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PubMed1981

Hemispheric asymmetries and early infantile autism.

The observation that language disorders constitute a major symptom of early infantile autism has led some researchers to speculate that the autistic syndrome may be a result of brain damage to the left hemisphere. Such speculation has fostered a number of studies in which attempts have been made to link autism with ostensibly positive signs of left hemisphere damage, such as left-handedness and preferences for "right hemisphere" functional and cognitive activities. In the present review, contributions to this area are systematically reviewed. Studies attempting to demonstrate that an unusually high incidence of left-handedness occurs in autistic samples are examined. Functional and morphological studies examining patterns of asymmetry in autistic samples are reviewed. It is shown that most studies on handedness fail to account adequately for the role that age of subjects may play in the manifestation of left-handedness. A simple cause-and-effect model of abnormal cerebral asymmetry and autism is rejected in favor of a more integrative yet parsimonious model that specifically attempts to explain the language disorder common to autism.

Adolescent↗
PubMed1995

Parental hand preference and manual functional asymmetry in preschool children.

Hand preference and hand skill in 1150 normal children between 3 and 6 years of age and hand preference of their parents were assessed to study the effect of parental hand preference on different dimensions of manual asymmetry in children. Children hand skill was measured with a computerized version of the Peg Moving Task which allowed us to split the overall performance into two components, a "transport time" and a "search time." Paternal and maternal left-handedness was significantly related to child left-handedness. Both components of hand skill asymmetry were reduced with mother's left-handedness. and one component (search time) with father's left-handedness. A significant impact of paternal and preference on child hand skill asymmetry, after controlling for child hand preference, was observed. When this analysis was limited to strong right-handed children, a greater paternal effect on child hand skill emerged. These results show the usefulness of performance tasks in detecting parent-child associations concerning manual functional asymmetry.

Child Development↗
PubMed2006

Laterally focused attention modulates asymmetric coupling in rhythmic interlimb coordination.

Peters (J Motor Behav 21:151-155, 1989; Interlimb coordination: neural, dynamical and cognitive constraints, Academic, Orlando, pp 595-615, 1994) suggested that expressions of handedness in bimanual coordination may be reflections of an inherent attentional bias. Indeed, previous results indicated that focusing attention on one of the limbs affected the relative phasing between the limbs in a manner comparable to the effects of hand dominance. The present study extended the comparison between the effects of attentional focus and handedness by testing their impact on the interactions between the limbs. Both left-handed and right-handed participants performed rhythmic bimanual coordination tasks (in-phase and antiphase coordination), while directing attention to either limb. Using brief mechanical perturbations, the degree to which the limbs were influenced by each other was determined. The results revealed that the non-dominant limb was more strongly affected by the dominant limb than vice versa and that, in line with Peters' proposition, this handedness-related asymmetry in coupling strength was reduced when attention was focused on the non-dominant limb, thereby highlighting the potential relation between inherent (handedness-related) asymmetries and voluntary attentional asymmetries. In contrast to previous findings, the (commonly observed) phase lead of the dominant limb was attenuated (rather than accrued) when attention was focused on this limb. This unexpected result was explained in terms of the observed attention-related difference in amplitude between the limbs.

Adult↗
PubMed1987

Asymmetries of brain dopamine metabolism related to conditioned paw usage in the rat.

Concentrations of dopamine, serotonin, and some of their metabolites were analyzed by means of high-performance liquid chromatography in brain samples obtained from rats operantly conditioned to use one paw for water-reinforced lever pressing. In the first experiment, the side of paw usage was determined by physical constraint (forced-handedness condition), whereas in the second experiment the side of paw usage was not restricted (paw-preference condition). Differences in dopamine metabolism were detected between brain samples from the hemispheres located ipsi- and contralaterally to the side of paw usage. A higher dopamine metabolism (indicated by higher metabolite/transmitter ratios) was found in the amygdala ipsilateral to the paw used both under the forced-handedness and paw-preference condition. A higher level of dopamine in the contralateral septum was found in rats sacrificed immediately after 15 min of forced-handedness and an ipsilateral increase was found in rats analyzed 2 h after performance of this task. In addition, a higher dopamine metabolism in the ventral striatum, dorsal striatum, and amygdala was found in the forced-handedness and yoked controls groups than in rats analyzed 2 h after lever pressing. In the second experiment, rats in the paw preference group had a lower dopamine metabolism in the ventral and dorsal striatum, septum, and substantia nigra than did their yoked controls. These results show that changes in dopamine metabolism during conditioned lever pressing can be asymmetrical with respect to the side of paw usage, indicating that the dopamine neurons in the two brain hemispheres are asymmetrically involved in such behavioral tasks.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1992

Hand preference, immune system disorder and cognitive function among gay/bisexual men: the Multicenter AIDS Cohort Study (MACS).

This study evaluated the self-reported patterns of handedness among a large subsample (n = 1612) of the gay/bisexual men comprising the Multicenter AIDS Cohort Study (MACS). There was a small but significant elevation in left-handedness among gay/bisexual men compared to available normative data. However, there were no differences within the cohort in measures of immune function, self-reported autoimmune disorders, asthma, or hay fever, although there was an association between handedness and allergy. Performance on neuropsychological tests also did not differ as a function of handedness.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Natural killer cell activity is associated with brain asymmetry in male mice.

The brain is known to modulate the immune system in an asymmetrical way. In mice, there is an association between handedness and immune response and it has also been shown that hemicortical ablation has opposite effects on some immune parameters. An association between autoantibody production and paw preference was previously observed in female mice, but not in males, suggesting that the association between immune reactivity and functional brain asymmetry is a sex-dependent phenomenon. In three independent experiments, natural killer (NK) cell activity, lymphocyte subset distribution, and mitogen-induced lymphoproliferation were assessed in male C3H/OuJIco mice selected for handedness and after unilateral cortical ablation. Handedness was shown to be associated with NK cell activity but not with lymphocyte subset distribution or lymphoproliferation. Left-handers exhibited lower NK cell activity compared to right-handed or ambidextrous animals. In contrast to previous results in female mice, mitogen-induced lymphoproliferation was not associated with handedness in males. Left cortical ablations depressed NK cell activity, while right lesions had no effect. Neither left or right lesions affected lymphocyte subsets. No interaction between paw preference and side of the lesion was found in the modulation of NK cell activity. These and previous data show that the association between paw preference and immune reactivity varies according to the sex of the animal and the immunological parameters studied. This indicates that the brain may modulate different components of the immune system in different ways, through mechanisms apparently involving sex hormones.

Animals↗
PubMed2003

Left planum temporale: an anatomical marker of left hemispheric specialization for language comprehension.

We report on a study aimed at investigating the relationships between handedness, anatomical data and functional data related to speech processing. Twenty subjects with variable handedness (Edinburgh score ranging from -100 to 100) underwent both anatomical magnetic resonance imaging (MRI) and Positron Emission Tomography (PET) during story listening and rest. The surface areas of the left and right planum temporale (PT) were measured on each subject's MRI scan. A multiple regression analysis of PET data was conducted using these PT surface areas as well as handedness scores as predictors. The surface of the left PT explained a significant part of the functional variability. We observed that subjects who had the larger left PT were likely to show a larger leftward functional asymmetry of several perisylvian areas, namely the inferior parietal lobule outside the supra-marginal gyrus (the angular gyrus and the cortex above), Heschl's gyrus, the rolandic operculum, and the temporal pole. The size of the right PT explained only a little part of functional variability and we found no evidence that the anatomical asymmetry of the PT explained functional variability. In addition, we could not evidence any relationship between handedness and functional data. These results, which confirm previous work, argue for a perceptive origin of hemispheric specialization for language comprehension as has been suggested by others.

Adult↗
PubMed1991

Hand preference in homosexual men.

The present study examined the distribution of hand preference and its relationship to immune system functioning and performance on neuropsychological tests in a sample of 993 homosexual men from the Multicenter AIDS Cohort Study comprising 502 HIV-1 seronegatives, 436 asymptomatic HIV-1 seropositives, and 55 men with diagnoses of AIDS or AIDS Related Complex. The prevalence of left-handedness in all of the groups (13.1-14.5%) was consistent with prior published reports of prevalent left-handedness in the general population. The distribution of hand preference scores (on a 5-item self-report questionnaire) was J-shaped and shifted to the right as in the general population. There were no differences between right- and left-handers in the immune system parameter of CD4 counts, nor was there any increase of self-reported allergies among the left-handers. We found a significantly larger number of 'outliers' on the neuropsychological measures for left-handers than for right-handers, both for HIV-1 seronegatives and seropositives. These results failed to replicate Lindesay's (1987) report of a leftward shift in manual preference among homosexual men, and failed to support Geschwind and Galaburda's (1985b) hypothesis of a link between homosexuality, handedness and autoimmune disorder. The differences between right- and left-handers on neuropsychological measures, independent of HIV-1 serostatus, are discussed in terms of Satz's (1972) model of pathological left-handedness.

Adult↗
PubMed1993

The prevalence and origins of left hand preference in high risk infants, and its implications for intellectual, motor and behavioural performance at four and six years.

This study investigates the origins of hand preference at 4 years in a cohort of 115 high risk and premature infants; the relationship between patterns of hand preference and intellectual, motor, temperament and behavioural status at 4 and 6 years; and evidence for brain injury in mediating the relationship between hand preference and development disorder. Increased left hand preference was independently associated with extreme prematurity, high neonatal risk, increased numbers of minor physical anomalies, lowered intellectual and motor abilities, and more difficult temperament. These findings supported the presence of intrauterine and neonatal pathological mechanisms leading to left hand preference in a small number of children. Neither poor function of the non dominant hand nor absence of a family history of left handedness could further define this pathological subgroup. Support for pathological mechanisms producing left handedness was found predominatly in the infants of high birth weight, whereas prevalence of left handedness was increased mainly among the extremely low birth weight infants. In this latter group the prevalence of left handedness was also increased among children of normal intelligence, suggesting that mechanisms other than brain damage lead to left hand preference in very premature infants.

Birth Weight↗
PubMed1988

A study of hand preference in myasthenia gravis.

A recent study reported an association between left-handedness and some pathologies, such as autoimmune diseases, including myasthenia gravis (MG). We studied hand preference in 102 patients with a generalized autoimmune form of myasthenia gravis and in a control group of 178 subjects. We employed Oldfield's inventory with a few minor modifications. The questionnaire also asked the hand preference of patients' and controls' relatives. For each subject, the laterality quotient (LQ) was calculated and submitted to ANOVA. The frequency of left-handedness in controls was similar to that reported in the literature. Although left-handedness occurred less often in myasthenics, the difference between the two groups was not significant. Also the frequency of left-handedness in relatives of myasthenic patients did not differ from that observed in controls.

Functional Laterality↗
PubMed1989

Inverted handwriting posture in left handers is related to familial sinistrality incidence.

McKeever (1979) reported that left handers who wrote with an inverted handwriting posture (IHP) had a higher incidence of left handedness in their families than did left handers who wrote with a non-inverted handwriting posture (NHP). Parlow and Kinsbourne (1981), however, failed to find a relationship between handwriting posture (HWP) and positive familial sinistrality (FS+). McKeever had classified his left handed subjects according to whether they had several, one, or no left handers among their first degree relatives and biologically-related second degree relatives. Parlow and Kinsbourne classified subjects as FS- or FS+ on the basis of first degree relatives and did not inquire about the handedness of second degree relatives. In the present study, handedness for writing of all first and second degree relatives was recorded for 216 NIP and 255 IHP left handers. Results showed a significant association of HWP and FS factors when second degree relatives were considered, but not when second degree relative handedness was ignored. The relationship was strongest within the maternal family line, where the proportion of left handers was more than twice as high for the IHP as for the NHP group. These findings suggest that HWP may well be of some importance for a complete understanding of the cerebral organization of left handers.

Adult↗
PubMed2002

Cerebellar morphology in developmental dyslexia.

Recent evidence has suggested cerebellar anomalies in developmental dyslexia. Therefore, we investigated cerebellar morphology in subjects with documented reading disabilities. We obtained T1-weighted magnetic resonance images in the coronal and sagittal planes from 11 males with prior histories of developmental dyslexia, and nine similarly-aged male controls. Proton magnetic resonance spectra (TE=136ms, TR=2.4s) were obtained bilaterally in the cerebellum. Phonological decoding skill was measured using non-word reading. Handedness was assessed using both the Annett questionnaire of hand preference and Annett's peg moving task. Cerebellar symmetry was observed in the dyslexics but there was significant asymmetry (right grey matter>left grey matter) in controls. The interpretation of these results depended whether a motor- or questionnaire-based method was used to determine handedness. The degree of cerebellar symmetry was correlated with the severity of dyslexics' phonological decoding deficit. Those with more symmetric cerebella made more errors on a nonsense word reading measure of phonological decoding ability. Left cerebellar metabolite ratios were shown to correlate significantly with the degree of cerebellar asymmetry (P<0.05) in controls. This relationship was absent in developmental dyslexics. Cerebellar morphology reflects the higher degree of symmetry found previously in the temporal and parietal cortex of dyslexics. The relationship of cerebellar asymmetry to phonological decoding ability and handedness, together with our previous finding of altered metabolite ratios in the cerebellum of dyslexics, lead us to suggest that there are alterations in the neurological organisation of the cerebellum which relate to phonological decoding skills, in addition to motor skills and handedness.

Adult↗
PubMed2003

Cerebral asymmetry in twins: predictions of the right shift theory.

A study of the heritability of lobar brain volumes in twins has introduced a new approach to questions about the genetics of cerebral asymmetry. In addition to the classic comparison between monozygotic (MZ) and dizygotic (DZ) twins, a contrast was made between pairs of two right-handers (RR pairs) and pairs including one or more non-right-hander (non-RR pairs), in the light of the right shift (RS) theory of handedness. This paper explains the predictions of the RS model for pair concordance for genotype, cerebral asymmetry and handedness in healthy MZ and DZ twins. It shows how predictions for cerebral asymmetry vary between RR and non-RR pairs over a range of incidences of left-handedness. Although MZ twins are always concordant for genotype and DZ twins may be discordant, differences for handedness and cerebral asymmetry are expected to be small, consistent with the scarcity of significant effects in the literature. Marked differences between RR and non-RR pairs are predicted at all levels of incidence, the differences slightly larger in MZ than DZ pairs.

Brain↗
PubMed2000

Differential contributions of the two hemispheres in intra-modal proprioceptive sensory matching in 7-10-year-old boys.

This study explores putative differential contributions of the two hemispheres when 7-10-year-old right-hand and left-hand preferent boys are required to carry out a 'foot-hand' target location and matching task. The task required subjects to locate a target pin with the big-toe (felt target), and match the located target position with the hand, without vision. Right-handed (n=25) and left-handed (n=22) boys were tested in a four-condition design. Two intra-hemispheric conditions (right foot locating-right hand matching, left foot locating-left hand matching), and two inter-hemispheric conditions (right foot locating-left hand matching, left foot locating-right hand matching) were used. When the criterion for handedness was writing hand only the results were found to be confounded by the large number of subjects with indeterminate handedness (isolated by use of the Edinburgh Handedness Inventory) originally assigned to the left-handed group. Reclassification of the handedness groups, on the basis of this inventory, showed the pure-left handers to be as good on those conditions mediated by the right hemisphere as pure right handers were with those conditions mediated by the left. These findings are discussed with respect to the contention that left handers are not just 'reversed' right handers.

Child↗
PubMed1998

Cerebral lateralisation and rate of maturation.

Multifactorial inheritance applied to brain development implies a large continuum of normal variation with deviation from the norm at the extremes of maturational rate. The greater population of neurons, greater arborization of neural networks and excessive synaptic density in early maturation imply that adaptability (plasticity) is a main advantage, as opposed to a deficit in adaptability associated with the reduced number of neurons, reduced connectivity and reduced synaptic density in late slow maturation. It is hypothesised that Planum Temporale (PT) asymmetry and hand-preference predict the rate of CNS maturation as does the cognitive profile on the Wechsler Adult Intelligence Scale (WAIS): PT leftward asymmetry, right-handedness and a left-hemisphere cognitive advantage signifies early fast maturation: PT rightward asymmetry, left-handedness and a right-hemisphere cognitive advantage signify late maturation, while PT symmetry and ambilaterality represent rates of maturation in between. The slower development of males implies a male predominance in disorders affecting late maturers: Developmental Dyslexia (DD) with a predominance of rightward PT asymmetry/symmetry, left-handedness and multiple functional deficits, as well as excessive regressive events confirmed on PT/MRI. Schizophrenia, hypothesised to be a disorder in late maturers, is distinguished by rightward asymmetry/symmetry. Left-handedness and DD are common as is prior delayed development supporting excessive regressive events as do the findings on PT/MRI. To reduce the risk of DD and schizophrenia requires a reduction in late maturation through the enhancement of maturational rate by optimal nutrition before and during pregnancy and later.

Adult↗
PubMed1996

Inheritance of randomness.

The mouse mutant iv is characterized by "a random determination of a developmental process' in that 50 rather than 100% of the homozygotes have situs inversus. The same explanation is given to the inheritance of situs inversus in the human immotile-cilia syndrome. There are probably two alleles of the responsible gene, one for control of the proper asymmetry and one without control and hence resulting in equal numbers of situs solitus and situs inversus in the homozygote. Left-handedness may be similarly inherited; furthermore, because of its high prevalence (around 10-12%) it has been assumed that there is an advantage of carrying both alleles ("balanced polymorphism'). With these two assumptions, a prevalence of left-handedness of 12.5% is expected, a 50% chance of left-handedness in matings between two left-handed persons, and equal numbers of discordant and left-handed concordant monozygotic twins. These values are close to those actually found. As the values for (female) homosexuality are similar to those of left-handedness a similar inheritance is proposed.

Adult↗
PubMed2002

Cerebral lateralization and cognitive deficits after congenital hemiparesis.

The purpose of this study was to investigate whether and how handedness is related to the processes of cerebral lateralization and cognitive performance in children with congenital insult. Fifty-six children (31 males and 25 females) with congenital hemiparesis and 14 control subjects were investigated. Of these children, 32 had a left hemisphere lesion, and 24 children had a right hemisphere lesion. There were 30 right-handed, 23 left-handed, and three ambidextrous children in the study group. The neuropsychologic assessment was performed using the NEPSY (a developmental neuropsychological assessment of child development) test battery. We found that 41% of the hemiparetic children and 72% of the children with a left hemisphere lesion were left-handed. In children contralateral to lesion handedness (no evidence of interhemispheric transfer of functions), we found diffuse cognitive deficits with impaired language abilities and poor visuomotor and narrative memory processing. In contrast, children with ipsilateral to brain lesion handedness (interhemispheric transfer of functions) demonstrated minimal or moderate side-specific cognitive dysfunction. Right-handed children with a right hemisphere lesion had attention, spatial, and short-term memory problems; left-handed children with a left hemisphere lesion had receptive language and visuomotor difficulties. Handedness combined with neuropsychologic assessment is a reliable indicator of the processes of cerebral reorganization after early brain insult.

Child↗
PubMed1999

The theory of an agnosic right shift gene in schizophrenia and autism.

The right shift (RS) theory (Annett, M., 1972. The distribution of manual asymmetry. Br. J. Psychol. 63, 343-358; Annett, M., 1985. Left, Right, Hand and Brain: The Right Shift Theory. Lawrence Erlbaum, London) suggests that the typical pattern of human cerebral and manual asymmetries depends on a single gene (RS+) which impairs speech-related cortex of the right hemisphere. The theory offers solutions to several puzzles, including the distribution of handedness in families (Annett, M., 1978. A Single Gene Explanation of Right and Left Handedness and Brainedness. Lanchester Polytechnic, Coventry; Annett, M., 1996. In defense of the right shift theory. Percept. Motor Skills 82, 115-137), relations between handedness and cerebral speech laterality (Annett, M., 1975. Hand preference and the laterality of cerebral speech. Cortex 11, 305-328; Annett, M., Alexander, M.P., 1996. Atypical cerebral dominance: predictions and tests of the right shift theory. Neuropsychologia 34, 1215-1227) and handedness and dyslexia (Annett, M. et al., 1996. Types of dyslexia and the shift to dextrality. J. Child Psychol. Psychiatry 37, 167-180). If Crow's (Crow, T.J. et al., 1989. Schizophrenia as an anomaly of development of cerebral asymmetry. A postmortem study and a proposal concerning the genetic basis of the disease. Arch. Gen. Psychiatry 46, 1145-1150; Crow, T.J., 1997. Is schizophrenia the price that Homo sapiens pays for language? Schizophr. Res. 28, 127-141) theory that schizophrenia is due to an anomaly of cerebral dominance is correct, and if the RS theory is correct, schizophrenia could be due to an anomaly of the RS+ gene. If the RS+ gene were at risk for a mutation which caused a loss of directional coding, the mutant could be described as 'agnosic' for left and right. Such a gene would impair either hemisphere at random. When paired with another RS+ gene, both hemispheres would be impaired in 50% of cases. The other 50% and people in whom the agnosic gene is paired with an RS-allele (neutral for asymmetry and not giving hemisphere impairment) would have one unaffected hemisphere and, thus, normal development. Quantitative predictions based on the RS genetic theory as previously developed, plus an agnosic mutant with frequency required to give schizophrenia in 1% of the population, are consistent with estimates of concordance for schizophrenia in relatives. Homozygotes of the agnosic mutant would occur at about the rate estimated for autism.

Autistic Disorder↗