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PubMed1988

Hand preference in a normal population.

The Edinburgh Inventory was used to assess handedness in a normal population. The incidence of strong right-handedness increased with age and the incidence of left-handedness fell with age, both significantly. A non-significant increase in the incidence of left-handedness in twins was observed. The difference in the incidence of left-handedness for males and females failed to reach significance but more males were left-handed than females. Any difference in the incidence of left-handedness between the sexes must be small (less than 1.5%) and this has major theoretical implications.

Adolescent↗

PubMed2000

[Motor assymetry].

Although the study of handedness and its association with hemispheric specialisation represents the prevailing focus of motor dominance research, recent inquiry into footedness and other motoric asymmetries has stimulated several interesting propositions. The present review show the variability of assessing motoric asymmetries. Asymmetry in hand use takes two forms: differential hand preference and differential dexterity between the hands. Motoric asymmetries are strongest and most manifest for handedness (hand preference, performance and dexterity), descending through footedness and other less known asymmetries (tonguedness, chewing preference). Handedness is the most easily observed expression of cerebral lateralization. The alpha and omega of relating handedness to other neuropsychological variables or indices of lateral specialization lies in the classification of handedness. A vast range of testing techniques have been used to assess handedness. Writing hand and self-report are two of the most popular techniques. Other preference measures include observation of how people use tools and questionnaires. Performance tests assess speed and accuracy in tasks stressing manipulative dexterity. Although questionnaires are generally thought to be reliable and valid instruments, there is a disagreement as to the nature, the number and weighting of the items to be included. The least stable results will be obtained if a categorization into "right-handers" and "non-right-handers" is made on the basis of exclusive "right" answers. Slightly more stable is a classification that is based on "right-handers", "mixed preference handers" and "left-hander" based on extreme choices in either direction and intermediate choices. We present shortly a possible inventory assessing motoric asymmetries.

Foot↗

PubMed1980

Human cerebral asymmetries evaluated by computed tomography.

The handedness of seventy-five persons without evidence of neurological disease, was assessed with a standardised test. An analysis of the CT scans of the same persons was performed to determine (1) presence and lateralisation of frontal and occipital "petalia," (2) width of frontal and occipital lobes of each hemisphere, (3) direction of straight sinus deviation. Results suggest that handedness and cerebral asymmetries are independent variables. There were no significant differences between right-handers and non-right-handers. Also there were no significant differences between strongly left-handed and ambidextrous individuals, nor were there differences between right-handers with or without family history of left-handedness. Irrespective of handedness, left occipital "petalia" was more common than right (p < 0.01), right frontal petalia was more common than left (p < 0.01), and straight sinus deviation was more commonly toward the right. The study does not support the concept that cerebral "symmetry" or "reverse asymmetry" are associated with left-handedness or ambidexterity. The noted asymmetries are more likely to be direct correlates of cerebral language dominance, than of handedness. Furthermore, the possibility that outside forces acting on the bone contributes to the asymmetries cannot be excluded. CT scan may be of value as a direct predictor of cerebral dominance.

Cerebral Cortex↗

PubMed2002

Language lateralization in left-handed and ambidextrous people: fMRI data.

BACKGROUND: It is generally accepted that most people have left-hemispheric language dominance, though the actual incidence of atypical language distribution in non-right-handed subjects has not been extensively studied. The authors examined language distribution in these subjects and evaluated the relationships between personal handedness, family history of sinistrality, and a language laterality index (LI) measured with fMRI. METHODS: The authors used whole-brain fMRI to examine 50 healthy, non-right-handed subjects (Edinburgh Handedness Inventory quotient between -100 and 52) while they performed language activation and nonlinguistic control tasks. Counts of active voxels (p < 0.001) were computed in 22 regions of interest (ROI) covering both hemispheres and the cerebellum. LI were calculated for each ROI and each entire hemisphere using the formula [L - R]/[L + R]. RESULTS: Activation was predominantly right hemispheric in 8% (4/50), symmetric in 14% (7/50), and predominantly left hemispheric in 78% (39/50) of the subjects. Lateralization patterns were similar for all hemispheric ROI. Associations were observed between personal handedness and LI (r = 0.28, p = 0.046), family history of sinistrality and LI (p = 0.031), and age and LI (r = -0.49, p < 0.001). CONCLUSIONS: The incidence of atypical language lateralization in normal left-handed and ambidextrous subjects is higher than in normal right-handed subjects (22% vs 4-6%). These whole-brain results confirm previous findings in a left-handed cohort studied with fMRI of the lateral frontal lobe. Associations observed between personal handedness and LI and family history of handedness and LI may indicate a common genetic factor underlying the inheritance of handedness and language lateralization.

Adult↗

PubMed1998

Handed asymmetry in nematodes.

Like most animals, C. elegans and other nematodes exhibit several internal left-right asymmetries with an essentially invariant (dextral) handedness. Handedness is established in early cleavage, resulting in a markedly left-right-asymmetric embryo on which bilateral symmetry must be superimposed later in embryogenesis. Some of the asymmetric cell interactions that accomplish this have been identified, but the mechanism that initially establishes dextral rather than sinistral handedness is not understood, in C. elegans or any other embryo. Analysis of mutations that result in reversal of handedness, such as spn-1 in C. elegans, should help elucidate this process. A model involving centriolar segregation is proposed as a possible mechanism for handedness choice.

Animals↗

PubMed1990

Aphasia due to lesions confined to the right hemisphere in right handed patients: a review of the literature including the Italian cases.

We review most of the work published, to our knowledge, between 1880 and 1988 on aphasia due to right cerebral lesions in right-handed patients ("crossed aphasia"). We summarize the 87 cases found in chronological order within defined groups, dealing in greater detail with the less well-known cases in English-language publications and with the cases from other sources that we consider most representative and convincing. The 87 cases fall into three groups on the following criteria: right-handedness (on standardized tests), absence of left-handers in the family, left hemisphere integrity. Group 1 comprises cases that are unreliable because the handedness data are missing and/or because left hemisphere lesions were known to be present or probably were so. Group 2 comprises cases with full clinical data but no formal test of handedness, with familial cases of left-handedness and/or without satisfactory evidence of left hemisphere integrity. Groups 3 comprises the 26 reliable cases, that is those with proven right-handedness, no left-handers in the family and with proven hemisphere integrity. We discuss the implications of these cases.

Adolescent↗

PubMed1994

Simultaneous verbal and affective laterality effects.

By analyzing the error scores of normal participants asked to identify a specific word spoken in a specific tone of voice (for example, the word "tower" spoken in a happy tone of voice), we have been able to demonstrate concurrent verbal and affective cerebral laterality effects in a dichotic listening task. The targets comprised the 16 possible combinations of four two-syllable words spoken in four different tones of voice. There were 128 participants equally divided between left- and right-handers, with equal numbers of each sex within each handedness group. Each participant responded to 144 trials on the dichotic task, and filled in the 32-item Waterloo Handedness Questionnaire. Analysis of false positive responses on the dichotic task (responding "yes" when only the verbal or only the affective component of the target was present, or when both components were present but were at opposite ears) indicated that significantly more errors were made when the verbal aspect of the target appeared at the right ear (left hemisphere) and the emotional aspect was at the left ear (right hemisphere) than when the reverse was the case. A single task has generated both effects, so that differences in participants' strategies or the way in which attention is biased cannot account for the results. While the majority of participants showed a right-ear advantage for verbal material and a left-ear advantage for nonverbal material, these two effects were not correlated, suggesting that independent mechanisms probably underly the establishment of verbal and affective processing. We found no significant sex or handedness effects, though left-handers were much more variable than were right-handers. There were no significant correlations between degree of handedness as measured on the handedness questionnaire and extent of lateralization of verbal or affective processing on the dichotic task. We believe that this general technique may be able to provide information as to the nature and extent of interhemispheric integration of information, and is easily adaptable to other modalities, thus holds great promise for future research.

Adult↗

PubMed1983

Autistic children's hand preferences: results from an epidemiological study of infantile autism.

Twenty-six autistic children, constituting a total population sample of children diagnosed in accordance with Rutter's criteria as suffering from infantile autism, were assessed with regard to handedness and certain associated factors. They were compared with 52 age-, sex-, and IQ-matched controls. Sixty-two percent of the autistic children were non-right-handed compared with 37% of the controls. Left-handedness in autism was associated with an abundance of delayed echolalia. Heredity for left-handedness in some cases, and assumed brain damage and immature patterns of lateralization in others, were considered the cause of non-right-handedness in the autistic children. Computed tomographic (CT) brain scans and other neurobiological examinations did not provide evidence indicating clear-cut unilateral left hemisphere dysfunction in autism. Rather, a slight trend in the opposite direction (i.e., an association with right hemisphere dysfunction) was seen in the left-handed autistic children. The result points toward the need for further studies of handedness in autism.

Adolescent↗

PubMed1988

Altered cerebral dominance in an atopic population.

Handedness was assessed in 853 subjects, 424 from an allergy office practice and 429 from a health screening clinic, using a modified Oldfield Handedness Inventory. Subjects also responded to a survey ascertaining both personal and family histories of allergy-related problems and left-handedness. A significant left-handed shift in mean laterality quotient and an increased incidence of left-handedness was found in participants from the allergy office and in subjects who considered themselves to be affected by allergy, allergic rhinitis, and/or asthma. Controlling for nonatopic responders from the allergy office and possibly atopic responders from the health screening clinic, mean laterality quotients were 66.4 +/- 51.6 vs 79.4 +/- 42.1 (p less than .001) and the incidence of left-handedness was 12.1% vs 6.8% (p less than .05). Mean laterality quotient of 125 asthmatics was 65.1 +/- 54.0, and 16 (12.8%) were left-handed. The mean percentage of left-handed children of 79 asthmatic parents was found to be increased: 16.7 +/- 26.3% vs 10.3 +/- 21.2% of children of 198 nonatopic parents (p less than .02). This was attributable to left-handed children of asthmatic women, 18.6 +/- 29.0% (p less than .01), but not asthmatic men. Both autonomic neurologic dysfunction and disordered immunoregulation typify atopic disease. Our results can be interpreted to reflect this duality and lend support to Geshwind's hypothesis of a relationship between cerebral dominance and immunologic set resulting from common developmental influences.

Adult↗

PubMed2006

Hand preference for writing and associations with selected demographic and behavioral variables in 255,100 subjects: the BBC internet study.

In an Internet study unrelated to handedness, 134,317 female and 120,783 male participants answered a graded question as to which hand they preferred for writing. This allowed determination of hand preference patterns across 7 ethnic groups. Sex differences in left-handedness were found in 4 ethnic groups, favoring males, while no significant sex differences were found in three of the groups. Prevalence of left-handedness in the largest of the ethnic groups (self-labelled as "White") was comparable to contemporary hand preference data for this group [Gilbert, A. N., & Wysocki, C. J. (1992). Hand preference and age in the United states. Neuropsychologia, 30, 601-608] but the prevalence of left-handedness in individuals >70 years of age was considerably higher in the present study. Individuals who indicated "either" hand for writing preference had significantly lower spatial performance (mental rotation task) and significantly higher prevalence of hyperactivity, dyslexia, asthma than individuals who had clear left or right hand preferences, in support of Crow et al. [Crow, T., Crow, L., Done, D., & Leask, S. (1998). Relative hand skill predicts academic ability: global deficits at the point of hemispheric indecision. Neuropsychologia, 36, 1275-1282]. Similarly, an association of writing hand preference and non-heterosexual orientation was clearest for individuals with "either" writing hand responses. We conclude that contradictions in the literature as to whether or not these variables are linked to handedness stem largely from different definitions of hand preference. Due to a lack of statistical power in most studies in the literature, the "either" hand writing preference group that yielded the most salient results in this study is not normally available for analysis.

Adolescent↗

PubMed2005

Hemispheric specialization for language: Brain volume matters.

Increasing brain volume may impose constraints, through longer information transfer delays, on the distributed networks supporting language. Here, we assessed the relative effects of brain volume and other putative predictors of the functional variability of perisylvian language areas, as probed with PET, during both a language comprehension and a language production task. In the case of language comprehension (story listening), a linear combination of planum temporale surface, brain volume and handedness could explain almost 60% of the functional asymmetry observed in the perisylvian area. Without brain volume, the goodness of fit was significantly decreased (39%, P < 0.05), and furthermore, the effect of handedness was not detected anymore. This was due to the fact that in our sample, left-handers (n = 12) had a significantly larger brain volume as compared to right-handers (n = 8, P = 0.03). As for language production (verb generation), brain volume and the planum temporale also played a role. However, in this case, the main predictor of functional variability was handedness, where a greater degree of right-handedness was associated with larger activation of left inferior frontal regions. Depending on the language component of interest, these results support different (yet compatible) theories on hemispheric specialization. Left specialization for comprehension could be attributed to the constraints of processing speech stimuli, while a gestural origin of language is mostly supported by the relation we observed between left specialization for production and right-handedness.

Adult↗

PubMed2002

Contribution of energy values to the analysis of global searching molecular dynamics simulations of transmembrane helical bundles.

Molecular interactions between transmembrane alpha-helices can be explored using global searching molecular dynamics simulations (GSMDS), a method that produces a group of probable low energy structures. We have shown previously that the correct model in various homooligomers is always located at the bottom of one of various possible energy basins. Unfortunately, the correct model is not necessarily the one with the lowest energy according to the computational protocol, which has resulted in overlooking of this parameter in favor of experimental data. In an attempt to use energetic considerations in the aforementioned analysis, we used global searching molecular dynamics simulations on three homooligomers of different sizes, the structures of which are known. As expected, our results show that even when the conformational space searched includes the correct structure, taking together simulations using both left and right handedness, the correct model does not necessarily have the lowest energy. However, for the models derived from the simulation that uses the correct handedness, the lowest energy model is always at, or very close to, the correct orientation. We hypothesize that this should also be true when simulations are performed using homologous sequences, and consequently lowest energy models with the right handedness should produce a cluster around a certain orientation. In contrast, using the wrong handedness the lowest energy structures for each sequence should appear at many different orientations. The rationale behind this is that, although more than one energy basin may exist, basins that do not contain the correct model will shift or disappear because they will be destabilized by at least one conservative (i.e. silent) mutation, whereas the basin containing the correct model will remain. This not only allows one to point to the possible handedness of the bundle, but can be used to overcome ambiguities arising from the use of homologous sequences in the analysis of global searching molecular dynamics simulations. In addition, because clustering of lowest energy models arising from homologous sequences only happens when the estimation of the helix tilt is correct, it may provide a validation for the helix tilt estimate.

Amino Acid Sequence↗

PubMed2001

Lateral preferences among indian school children.

In the first study, 718 children from India, aged 4 to 11 years, were observed for their hand preference for ten common unimanual activities. The prevalence of left-handedness was found to be only 3.2 percent, i.e. one-third of that (9.6%) observed in a French study using a similar procedure. The degree (weak to strong) but not the direction of hand preference was found to be related to the children's age, with stronger preference among older children. The factor structure of handedness items was similar in France and India. In the second study, 400 schoolchildren from India, aged 6 to 18 years, were examined for handedness, footedness, eyedness, use of hand in space, and absolute and relative hand skill assessed by a peg-moving task and a dot-filling task. Prevalence of left-handedness was 4.2%. A sex difference was observed for handedness, footedness, use of hand in space. and relative hand skill, with higher proportions of right preferences and higher degree of lateralization (i.e., relative between hands asymmetry) in females. The degree of hand skill asymmetry increased with age. These results are discussed in relation to findings from previous studies in other countries using similar procedures.

Adolescent↗

PubMed1975

Patterns of hand preference in a student population.

The handedness of 1599 college students was assessed using a modification of Annett's (1967) inventory. The addition of a strength of preference scale makes the "mixed" classification a better indicator of ambidexterity than in the original inventory by eliminating from it subjects who show preference for the same hand for nearly all tasks. Contrary to previous reports, sex was not significantly related to handedness. It was found that a family history of left-handedness was significantly related to the handedness of the subject. The present form of the Annett inventory provides an easily scorable inventory for determining handedness of large groups as well as for use in individual testing situations. A further advantage of the present inventory is the ease with which data may be transferred by key-punch operators prior to special analysis or sorting procedures.

Adolescent↗

PubMed1998

Right-handers and left-handers have different representations of their own hand.

The visual control of our own hand when dealing with an object and the observation of interactions between other people's hand and objects can be involved in the construction of internal representations of our own hand, as well as in hand recognition processes. Therefore, a different effect on handedness recognition is expected when subjects are presented with hands holding objects with either a congruent or an incongruent type of grip. Such an experiment was carried out on right-handed and left-handed subjects. We expected that the different degree of lateralisation in motor activities observed in the two populations [J. Herron, Neuropsychology of left-handedness, Academic Press, New York, 1980.] could account for the construction of different internal hand representations. As previously found [L.M. Parsons, Imaged spatial transformations of one's hands and feet, Cogn. Psychol., 19 (1987) 178-241.], in order to identify handedness, subjects mentally rotated their own hand until it matched with the presented one. This process was confirmatory, being preceded by an implicit visual analysis of the target hand. Presentation of hands holding objects with congruent or incongruent types of grip influenced handedness recognition at different stages in right-handed and left-handed subjects. That is, the mental rotation stage was affected in right-handed subjects, whereas the initial phase of implicit hand analysis was affected in left-handed subjects. We suggest that in handedness recognition, left-handers relied more on a pictorial hand representation, whereas right-handers relied more on a pragmatic hand representation, probably derived from experience in the control of their own movements. The use of different hand representations may be due to differential activation of temporal and premotor areas.

Adult↗

PubMed2004

Chimpanzees (Pan troglodytes) are predominantly right-handed: replication in three populations of apes.

Population-level right-handedness has historically been considered a hallmark of human evolution. Even though recent studies in chimpanzees (Pan troglodytes) have demonstrated population-level right-handedness for certain behaviors, some have questioned the validity and consistency of these findings by arguing that reported laterality effects are specific to certain colonies of apes and to those chimpanzees reared by humans. The authors report evidence of population-level right-handedness in 3 separate colonies of chimpanzees. Moreover, handedness in the 3 colonies was unrelated to the proportion of subjects that were raised by humans. This is the strongest evidence to date that population-level handedness is evident in chimpanzees and is not an artifact of human rearing.

Animals↗

PubMedDate not supplied

Chiral selection in poly(C)-directed synthesis of oligo(G).

Theories of the origin of optical asymmetry in living systems place fundamental importance on the amplification of optical asymmetry by an autocatalytic process. The replication of a polynucleotide is one obvious choice for such an autocatalytic growth mechanism. If an optically homogeneous polynucleotide could replicate by directing the polymerization of monomers of the same handedness, while excluding monomers of the opposite handedness, its chiral descendants would come to dominate what was once an achiral environment. Recently, two highly efficient template-directed reaction systems have been developed for the oligomerization of activated guanosine mononucleotides (Fig. 1) on a poly(C) template. The synthesis of L-guanosine 5'-mononucleotide makes it possible to study chiral selection in these systems. We report here that poly(C)-directed oligomerization of activated guanosine mononucleotides proceeds readily if the monomers are of the same optical handedness as the template, and is indeed far less efficient if the monomers are of the opposite handedness. However, in template-directed reactions with a racemic mixture, monomers of the opposite handedness to the template are incorporated as chain terminators at the 2'(3') end of the products. This inhibition raises an important problem for many theories of the origin of life.

Chromatography, High Pressure Liquid↗

PubMed2004

Biobehavioural correlates of hand preference in free-ranging female primates.

In this research we examined biological and behavioural correlates of handedness in a subject cohort of 41 free-ranging young female rhesus macaques (Macaca mulatta). Specifically, we examined relationships between handedness and cerebrospinal fluid (CSF) concentrations of the monoamine metabolites 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA), plasma concentrations of the hormones cortisol and adrenocorticotropin (ACTH), prolactin, and multiple indices of social behaviour, including proximity to other animals, grooming, submission, and aggression. Handedness was determined through systematic observation of animals reaching for food in their unrestricted home environment. We found a population-level bias for left-hand use in this cohort of young females. The frequency of right versus left hand use was positively correlated with CSF 5-HIAA, plasma cortisol concentrations, the frequency of submissive behaviour, and with the frequency of bouts in which animals received low-level aggression. The positive correlation between right versus left hand use, submissive behaviour, and received aggression found here in females contrasts with the negative correlation among these same variables that we have previously reported in rhesus males. We conclude that these results may be explicable in terms of sex-based differences in rhesus life-history patterns, and that the influence of the serotonergic system on patterns of male aggression, social behaviour, and handedness, and the associations between handedness and social behaviour found previously among males may not be generalised to female rhesus macaques.

Adrenocorticotropic Hormone↗