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PubMed2004

An assessment of sleep architecture as a function of degree of handedness in college women using a home sleep monitor.

The present study examined sleep architecture as a function of handedness in a population of undergraduate college women using a home sleep monitor. Compared to strongly handed individuals, participants with a tendency toward mixed-handedness had a shorter sleep latency and spent a greater percentage of their sleep period asleep and less awake. Increasing mixed-handedness was also associated with increased NREM; strong-handedness was associated with increased REM. Results are placed in a neurophysiological framework wherein corpus callosum mediated differences in interhemispheric interaction during Wake, REM, and NREM on the one hand, and individual differences in corpus callosum morphology and hemispheric communication as a function of handedness on the other, interact to result in handedness differences in sleep architecture.

Adolescent↗
PubMed2004

Antenatal maternal anxiety is linked with atypical handedness in the child.

BACKGROUND: Animal studies have shown that prenatal stress is linked with altered laterality in the offspring. AIMS: The aim of this study was to test the hypothesis that antenatal maternal anxiety was associated with altered lateralisation in children, as demonstrated by mixed handedness. STUDY DESIGN AND SUBJECTS: We used the Avon Longitudinal Study of Parents and Children (ALSPAC), a prospective longitudinal study that has followed women since pregnancy. The final analysis included data on 7431 mother-child pairs. Maternal anxiety was measured at 18- and 32-week gestation and 8 weeks postnatally using a self-report inventory. Child handedness was assessed at 42 months using an established maternal report scale. Information on maternal and paternal handedness, as well as data on possible confounding variables such as obstetric and antenatal risks, were also assessed. RESULTS: Univariable analysis showed that antenatal anxiety at 18 weeks was associated with mixed-handedness in the child, OR=1.28 (95% CI 1.09-1.50, p<0.01). Although boys were more likely than girls to be mixed handed, the link with antenatal anxiety was similar. There was no significant association with antenatal anxiety at 32 weeks. Multivariable analyses indicated that maternal anxiety at 18 weeks of pregnancy predicted an increased likelihood of mixed-handedness in the child (OR=1.23, 95% CI 1.02-1.48, p<0.05), independently of parental handedness, obstetric and other antenatal risks, and postnatal anxiety. CONCLUSION: This result provides further evidence for a link between antenatal anxiety and fetal programming in humans.

Adult↗
PubMed2001

In-vivo analysis of the human planum temporale (PT): does the definition of PT borders influence the results with regard to cerebral asymmetry and correlation with handedness?

The aim of our study was to examine whether the degree of planum temporale (PT) asymmetry and the possible correlation of morphological PT asymmetries with handedness are influenced by the definition of PT borders. For this reason, we applied three different anatomical PT definitions formerly used in the literature. The PT total (with the end of the Sylvian fissure (SF) as its posterior border) was separated into anterior and posterior regions. The border between anterior and posterior PT was set according to the following definitions: at the end of Heschl's gyrus (1st definition); at the start of the ascending SF ramus according to the 'knife-cut' method (2nd definition); and at the bifurcation of the SF (3rd definition). Thirty right-handed healthy men were recruited. MRI data sets analyzed with the software program BRAINS were used for in vivo PT volumetry. The Edinburgh Handedness Inventory (EHI) and the Hand Dominance Test were used to determine the degree of handedness. In summary, we detected that the type and the degree of asymmetry between left and right PT were strongly dependent on the definition used for PT borders: a left>right asymmetry was found in all PT regions, except a right>left asymmetry of the anterior PT according to our 1st PT definition (lateral to Heschl's gyrus) and a symmetry of the posterior PT according to our 3rd PT definition (posterior to SF bifurcation). In addition, a significant correlation was found between the degree of handedness measured by the EHI and the right posterior PT (3rd definition). We conclude that the influence of the definition of PT borders on the investigated variables may explain some of the variances between former investigations on PT asymmetry and handedness. The possible implications of the correlation between handedness and the extension of the right parietal PT are discussed and have to be elucidated by further studies.

Adolescent↗
PubMed1999

Left-handedness as a function of sex, maternal versus paternal inheritance, and report bias.

The right-shift (RS) theory suggests that sex differences for handedness are due to the displacement of a chance distribution of asymmetry farther to the right in females than males by about 20%. An analysis of studies in the literature shows that when handedness is assessed by self-report, paired samples of males and females differ for incidence of left-handedness as predicted, but for parents assessed by indirect-report, there are fewer left-handed mothers than expected. When handedness is assessed by self-report in both generations, the RS genetic model successfully predicts the distribution in families. It is also successful at different levels of criterion from left-writing to non-right-handedness. The RS predictions are not always consistent with the findings of studies that depended on indirect report of parental handedness. When parental incidences are low the proportion of left-handed children in the families of left-handed mothers is higher than expected. When parental incidences are high, predictions for the families of left-handed mothers are excellent, but the percentage of left-handed children in the families of left-handed fathers is lower than expected. Data for all indirect-report studies are combined to test the idea that the chief cause of poor fit is underreporting of left-handed mothers by right-handed children. Transfer of right-handed children from R x R to R x L families, thereby raising the percentage of left-handed mothers by about 1%, is sufficient to give good fits to RS predictions for both sexes.

Adult↗
PubMed1989

For better or for worse: left-handedness, pathology, and talent.

Geschwind and his colleagues have hypothesized that left-handedness may be a marker for anomalous dominance and is associated with certain immune disorders, learning disorders, and special talents. The few relevant studies done to date have yielded somewhat mixed findings, and little had been done to study the relationship of relevant findings to the definition of handedness employed in a given study. The present study assessed the association between handedness and a variety of disorders, talents, and skills in subjects and their parents and siblings. Results showed that mathematical, artistic, and musical talents varied systematically as a function of handedness. Verbal skills, stuttering, and asthma were also significant discriminators in some discriminant function analyses, and certain variations in the definition of handedness produced systematic variations in results. Finally, certain disorders, particularly eczema, stuttering, and epilepsy, in the parents were related to handedness in their offspring.

Adult↗
PubMed2002

Determinants of handedness in twins.

It is well established that the distribution of the combinations of handedness (LL, LR, and RR) in twin pairs is roughly binomial regardless of zygosity or sex. This fact has challenged current genetic models of handedness. We show here that: (a) there must be at least one environmental determinant of handedness; and (b) the binomial distribution does not in itself invalidate genetic models of handedness. In singletons, left-handedness is strongly associated with low birth weight. In twins, this association is weaker (apparently as a consequence of a stronger association with birth order--i.e., with being first-born--within the pair). We speculate that the hazards associated with being first-born in twin pairs (e.g., trauma) are more closely associated with left-handedness than are the hazards associated with being second-born (e.g., hypoxia).

Journal Article↗
PubMed2000

Handedness and hemispheric language dominance in healthy humans.

In most people the left hemisphere of the brain is dominant for language. Because of the increased incidence of atypical right-hemispheric language in left-handed neurological patients, a systematic association between handedness and dominance has long been suspected. To clarify the relationship between handedness and language dominance in healthy subjects, we measured lateralization directly by functional transcranial Doppler sonography in 326 healthy individuals using a word-generation task. The incidence of right-hemisphere language dominance was found to increase linearly with the degree of left-handedness, from 4% in strong right-handers (handedness = 100) to 15% in ambidextrous individuals and 27% in strong left-handers (handedness = -100). The relationship could be approximated by the formula: f1.gif" BORDER="0">. These results clearly demonstrate that the relationship between handedness and language dominance is not an artefact of cerebral pathology but a natural phenomenon.

Adolescent↗
PubMed1999

Atypical handedness in schizophrenia: some methodological and theoretical issues.

An updated review of the literature strongly supports the view that in schizophrenia there is an atypical leftward shift in the handedness distribution that, while comprising different subtypes, is characterized by a more variable and less completely lateralized pattern of manual preference, referred to as mixed handedness (MH) or ambiguous handedness (AH). Only two studies revealed an increased prevalence of left-handedness suggestive of pathological left-handedness (PLH). This article also examines the current status of neurodevelopmental factors and mechanisms in schizophrenia that purport to explain these pathological shifts in handedness (PLH, MH, AH). Different theoretical positions were evaluated, each involving some aspect of left hemisphere insult (unilateral or bilateral). Finally, it was shown that these shifts predict certain key symptoms and neural substrates in schizophrenia including thought disorder, negative symptoms, neuropsychological impairment, family history, and brain anatomy. These subtypes may represent neurodevelopmental markers of insult during intrauterine life that are nongenetic in origin.

Cerebral Cortex↗
PubMed1985

Left-handedness and inflammatory bowel disease.

Handedness has been reported to be associated with several disorders, including "immune disease." We examined the specific association between left-handedness and inflammatory bowel disease in 213 persons. We personally questioned 43 patients with Crohn's disease, 40 with ulcerative colitis, 70 control patients with various gastrointestinal disorders, and 60 hospital employees with no known immune or gastrointestinal disorder. The clinical diagnosis of each patient was rigorously established. Handedness was determined by The Oldfield Inventory. Study groups were well matched for age, sex, socioeconomic, and cultural backgrounds. The incidence of left-handedness among these groups was 9.3% for those with Crohn's disease, 15.0% among those with ulcerative colitis, 11.4% and 13.3% among the control groups, respectively. There was no excess of left-handedness, within any subgroup, when those with inflammatory bowel disease were analyzed according to sex; or disease location, duration, or overall severity. Our data do not confirm the previously suggested association of left-handedness and inflammatory bowel disease.

Adolescent↗
PubMed1994

Handedness, age at menarche, and age at menopause.

OBJECTIVE: To investigate the relation between handedness and age at menarche or age at menopause, as both handedness and reproductive variables have been suggested to be influenced by the intrauterine endocrine environment. METHODS: Self-reported information on handedness, age at menarche, age at menopause, and other demographic and reproductive variables was recorded for 10,328 women still menstruating or in natural menopause. These women had been selected as controls in a multicenter case-control study of breast cancer conducted in the 1960s. Left-handedness (including ambidexterity) was modeled as the outcome variable through multiple logistic regression. RESULTS: After adjusting for center, age, menopausal status, age at menopause, years of schooling, and parity, there was no significant relation of handedness to age at menarche (odds ratio for each year delayed 1.01, 95% confidence interval [CI] 0.97-1.06) or age at menopause (odds ratio 1.00, 95% CI 0.98-1.02). CONCLUSION: These findings lend no support to the hypothesis that intrauterine endocrine variables associated with handedness also are related to reproductive variables.

Adolescent↗
PubMed1996

Frequency-dependent maintenance of left handedness in humans.

The percentage (10-13%) of left handedness in human has apparently not changed since the Neolithic. Left handedness is heritable and appears to be repeatedly associated with some reduced fitness components; the persistence of left handedness implies that left handers have a fitness advantage in some situations. We propose that left handers have a frequency-dependent advantage in fights and for that reason a fitness advantage. To test this hypothesis, left handedness frequencies in the general population and in sporting individuals (both students and the sporting elite) have been compared, as sporting performance is likely to be a good indicator of fighting abilities. The higher proportion of left-handed individuals in interactive sports (reflecting some fighting elements), reaching 50% in some sports categories, but not in noninteractive sports, is consistent with the fighting hypothesis. The greater frequency of left handedness in males than in females is also consistent with this hypothesis, as male-male fights are universally more frequent than other combinations. The frequency-dependent advantage in fights of left handers might explain the stability of left handedness.

Adolescent↗
PubMed1985

Handedness in the mentally handicapped.

The prevalence of left-handedness and the degree of handedness were examined in 130 normal and mentally handicapped pupils of both sexes, aged between seven and 18 years. Handedness was assessed by means of 10 performance items. The prevalence of left-handedness among normal pupils (10.6 per cent) was significantly lower than that for the mentally handicapped group (26.5 per cent). There was no significant difference in the prevalence of left-handedness between the mentally handicapped pupils with and without Down's syndrome. The degree of handedness was also reduced in the mentally handicapped group, but again there was no difference between those with and without Down's syndrome.

Adolescent↗
PubMedDate not supplied

Non-right-handedness and obstetrical complications in paranoid hallucinatory schizophrenics.

In previous studies a link between pregnancy complications, minor physical anomalies and non-right-handedness was described in schizophrenic patients. There is evidence of an anomaly in the lateralization process in schizophrenia. Many studies of handedness and schizophrenia have found that schizophrenic patients have an increased rate of non-right-handedness compared with normal subjects. The contemporary neurodevelopmental hypothesis of schizophrenia emerged from pathobiological findings. In addition there is evidence for early brain lesions and malformations in fetal brain development. Especially pregnancy and birth complications have been found to be a risk factor for the later development of schizophrenia. In this study we set out to test the possible association between diagnosis and handedness, diagnosis and risk factors, as well as gender and handedness for 60 patients (30 men, 30 women) and 60 controls. The percentage of non-right-handedness was significantly elevated in the patient group (p = 0.0025). In a gender-specific analysis this result could be confirmed only for male patients. Peri- and postnatal developmental risk factors were significantly elevated in schizophrenics compared with controls. The percentage of all risk factors in the male group of schizophrenic non-right-handers was significantly elevated compared with right-handed male schizophrenics.

Adult↗
PubMed1990

Handedness and epileptic schizophrenia.

Thirty-two epileptic patients with RDC diagnoses of schizophrenia were tested for handedness on the Annett Handedness Schedule, and handedness was assigned on the basis of Annett-Maudsley criteria. They were compared with three other groups of patients. Five (15.6%) of the epileptic schizophrenic patients were mixed or left handed. The prevalence of mixed and left handedness did not differ between the samples studied. However, there was a significant reduction of mixed and left handedness in male epileptics with schizophrenia. Mixed or left handedness in male epileptics appears to be protective against the development of psychiatric illness in general.

Adult↗
PubMed2006

Degree of handedness and cerebral dominance.

OBJECTIVE: To examine the relationship between the degree of handedness and hemispheric language dominance in patients with epilepsy. METHODS: The authors examined the relationship between degree of handedness and hemispheric language dominance in 174 epilepsy surgery candidates using the intracarotid amobarbital procedure and results from a modified version of the Edinburgh Handedness Inventory. RESULTS: The incidence of atypical language dominance increased linearly with the degree of left-handedness, from 9% in strong right-handers (laterality quotient [LQ] = +100) to 46% in ambidextrous individuals and 69% in strong left-handers (LQ = -100). CONCLUSIONS: The incidence of atypical language dominance depends not only on the direction but also on the degree of handedness. In addition, direction of language dominance varies with hemisphere of seizure focus and degree of handedness. A familial history of sinistrality may have an additional effect on the likelihood of atypical dominance.

Adolescent↗
PubMed1990

The development of handedness in left/right asymmetry.

The development of handed asymmetry requires a special mechanism for consistently specifying a difference between left and right sides. This is to be distinguished from both random asymmetry, and from those left/right differences that are mirror symmetrical. We propose a model for the development of handedness in bilateral animals, comprising three components. (i) A process termed conversion, in which a molecular handedness is converted into handedness at the cellular level. A specific model for this process is put forward, based on cell polarity and transport of cellular constituents by a handed molecule. (ii) A mechanism for random generation of asymmetry, which could involve a reaction-diffusion process, so that the concentration of a molecule is higher on one side than the other. The handedness generated by conversion could consistently bias this mechanism to one side. (iii) A tissue-specific interpretation process which responds to the difference between the two sides, and results in the development of different structures on the left and right. There could be direct genetic control of the direction of handedness in this model, most probably through the conversion process. Experimental evidence for the model is considered, particularly the iv mutation in the mouse, which appears to result in loss-of-function in biasing, and so asymmetry is random. The model can explain the abnormal development of handedness observed in bisected embryos of some mammalian, amphibian and sub-vertebrate species. Spiral asymmetry, as seen in spiral cleavage and in ciliates, involves only conversion of molecular asymmetry to the cellular and multicellular level, with no separate interpretation step.

Animals↗
PubMed2006

Evaluation of some tasks used for specifying handedness and footedness.

Healthy men (n = 42) and women (n = 45) who were right-handed and men (n = 21) and women (n = 20) who were left-handed were studied. Men's mean age was 21.1 +/- 3.5 yr. and women's 20.7 +/- 3.1 yr. These students in various faculties reported they were right- or left-handed. Then their hand and foot preferences (handedness and footedness) were ascertained by asking each of the subjects to perform 11 tasks for handedness and 9 tasks for footedness. A discriminate function analysis test showed that each of the 11 tasks used for assessing their self-reported handedness was significant, but, of the 9 tasks used for assessing self-reported footedness, only 7 were significant. Strength of the hand or foot played no role in reports of handedness or footedness. A combination of four tasks, such as pulling a door, pushing a door, holding an object, and hammering a nail, on which the maximum number of subjects performed with the right or left hand, depending upon their self-reported handedness, would be ideal for ascertaining handedness. A combination of three tasks, namely, kicking a football, pushing an object with the foot, and stamping on the ground, would be ideal for ascertaining footedness.

Adult↗
PubMed1993

Measurement of handedness via self-report: the relationship between brief and extended inventories.

Three self-report measures of handedness were explored. For simple dichotomous classification into right- versus left-handed groups, a brief (4-item) and an extended (12-item) inventory produced 98.8% classification concordance in a sample of 250 subjects. When handedness was treated as a continuous variable, indexes based upon the short and expanded scales correlated highly (r = 0.95). A single-item handedness measure was also created which produced handedness classifications which were better than 97% concordant with the brief and extended handedness scales for dichotomous classification. The methodological implications of these findings for handedness measurement are discussed.

Adolescent↗