Biomedical subjects

J Liederman

Publications and source records attributed to J Liederman.

At least 19 recordsLinked to original sources

PubMed2000

Male prevalence for reading disability is found in a large sample of black and white children free from ascertainment bias.

Male vulnerability to neurodevelopmental disorders remains controversial. For one disorder, reading disability, this sex bias has been interpreted as an artifact of referral bias. We investigated sex differences for the incidence of reading disability within a large prospective sample of White (N = 16,910) and Black (N = 15,313) children derived from the National Collaborative Perinatal Project (NCPP). Children were classified as having either moderate or severe reading disability when they had reading scores lower than 1.5 or 2.0 standard errors of prediction, respectively, given their age and intelligence. Reading disability was about twice as common in boys than girls (p < .001), irrespective of race, severity of disability, or exclusion of children with attentional disturbances or high activity levels. We conclude that there is a clear sex bias toward males for the incidence of reading disabilities.

Black or African American↗

PubMed1999

Presentation of words to separate hemispheres prevents interword illusory conjunctions.

We tested the hypothesis that division of inputs between the hemispheres could prevent interword letter migrations in the form of illusory conjunctions. The task was to decide whether a centrally-presented consonant-vowel-consonant (CVC) target word matched one of four CVC words presented to a single hemisphere or divided between the hemispheres in a subsequent test display. During half of the target-absent trials, known as conjunction trials, letters from two separate words (e.g., "tag" and "cop") in the test display could be mistaken for a target word (e.g., "top"). For the other half of the target-absent trails, the test display did not match any target consonants (Experiment 1, N = 16) or it matched one target consonant (Experiment 2, N = 29), the latter constituting true "feature" trials. Bi- as compared to unihemispheric presentation significantly reduced the number of conjunction, but not feature, errors. Illusory conjunctions did not occur when the words were presented to separate hemispheres.

Adult↗

PubMed1998

The dynamics of interhemispheric collaboration and hemispheric control.

This article reviews recent models of how the two hemispheres collaborate to facilitate efficient information processing. The strengths and weaknesses of behavioral techniques and structural and functional neuroimaging techniques are considered as they apply to these problems. The role of the corpus callosum as an equilibrator of activation between the two hemispheres is discussed and linked with its role as a dynamic modulator for the mobilization of hemispheric resources. Issues related to metacontrol and dynamic fluctuations in hemispheric control are also considered.

Brain↗

PubMed1996

Division of inputs between hemispheres eliminates illusory conjunctions.

We demonstrate that division of inputs between the hemispheres does not just generally improve performance but specifically reduces inter-item perceptual interference relative to single hemisphere presentation. Subjects verified the presence of colored letter targets in briefly presented letter pairs presented to the same (unihemispheric condition) or different (bihemispheric condition) sides of space. Four experiments showed consistently that although illusory conjunctions (i.e. perceptual miscombinations of stimulus features) occurred commonly during unihemispheric presentations, they never occurred during bihemispheric presentations, even though accuracy of detecting individual stimulus features was held constant across the conditions. Increasing inter-item similarity resulted in a general interference effect based in discrimination difficulty that was sufficient to eliminate illusory conjunctions even in the unihemispheric condition. However, when inter-item interference was manipulated using perceptual grouping by movement the bihemispheric illusory conjunction advantage increased with increasing interference. Our findings suggest that the two cerebral hemispheres can operate as relatively independent work stations during visual perceptual processing, thereby maximizing the efficiency of information processing.

Adult↗

PubMed1996

A re-examination of the sex ratios of families with a neurodevelopmentally disordered child.

It has been claimed that mothers with certain hormonal imbalances and/or immunological disorders are more likely to give birth to male than female children and that they are more likely to give birth to a neurodevelopmentally disordered (ND) child. Liederman and Flannery (1995) reported that the sex ratio of families with an index ND child did not significantly differ from the sex ratio of families without an index ND child. The data were derived from the National Collaborative Perinatal Project (NCPP). James (in the current issue) challenged us to reconsider the standard against which we judged the sex ratio of siblings of ND children, since the 1.10 sex ratio that we obtained for the siblings of non-ND children is much higher than the sex ratio of children born during that period according to the U.S. Census Bureau. In the current paper, the NCPP data were reexamined and it was demonstrated that the high sex ratio of siblings in our non-ND sample was not due to various retention or recruitment biases. Thus, we suggest that use of the sex ratio of siblings of non-ND children was the proper standard against which to judge the sex ratio of ND families, and that our data provide no evidence to support the notion that these families are male biased.

Bias↗

PubMed1995

Is there really a syndrome involving the co-occurrence of neurodevelopmental disorder talent, non-right handedness and immune disorder among children?

This paper is the first large-scale attempt to test Geschwind and Galaburda's (1985a, 1985b, 1985c) hypothesis that there should be a four-way association among neurodevelopmental disorders (NDs), special talents, non-right handedness, and immune disorders. In a sample of 11,578 children, several two-way associations were found, but not those most strongly predicted by the theory. For example, non-right handedness was not associated with NDs considered to be secondary to left hemisphere dysfunction (e.g., articulation disorder, reading disability, verbal aptitude deficits). Instead, non-right handedness was associated with NDs that involve generalized brain damage (e.g. cerebral palsy, mental retardation, and seizures). One immune disorder (asthma) was associated with one ND (attention deficit disorder); immune disorder was not associated with non-right handedness. Less than 1% of this sample manifested the co-occurrence of any three or four of these markers. In sum, there was little evidence in support of the syndrome suggested by Geschwind and Galaburda (1985a, 1985b, 1985c).

Aptitude↗

PubMed1995

The sex ratios of families with a neurodevelopmentally disordered child.

It has been conjectured that mothers who give birth to neurodevelopmentally disordered (ND) children may have hormonal or immunological characteristics that bias them toward giving birth to male children. We examined this hypothesis in an epidemiological sample of 2,080 ND children drawn for the National Collaborative Perinatal Project (NCPP) who had one of nine kinds of NDs. No assumptions were made regarding the sex ratio of non-ND children since this could be computed from NCPP data for 11,213 families. The sex ratio of families with ND children was not significantly biased toward boys as compared to the sex ratio of families with non-ND children, provided that the index ND child was excluded from the analysis.

Articulation Disorders↗

PubMed1995

Effectiveness of individualized developmental care for low-risk preterm infants: behavioral and electrophysiologic evidence.

OBJECTIVE: We assessed the effectiveness of individualized developmental support in the special care nursery for low-risk preterm infants. SETTING: A university-affiliated teaching hospital. PARTICIPANTS: Twelve healthy full-term infants, and 24 low-risk preterm infants randomly assigned to a control or an experimental group. DESIGN: The preterm control group received standard care and the preterm experimental group received individualized developmental care at the same special care nursery. OUTCOME MEASURES: Medical, behavioral (Assessment of Preterm Infants' Behavior and Prechtl's Neurological Examination of the Full-Term Newborn Infant), and electrophysiologic outcome (using quantitative electroencephalography with topographic mapping) of all three groups was assessed 2 weeks after the expected due date. RESULTS: No between- or among-group medical differences were seen for this low-risk, healthy sample. The preterm experimental group showed behavioral and electrophysiologic performances comparable to those of the full-term group, whereas the preterm control group performed significantly less well. Behavioral measures suggested significantly poorer attentional functioning for the preterm control group. Electrophysiologic results implicated the frontal lobe. CONCLUSIONS: Individualized developmental intervention supports neurobehavioral functioning as measured at 2 weeks post-term. It appears to prevent frontal lobe and attentional difficulties in the newborn period, the possible causes of behavioral and scholastic disabilities often seen in low-risk preterm infants at later ages.

Child Development↗

PubMed1994

A test of the immunoreactive theory for the origin of neurodevelopmental disorders in the offspring of women with immune disorder.

Gualtieri and Hicks (1985) proposed that male vulnerability for neurodevelopmental disorders (NDs) was partially due to intrauterine immune attack of the fetus. One group of mothers with heightened immunoreactivity might be women with immune disorder. This was tested within an epidemiological sample of 17,283 mother/child pairs. Maternal immune disorders considered were ulcerative colitis or asthma. NDs in the child included: cerebral palsy, mental retardation, seizures, articulation disorder, reading, or arithmetic disability, verbal or performance aptitude deficits, and attention deficit disorder. Unlike prior studies, we controlled for demographic perinatal variables that might confound interpretation of the data. Results indicated that immune dysfunction in the mother, be it autoimmune (ulcerative colitis) or defensive (asthma) was not associated with an increased incidence of any NDs in the offspring, but mothers with ulcerative colitis did have a disproportionate number of offspring who were non-right handed. Few variables discriminated between the children of ulcerative colitis mothers who became right handed when compared to those who did not. We suggest that a) only certain maternal autoimmune disorders such as systemic lupus erythematosus (but not ulcerative colitis or asthma) elevate the risk of intrauterine immune attack and b) the elevated rate of non-right handed offspring among ulcerative colitis mothers was not an instance of immune attack but instead represents some kind of genetic association.

Achievement↗

PubMed1994

Fall conception increases the risk of neurodevelopmental disorder in offspring.

Hormonal imbalances in utero may render males more vulnerable to neurodevelopmental disorder (ND) than females. Since hormonal activity can be influenced by photoperiod, the relationship between season of conception and incidence of ND in offspring was examined within 11,578 mother/child pairs. Fall conception significantly elevated the odds for mental retardation, reading, arithmetic disability, or performance aptitude deficits (but not seizures, articulation disorder, cerebral palsy, or verbal aptitude deficits), and decreased the odds for reading talent (even when socioeconomic class, prenatal visits, infections, fever, vomiting, edema, anemia, and weight loss were covaried). Since the seasonality effect was not stronger in males, and was not specific to those NDs caused by left hemisphere dysfunction, the predictions of Geschwind and Galaburda (1985a, 1985b, 1985c) were not confirmed.

Aptitude Tests↗

PubMed1991

Right hemisphere participation in reading.

This study examined whether the right hemisphere's contribution to lexical semantic processing is greatest when it is "disinhibited." Skilled reading may require the controlled modulation of interhemispheric interaction: the left hemisphere (or some other control mechanism) may regulate the subprocesses of reading by selectively "inhibiting" and "disinhibiting" right hemisphere function. Right-handed undergraduates concurrently performed two tasks: a lateralized semantic or rhyme task and a verbal memory task. It was hypothesized that right hemisphere reading processes would be disinhibited when the left hemisphere was "occupied" with the memory task. This hypothesis was supported for a subgroup of subjects who showed evidence of inhibition of right hemisphere function (i.e., left hemisphere dominance for lexical processing) when the lateralized semantic task was performed alone. Across subjects, there was a strong correlation between the degree of left hemisphere dominance in the single-task semantic conditions and the degree of disinhibition of right hemisphere function in the dual-task semantic condition.

Adult↗

PubMed1990

The effect of task difficulty upon the extent to which performance benefits from between-hemisphere division of inputs.

The means by which the two hemispheres coordinate processing of information are not well understood. By means of a tachistoscopic paradigm, we have shown repeatedly that performance is better when two conflicting tasks are presented to separate hemispheres than when both tasks are presented to a single hemisphere. The present study examines whether this effect is restricted to a specific range of task difficulty. Adult right-handers viewed two conflicting naming tasks by means of a tachistoscope. Task difficulty was lowered by reducing processing load (Experiment I: N = 32). Task difficulty was raised by projecting a visual mask 40 ms after offset of the visual displays (Experiment II: N = 10). At lower levels of processing load, dividing conflicting tasks between the hemispheres was beneficial, but not significantly so. At higher levels of load, and at either higher or lower loads with a visual mask, there were significant benefits associated with dividing conflicting tasks between the hemispheres. Three alternative explanations are discussed for the absence of an advantage associated with between-hemisphere division of inputs when task difficulty is reduced.

Brain↗

PubMed1988

The brainstem auditory evoked potential asymmetry is replicable and reliable.

Lateralization of neural function is generally thought to occur only at the level of the cerebral cortex and perhaps the thalamus. Levine and McGaffigan [EEG Clin. Neurophysiol. 55, 532-537, 1983] challenged this view by identifying a neural asymmetry at the level of the brainstem. They analyzed brainstem auditory evoked potentials (BAEPs) and found that peak III(+) amplitude (baseline-to-peak) was significantly larger in response to right than to left ear stimulation. The current paper demonstrates that this BAEP asymmetry is (a) reliable within and between subjects, (b) present for 33/sec and 10/sec click rates, and (c) more reliable when amplitude is measured peak-to-peak. This brainstem asymmetry may reflect the general tendency of humans to orient rightward and/or may be a precursor of higher level asymmetries.

Adult↗

PubMed1987

A modified finger lift test reveals an asymmetry of motor overflow in adults.

A method of eliciting motor overflow in neurologically intact adults is reported. A weight was placed on either the middle or ring finger of the left or right hand, and the subject was instructed to lift that finger. Involuntary finger lifts of the contralateral hand were recorded. There were 32 right-handers per experiment. In Experiments I and II, the amount of weight placed on the subject's finger was in proportion to body weight, whereas in Experiment III, it was in proportion to each finger's strength. Across experiments, motor overflow was more prevalent when the left, rather than the right, hand was weighted. This shows that the asymmetry in motor overflow previously reported in children and brain-damaged adults also occurs in healthy adults, and that this movement asymmetry is not an artifact of the relative weakness of the left hand in right-handed individuals.

Body Weight↗

PubMed1987

Developmental versus individual differences in the ability of the hemispheres to operate independently.

We have claimed that the ability to use the two cerebral hemispheres independently improves during early adolescence: Adults benefited from division of conflicting tasks between the hemispheres (Liederman & Meehan, in press; Merola & Liederman, 1987), whereas 10-year-old children did not (Merola & Liederman, 1985). The current research was undertaken to rule out the possibility that differences in the degree of hemispheric independence between adults and children were due to: (a) differences in overall performance or (b) differences in cognitive ability. The performance of ten adults was reduced to that of the 10-year-olds (by inserting a visual mask between trials). Nonetheless, 90% of the adults showed hemispheric independence, whereas only 50% of the children did. In addition, when high scholastic aptitude children were compared to adults, the difference in hemispheric independence remained. A causal model indicated that age and scholastic aptitude have unique effects upon hemispheric independence. Thus, there are both developmental and individual differences in the degree of hemispheric independence.

Adolescent↗

PubMed1987

An analysis of the naming deficit of left-handers.

Left-handers have been found to have a naming deficit when confronted with briefly flashed words. Three alternative explanations of this deficit were tested: whether it was due to deviant interhemispheric cooperation, relatively diffuse neural organization, or left hemispheric dysfunction. In Experiment I, four words were presented for 190 ms, unilaterally (to a single hemisphere), or bilaterally (between the hemispheres). Although left-handers (N = 48) named significantly less than right-handers (N = 30), performance was parallel across hemispheric conditions. Experiment II required semantic categorization, but not naming. The performance of the left-handers (N = 27) was indistinguishable from that of right-handers (N = 27) both in terms of overall performance and interhemispheric collaboration. It is concluded that the linguistic deficit of left-handers is specific to oral naming and that it is not caused by deviant interhemispheric cooperation.

Brain↗

PubMed1987

Reconciling stable asymmetry with recovery of function: an adaptive systems perspective on functional plasticity.

This article examines alternative ways of resolving an apparent paradox that has emerged from neuropsychological studies of language development: How can the developmentally stable functional asymmetry ("hemispheric specialization") observed in neurologically intact children be reconciled with the dramatic recovery of function often displayed following unilateral brain damage? The alternative resolutions we consider differ most critically in the roles they assign to lesion-induced neural reorganizations versus lesion-related release of preexisting functional potentials. Though arguments are given in favor of the latter as the primary factor in functional recovery, the primary goal of the article is to clarify the conceptual issues raised by recent empirical research.

Brain↗

PubMed1986

When is between-hemisphere division of labor advantageous?

Division of labor between the hemispheres is sometimes advantageous. Merola and Liederman (1985) have shown that adolescents' naming performance is superior when two different kinds of letter input are divided between the hemispheres than when both kinds of letter input are projected to a single hemisphere. We now investigated whether the advantage of between-hemisphere division of inputs increases from adolescence to adulthood; occurs when a secondary, concurrent verbal memory task is added; and corresponds with superior performance on the secondary task. Results indicated that use of the hemispheres as insulated work stations increased from adolescence to adulthood, and did not diminish when memory was stressed. However, between-hemisphere division of labor for the primary task did not facilitate secondary task performance.

Adolescent↗