signed-ranks test was computed on the mean laterality ratios (L-R/L+R) obtained for each subject with the verbal and nonverbal tasks. The laterality ratio

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equals the number of left 40 Hz peaks minus the number of right 40 Hz peaks divided by left peaks plus right peaks. Results of these analyses revealed that the control group exhibited a significant task-dependent shift in lateralization of 40 Hz EEG (Z= -2.09, p < .05), while a task-dependent shift in 40 Hz activity did not occur in either the ALD group (Z = -0.56, p > .05) or RLD group (2= -0.84, p > .05). Two sets of between-subjectcomparisons were then made using Mann-Whitney tests. The dependent variables were the percentage of verbal trials in which a greater number of 40 Hz peaks were recorded over the left hemisphere, as compared to the right (Verbal % L > R), and the percentage of nonverbal trials in which a greater number of 40 Hz peaks were recorded over the right hemisphere, as compared to the left (Nonverbal % R > L). The average percentages obtained by subjects in each group are contained in Table 3 and illustrated in Figure 1. Pairwise group comparisonsdetermined that RLD subjectsexhibitedproportionally less left hemisphere 40 Hz EEG during verbal cognitive activity than did controls (U= 8.5, p < .02) or ALD children (U= 11.0, p c .02). During the nonverbal task, ALD subjects exhibited proportionally less right hemisphere activation than did RLD children (U = 11.O, p < .03). The difference between ALD children and controls on the nonverbal task approached significance (U= 20.0, p < .08).Differences between the ALD group and control group during the verbal task and between the RLD group and the control group during the nonverbal task were not significant (p = .65 and p = .42, respectively).

loo 80

1 4

Verbal Trials

-

L> R

o Nonverbal Trials

-

Controls

RLD

ALD

R>L

Fig. 1. Lateralization of 40 Hz EEG activity during verbal and nonverbal cognitive tasks by group.

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LATERALIZED PROCESSING DISTURBANCES

Table 2. Mean Verbal Trials (Left > Right) and Nonverbal Trials (Right > Left) Percentages By Group on the 40 hertz (Hz) EEG Measure. Percentage Verbal Trials Left 40 Hz > Right 40 Hz

Percentage Nonverbal Trials Right 40 Hz > Left 40 Hz

~

Controls M SD

74.0 (21.1)

51.7 (24.2)

34.6 (26.9)

61.5 (23.6)

73.9 (24.8)

29.4 (27.5)

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M

SD Arithmetic Disabled M SD

DISCUSSION The results obtained in this study support the hypothesis that there is an interaction between the lateralization of 40 Hz EEG during cognitive activity and LD academic subtypes. A task-dependent shift in lateralization of 40 Hz EEG occurred in controls. This suggests that, in children as well as adults, the left hemisphere mediates the processing of verbal information, whereas the right hemisphere is relatively more involved in the processing of nonverbal information. In addition, the absence of this shift in both LD groups suggests lateralized processing deficits. During the verbal task, RLD children evidenced proportionally less left hemisphere 40 Hz EEG activity than did either the control children or the children with arithmetic learning disorders (ALD). This finding is consistent with the results obtained by Sheer (1974; 1976), Auerbach (1981), and Stelmack and Miles (1990). In addition, this finding demonstrates a dissociation between reading and arithmetic disorders, providing external validation of Rourke’s WRAT learningdisability classification (Rourke, 1982; Strang & Rourke, 1985). During the nonverbal task, children with arithmetic learning disorders generated proportionally less right hemisphere 40 Hz activity than did either the readingdisabled children or controls. The last finding was less robust, which may be due to several factors. First, performance on the facial recognition task does not appear to be as strongly “lateralized” to the right hemisphere as is the verbal task to the left hemisphere. This is evident by the control group’s overall lower percentage of nonverbal trials (52%) which elicited greater 40 Hz EEG activity on the right, compared to verbal trials (74%) which elicited greater activation of the left-hemisphere (Table 3 and Figure 1). These results are consistent with Kimura’s (1973) report that the magnitude of left hemisphere superiority for verbal tasks is greater than the magnitude of right hemisphere superiority for nonverbal tasks. On the nonverbal task used in this study, for example, subjects

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may have used verbal mediation strategies to help solve the problems, thus engaging both hemispheres. Young (1986) reviewed the literature on recognition of unfamiliar faces and concluded that subjects can be made to shift from showing a lateral difference simply by changing task requirements. Young emphasized that it is important to exert control over the strategies and cognitive processes used in performing facial perception tasks. If subjects in the present study used verbal mediation strategies, differences between the ALD group and controls would be diminished. However, differencesbetween the ALD and RLD groups would not be significantly influenced, reflecting the RLD group’s inability to efficiently activate left hemisphere processing systems. A second potential factor that may have contributed to less robust differences in 40 Hz EEG between ALD and control subjects during the nonverbal task is that all of the ALD children may not have had right hemisphere dysfunction. Rourke’s (1987; 1988; 1989) recently developed model of nonverbal learning disorders, which encompasses children who exhibit deficits in computational arithmetic, proposes that white matter damage or dysfunction can cause a disruption of intermodal integration, resulting in these impairments. Results of a study conducted by Grunau and Low (1987) also suggest that this may be the case. They performed a discriminant analysis to classify adolescents into groups with high and low calculation ability using a combination of cognitive and taskrelated EEG variables. Task-related decreases in theta and alpha EEG activity at both right and left hemisphere locations made significant contributions to the discriminant analysis. Based partially on these findings, it was concluded that arithmetic ability is dependent upon left and right hemisphere cooperation. Lastly, it could be argued that our findings are an artifact of differences in IQ, rather than due to lateralized processing deficiencies (Table 1). This argument is limited, however, since significant differences were not found between the arithmetic-disabled group and control group in left hemisphere activation during the verbal task, nor between the reading-disabled and control groups in right hemisphere activation during the nonverbal task. Furthermore, the most robust differenceswere between the ALD and RLD groups, who had relatively comparable mean Full Scale IQ scores. A limitation of this study, which should be noted, is that data regarding subjects’ performance on the cognitive tasks was not collected. As a result, statements cannot be made regarding the relationship between levels of ‘focused arousal’ and variation within a subject’s performance across trials. In future studies, this relationship should also be examined. Considering the relatively small sample size in this study, however, the findings obtained provide strong evidence that lateralized processing deficits underlie, at least in part, the differences in performance exhibited by children with various academic LD subtypes. Forty Hz EEG methodology appears to be a valuable tool for investigating electrophysiological correlates of cognitive processing in LD children. In addition, in his model Sheer (1984; 1989) integrated results of

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neuroanatomical, neurochemical, and neurophysiological investigations into the neural substrates of attention; and delineated the brain circuitry believed to be involved in the generation of 40 Hz EEG activity and the neural mechanisms that, presumably underlie ‘focused arousal’. As a result, insights regarding the neurophysiological basis of learning disorders may be gained through the continued application of 40 Hz EEG methodology.

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REFERENCES Auerbach, V. (1981). 40 hertz EEG activity in LD and normal children during baseline and verbal task conditions. Unpublished master’s thesis, University of Houston, Houston, TX. Baker, H., & Leeland, B. (1967). Detroit Tests of Learning Aptitude. Indianapolis: BobbsMemll. Benton, A.L., Van Allen, M.W., Hamsher, K. des, & Levin, H.S. (1975). Test of Face Recognition, Form SL. Iowa City: Department of Neurology, University of Iowa HOSpitals. Douglas, V.I. (1983). Attentional and cognitive problems. In M. Rutter (Ed.), Developmental neuropsychiatry (pp. 280-330). New York: Guilford Press. Fletcher, J.M. (1985). External validation of learning disability typologies. In B.P. Rourke (Ed.), Neuropsychologyof learning disabilities: Essentials of subtype analysis (pp. 18721 1). New York: Guilford Press. Fletcher, J.M., &Morris, R. (1986). Classification of disabled learners: Beyond exclusionary definitions. In S.J. Ceci (Ed.), Handbook of cognitive, social, and neuropsychological aspects of learning disabilities (Vol. 1) (pp. 55-80). Hillsdale, NJ: Erlbaum. Fletcher, J.M., & Satz, P. (1985). Cluster analysis and the search for learning disability subtypes. In B. P. Rourke (Ed.), Neuropsychology of learning disorders: Essentials of subtype analysis (pp. 40-64).New York: Guilford Press. Grunau, R.V.E., & Low, M.D. (1987). Cognitive and task-related EEG correlates of arithmetic performance in adolescents. Journal of Clinical and Experimental NeuroPSycholOgy, 9 , 563-574. Hasher, L., & Zacks, R.T. (1979). Automatic and effortful processes in memory. Journal of Experimental Psychology: General, 108,356-388. Jasper, H. (1958). Appendix toreport of the committee on methods of clinical examination in electroencephalography: The ten twenty electrode system of the International Federation. Electroencephalography and Clinical Neurophysiology, 10,370-375. Jastak, J., & Jastak, S. (1978). The Wide Range Achievement Test. Wilmhgton, DE: Guidance Associates. Kimura, D. (1973). The assymmetry of the human brain. Scientific American, 228.70-78. Kinsboume, M. (1973). The control of attention by interaction between the cerebral hemispheres. In S . Kornblum (Ed.), Attention andperformance ZV (pp. 239-258). New York: Academic Press. Loring, D., & Sheer, D.E. (1984). Laterality of 40 hertz EEG and EMG during cognitive task performance. Psychophysiology, 21,34-37. Ozols, E.J., & Rourke, B.P. (1988). Characteristics of young learning-disabled children classified according to patterns of academic achievement: Auditory-perceptual and visual-perceptual abilities. Journal of Clinical Child Psychology, 17.44-52. Posner, M.I. (1988). Structures and functions of selective attention. In T. Boll & B.K. Bryant (Eds.), Clinical neuropsychology and brain function: Research, measurement and practice (pp. 196-202). Washington, DC: American Psychological Association. Raghavan, N., Glover, J.R., Jr., & Sheer, D.E. (1986). A microprocessor-based system for

Downloaded by [New York University] at 19:13 17 October 2015

716

AUDREY J. MAlTSONET AL.

diagnosis of cognitive dysfunction. IEEE Transactions on Biomedical Engineering, 33, 942-948. Rourke, B.P. (1982). Central processing deficiencies in children: Toward a developmental neuropsychological model. Journal of Clinical Neuropsychology. 4. 1-18. Rourke, B.P. (1 985). Newopsychology of learning disabilities: Essentials of subtype analysis. New York: Guilford Press. Rourke, B.P. (1987). Syndrome of nonverbal learning disabilities. The final common pathway of white-matter disease/dysfunction? The Clinical Neurop&wlogist, 1,209-325. Rourke, B.P. (1988). The syndrome of nonverbal learning disabilities: Developmental manifestations in neurological disease, disorder, and dysfunction. The Clinical Neuropsychologist. 2,293-330. Rourke, B.P. (1989). Nonverbal learning disabilites: The syndrome and the model. New York: Guilford h s s . Rourke, B.P.. & Finlayson, M.A.J. (1978). Neuropsychological significance of variations in patterns of academic performance: Verbal and visual-spatial abilities. Journal of Abnormal Child Psychology, 6,121-133. Rourke, B.P., & Strang, J.D. (1978). Neuropsychological significance of variations in patterns of academic performance: Motor, psychomotor, and tactile-perceptual abilities. Journal of Pediatric Psychology, 3,62-66. Sheer, D.E. (1974). Electrophysiologic studies in learning disabilities. In H.Eichenwald & A. Talbot (Eds.), The learning disabled child (pp. 47-58). Austin: University of Texas Press. Sheer, D.E. (1976). Focused arousal and 40 hertz EEG. In R.M. Knights & D.J. Bakker (Us.). The neuropsychology of learning disorders (pp. 71-87). Baltimore: University Park Press. Sheer, D.E. (1984). Focused arousal, 40 hertz EEG and dysfunction. In T. Elbert, (Ed.), Self-regulation of the brain and behavior (pp. 63-84). New York: Springer-Verlag. Sheer, D.E. (1989). Sensory and cognitive 40-Hz event-related potentials: Behavioral correlates, brain function, and clinical application. In E.Basar & T. H. Bullock (Eds.), Brain Dynamics (pp. 339-374). New York Springer-Verlag. Sheer, D.E.,& Schrock, B. (1986). Attention. In J. Hannay (Ed.), Experimental techniques in human neuropsychology (pp. 95-137). New York Oxford University Press. Spreen, O., & Benton, A.L. (1969). Sentence Repetition Test. Neuropsychology Laboratory, University of Victoria. Spydell, J.D., Ford, M.R., & Sheer, D.E. (1979). Task dependent cerebral lateralization of the 40 h e m EEG rhythm. Psychophysiology. 16,347-350. Spydell. J.D., & Sheer, D.E. (1982). Effect of problem solving on right and left hemisphere 40 hertz EEG activity. Psychophysiology, 19,420-425. Stelmack, R.M.& Miles, J. (1990). The effect of picture priming on event-related potentials of normal and disabled Eaders during a word recognition memory task.Journal qfclinical and Experimental Neuropsychology, 12,887-903. Strang. J.D., & Rourke, B.P. (1985). Arithmetic disability subtypes: The neuropsychological significance of specific arithmetic impairment in childhood. In B.P. Rourke (Ed.), Neuropsychology of learning disabilities: Essentials of subtype analysis (pp. 167-183). New York Guilford. Taylor, H.G., & Fletcher, J.M. (1983). Biological foundations of “specific developmental disorders”: Methods, findings, and future directions. Journal of Child Clinical Psy~hology.12,46-65. Wechsler, D. (1974). Manualfor the WechslerIntelligence Scalefor Children-Revised. New York Psychological Corporation. Young, A.W. (1986). Subject characteristics in lateral differences for face processing by normals: Age. In R. Bruyer (Ed.), The neuropsychology of face perception and facial expressiun (pp. 167-200). Hillsdale: Lawrence Erlbaum.

Electrophysiological evidence of lateralized disturbances in children with learning disabilities.

This study used an electrophysiological measurement operation to investigate lateralized processing deficits associated with academic learning-disabil...
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