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PubMed2004

Hippocampal and amygdalar volumes in relation to handedness in adults aged 60-64.

We evaluated the association between handedness and manual tracings of hippocampal and amygdalar volumes. Brain MRI and handedness data were obtained for 441 community dwelling participants aged 60-64 years of whom 31 were left-handed. Both absolute and normalized hippocampal volumes were larger in left-handed women than right-handed women. Hippocampal volume was not associated with handedness in men, and amygdalar volume was not associated with handedness in men or women. There was no right-left asymmetry in hippocampal or amygdalar volumes in either gender. We conclude that volumetric differences by handedness must be taken into account where hippocampal volumes are of clinical importance. Our results may also explain reports of lower rates of dementia in left-handed individuals.

Adult↗
PubMed1993

Left-handedness as a risk factor for unintentional injury in children.

OBJECTIVE: To determine whether left-handedness is a risk factor for unintentional injury among children and adolescents. DESIGN: Case-control study. SETTING: Pediatric emergency department of Arkansas Children's Hospital. PATIENTS: 265 patients sustaining unintentional trauma aged 6 to 18 years and 494 control patients who did not have trauma were given a questionnaire to determine handedness, past unintentional injury, and parental perception of injury proneness. RESULTS: The frequency of left-handedness in the trauma group (18.1%) was significantly greater than frequency of 10.5% in the control group (P < .003, odds ratio = 1.80, 95% confidence interval 1.20 to 2.72). Multivariate analysis revealed handedness as the only significant variable between trauma and control (P < .04). The proportion of left-handers who had been hospitalized previously for injury treatment (20.0%) was larger than the proportion of right-handers, (12.0%) (P < .026, odds ratio = 1.84, 95% confidence interval 1.03 to 3.27). More parents of left-handers rated their child as "more clumsy than average" than parents of right-handers (26.0% vs 15.2%, P < .007). CONCLUSIONS: Left-handedness appears to be a risk factor for unintentional injury in children and adolescents in a pediatric emergency department population.

Accident Proneness↗
PubMed1998

Cuticle chirality and body handedness in Caenorhabditis elegans.

Caenorhabditis elegans adult animals exhibit an inherent chirality of fiber orientation in the basal layer of the cuticle, as well as a naturally invariant but experimentally reversible handedness in the left-right (L-R) asymmetry of the body plan. We have examined the relationship between cuticle chirality and body handedness in normal and L-R reversed animals, using Roller (Rol) mutants and transmission electron microscopy to monitor cuticle properties. Rol phenotypes, several of which have been shown to result from mutations in cuticle collagen genes, are characterized by an invariant, allele-specific handedness in their direction of rolling. We show for several alleles that this direction is not affected by L-R reversal of the body plan. We further show, by electron microscopy, that the chiral orientation of cuticle fibers in animals with normal cuticle is not reversed by L-R body-plan reversal. We conclude that cuticle chirality must be established independently of body-plan handedness. The cues that establish cuticle chirality are still unknown, as are the causes for different rolling directions in different Roller mutants. We discuss the question of how cuticle chirality maintains its independence, and how the orientations of the fiber layers may be determined.

Animals↗
PubMed1993

Handedness in musicians: bimanual constraints on performance.

Handedness in musicians was examined in terms of the relative roles of the hands in bimanual motor activity involved in instrumental performance. Musicians playing instruments requiring temporally integrated (e.g., strings and wood-winds), as opposed to independent (e.g., keyboard instruments), bimanual motor activity were found to exhibit weaker degrees of handedness. There were no significant differences between groups in direction of handedness. Results are interpreted in terms of greater bilateral hemispheric integration and control of fine motor movements among subjects exhibiting mixed-handedness.

Brain↗
PubMed1994

Handedness and hemispheric differences for feature perturbations.

The influence of handedness on hemispheric differences for feature perturbations was assessed in left- and right-handed normal subjects, with equal numbers of each sex in each group. Stimulus displays consisting of five small squares arranged in a single row were presented tachistoscopically to the left or right of fixation, and the size of the squares was manipulated in different conditions. Subjects were instructed to state in which square a horizontal "tick" mark was located. The handedness of the subjects contributed to the pattern of hemispheric differences for tick mislocations resulting from feature perturbations in the toward-fovea direction. For left-handed subjects, fewer errors occurred when stimuli were presented to the left hemisphere; for right-handed subjects, fewer errors occurred when stimuli were presented to the right hemisphere. Increasing stimulus size tended to enhance the handedness and hemispheric feature perturbation effects. The data suggest that handedness contributes to hemispheric organization of featural extraction processes.

Adult↗
PubMed1998

Implicit visual analysis in handedness recognition.

In the present study, we addressed the problem of whether hand representations, derived from the control of hand gesture, are used in handedness recognition. Pictures of hands and fingers, assuming either common or uncommon postures, were presented to right-handed subjects, who were required to judge their handedness. In agreement with previous results (Parsons, 1987, 1994; Gentilucci, Daprati, & Gangitano, 1998), subjects recognized handedness through mental movement of their own hand in order to match the posture of the presented hand. This was proved by a control experiment of physical matching. The new finding was that presentation of common finger postures affected responses differently from presentation of less common finger postures. These effects could be not attributed to mental matching movements nor related to richness in hand-finger cues useful for handedness recognition. The results of the present study are discussed in the context of the notion that implicit visual analysis of the presented hands is performed before mental movement of one's hand takes place (Parsons, 1987; Gentilucci et al., 1998). In this process, hand representation acquired by experience in the control and observation of one's and other people's hand gestures is used. We propose that such an immediate recognition mechanism belongs to the class of mental processes which are grouped under the name of intuition, that is, the processes by which situations or people's intentions are immediately understood, without conscious reasoning.

Adult↗
PubMed2001

Development and evolution of a variable left-right asymmetry in nematodes: the handedness of P11/P12 migration.

In Caenorhabditis elegans, two lateral blast cells called P11/12L and P11/12R are symmetric left-right homologs at hatching, migrate subsequently in opposite anteroposterior directions during the first larval stage, and adopt two different fates, thus breaking the symmetry between them. Our results show that, unlike most other cell fate decisions in C. elegans, the orientation of P11/12L/R migration is highly biased, but not fixed. The handedness of their migration is linked to whole body handedness and is randomized in lin-12/Notch mutants and by ablation of the Y cell. Migration handedness is independent of P11 and P12 fate determination, previously shown to require the LIN-44/Wnt and the LIN-3/EGF pathways (L. I. Jiang and P. W. Sternberg, 1998, Development 125, 2337-2347). We further show that several changes in P11/12L/R asymmetry have occurred during nematode evolution: loss of asymmetry or reversals in orientation of migration. Strikingly, for most species studied, handedness of migration is highly biased but not fixed. Thus, whereas the final cell fate pattern of P11/12 is invariant, the developmental route leading to it is subject both to developmental indeterminacy and to evolutionary variations.

Animals↗
PubMed1994

Are fingerprints a genetic marker for handedness?

Fingerprints and handedness were measured in 2169 subjects. Left-handers were more likely to have an increased number of arches and radial loops, while having fewer whorls and lower pattern intensity than right-handers. Analyzing by hand and digit, the differences were most marked on the left hand, which showed significant differences on four of the five digits which were related to handedness. On the right-hand, handedness was associated with fingerprint patterns only on digit IV (ring finger). This finding suggests a genetic mechanism in the development of handedness and may provide a means of separating pathological from natural left-handers.

Adolescent↗
PubMed1995

Family patterns in handedness: evidence for indirect inheritance mediated by birth stress.

The most common alternative to a genetic explanation of left-handedness is that sinistrality arises because of birth stress factors. In a sample of 1398 subjects, the association between birth stress and left-handedness was confirmed. More importantly, it was found that left-handed mothers are more likely to have birth-stressed offspring and that the presence of any left-handed sibling increases the likelihood of a history of birth stress in the proband. This was interpreted as suggesting that a plausible alternative to the genetic explanation for the usual pattern of association observed in family studies of handedness (where a left-handed mother increases the probability of left-handed offspring) is that the mother-offspring association may actually be mediated by birth stress rather than representing heritable aspects of handedness.

Adolescent↗
PubMed1996

Handedness in homosexual and heterosexual men in the Kinsey interview data.

The relationship between sexual orientation and handedness in a large sample of men was examined. Subjects were 6544 nondelinquent men interviewed by the Kinsey Institute for Research in Sex, Gender, and Reproduction from 1938 to 1963. Subjects were classified as either homosexual (n = 1004) or heterosexual (n = 4579). Results failed to demonstrate a difference in handedness, with both groups having rates of non-right-handedness (i.e., 11-12%) approximately equal to establish norms. These findings do not replicate some recent studies indicating an increased level of non-right-handedness in homosexual men.

Functional Laterality↗
PubMed1981

The relationship between right-handed children's assessed and familial handedness and lateral specialization.

Eighty right-handed males (6-12 yr of age) stratified into age x degree of handedness x family history of handedness groups were administered three dichotic (digit, syllable, environmental sound) tests. Older subjects accurately identified more stimuli than the younger subjects across tasks. There were significantly laterality differences for both verbal and nonverbal stimuli between family history of handedness groups regardless of the subjects' age and degree of handedness. Those subjects with familial sinistrality had attenuated right-side advantage for verbal and non-verbal stimuli and decreased nonverbal accuracy scores compared to the familial dextral subjects who evidenced at right-ear (left hemisphere) advantage for verbal stimuli and a left-ear (right hemisphere) advantage for nonverbal.

Age Factors↗
PubMed1987

Pathological left-handedness: is it familial?

Hand preferences and the incidence of familial sinistrality of developmentally retarded. Down's syndrome and non-retarded individuals were compared. The incidence of left-handedness in the retarded groups was higher than in the normal group. The incidence of familial left-handedness was also raised in the retarded groups. These results are inconsistent with the popular theoretical distinction between pathological left-handedness in special groups and familial left-handedness in the general population.

Adolescent↗
PubMed1990

Association between left-handedness and allergy: a reappraisal.

There are conflicting reports in the literature about the possible association between left-handedness and immune disorders, including autoimmune diseases as well as allergies. In this study we compared the distribution of right- and left-handers, assessed with the Edinburgh Handedness Inventory, in a group of patients consulting an allergy clinic and a control population with a similar sex and age distribution. There was no overall association between left-handedness and allergies, although we found a tendency towards left-handedness in patients whose allergic symptoms started before puberty, suggesting that left-handers may have an increased predisposition to allergic disease that manifests itself during early life.

Adolescent↗
PubMed1990

Relationships between the direction of movements and handedness in children.

It has been proposed that human handedness can be deduced from the direction of voluntary movements. To test this assumption, children of an elementary school were observed as they performed several tasks with their dominant hand; drawing circles on a piece of paper, making circular movements in the air with their index finger, drawing a human profile, boring and drawing a horizontal line. Both handedness of the children and the directionality of their drawings and movements were assessed. It appeared that the direction of drawing a horizontal line is the only variable that differentiates well between handedness groups. While this variable was hardly influenced by age, other variables were. Circling, for instance, was predominantly clockwise in the youngest and counter-clockwise in the older children. It was argued that the handedness of individual subjects cannot safely be determined from these measures.

Child↗
PubMed1991

Mathematical ability and the right-shift theory of handedness.

A genetic theory of handedness, the right-shift theory, associates differential patterns of cerebral functioning with contrasting handedness groups and suggests that individuals with an rs + + genotype will be disadvantaged in mathematical performance. This hypothesis is investigated with contrasting handedness groups drawn from a national sample of over 11,000 children from the National Child Development Study. Some differentiation in cognitive performance between handedness groups is found in the direction predicted by the right-shift theory but the level of the findings is not statistically significant. The rs+ +/mathematical deficit hypothesis is not confirmed.

Achievement↗
PubMed1992

Cluster analysis reveals at least three, and possibly five distinct handedness groups.

Multivariate techniques have used data from hand preference questionnaires to group hand preference items, but no attempt has been made to date to use multivariate analyses to group individuals in terms of handedness groups. This study analyzed the responses of 645 subjects on the Waterloo 60-item handedness questionnaire with a cluster analysis (BMDP) in order to determine the grouping of individuals in terms of hand preference patterns. Five distinct handedness groups were recognized by this procedure and a Discriminant Function Analysis revealed a very high accuracy of assigning individuals to the five groups. A cluster analysis of a shorter 14-item questionnaire suggested three distinct handedness groups, and the degree of accuracy of assigning individuals to these groups was also very high. As is the case with all multivariate techniques in neuropsychology, the question of whether the clusters form meaningful groupings awaits an answer in terms of their different neuropsychological properties.

Adult↗
PubMed1991

Breast size, handedness and breast cancer risk.

Bra cup size and handedness were studied as possible risk factors for breast cancer. Data for 3918 cases and 11,712 controls from 7 centres were used to examine the association of handedness with laterality of breast cancer; data for 2325 cases and 7008 controls from 4 centres were used to assess the relation of bra cup size to breast cancer risk. There was a suggestive (P about 0.10) association of handedness with breast cancer laterality: odds ratio of a left-handed (or ambidextrous) woman having a left-sided cancer 1.22 (95% CI 0.96-1.56). Handedness may affect the lateral occurrence of breast cancer, although this tumour is in general more common in the left breast, possibly because this breast is usually slightly larger. Premenopausal women who do not wear bras had half the risk of breast cancer compared with bra users (P about 0.09), possibly because they are thinner and likely to have smaller breasts. Among bra users, larger cup size was associated with an increased risk of breast cancer (P about 0.026), although the association was found only among postmenopausal women and was accounted for, in part, by obesity. These data suggest that bra cup size (and conceivably mammary gland size) may be a risk factor for breast cancer.

Adult↗
PubMed1984

Pathological left-handedness and familial sinistrality in relation to degree of mental retardation.

The relationship between personal and familial hand preference and mental retardation was examined. Six unimanual tasks were performed by 232 subjects within four mental retardation severity groups. Family handedness histories were obtained. Right hand preference varied inversely with severity of mental retardation. The handedness of mentally retarded groups at the different functional levels paralleled, but tended much more to the sinistral, than that of the corresponding parent groups. The parent-proband handedness correlations were largely insignificant, especially in lower functioning groups. The findings support both pathological left-handedness theory and an association between brain damage causing mental retardation and familial sinistrality.

Brain Damage, Chronic↗