The effects of hemispatial and asymmetrically focused attention on dichotic listening with normal and learning-disabled children.

The effects of hemispatial and focused attention were examined with 50 normal and learning-disabled children to determine the extent of these two attentional strategies influenced perceptual laterality as reflected by the dichotic listening right-ear advantage (REA). Twenty-five normal children (8 females, 17 males, mean age 9.10 yr) matched with 25 learning-disabled children (8 females, 17 males, mean age 10.1 yr) were administered a dichotic consonant-vowel (CV) and consonant-vowel-consonant (CVC) syllable task. The two types of stimuli were compared across focused attention (free report, focused left, focused right) and hemispatial (central, left hemispace, right hemispace) conditions implemented independently and in systematic combinations. A four-factorial analysis of variance (groups x stimuli x conditions x ears) resulted in a significant REA for normal children across all attentional conditions whereas learning-disabled did not produce a consistent REA across all attentional conditions, and in several instances, produced equivalent left and right hemisphere processing. Right hemispatial orientation increased the magnitude of the REA (i.e., left hemisphere processing) for both groups, whereas left hemispatial orientation increased the magnitude of the left ear report (i.e., right hemisphere processing) only in learning-disabled subjects. Focused attention to the right ear also increased left hemisphere efficiency for both groups of children; however, focused attention to the left ear produced symmetrical functioning by learning-disabled subjects. Congruent combinations of focused attention and hemispatial orientation were not found to enhance the REA beyond its magnitude when each strategy was assessed independently. When focused attention and hemispatial conditions were employed in opposing directions, normal children were more susceptible to the "rightward" direction regardless of the strategy whereas learning-disabled subjects were more susceptible to the "verbal" nature of the strategy. Higher overall processing performance was exhibited for CVC stimuli when compared to CV stimuli. These findings lend support to the hypothesis that hemispatial and asymmetrically focused attention strategies interact with structural mechanisms in producing the observed REA in dichotic listening and do so differentially for normal and learning-disabled children.

The influence of attention on the dichotic REA with normal and learning disabled children.

Recently, Mondor and Bryden (Neuropsychologia, 29, 1179-1190, 1991; Percept. Psychophys. 52, 393-402, 1992) developed a lateralized cueing technique which appears to be a more powerful method than is the forced-attention technique (Bryden, 1978) of controlling the contribution of attentional biases to auditory perceptual asymmetries. This lateralized cueing technique was used to determine the influence of attentional biases on perceptual asymmetries obtained for normal and specific learning disabled (LD) children. Subjects were instructed to attend to, and report from, only the ear in which the cue sounded. The interval between the onset of the cue and the onset of the dichotic trial is varied so as to control the amount of time available to subjects to allocate attention to the cued ear. Results indicated that, for normal children capable of performing the task at a better than chance level, a large REA apparent at 150 msec Stimulus Onset Asynchromy (SOA) was attenuated at longer cueing intervals (450 and 750 msec SOA). For LD children, the magnitude of the initial REA appeared to be attenuated at 450 msec SOA. Thus, these data demonstrate that for normal children as well as for children with specific learning disabilities, attentional factors may contribute to the magnitude of the REA.

Spatial lateralization: the relationship among sex, handedness and familial sinistrality.

Spatial lateralization was examined in 80 subjects by use of a strictly balanced design contrasting sex, handedness and familial sinistrality (absent and present). A modified version of Witelson's dichaptic stimulation task (verbal and nonverbal) was employed. The verbal task showed a significant main effect for the right-hand score. On the nonverbal task only two groups displayed a significant difference between hand scores: left-handed males with familial sinistrality and right-handed females with no familial sinistrality. Results are discussed in relation to previously reported data.

Verbal and nonverbal auditory processing among left- and right-handed good readers and reading-disabled children.

Cerebral lateralization of left- and right-handed good readers and left- and right-handed reading disabled was examined with a sample of 60 children who ranged in age from 7-13 years via a dichotic selective attention task (free recall, directed left, directed right) using consonant-vowel (CV) and tonal stimuli. Several ANOVAs were conducted to evaluate gender, reader group, handedness, and stimuli effects of left- and right-ear reports across dichotic conditions. Results indicated males outperformed females across stimuli and conditions regardless of handedness and all subjects recalled more tonal stimuli than CV stimuli. More importantly, the expected REA (left hemisphere processing) was found for CV stimuli only by right-handed good readers across all three dichotic conditions. The left-handed good readers and left-handed reading-disabled children were left ear (LE) dominant in free recall and in the directed left condition, but were right ear (RE) dominant in the directed right condition. Conversely, right-handed reading-disabled children produced a REA during free recall and directed right conditions, but were LE dominant in the directed left condition. In contrast, a significant LEA (right hemisphere processing) was found for tonal stimuli across all dichotic conditions for all four groups. These findings lend support to the hypothesis that attentional factors have a greater influence on auditory processing of verbal than nonverbal stimuli for various groups of children and also suggest reversed or bilateralized processing abilities for language in strongly left-handed children with sinistral relatives.

Cued dichotic listening with right-handed, left-handed, bilingual and learning-disabled children.

This study used cued dichotic listening to investigate differences in language lateralization among right-handed (control), left-handed, bilingual, and learning-disabled children. A sample of 60 subjects ranging in age from 7-13 yr were administered a CVC dichotic paradigm with three experimental conditions (free recall, directed left, directed right). A three-factor ANOVA design conducted on the data revealed that control, bilingual, and learning-disabled children produced the expected REA suggestive of left hemisphere dominance for language processing whereas left-handed children produced an LEA suggestive of right hemisphere superiority for language processing. The cued attention data derived from groups as well as from individual subjects suggested that in comparison with control children, left-handed children were greatly susceptible to attentional manipulation similar to learning-disabled children only in the opposite hemisphere. Bilingual children were found to have a REA much like control children although recall accuracy was depressed. Further, lambda (lambda) analyses conducted on individual subjects indicated that the magnitude and degree of perceptual asymmetry varied widely among individuals of various anomaly groups. These findings lend support to the hypothesis that attentional factors play a larger role in unilateral processing for some anomalous groups of children (i.e. left-handers and learning-disabled) while not affecting others (i.e. controls and bilinguals).

Construct validity of neuropsychological instrumentation with a learning disabled population.

The construct validity of the Reitan-Indiana Neuropsychological Test Battery (R-INB)for Children with a learning disabled population was examined. Forty-two subjects classified as learning disabled also were administered the Wechsler Intelligence Scale for Children-Revised (WISC-R) and Wide Range Achievement Test (WRAT) subtests. Factor analysis of the data revealed four factors: verbal intelligence, psychomotor speed, achievement, and memory. Evidence from this study indicates that the overall construct paradigm as conceptualized by the author of the R-INB does not exist. Implications of these findings are discussed.

Information processing and speech lateralization in learning-disabled children.

The relationship between information processing and speech lateralization was investigated in learning-disabled children. The Kaufman Assessment Battery for Children (K-ABC) assessed simultaneous and successive processing while a dichotic listening paradigm with free recall and directed attention conditions assessed speech lateralization. A three-factor ANOVA design conducted on the dichotic data revealed that normal children demonstrated stronger right ear advantage (REA); whereas learning-disabled showed weaker right ear advantage. Further, lambda analyses conducted on individual subjects revealed that the learning-disabled did not demonstrate the REA, were not biased attenders, and did not get more right ear than left ear items when attention was directed to one ear. Multiple-regression analysis was used to predict sequential processing from the dichotic data for both groups. Learning-disabled children demonstrated a substantial deficit in sequential processing as compared to normal children. These results indicate that learning-disabled children may not have adequate cerebral lateralization of receptive speech processes, shift their attention more readily, and are more inadequate in sequential processing that presumably subserves language functioning. Perhaps learning-disabled children have deficiencies of processor capacity of salient areas of the left (language) hemisphere.

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.

Taxonomic clustering and frequency associations as features of semantic memory development in children with learning disabilities.

This study investigated taxonomic clustering and use of frequency associations as features in the semantic memory development of children with learning disabilities (LD). Free-recall organization of second- and sixth-grade children with and without LD was analyzed for two types of primary and secondary word lists: (a) items associated with frequency (FA), and (b) items related by category members (CM). In contrast to expected findings, younger, non-disabled children organized words categorically as proficiently as their older nondisabled peers, and the categorization abilities of children with LD were comparable to those of nondisabled subjects, with one exception: Subjects with LD showed less clustering for secondary FA. These results indicate that when individual child-generated word lists (i.e., meaningful and familiar words) are used, children with LD may not be impaired in their ability to recognize and utilize semantic structure to facilitate learning.

Neuropsychological consequences of traumatic brain injury in children and adolescents.

The study of the relationship between neuroscientific information and cognitive function and dysfunction is clearly a widely expanding field. In particular, there has been a growing body of research on traumatic brain injury (TBI) in children and adolescents. This article conveys recent findings concerning cognitive outcomes, with a particular focus on age differences with TBI, suggests a relationship between specific learning disorders and brain dysfunction, addresses differential hemisphere functioning with TBI, and alludes to recent developments in assessment of TBI.

Neuropsychological treatment of dyslexia in the classroom setting.

The purpose of this study was to validate Bakker's (1990, 1992) clinical neuropsychological balance model of dyslexia when implemented in a traditional general education classroom environment. The sample included 45 middle school, right-handed boys and girls (mean age = 12.78) with L-type dyslexia (excessively fast readers who make substantive reading errors), P-type dyslexia (displaying accurate but slow and laborious reading), and M-type dyslexia (readers who commit a combination of L-type and P-type dyslexia errors). The experimental groups (L and P type dyslexia) were presented with hemisphere specific stimulation (HSS) and hemispheric alluding stimuli (HAS). HSS involves the presentation of words into the right visual field (RVF) or the left visual field (LVF) or through tactile exercises with the right or left hand. HAS is achieved by constructing semantically and phonetically challenging letters and words. The children with M-type dyslexia served as a control group and received traditional decoding and comprehension exercises. The readers were exposed to a specific treatment model for 16 weeks, depending on their reading accuracy and comprehension. Statistical analyses indicated that, although there were no significant changes in word recognition for the dyslexia subtypes, the readers with L-type, P-type, and M-type dyslexia exhibited significant improvement in reading accuracy and comprehension as assessed by results from pretest to posttest. These results suggest that Bakker's clinical neuropsychological intervention can be effectively applied to the general education setting as well.

Development of reciprocal hemispheric inhibition in normal and learning-disabled children.

Matched populations (N = 90) of learning-disabled and normal children representing an age range of approximately five years were administered a dichotic listening task to examine the hypothesized development of reciprocal control by the left cerebral hemisphere over the right. An analysis of the free-recall raw scores for each ear by the two groups of children at three developmental levels supported the notion that age-related changes occur in the right cerebral hemisphere and not in the left. Consequently, the notion that the left hemisphere becomes more lateralized during development was not supported. Rather, a differential model of cerebral inattention and suppression of stimuli perceived transcallosally by the left hemisphere was adopted as more appropriate in conceptualizing neuropsychological accomodation and functioning in learning-disabled children.

The effectiveness of visual information processing training with hispanic children.

The purpose of this study was to determine whether one kind of visual information processing training improves performance on visual tasks and on academic achievement. One hundred fifty-three kindergarten, first- and second-grade Hispanic children who were poor visual processors were randomly assigned to either a training, a contrast, or a control group. The training group received tutoring in visual-information processing for approximately seven weeks while the contrast group was given small group instruction with regular curriculum materials. At the conclusion of the training all Ss were administered several visual tasks and achievement measures. Results indicated that only the tutored children performed significantly better than the other children on the Bender Gestalt test and that the attained visual motor integrative skills were maintained over a period of time. However, training in visual processing skills did not increase performance on academic tasks or on a task of basic concepts.

Free recall and rehearsal strategies in average and severely disabled readers.

Free recall and rehearsal strategies were investigated in 43 boys and 24 girls in fifth and sixth grades; they were 18 average and 49 severely disabled readers. Memory abilities were measured by recall in the overt recall condition in a written free-recall test of three lists of 20 words each that required second-grade reading ability or less. Average readers performed better than severely disabled readers in terms of total recall and long-term memory. Elaborative rehearsal strategies rather than non-elaborative rehearsal strategies (repetition only) discriminated between the two groups. The organizational ability represented in elaborative rehearsal strategies was the hypothesized mechanism responsible for the better long-term memory and total recall observed in average readers.

Effects of verbal labeling on visual recall with reading disabled subgroups.

Effects of learning names for random nonsense shapes prior to a probe-type serial-recall task were investigated in disabled readers. 33 10-yr.-old, right-handed boys were subjects in a 3 (reading groups) X 2 (training conditions) X 6 (serial positions) repeated-measures, split-plot level analysis of covariance design. No differences among reading groups on recall strength or primary recall were found, suggesting similar verbal skills. Deficiencies in verbal mediation did not appear to account for the reading disability of these subgroups.

Attentional deficits and word attributes preferred by learning disabled children in grades 2, 4, and 6.

This study investigated the postulated effects of attentional deficits on the relative preferences for associative, acoustic, and orthographic attributes in word recognition by 15 learning disabled children each in Grades 2, 4, and 6. An analysis of errors in recall suggests that the children in the second grade did not encode and retrieve information as did their normal counterparts but rather used several stimulus attributes in retrieval. The children in the sixth grade, however, evidenced a significant preference for the orthographic attribute in recall as did normal second grade children. These findings are discussed as they relate to attention deficits, the capacity of short-term memory and achievement in learning disabled children.