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PubMed1988

Handedness and manual specialization in the baboon.

Manual preferences of six baboons were tested with three kinds of experimental tasks: (1) a simple reaching on a board or in a hole; (2) a box opening; (3) two visuo-spatial tasks requiring precise alignments of apertures. The distribution of right and left hand preferences was found to be symmetrical for the simple reachings (3 right- and 3 left-handers) and was consistent with the preferences in the box opening task. However, manual tasks with strong visuo-spatial components gave a unimodal distribution with a left hand preference for the group for aligning and adjusting the apertures. These results suggest the coexistence within an individual of two types of preferences according to the distinction between handedness and manual specialization.

Animals↗
PubMed1988

Demography of handedness in two samples of randomly selected adults (N = 2083).

Handedness was examined in relation to sex, race, age, education, occupation, marital status, and religious preferences for two random samples of adults drawn from an urban population. There were statistically significant differences on each variable for the total of 2083 respondents as well as for many subgroups based on combinations of sex, race, and age. The results are compared to previous findings.

Adolescent↗
PubMed1989

Asymmetries in event-related potentials during rhyme-matching: confirmation of the null effects of handedness.

Event-related potentials (ERPs) were recorded from 16 right- and 16 left-handed subjects during two variants of a sequential rhyme-judgement task. These variants manipulated the demands placed on short-term memory, by requiring subjects to match a word either with one or with three previously presented words. In both tasks, ERPs exhibited two lateral asymmetries: (i) during the interval prior to the final word, the CNV was more negative over the left hemisphere, and (ii) rhyme/non-rhyme differences in the amplitude of the N450 component of the ERPs to the final word were larger over the right than the left hemisphere. Neither of these asymmetries was smaller or more variable in left- than in right-handed subjects. It is suggested that these data may indicate that some aspects of language processing are, irrespective of handedness, relatively invariant in the direction and degree of their cerebral lateralization.

Adult↗
PubMed1989

Exceptions to the male advantage on a spatial task: family handedness and college major as factors identifying women who excel.

Two factors, family handedness and college major, were investigated in order to identify the characteristics of women likely to excel on a mental rotation task. It was found that those likely to have the necessary combination of genetic potential and spatial experiences were right-handed women with nonright-handed relatives, majoring in math-science fields. Across three samples, this subgroup significantly outperformed all other groups of undergraduate women and did as well as undergraduate men on the Vandenberg Mental Rotation Test. This study provides new information on possible genetic and environmental factors influencing mental rotation ability in women.

Adult↗
PubMed1989

Temporal integration of form as a function of subject handedness and retinal locus of presentation.

Two experiments are reported examining differences in perceptual processing as a function of subject handedness. Experiment 1 compared performance in the left vs right visual fields of right- vs left-handed subjects. Only right-handed subjects exhibited an interaction of visual field with spatial frequency (as mediated by interflash interval), suggesting that left-handers are not differentially lateralized for high vs low spatial frequency processing. Experiment 2 examined foveal performance in left-handers vs right-handers with or without familial sinistrality. Subjects with personal or familial sinistrality exhibited superior performance when the processing of low frequencies was required, suggesting that sinistrality may confer an advantage in the processing of lower spatial frequencies.

Adult↗
PubMed1990

Subclassification of non-pathological left-handers poses problems for theories of handedness.

The throwing performance of 104 right-handers, and 96 left-handers with inconsistent and consistent hand preferences, as classified by the procedure used by Ponton (Neuropsychologia 25, 305-311, 1987), was examined. Left-handers with inconsistent hand preference write with the left, tap faster with the left, and perform better with the left on the Purdue Pegboard task (Peters and Servos, 1989), but are stronger in the right hand and throw better with the right hand. In the other two groups, strength and skill activities are laterally congruent. This poses difficulties for theories of handedness.

Adult↗
PubMed1990

Differences in feminine and masculine characteristics in women as a function of handedness: support for the Geschwind/Galaburda theory of brain organization.

The Geschwind/Galaburda testosterone theory successfully predicted differences in feminine sex role identification and behavior between women with anomalous dominance and standard dominance. The women with anomalous dominance (consisting of left-handed and ambidextrous as well as right-handed women with first-degree non-right-handed relatives) were compared to women with standard dominance (right-handed women with all right-handed first-degree relatives) on the Bem Test of Sex Role Identity and a tomboy scale. Across three samples, handedness classifications were related to both tomboy characteristics and sex role identification. In addition, the study showed that the anomalous dominance women had a higher masculine sex role identification as compared to the college normative sample for the Bem, while the standard dominance women had a higher feminine identification than the normative sample.

Adolescent↗
PubMed1991

Left out axons make men right: a hypothesis for the origin of handedness and functional asymmetry.

The origin and underlying mechanisms of hand preference are still unresolved, despite extensive research and discussion. Numerous possibilities have been considered, including genetic and hormonal factors, brain insult and learning. We suggest here that naturally occurring loss of axons of the corpus callosum (either symmetric or asymmetric, with or without neuron death) may be one mechanism underlying the embryological development of hand preference and hemispheric anatomical and functional asymmetries in males. We note supporting evidence for this hypothesis from a report of increased prevalence of left-handedness in children born prematurely at the gestational age prior to the likely onset of axon loss. The practical implications of this hypothesis for clinical management in neonatal intensive care units are discussed. It is suggested that the course of loss of callosal axons may have a genetic component which is associated with a sex-related influence and which is modifiable by prenatal and early postnatal events.

Axons↗
PubMed1992

The measurement of handedness: a cross-cultural comparison of samples from England and Papua New Guinea.

Handedness was compared in 125 English children and 185 young people from Papua New Guinea (PNG). Many of the latter were unfamiliar with implements such as pencils and spoons. The PNG subjects showed strong hand preferences, usually for the right, and on some items were more consistent in hand use than the English subjects. However, they had smaller hand differences on peg-moving and tapping than the English children. A factor analysis identified one factor with high loadings from items involving precise motor control, and another with positive loadings from only card-dealing, block-building and threading. The first factor was impervious to cultural influences, whereas the second showed considerable cultural variation.

Adolescent↗
PubMed1992

Pathological left-handedness revisited: dichotic listening in children with left vs right congenital hemiplegia.

Thirty-one children with right (n = 18) and left (n = 13) congenital hemiplegia were compared for incidence of hand- and foot-preference, eye-dominance, and familial sinistrality. In addition, they were tested with dichotic listening for correct reports of consonant-vowel syllables. The two groups of children were closely matched on IQ and sensory functioning. Children with mental retardation, or epileptic seizures were not included. The results showed that 89% of the left hemisphere impaired (LHI) children were left-handed, all of them preferred the left foot, and 72% were left eye-dominant. In the right hemisphere impaired (RHI) group, everyone (100%) preferred the right hand and foot, and 62% were right eye dominant. The dichotic listening results showed a significant right ear advantage (REA) in the RHI-group, and a significant left ear advantage (LEA) in the LHI-group. The results are discussed in the framework of pathological handedness and shifts in hemisphere control of language in children with early brain injury. It is argued that the homogeneous samples, except for the site of lesion, provides an interesting possibility to compare cognitive effects of left and right hemisphere impairment in children.

Adolescent↗
PubMed1994

Normal lateralization for handedness and ear advantage in a verbal dichotic listening task in women with congenital adrenal hyperplasia (CAH).

Functional cerebral asymmetry was studied in 22 women, 17-34 years old, with prenatal virilization due to congenital adrenal hyperplasia (CAH) (21-hydroxylase deficiency) and 22 matched, healthy controls. The theory of an androgen influence on cerebral lateralization has been supported by the observation of sex differences in cognitive performance, anatomical cerebral differences between the sexes and atypical patterns of functional asymmetry in certain anomalous hormonal states. The result of the present study did however not show a significantly different pattern of functional asymmetry for women with CAH and prenatal exposure to high levels of androgens. No significant differences with the controls were found for the Finger Tapping Test (FTT), Edinburgh Handedness Inventory (EHI) or Dichotic Listening (Consonant-Vowel) Test (DL). The CAH group included four non-right-handers (18%) vs two (9%) in the control group. As sex differences generally are small, the present result, may have been influenced by the limited size of the sample.

Adolescent↗
PubMed1991

An assessment of handedness in mice.

Mice from a pool of inbred strains (384 males and 329 females) were tested for handedness according to Collins' protocol in order to assess the reliability of this measurement. As previously reported by Collins these data revealed that a) approximately half of the mice were right-handed and half left-handed, b) most of the mice were strongly lateralized and c) females were more lateralized than males. The study of the psychometric characteristics of the test suggested that this measurement of behavioral asymmetry is both stable and observer independent. The test of paw preference also appeared to measure preexisting lateralization and was not a function of training during the test.

Animals↗
PubMed1988

The metaphase scaffold is helically folded: sister chromatids have predominantly opposite helical handedness.

We have studied the three-dimensional folding of the scaffolding in histone H1-depleted chromosomes by immunofluorescence with an antibody specific for topoisomerase II. Two different types of decondensed chromosomes are observed. The majority of the chromosomes are expanded, and the central fluorescence signal is surrounded by a large halo of chromatin. A much smaller number of chromosomes are more compact in length; they contain a smaller halo of chromatin and their scaffolds are not extended but folded into a genuine, quite regular helical coil. This conclusion is based on a three-dimensional structural analysis by optical sectioning. The number of helical coils is related to chromosome length. Surprisingly, sister chromatids have predominantly opposite helical handedness; that is, they are related by mirror symmetry.

Cell Line↗
PubMed1992

Responsiveness patterns and handedness differences in bilateral electrodermal asymmetry.

The aim of the present study was to examine the relationship between subjects' handedness and electrodermal asymmetry when subjects were divided according to their electrodermal Responsiveness Patterns, obtained during a stimulus-free period. Skin conductance was bilaterally recorded in a sample of 48 subjects (24 dextrals and 24 sinistrals) during the performance of two tasks (watching a film and listening to neutral tones). Subjects were divided into four groups of 12 subjects each (dextral right-hand responders, dextral left-hand responders, sinistral right-hand responders and sinistral left-hand responders). No differences were found between dextral and sinistral subjects. Orientation of electrodermal asymmetry in each Responsiveness Patterns remained constant throughout the two conditions: right-hand responders showed higher electrodermal activity on their right hand, while left-hand responders showed higher electrodermal activity on their left hand. In addition, left-hand responders showed a slower habituation rate on their left hand than on their right hand, whereas right-hand responders showed no significant differences between hands.

Acoustic Stimulation↗
PubMed1994

Auditory event-related potentials, dichotic listening performance and handedness as indices of lateralisation in dyslexic and normal readers.

Evidence suggests that children with developmental dyslexia have poor phonological processing skills, are less likely to show lateralised activation during the processing of verbal information than children with normal reading ability and tend towards the left of the handedness continuum. The present study investigated this relationship between cerebral lateralisation and reading ability in children with and without dyslexia, directly using a dichotic listening paradigm with contemporaneous recording of auditory evoked potentials and indirectly using measures of hand preference and hand skill. The two groups were significantly different on a phonemic awareness task, particularly with reference to rime rather than phoneme onset. The two groups performed equally well on the dichotic listening task. However, normal readers produced significantly greater N100 amplitudes in the left temporal region during dichotic listening than the dyslexics who displayed approximately equivalent levels of amplitude bilaterally. In terms of hand preference the dyslexics were significantly less right-hand preferent than the controls, although the groups did not differ on a measure of right/left hand skill. The AEP lateralisation indices and the hand preference scores were significantly related to phonemic awareness performance. The different patterns of AEP activity produced by the two groups of children during the dichotic listening task and the differences in hand preference may be related to abnormal cerebral lateralisation of language functions. The failure of the dichotic listening task to discriminate between the two groups in spite of evidence of differences in cortical activation suggests that the processing difficulties which may be indexed by these differences in cortical activation affect the reading process at a later stage than that tapped by dichotic listening.

Child↗
PubMed1985

The pathological left-handedness syndrome.

A clinical syndrome of pathological left-handedness (PLH) is proposed to identify the pattern of correlative changes in lateral development associated with early brain injury in some manifest left-handers. This syndrome is believed to be caused by a hemispheric lesion that is predominantly left-sided (or bilateral asymmetric), which onsets before Age 6, and which encroaches upon the critical speech zones of the frontotemporal/frontoparietal cortex. The pattern of changes may include any or all of the following features: shifts in manual dominance, trophic changes in the extremities, transfer of hemispheric speech, and/or intrahemispheric reorganization of visuospatial cognitive functions. Although some of these correlates of PLH have long been known, they have not been recognized as an interrelated pattern of traits that constitute a clinical syndrome. Identification of these individuals, all manifest left-handers, will be shown to have implications for diagnosis/remediation and for models of recovery of function.

Adolescent↗
PubMed1990

Handedness and hemispheric asymmetry of pattern reversal visual-evoked potentials.

Pattern reversal visual-evoked potentials (EP) from temporal leads in the two hemispheres of 26 right-handed (14 right-eye-dominant and 12 left-eye-dominant) and 10 left-handed (left-eye-dominant) adults were recorded. Checkerboard patterns (check sizes: 5.7 and 17 min of arc) at 1 and 8 Hz were reversed. Stimuli (a) subtended 6 degrees of visual field, (b) subtended 1 degree of visual field (foveal condition), and (c) were restricted to the annular portion of the visual field around the fovea (peripheral condition). Larger EP amplitudes in right or left hemisphere in relation to handedness, temporal frequency, and visual field condition were recorded. Eye dominance of dextrals appeared to play a role in determining the hemispheric asymmetry. Previous literature data and present results in relation to the hypothesis of different hemispheric specialization for basic visual information are discussed.

Adult↗