Micromotion of cementless tibial components.
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Cadaver↗
Biomedical subjects
J R Kershner
Publications and source records attributed to J R Kershner.
Methylphenidate slows right hemisphere processing in children with attention-deficit/hyperactivity disorder.
To examine the effects and particularly, any potential detrimental effects of methylphenidate on right hemisphere processing in children with attention-deficit/hyperactivity disorder (ADHD), the performance of 26 children (aged 8-15 years) with ADHD was compared under methylphenidate and placebo on various cognitive tasks in a double-blind within-subjects design. Results indicated that reaction times on a tachistoscopic task were slower on methylphenidate for stimuli that produced a left visual field advantage (reflecting better right hemisphere functioning) but not for stimuli that produced a right visual field advantage (reflecting better left hemisphere functioning) or for bilateral stimuli. It is argued that methylphenidate induces a slower response on tasks involving right hemisphere processing, resulting in slower reaction times and unchanged accuracy rates. Findings on two tasks that more closely reflect classroom-type tasks revealed an improvement in performance on methylphenidate, suggesting that any stimulant-induced benefits on learning style may have overcome detrimental effects on unilateral processing. These findings may help understand the complex, diverse, and sometimes unpredictable effects of psychostimulants on cognitive functioning that are observed clinically in individuals treated for ADHD.
Adolescent↗
Attentional control over language lateralization in dyslexic children: deficit or delay?
Two previous verbal dichotic studies by Kershner and Morton (Neuropsychologia 28, 181-198, 1990) using the forced-attention methodology (Bryden, Strategies of Information Processing, Academic Press, London, 1978) demonstrated that the order in which the ears were monitored (LE first or RE first) determined whether learning disabled children compared to age-matched nondisabled children were more weakly or strongly lateralized. The same technique was used with the addition of controls for lateral head and eye movements, specific diagnostic criteria to include only phonological dyslexics, IQ and reading level. Dyslexic vs age-matched comparisons replicated the previous studies. The dyslexics produced a weaker REA in the LE first order but a greater number of subjects with a REA in the RE first order. Reading-matched comparisons suggested that the order-specific reduced REA in the dyslexics may reflect a causal deficit of the disorder, whereas the order-specific increase in the number of dyslexic subjects with a REA was no different than the reading-matched group, implicating a developmental delay. The results suggest that children with dyslexia may suffer from a primary attentional impairment in altering the REA. This implicates an underlying difficulty of flexible verbal processing in response to the rapidly changing cognitive requirements of reading.
Attention↗
Hemispheric processing and methylphenidate effects in attention-deficit hyperactivity disorder.
To advance our understanding of attention-deficit hyperactivity disorder and medication effects we draw upon the evidence for (1) a neurotransmitter imbalance between norepinephrine and dopamine in attention-deficit hyperactivity disorder and (2) an asymmetric neural control system that links the dopaminergic pathways to left hemispheric processing and links the noradrenergic pathways to right hemispheric processing. It appears that attention-deficit hyperactivity disorder may involve a bihemispheric dysfunction characterized by reduced dopaminergic and excessive noradrenergic functioning. In turn, favorable medication effects may be mediated by a restoration in neurotransmitter balance and by increased control over the allocation of attentional resources between hemispheres.
Attention↗
Cognitive and neuropsychological response asymmetries for adults on the left-right seating axis.
Six studies of the relationship between classroom seating and information processing were conducted with adult subjects. Findings converged to support a hemisphericity-based explanation of effects with right-side-sitters more inclined to a response style associated with the right hemisphere--perhaps, less analytical or less cautious in responding (Experiments 1-4), more "artistic" (Experiment 5), and less lateralized (Experiment 6), and vice versa for left side sitters. First, using incidental memory tasks, subjects (N = 164) with a right side seating preference (i.e., to the speaker's left side) were found, in their test-taking behavior, to respond more positively to inaccurate distractor words (Experiments 1 and 2), particularly those with an ambiguous semantic reference (Experiment 3). For different levels of processing, seating location did not influence auditory memory (Experiments 1 and 2) but right side sitters showed enhanced visual memory for accurate words (Experiment 3). In a sample of 366 subjects, males selecting right side seating were less successful on multiple-choice test performance (Experiment 4), but there were no Side differences in test taking speed or review time. In a sample of 286 subjects (Experiment 5), personality measures on the Vocational Preference Inventory revealed right sitters scored higher on the "Artistic" scale and on femininity on the Masculine-Feminine scale. The final study (N = 90) revealed reduced dichotic processing on verbal tasks (digits and voiced CVs) for right side sitters. Implications are discussed.
Adult↗
Effects of reading and writing on cerebral laterality in good readers and children with dyslexia.
The present study evaluated the idea that the hemisphere-specific cognitive demands of reading and writing may induce task-specific maladaptive patterns of language lateralization in children with dyslexia. Situation-specific lateralization was examined in a repeated measures design under three dichotic listening conditions: baseline, concurrent reading, and concurrent writing. Twelve males with phonological dyslexia, 8 to 12 years old, were compared to 12 age-matched and 12 younger reading-matched good readers. Lateralization patterns were examined for condition-specific relationships to pseudoword decoding, word recognition, reading comprehension, spelling, and arithmetic. The results show that dyslexia is not related to incomplete lateralization or to a failure to inhibit verbal processing in the right hemisphere during reading and writing. Reading increased the lateralization of the children with dyslexia, which had a negative relation to arithmetic; writing caused a decrease in lateralization, which was linked specifically to deficits in phonological decoding and visual word recognition. The results suggest that children with dyslexia suffer from a selective linguistic vulnerability to left-hemisphere interference from the idiosyncratic attentional and processing demands of particular school tasks. Dyslexia is a much more dynamic and environmentally sensitive disorder than previously thought.
Achievement↗
Effects of time-of-day on neuropsychological testing as measured by dichotic listening.
In a study of 30 reading-disabled and 30 normal-achieving children tested on a dichotic listening task using digits in either morning or afternoon settings neither laterality nor capacity differences were evident between groups in the afternoon. In the morning, the normal-achieving children compared to the disabled readers were more strongly lateralized when attending selectively to the right channel and less lateralized when attending to the left channel, suggesting disabled readers do not respond normally to circadian influences and may suffer from a time-locked dysfunction which reduces their control over attentional resources in the morning. To examine the normal circadian effect further a second study (using 40 normal-achieving, right-handed male children) was conducted using the same dichotic listening stimuli with an order variable included. The increased report in the morning was seen to be linked to a right ear (left hemisphere) priming effect which served to increase the overall report. The effect was evident only for subjects directed to report the right ear first. The results are consistent with a prepotent left hemisphere in the morning which appears to facilitate attending in the morning for subjects directed to attend to their right ear (left hemisphere) first. Potential research and educational implications are discussed.
Arousal↗
Differential negative air ion effects on learning disabled and normal-achieving children.
Forty normal-achieving and 33 learning disabled (LD) children were assigned randomly to either a negative ion or placebo test condition. On a dichotic listening task using consonant-vowel (CV) combinations, both groups showed an ion-induced increase in the normal right ear advantage (REA). However, the mechanisms for this effect were different for each group. The LDs showed the effect at the right ear/left hemisphere (enhancement). The normal achievers showed the effect at the left ear/right hemisphere (inhibition). The results are consistent with an activation-inhibition model of cerebral function and suggest a functional relationship between arousal, interhemispheric activation-inhibition, and learning disabilities. The LDs may have an interhemispheric dysfunction. Both groups showed superior right ear report and the normal achievers showed overall superiority. Normal achievers showed higher consonant intrusion scores, probably due to a greater cognitive capacity. Age was a significant covariate reflecting developmental capacity changes. Negative air ions are seen to be a tool with potential theoretical and remedial applications.
Air Ionization↗
Directed attention dichotic listening in reading disabled children: a test of four models of maladaptive lateralization.
In two experiments, critical a priori tests compared four competing LD theories of maladaptive language lateralization (Poor Structural Lateralization; Excessive RH Activation; Excessive LH Activation; Excessive LH or RH Activation). In Experiment 1, 32 auditory-linguistic LD children from public schools were compared to 32 high-achieving, age-matched controls. Experiment 2 replicated the main findings of Experiment 1 by comparing 14 LD children to 14 controls attending a private school. The effect of priming or ear order was analyzed in a directed attention, dichotic paradigm with strings of quadruple digit names as stimuli. The order in which the ears were monitored (LE first or RE first) determined (1) in both experiments whether the LD children compared to controls were more weakly or strongly lateralized and (2) in Experiment 2 whether the REA correlated negatively of positively with reading and spelling achievement. The results indicate that the hemispheric processes involved in disengaging and shifting response strategies between dichotic channels may share common neuronal mechanisms with cognitive processes that are important to school achievement. Rather than LD children suffering from a fixed laterality deficit, the results are consistent with the view that a task-dependent attentional dysfunction may interfere with left hemisphere language processes by overengaging either hemisphere. However, pronounced asymmetry in the relative magnitude of the effects at each channel also suggests greater interference in LD children between the systems controlling auditory-linguistic attention and lateral orienting.
Achievement↗
The effects of methylphenidate on levels of processing and laterality in children with attention deficit disorder.
Effects of stimulant medication (methylphenidate) on levels (feature, name, semantic) of word processing by the left and right hemisphere were assessed in 31 attention-deficit-disordered children. In a double-blind procedure, same-different decisions were made to tachistoscopically presented word pairs under medication and placebo. Analysis of manual response times failed to show any negative effects of medication. Feature decisions were faster than name decisions, which were faster than semantic decisions. Methylphenidate induced a right visual field advantage (left hemisphere) for the name decision, which was interpreted as a normalization effect. The results suggest that (1) methylphenidate may selectively improve the phonological level of word processing and (2) methylphenidate's favorable therapeutic effect is produced through inhibition of excessive right hemisphere activity in response to task demands that engage the left hemisphere.
Adolescent↗
Hemisphere asymmetries, spelling ability, and classroom seating in fourth graders.
Fourth grade children (N = 159) from eight classes who were free to select their seating location in the classroom were tested for spelling ability. On 100 word spelling lists, the children (males and females) seated on the right side of the classroom (facing the teacher) were superior to children on the left. Analysis of spelling errors for reliance on phonological processing in a subsample (N = 28) revealed that right sitters made more phonetically inaccurate misspellings, whereas, on the left, females, but not males, committed more phonetically accurate misspellings. The results support the view that hemispheric information processing is correlated with classroom seating location or preference, but casual inferences regarding the neuropsychological mechanisms underlying these findings are unwarranted pending clarification of several major theoretical issues.
Child↗
Negative ion effects on hemispheric processing and selective attention in the mentally retarded.
The effect of high concentrations of negative air ions on a dichotic digits task was investigated in 19 mentally retarded individuals. Subjects were assigned randomly to an ion or to an unmodified-air placebo condition under double-blind testing. Left and right ears were precued for report order and this order was reversed for the second set of trials. Negative ions promoted greater left hemisphere lateralization on the first set of trials, and enhanced recall when switching to the opposite channels, in the second set of trials. However, the ion-induced REA occurred at the expense of selective attention to the left channel and superior left ear recall after the right ear first condition is an anomalous dichotic listening pattern. Such paradoxical results suggest that negative ions are not necessarily beneficial or detrimental to processing. Negative ions may increase arousal, in this case amplifying a time-phased, information processing disorder in the retarded characterized by excessive right hemisphere inhibition during early processing of receptive speech and diffuse interhemispheric excitatory activation during later processing.
Air Ionization↗
Negative air ionization improves memory and attention in learning-disabled and mentally retarded children.
The effect of increased concentrations of ambient negative air ions on incidental visual memory for words and purposive auditory memory for dichotic digits was investigated in 20 normal grade 4 children, 8 learning-disabled children, and 8 mildly mentally retarded children. Half in each group were assigned randomly to an unmodified air-placebo condition under double-blind testing procedures. All of the children breathing negatively ionized air were superior in incidental memory. In dichotic listening, the negative ions produced a counter-priming effect in the two learning-impaired groups, offsetting the difficulties that they showed under placebo in switching attention selectively from one ear to the other. The action of negative ions on the neurotransmitter, serotonin, may be the mechanism by which negative ions produce such behavioral effects. In view of the important environmental and remedial implications of these novel findings, interpretations should be made cautiously pending larger-scale replications.
Air Ionization↗
Do individuals with Down's syndrome possess right hemisphere language dominance?
A dichotic digits task with selective listening and attention-switching instructions, was administered to 10 mentally retarded individuals with Down's Syndrome between the ages of 10 and 37 years. Attention was focused on one ear for 20 trials before switching attention to the opposite ear after a 5-minute interval. A majority displayed a right ear-left hemisphere advantage for correct responses, although this advantage failed to reach significance. Comparison of left and right ear intrusion errors when each ear was attended first showed significantly more intrusions from the unattended right ear. No priming effects were found. The results do not support the hemispheric reversed specialization hypothesis. Rather, it is suggested that while Down's Syndrome individuals do possess an inherent left hemisphere advantage for language, such individuals may suffer from a left hemisphere information processing disorder that can produce functional reversals in dichotic listening.
Adolescent↗
Rotation of mental images and asymmetries in word recognition in disabled readers.
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Child↗
Pilot study of high-protein, high-vitamin, low-carbohydrate, sugar-free diet in learning-disabled children.
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Child↗
Lateralization in normal 6-year-olds as related to later reading disability.
The differentiation of lateral preference in hand, eye, ear, and foot was measured in 110 normal Grade 1 children and reading achievement was tested 3 and 5 years later. No support was found for the widely held belief that delays in early lateralization underlie subsequent reading impairment. Paradoxically, boys with serious reading disability showed a strong degree of early lateral concordance. Male, impaired readers displayed a tendency when they were in Grade 1 to be either uniformly right- or left-preferring across all 4 sensory-motor modalities. The results contradict the popular notion that lateral usage emerges from an undifferentiated state in the direction of greater degrees of specialization. Lateralization may be an expression of reflex constraints bound initially to the infant's tonic-neck posture, with later development less reflex-patterned during the acquisition of more sophisticated information-processing strategies. Such an interpretation implies a progressive discontinuity between lateral usage and neuro-maturational processes. Alternatively, the results can be accounted for by (1) a new maturational delay model in which maturation-dependent lateralization proceeds in graduated stages from a highly specialized beginning toward greater levels of neuromotor integration; or (2) a model that maintains the notion of emergent lateralization but in which delays in the lateralization process are actually beneficial to later performance.
Achievement↗
Cerebral dominance in disabled readers, good readers, and gifted children: search for a valid model.
A group of 10 reading-disabled children with average intelligence were compared with 11 good readers of average intelligence and 12 academically accelerated, gifted children on their recognition of words presented tachistoscopically under simultaneous, bilateral viewing conditions. The poor readers were inferior in right-field performance compared with the gifted children and good readers. With IQ as a covariate, the poor readers produced a higher left-field score and a lower visual-field difference score in comparison with the gifted children. It is argued that the skills needed to become literate are not isomorphic biologically with general linguistic competence. The results suggest (1) that reading acquisition involves enhanced left-hemisphere decoding of written language and (2) that reading disability is related to the prevalence of a right-hemisphere-based perceptual coding strategy.
Child↗