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PubMed1999

A lack of cerebral lateralization in schizophrenia is within the normal variation in brain maturation but indicates late, slow maturation.

The planum temporale (PT) bias, PT leftward, PT symmetry, and PT rightward reversal and sidedness preference, consistent right-handedness, ambilaterality, and consistent left-handedness are placed on a continuum mirroring the normal variation in rate of brain maturation. Maturational rate declines as we pass from PT leftward bias and consistent right-handedness to PT reversal and consistent left-handedness. Concomitantly, we expect an increased prevalence of males due to their pubertal age being about 2 years later than that of females, and a shift in cognitive profile from higher verbal scores than performance scores on the WAIS to higher performance than verbal scores. Three disorders fulfilling the criteria of late CNS maturation apart from the corresponding cognitive profile were studied: infantile autism (IA), schizophrenia (S), and developmental dyslexia (DD). These disorders have in common deficits in cognition, perception, and somatomotor function. The deficits range from an arrest in brain development (which is evident in infancy superimposed on late maturation in IA) to overall delayed brain and somatic development in S (culminating in postpubertal psychotic episodes and persistent and generalized residual deficits). Finally, reading inability, problems in perception (vision and hearing) and in motor coordination, particularly between the two hemispheres, characterize DD. Enhancing brain maturation and the prevalence of 'normal' cerebral asymmetry--laterality is preferable if we want to reduce the risk of developing the above-mentioned disorders. It is suggested that in the past environmental challenges have favored early maturation, with its abundant neuronal population, arborization and excessive density of synapses and cerebral excitability which has powered evolution through the mechanism of natural selection. Early maturation is obtainable through optimal nutrition, including a satisfactory amount of marine fat (PUFA), before and during pregnancy and later in life.

Autistic Disorder↗
PubMed2005

Crystal structure of a partly self-complementary peptide nucleic acid (PNA) oligomer showing a duplex-triplex network.

The X-ray structure of a partly self-complementary peptide nucleic acid (PNA) decamer (H-GTAGATCACT-l-Lys-NH(2)) to 2.60 A resolution is reported. The structure is mainly controlled by the canonical Watson-Crick base pairs formed by the self-complementary stretch of four bases in the middle of the decamer (G(4)A(5)T(6)C(7)). One right- and one left-handed Watson-Crick duplex are formed. The two PNA units C(9)T(10) change helical handedness, so that each PNA strand contains both a right- and a left-handed section. The changed handedness in C(9)T(10) allows formation of Hoogsteen hydrogen bonding between C(9)T(10) and G(4)A(5) of a PNA strand in an adjacent Watson-Crick double helix of the same handedness. Thereby, a PNA-PNA-PNA triplex is formed. The PNA unit A(3) forms a noncanonical base pair with A(8) in a symmetry-related strand of opposite handedness; the base pair is of the A-A reverse Hoogsteen type. The structural diversity of this PNA demonstrates how the PNA backbone is able to adapt to structures governed by the stacking and hydrogen-bonding interactions between the nucleobases. The crystal structure further shows how PNA oligomers containing limited sequence complementarity may form complex hydrogen-bonding networks.

Base Pairing↗
PubMed2005

A meta-analysis of primate hand preferences, particularly for reaching.

P. F. MacNeilage, M. G. Studdert-Kennedy, and B. Lindblom (1987) proposed a progression for handedness in primates that was supposed to account for the evolution of a right bias in human handedness. To test this proposal, the authors performed meta-analyses on 62 studies that provided individual data (representing 31 species: 9 prosimians, 6 New World monkeys, 10 Old World monkeys, 2 lesser apes, and 4 greater apes), of the 118 studies of primate handedness published since 1987. Although evidence of a population-level left-handed bias for prosimians and Old World monkeys supports P. F. MacNeilage et al., the data from apes, New World monkeys, and individual species of prosimians and New World monkeys do not. Something other than primate handedness may have been the evolutionary precursor of the right bias in hand-use distribution among hominids.

Animals↗
PubMed2006

Hemispheric interactions are different in left-handed individuals.

In a previous study, N. Cherbuin and C. Brinkman (2006) showed that in right-handed participants, interhemispheric transfer time (measured with A. T. Poffenberger's, 1912, paradigm) was a significant predictor of the efficiency of hemispheric interactions (measured with a split visual field, letter-matching task). No effect was found for degree of handedness in this study. This was surprising because handedness has been shown to be associated with differences in the morphology and the structure of the corpus callosum, and cerebral anatomical lateralization, as well as functional lateralization both in behavioral and scanning studies. Because these findings were found in a large sample, but one limited to right-handed participants, the aim of the present study was to determine whether a similar relationship was present between interhemispheric transfer time and hemispheric interaction in left-handed participants (using identical measures) and to assess whether the analysis of a larger sample that comprised both left- and right-handed participants might reveal an effect of handedness. Results demonstrate significant handedness effects, suggesting that left-handed individuals tend to have more efficient hemispheric interactions.

Adolescent↗
PubMed1987

[Origin of mirror writing in children].

In left-handedness it is not the right hemisphere which usually dominates, as previously assumed but rather the left, as recent studies show. The development of right- and left-handedness is considered here in the light of the findings of Eccles, who substantiated the hypothesis of a relationship between the brain and a consciousness which is to be seen as basically independent of this organ. Right- and left-handedness are engendered by the interplay between consciousness and certain liasion areas in the brain. When the subject's will dictates a movement, consciousness exercises a strong influence on the impulse pattern of the modules. In genetically conditioned left-handedness it is not primarily motoric, but rather neuronal factors which are responsible for the reversal in the direction of writing and mirror-image script. Left-handed children who produce mirror-handwriting can be retrained to write normally by exercises and by assimilating conscious experience.

Aged↗
PubMed1993

Assessment of hand preference in two language-trained chimpanzees (Pan troglodytes): a multimethod analysis.

The nonhuman primate literature concludes that monkeys and apes do not exhibit handedness preferences at the population level. This discrepancy between human and nonhuman primate findings may be due to differences in the methods of assessment of handedness, lack of reliability between various measures of handedness, and a paucity of studies involving great apes. This paper presents the results of extensive hand preference studies with two language-trained chimpanzees (Pan troglodytes). Both naturalistic and experimental paradigms are described. In particular, various methodologic factors involved in handedness assessment, including the use of a hand preference measure previously used with human subjects were examined. Both chimpanzees exhibited a right-hand preference for fine motor tasks requiring manual dexterity.

Animals↗
PubMed2002

Hand preference and hand skill in families with schizophrenia.

Direction and degree of handedness in humans are variable between individuals and thought to be in part inherited. Several studies have shown an increase in non-right handedness among patients with schizophrenia, and some have included unaffected relatives. The present study was designed to determine whether reduced right handedness is more frequent among individuals with schizophrenia as compared with their well relatives and whether it clusters within families having multiple ill members. A total of 259 families comprising 418 individuals diagnosed with schizophrenia or schizoaffective disorder, 54 individuals with other psychoses, 145 family members with depression and other minor diagnoses, and 288 unaffected individuals were included. Hand preference was assessed by the Annett Scale and right relative to left hand skill measured using the Tapley-Bryden test. For all assessments of hand preference and hand skill, females were significantly more lateralised towards the right than males. Those individuals with schizophrenia or schizoaffective disorder had significantly less right hand preference than their unaffected relatives when measured as a quantitative index of items from the Annett Scale (p = .019), but not categorically (right, left or mixed). In contrast, there was no difference in hand skill between diagnostic groups. Hand preference was significantly correlated among male-male affected sibling pairs (p = .01) and similar results were found for hand skill among the total group of affected pairs (p = .001). Although these results only partially support a relationship between handedness and schizophrenia, they nevertheless draw attention to sex differences in hand preference and the familial aspects of hand preference in this disorder. More direct approaches to the genetics of cerebral dominance and psychosis are required.

Journal Article↗
PubMed2001

Can I twist your arm? The influence of target orientation on the magnitude of the right-hand advantage.

Controversy exists concerning whether handedness is a unidimensional trait or a multidimensional trait. However, researchers espousing the view that handedness is multidimensional are in disagreement regarding what the dimensions are that underlie handedness. Healey, Liederman, and Geschwind (1986) have provided some evidence that the type of musculature utilised (i.e., proximal versus distal) may be an underlying factor in determining handedness. The present research attempted to test this notion by examining the effects of target orientation on the relative performance of the two hands, using a peg-moving task. Target orientation was examined by utilising key-shaped pegs that fit securely into key-shaped holes. The results showed that the presence of target orientation increased the preferred-hand advantage. It is considered that this increased advantage for the right hand may be due to the hemispheric control of proximal versus distal musculature suggested by Geschwind and Galaburda (1985).

Journal Article↗
PubMed2001

Genetic influence on the expression of hand preferences in chimpanzees (Pan troglodytes): evidence in support of the right-shift theory and developmental instability.

Genetic mechanisms have been proposed to explain the pervasive representation of right-handedness in humans, whereas random, nongenetic factors have been posited to explain the lack of population-level right-handedness in nonhuman primates. We report evidence that hand preferences in chimpanzees are heritable, even among related individuals raised in different environments. Furthermore, we report that the degree of heritability is modified by factors associated with developmental instability, notably, offspring parity. The data are interpreted to reconcile both genetic models for handedness and hypotheses suggesting that developmental instability influences variation in handedness.

Animals↗
PubMed1979

Normal development and ear effect for contralateral acoustic reflex in children six to twelve years old.

This study investigated the acoustic reflex, which uses the ventro-medial brain-stem system, to determine laterality superiority with respect to age, sex, dominance for handedness, and their various interactions, 54 normal children and 21 normal adults were evaluated. No major effects for age, sex or handedness for the reflex were found, but the right ear appeared slightly more sensitive to broad-band white noise stimuli than the left, regardless of handedness. An age-handedness effect was also present which suggested that left-handed children mature differently from right-handed children in the acoustic reflex. Data on adults were inconclusive as to whether this maturity effect carried over into adulthood. The findings suggest that there was a laterality effect for the acoustic reflex using the ventro-medial brain-stem, which was thus brain-stem related rather than cortex-level related.

Age Factors↗
PubMed1990

Hand dominance of parents and other relatives of autistic children.

Hand preferences of 219 mothers and 186 fathers of autistic children were assessed using the Annett Handedness questionnaire. Subgroups of 54 mothers and 57 fathers with a family history of language-related developmental disorders were identified. Parents also reported the handedness of other relatives. Mothers (but not fathers) in the main group were significantly more likely to be consistently right-handed than females in the general population, but this was not specifically associated with a family history of language problems. There was no evidence of an increased incidence of consistent left-handedness in either the whole group of parents or the subgroups. Reported handedness of other relatives showed no abnormal distribution in relation to a comparison group. The findings are discussed in relation to theories about genetic factors in language-related developmental disorders in general, and autism in particular.

Adult↗
PubMed2005

Antenatal exposure to betamethasone: psychological functioning and health related quality of life 31 years after inclusion in randomised controlled trial.

OBJECTIVES: To determine if antenatal exposure to betamethasone for the prevention of neonatal respiratory distress syndrome alters psychological functioning and health related quality of life in adulthood. DESIGN: Follow-up of the first and largest double blind, placebo controlled, randomised trial of a single course of antenatal betamethasone for the prevention of neonatal respiratory distress syndrome. SETTING: Tertiary obstetric hospital in Auckland, New Zealand. PARTICIPANTS: 192 adult offspring, mean age 31 years, of mothers who took part in a randomised controlled trial of antenatal betamethasone for the prevention of neonatal respiratory distress syndrome (87 exposed to betamethasone and 105 exposed to placebo). INTERVENTIONS: Mothers received two doses of betamethasone or placebo 24 hours apart. MAIN OUTCOME MEASURES: Cognitive functioning assessed with Wechsler abbreviated scale of intelligence; working memory and attention assessed with Benton visual retention test, paced auditory serial addition test, and Brown attention deficit disorder scale; psychiatric morbidity assessed with Beck depression inventory II, state-trait anxiety inventory, and schizotypy traits questionnaire; handedness assessed with Edinburgh handedness inventory; health related quality of life assessed with short form 36 health survey. RESULTS: No differences were found between groups exposed to betamethasone and placebo in cognitive functioning, working memory and attention, psychiatric morbidity, handedness, or health related quality of life. CONCLUSIONS: Prenatal exposure to a single course of betamethasone does not alter cognitive functioning, working memory and attention, psychiatric morbidity, handedness, or health related quality of life in adulthood. Obstetricians should continue to use a single course of antenatal betamethasone for the prevention of neonatal respiratory distress syndrome.

Adult↗
PubMed2001

Lateralities in normal children ages 3 to 8 and their role in cognitive performances.

The presence and type of correlations between laterality and cognitive skills in normal adults or children remains controversial. This study examines relations between different lateralities, that is, handedness, footedness, eyedness, parental left-handedness, asymmetry of hand skill on a computerized version of the Peg-Moving Task (CPMT) proposed by Annett (1985), and different verbal and non-verbal skills assessed by 13 tasks in 254 normal children, aged 3 to 8 years. Results showed increasing performances with increasing dextrality on the CPMT for 2 tasks involving phonology (Phonological Fluency and Reading Nonwords), 2 tasks involving visual memory and visuospatial skills, and for finger localization. Footedness, eyedness, and parental left-handedness had no significant effect on cognitive performance. The pattern of performance according to the sinistrality-dextrality continuum was highly variable from one cognitive task to the other. The previously mentioned results suggest that relative hand skill is a better correlative of cognitiveperformance than the usual measures of handedness. Further study is needed to specify the pattern of associations.

Age Factors↗
PubMed2002

Functional and postural lateral preferences in humans: interrelations and life-span age differences.

This study aimed to provide data on lateral preferences among older subjects, to analyze age differences, and to determine interrelations between lateral preferences. Four functional preferences (handedness, footedness, eyedness, earedness) and three postural lateral preferences (hand-clasping, arm-folding, leg-crossing) were assessed in 628 Germans (252 men, 376 women) aged between 19 and 90 years. Sex differences, age differences, and associations between lateralities were analyzed applying chi-square tests. Logistic regression analyses considering age, sex, and interactions between variables were applied to analyze combined effects on laterality measures. Right-sided preference for handedness, footedness, eyedness, earedness, and leg-crossing characterized 86.8%, 77.1%, 70.9%, 67.8%, and 56.6%, respectively, of subjects, while a left-sided preference for hand-clasping and arm-folding characterized 56.4% and 60.2%, respectively, of all participants. Results are within the range of other populations. Only footedness differed between the sexes: there were more left-footed men. Older cohorts showed a rightward shift in handedness, eyedness, earedness, and leg-crossing, the opposite for arm-folding. No age-related differences exist in footedness or hand-clasping. Logistic regression models indicate no interaction between age and sex for each laterality measure. The four functional lateralities are significantly interrelated. All also are positively associated with leg-crossing. Conversely, the postural lateralities generally are not correlated, although leg-crossing and arm-folding are, inversely. The observed relationships among lateralities support the hypothesis that handedness, footedness, leg-crossing, and earedness might be aspects of a larger phenotype that is independent of hand-clasping and arm-folding.

Adult↗
PubMed1998

Correlations between hand preference and durations of hearing for right and left ears in young healthy subjects.

In this study, to test an inference from the 1991 Previc hypothesis that right-handers have a right-ear advantage, the durations of hearing for the right and left ears were compared for 81 right- and 45 left-handed high school students. In the present study, right-handedness was associated with a right-ear advantage and left-handedness was associated with a left-ear advantage. In addition, there was a significant positive correlation between the durations of hearing for the right and left ears and the scores for right-handedness for right-handed subjects. The durations of hearing for the right and left ears were negatively correlated with the left-handedness for left-handed subjects. These results suggest hand preference may be related to asymmetry of aural sensitivity.

Acoustic Stimulation↗
PubMed1991

The relationships between nonverbal intelligence and the strength of left-hand preference in left-handers to sex and familial sinistrality.

The relationship between the strength of left-handedness and spatial reasoning ability was studied in left-handed male and female subjects with and without familial sinistrality (FS). The degree of left-handedness was assessed by the Edinburgh Handedness Inventory. The spatial reasoning ability was measured by Cattell's Culture Fair Intelligence Test. It was found that there was a negative linear correlation between nonverbal IQ and the strength of left-handedness in females with and without FS, a quadratic relationship in male left-handers without FS and a positive linear correlation in male left-handers with FS. These results indicate that the brain may exhibit different patterns of cerebral organization in left-handers to sex and FS. It was concluded that the "crowding" hypothesis may apply only to a subgroup of left-handers, i.e., females with a greater bilaterality of cognitive functions than males.

Adolescent↗
PubMed2002

Right- and left-handed dentists in periodontal therapy.

The purpose of this study was to determine whether successful dental therapy (scaling and root planing) depends upon handedness of dentists in right-handed dental chairs (units) Participants were 28 voluntary dentists (14 female and 14 male, ranging in age from 26 to 34 years). Patients (7 female and 7 male with a mean age of 39.6 years) had advanced periodontitis. Handedness was assessed using the Turkish version of the Edinburgh Handedness Inventory. There were two equal groups of dentists: left-handers (7 female, 7 male) and right-handers (7 female, 7 male). Initial examination of patients was performed using a pressure-controlled periodontal probe. During scaling and root planing, the negative interstroke forces were recorded using a piezo-electric receiver, an electronic transducer, and an analogue writer. The results showed that during scaling, mean negative forces reached a mean of 0.74 N in left-handed dentists and 0.52 N in right-handed dentists. During root planing, these forces were 0.86 N in left-handed dentists, and 0.63 N in right-handed dentists. These differences were statistically significant. The right-handed dentists were more successful than the left-handed dentists at scaling and root planing, provided that both of them used the same right-sided dental chairs. The importance of handedness of the dentists was accentuated in dental practice.

Adult↗
PubMed2003

MR imaging volumetry of subcortical structures and cerebellar hemispheres in normal persons.

BACKGROUND AND PURPOSE: Volume changes in subcortical structures and cerebella have been associated with localization-related epilepsy and psychiatric illnesses. This study evaluated the effect of handedness and sex on the volumes of selected subcortical structures and cerebellar hemispheres in normal persons. METHODS: Volumetric measurements were performed of the caudate heads, thalami, and cerebellar hemispheres in 34 (20 right- and 14 left-handed, 19 female and 15 male) normal persons. Amygdalar and hippocampal volumes were reported previously for these persons. All study participants completed a 10-item handedness questionnaire. The MR imaging sequence was a 3D T1-weighted gradient-echo acquisition of the whole brain (24/6 [TR/TE]; flip angle, 25 degrees). MR images were spatially normalized, and volumes were painted with a 1.0 mm(3) resolution cursor on an SGI workstation. The effects of handedness and sex on standardized volumes and right-to-left volume ratios were calculated, and volumes were compared between right and left sides for each structure. RESULTS: Handedness did not affect standardized volumes or asymmetries of the caudate heads, thalami, or cerebellar hemispheres. The volumes of subcortical structures were bilaterally larger in women than in men. Right-to-left asymmetries were significant for the caudate head and cerebellum but not for the thalamus. CONCLUSION: These findings show that women have significantly larger subcortical structures than do men after spatial normalization to account for differences in brain size. Sex-specific normal ranges may be needed for evaluating volume changes related to epilepsy or other disease processes.

Adult↗