Neuropsychological assessment of learning disabilities: a discriminant analysis

The neuropsychological test scores of 23 learning disabled children were compared with those of a matched population of normal children in the 9-1 to 13-1 age range. All children were administered the Wechsler Intelligence Scale for Children-Revised (WISC-R), a dichotic listening task involving both free and directed recall conditions, a handedness inventory, the Tactile Performance Test and the Category Test from the Halstead-Reitan Neuropsychological Test Battery. A multivariate analysis of variance resulted in a significant separation between groups (p less than .001) using these procedures. A stepwise discriminant function analysis revealed that both of the directed dichotic tasks contributed the most of all 13 measures to the significant group separation. In addition, other cognitive tasks found to discriminate normal from learning disabled children include general verbal processes, concept formation, and tactile memory. These findings suggest that the directed dichotic listening procedure and the WISC-R Verbal IQ measure are reasonably valuable clinical tools in the classification of learning disabilities.     

Development of cerebral dominance: dichotic listening asymmetry in normal and learning-disabled children

The magnitude of the dichotic right-ear advantage was assessed in 48 normal and 48 learning-disabled children representing an age range of approximately 5 years. All subjects were matched according to age, sex, and handedness. An analysis of results indicated a significant right-ear advantage in both the normal and learning-disabled children, but revealed no developmental trends for either group. Differences observed in the performance of the learning-disabled and normal children may reflect variability in selective attention rather than differences in the degree of cerebral lateralization. These results suggest a need for a reconceptualization of the causative factors affecting children with learning disorders and lend support to the notion that cerebral lateralization is not a developmental phenomenon.     

Concurrent Verbal and Emotion Laterality Effects Exhibited by Normally Achieving and Learning Disabled Children

This study assessed both left- and right-hemisphere functions simultaneously when two-syllable words differing only in the initial stop consonant and spoken in different emotional tones were paired dichotically. Seventy-two right-handed normally achieving children, 12 boys and 12 girls at each of grades 1, 3, and 5, were instructed to detect either the presence of a specific word or of a specific emotion. In addition, 30 right-handed learning disabled (LD) children (age-matched to the normal controls) were assessed to determine whether LD children distribute verbal and nonverbal functions to different hemispheres. Results indicated that although both control and LD children demonstrated an overall REA for word stimuli and an LEA for emotional stimuli, and that emotional stimuli were easier to process than word stimuli, LD children were less accurate in processing both types of stimuli than their control counterparts. ‘Complementary specialization,’ as assessed through distribution of laterality effects, was found to be greater for control children than for LD children. However, the lack of consistency in complementary specialization found among the three developmental grade levels may be indicative that independent brain mechanisms underlying verbal and emotional processing have yet to be fully established in children. Further, in contrast to adult findings, a larger LEA was obtained for the emotion ‘happy’ than for the emotion ‘sad.’ It was concluded that whereas independent hemisphere processing for words and emotions is somewhat prevalent for control children, LD children might not be as strongly lateralized for opposite hemisphere processing of these functions.     

Attentional deficit in learning-disabled children: evidence from visual half-field asymmetries

The structural theory of cerebral lateralization has been typically used to explain hemispheric asymmetries. However, the attentional model of brain functioning may help resolve some of the inconsistent findings with groups of learning-disabled children. To test this hypothesis, a visual half-field paradigm for word recognition was employed in a group of 26 learning-disabled and 26 normal children matched for sex, chronological age, and handedness. Three experimental conditions (unilateral, cued unilateral, and bilateral) and two word error types (visually and acoustically confusable words) were analyzed. The results indicated that normals produced the expected RVHF superiority under all experimental conditions, but the learning-disabled produced the expected RVHF superiority only under the cued unilateral condition. Learning-disabled children also made significantly more visually and acoustically confusable errors than normals and unlike normal children increased the number of acoustic errors in the RVF under bilateral stimulation. These results provide evidence that learning-disabled children may process information inefficiently and have brain activation patterns that are more susceptible to attentional effects.     

Concurrent verbal and emotion laterality effects exhibited by normally achieving and learning disabled children.

This study assessed both left- and right-hemisphere functions simultaneously when two-syllable words differing only in the initial stop consonant and spoken in different emotional tones were paired dichotically. Seventy-two right-handed normally achieving children, 12 boys and 12 girls at each of grades 1, 3, and 5, were instructed to detect either the presence of a specific word or of a specific emotion. In addition, 30 right-handed learning disabled (LD) children (age-matched to the normal controls) were assessed to determine whether LD children distribute verbal and nonverbal functions to different hemispheres. Results indicated that although both control and LD children demonstrated an overall REA for word stimuli and an LEA for emotional stimuli, and that emotional stimuli were easier to process than word stimuli, LD children were less accurate in processing both types of stimuli than their control counterparts. 'Complementary specialization,' as assessed through distribution of laterality effects, was found to be greater for control children than for LD children. However, the lack of consistency in complementary specialization found among the three developmental grade levels may be indicative that independent brain mechanisms underlying verbal and emotional processing have yet to be fully established in children. Further, in contrast to adult findings, a larger LEA was obtained for the emotion 'happy' than for the emotion 'sad.' It was concluded that whereas independent hemisphere processing for words and emotions is somewhat prevalent for control children, LD children might not be as strongly lateralized for opposite hemisphere processing of these functions.     

The impact of frontal and non-frontal brain tumor lesions on Wisconsin Card Sorting Test performance

Several lesion and imaging studies have suggested that the Wisconsin Card Sorting Test (WCST) is a measure of executive dysfunction. However, some studies have reported that this measure has poor anatomical specificity because patients with either frontal or non-frontal focal lesions exhibit similar performance. This study examined 25 frontal, 20 non-frontal low-grade brain tumor patients, and 63 normal controls (NC) on the WCST. The frontal patients were also assigned to either a left frontal (n=10) group or a right frontal group (n=15) and compared with the non-frontal group and NC. It was hypothesized that the frontal brain tumor patients would display greater deficits on categories achieved and a higher number of perseverative errors than non-frontal brain tumor patients on the WCST. Finally, it was predicted that right frontal brain tumors would result in greater executive functioning deficits than left frontal or non-frontal brain tumors. Results indicated that the left frontal group achieved the fewest categories and committed the most perseverative errors compared to the other patient and normal control groups. In addition, the left frontal group committed significantly more perseverative errors than the right frontal group. These results suggest that the WCST is sensitive to the effects of low-grade brain tumors on executive functioning.     

The Relationship of Cognitive Tempo to Psychological Differentiation and Locus of Control

In this study, we investigated the relationship of cognitive tempo to psychological differentiation and locus of control. The 103 male and female undergraduate students who participated in this study were administered the adolescent and adult version of the Matching Familiar Figures Test, the Group Embedded Figures Test, and the Adult Nowicki-Strickland Internal-External Scale. Using multiple regression analyses, we found that field dependence and independence were significantly related to both cognitive tempo latency and cognitive tempo errors. Contrary to expectation, no relationship was found between locus of control and cognitive tempo. We concluded that psychological differentiation is highly useful in the direct prediction of cognitive tempo, although locus of control is not. Overall, the value of examining cognitive tempo latency and errors separately was upheld. The importance of these relationships is discussed.     

The role of dichotic listening performance and tasks of executive functions in reading impairment: a discriminant function analysis.

This study focused on the role of dichotic listening performance for the identification of reading impaired subtypes. Dichotic listening (DL), using verbal stimuli, has shown to be a valid measure of language lateralization. Usually, lateralization is estimated from the proportion of right ear over left ear accuracy during a free recall test procedure. However, it has been suggested that a more accurate estimate of laterality can be obtained by using a directed attention procedure. A sample of 43 reading disabled children of whom 18 showed signs of impaired language comprehension skills and 25 without language comprehension impairments, were compared to 20 age, and gender, matched controls on dichotic listening performance in both an unbiased free recall task and in a directed attention task using consonant-vowel syllables as dichotic stimuli. A laterality index was calculated for left and right ear stimuli reported during both the free recall condition and the attended ear-scores for the two directed attention conditions. Although both DL procedures yielded significant group differences, with a lower laterality score for the reading disabled compared to the controls, there was no main effect of DL-procedure or group x procedure interaction. Taken alone, DL performance could correctly classify 42% of the reading impaired samples, but together with other measures of executive functions, discriminant function analyses yielded 90.74% accuracy in classifying reading impaired children. The result indicates that DL together with tests of executive functions are valuable tools for assessment of reading impaired subjects.