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PubMed2003

Neurological soft signs in never-treated schizophrenia.

OBJECTIVE: Studies of Neurological Soft Signs (NSS) in schizophrenia are confounded by handedness, inconsistent methodology, and prior treatment with neuroleptics. The study objective is to examine NSS in never-treated schizophrenia. METHOD: We examined the NSS in treatment-naïve schizophrenia patients (n = 21) and age, sex, education, and handedness matched normal controls (n = 21) using the modified Neurological Evaluation Scale with good inter-rater reliability. RESULTS: Schizophrenia patients had significantly more NSS than normals. No significant correlation was found between illness duration and NSS. CONCLUSION: Higher neurological signs in never-treated patients and their lack of association with illness duration suggest neurodevelopmental etiopathogenesis of schizophrenia.

Adult↗
PubMed1997

Developmental instability and cerebral lateralization.

On the basis of prior studies of handedness, it was predicted that variations from modal asymmetry scores on cognitive tasks, in either direction from the mean, would be associated with an elevated incidence of classic markers of developmental instability (minor physical anomalies and fluctuating anatomic asymmetries). University students (N = 146) were administered 4 tasks that typically reveal functional asymmetries: the fused rhymed words dichotic listening task, the line bisection task, the chimeric faces task, and the cartoon faces task. A composite measure of developmental instability was computed from minor physical anomalies and fluctuating asymmetries. Participants with greater evidence of developmental instability had more atypical lateralization scores, deviating more from the sample mean, in either direction. Directional asymmetries were unrelated to developmental instability. These results suggest that developmental instability influences variation in the lateralization of cognitive skills as well as handedness.

Adolescent↗
PubMed1989

Dyslexia and brain morphology.

Although the neurological basis of dyslexia has long been assumed, little direct evidence documents a relation between deviations in brain morphology and behavioral correlates of dyslexia. This article reviews two sources of evidence. Results of CT/MRI studies suggest that in the brains of dyslexics there is an increased incidence of symmetry in the region of the planum temporale and parietooccipital cortex that may be associated with language delay and handedness. Postmortem/cytoarchitectonic studies document symmetry of the plana, provide evidence of thalamic involvement, and chart widely distributed focal dysplasias preferentially involving the left frontal, left temporal, and right frontal regions. Methodological deficiencies characterize this literature, however, particularly regarding the diagnosis of dyslexia, appraisal of handedness and neurolinguistic deficits, and a failure to provide evidence that this pattern of involvement is unique to the dyslexic syndrome. These findings are discussed as they relate to neurobiological theory.

Brain↗
PubMed1995

Effect of posture on hand preferences during experimental food reaching in bonobos (Pan paniscus).

The effect of posture on hand preferences was examined in an experiment with 5 bonobos (Pan paniscus). To obtain a food reward, the animals had to adopt 1 out of 7 different postures. These postures represented an increasing problem to the maintenance of body equilibrium. It was expected that an increasing demand for equilibrium maintenance would elicit individual preferences and a population-level bias. All animals showed an increasing trend toward left-handedness while shifting to a bipedal posture from a seated posture by way of a quadrupedal posture. The importance of bipedalism in the evolution of left- and right-handedness is discussed briefly.

Animals↗
PubMed1996

Postural asymmetries and language lateralization in humans (Homo sapiens).

Is hemispheric specialization for speech more closely related to left hemisphere specialization for manual skill and sequencing, as is usually supposed, or to control of asymmetries in whole body posture, as recent findings of right-handedness in nonhuman primates suggest? This question can be evaluated in the 10% of humans who have mixed handedness and footedness. Footedness entails postural asymmetry, and persons with mixed limb preferences often prefer the hand ipsilateral to the preferred foot in asymmetrical actions for which whole body postural adjustments are obligatory (e.g., throwing). The dichotic listening test , and indicator of language laterality, was administered to 4 groups of 48 persons with the 4 possible combinations of hand and foot preference. As in 2 past studies, language lateralization was somewhat more strongly related to postural asymmetries than to asymmetries in manual skill and sequencing.

Adolescent↗
PubMed2006

Increased interhemispheric interaction is associated with earlier offset of childhood amnesia.

Experiment 1 found that mixed-handedness, which is associated with increased interaction between the left and right cerebral hemispheres relative to strong right-handedness, was associated with an earlier offset of childhood amnesia. In Experiment 2, bilateral saccadic eye movements, which have been shown to enhance interhemispheric interaction, were also associated with an earlier offset of childhood amnesia. These results build upon a growing body of research indicating an interhemispheric basis for the retrieval of episodic memories. Moreover, the results of Experiment 2 suggest that interhemispheric interaction has its effect on the retrieval, not encoding, of episodic memories.

Adolescent↗
PubMed2006

The Concept Shifting Test: adult normative data.

The Concept Shifting Test (CST) is a newly developed Trail Making Type test that measures concept shifting and executive functioning. The purpose of the present study was to determine whether CST performance was affected by age, gender, educational level, or handedness and to establish the normal range of test performance. The CST was administered to a large sample (N = 1,794) of cognitively intact adults (age range 24 to 81 years). The results showed that CST performance was superior in women, decreased with age, and increased with level of education. Handedness did not affect CST performance. Normative data that are corrected for the influences of these demographical variables were established with a regression-based normative approach.

Adult↗
PubMed1990

Overt attempts to change hand preference: a study of group and individual characteristics.

Previous work by Porac, Coren, and Searleman (1986) looked at overt attempts to change hand preference from the left to the right side. We extended this research by studying individuals who shifted their handedness from the left to the right side as well as a group who attempted a shift in the opposite direction (right to left). Comparisons of the two shift attempts revealed that the timing, method, and agent of change differed significantly for right versus left shifts. More right than left shifts were successful. Overall, most shift attempts were rated as unsuccessful because they did not result in a handedness classification consistent with the direction of the shift. Individuals classified as successful shifters, whether in the right or left direction, displayed a more ambihanded behavioural pattern than either unsuccessful shifters or the no shift control group. Evidence suggested that left-shift attempts were promoted by original ambihanded tendencies but that ambihandedness in successful right shifts stemmed from the partial success of the switch attempt.

Adult↗
PubMed2002

Conserved function for embryonic nodal cilia.

How left right handedness originates in the body plan of the developing vertebrate embryo is a subject of considerable debate. In mice, a left right bias is thought to arise from a directional extracellular flow (nodal flow) that is generated by dynein-dependent rotation of monocilia on the ventral surface of the embryonic node. Here we show that the existence of node monocilia and the expression of a dynein gene that is implicated in ciliary function are conserved across a wide range of vertebrate classes, indicating that a similar ciliary mechanism may underlie the establishment of handedness in all vertebrates.

Animals↗
PubMed1995

Is ultrasound unsound? A review of epidemiological studies of human exposure to ultrasound.

We have reviewed the epidemiological studies of human exposure to diagnostic ultrasound during pregnancy. Studies have concentrated on possible associations between ultrasound exposure in utero and childhood malignancies, neurological maldevelopment, dyslexia, left-handedness, delayed speech development and low birth weight. It is concluded that no associations between ultrasound exposure in utero and childhood maldevelopment have been proven. There are, however, some issues, such as non-right handedness and low birth weight after frequent Doppler ultrasound exposures, for which no firm conclusions can yet be drawn. These issues need to be tested in future studies.

Birth Weight↗
PubMed1999

Pressure pain thresholds asymmetry in left- and right-handers: Associations with behavioural measures of cerebral laterality.

Pressure pain threshold (PPT) asymmetry of the left and right third digits was assessed in 12 right-handed and 12 left-handed subjects using an automatised pressure algometer. A clear PPT asymmetry was found in right-handed participants, while left-handed participants revealed no PPT asymmetry. The PPT asymmetry of right-handed participants was due to a reduced PPT or increased pain sensitivity at the left hand. Behavioural laterality tests revealed a right ear or left hemisphere advantage for the processing of verbal material (consonant-vocal syllables) and a left visual field or right hemisphere advantage for the processing of emotional faces in all participants. PPT asymmetry was not associated with cerebral laterality assessed with these tests. We conclude that PPT asymmetry is associated with handedness, but neither PPT asymmetry nor handedness are closely associated with measures of cerebral laterality. Copyright 1999 European Federation of Chapters of the International Association for the Study of Pain.

Journal Article↗
PubMed1988

Factors determining the preference of takeoff leg in jumping.

The takeoff (= push-off) leg in jumping, handedness, and leg length inequality as measured radiographically were recorded for 892 young healthy subjects, 62 of whom were top-level athletic jumpers, 654 competetive athletes representing other sports, and 176 Finnish Army conscripts. Correlation between the laterality of takeoff leg and handedness was poor, but a significant majority (81.4% of jumpers, 65.1% of other athletes, and 76.8% of conscripts) invariably used the longer leg for takeoff. Incidence of leg length inequality was highest in the group of athletic jumpers, the difference between top-level jumpers and runners being statistically significant.

Adolescent↗
PubMed1997

Differential behavior of curved DNA upon untwisting.

We have synthesized DNA segments with different handedness, twisting and radii of curvature, and have analyzed the effect of untwisting on them. The results indicate that the dynamic behavior of curved DNA upon untwisting is strongly determined by the initial sequence-dependent DNA trajectory. In particular, DNA with the same radii but with opposite handedness of superhelix twisting can show very different conformational responses to ethidium bromide untwisting. Upon treatment with ethidium bromide, right-handed superhelixes decrease their twist and increase the planarity of the superhelix, while left-handed superhelixes increase twisting and decrease their degree of planarity.

DNA↗
PubMed2003

The concept of cerebral chemical dominance.

The study assessed the biochemical differences between right hemispheric dominant and left hemispheric dominant individuals detected by handedness and the dichotic listening test. The isoprenoid metabolites--digoxin, dolichol, and ubiquinone, glycoconjugate metabolism, free radical metabolism, and the RBC membrane composition were studied in individuals with differing hemispheric dominance. The results showed that all right hemispheric dominant individuals and 50% of left hemispheric dominant individuals had increased HMG CoA reductase activity, elevated digoxin and dolichol levels. The serum magnesium, RBC membrane Na+-K+ ATPase activity and serum ubiquinone levels were reduced in all right hemispheric dominant individuals and 50% of left hemispheric dominant individuals. The tryptophan-derived neurotransmitters--serotonin, quinolinic acid, strychnine, and nicotine--were increased while the tyrosine derived neurotransmitters--dopamine, noradrenaline, and morphine--were reduced in all right hemispheric dominant individuals and 50% of left hemispheric dominant individuals. The other 50% of left hemispheric dominant individuals had decreased HMG CoA reductase activity, reduced digoxin, and dolichol levels. The serum magnesium, RBC membrane Na+-K+ ATPase activity, and serum ubiquinone levels were increased in this group. The tryptophan derived neurotransmitters--serotonin, quinolinic acid, strychnine, and nicotine were reduced, while the tyrosine-derived neurotransmitters--dopamine, noradrenaline, and morphine-- were increased in the rest (50% of left hemispheric dominant individuals). Hemispheric dominance detected by the dichotic listening test and handedness has no correlation with cerebral chemical dominance.

Adult↗
PubMed2005

Hand preference in Turkish population.

The distribution of hand preference (self report) was studied in siblings and their parents originating from all parts of Turkey (N = 22,461). In total sample and siblings, there were significantly more right-handed women than men, and significantly more left-handed men than women--no significant sex difference for parents' handedness. The relative number for the right-handed parents significantly exceeded that for the right-handed siblings; the relative number for the left-handed siblings significantly exceeded that for the left-handed parents. It was concluded that there may be a sex difference in hand preference, but being only about 1% more left-handed men, and only about 1% more right-handed women; the right-handedness in new generation (siblings) is less than that in old generation (parents), due to freeing from cultural pressures against the left-hand use in everyday activities.

Adolescent↗
PubMed2000

What determines choice of limb for unimanual reaching movements?

Currently, relatively little is known about what drives the choice of limb for goal-oriented reaching. Traditionally, the explanation has been tied predominately to motor dominance as manifested in handedness. This article offers data and an argument suggesting that handedness can be modified by attentional (spatial) information. Although motor dominance may be the controlling factor in the programming and execution of reaching movements at the midline and hemispace ipsilateral (same side) to the dominant limb, attentional information alters the programming of movements in what would be contralateral space. The general trend of behavior is characterized by reaching on the same side as the stimulus, in ipsilateral fashion, a phenomenon explained by kinesthetic efficiency and hemispheric bias.

Attention↗
PubMed1977

A review of directionality trends in the horizontal dimension as a function of innate and environmental factors.

This report reviews research on directionality trends in the horizontal dimension. The literature reviewed shows that such trends are predominantly a function of handedness and acquired reading-writing habits and that innate directional tendencies of left-handers are more influenced by acquired habits than those of right-handers. It is suggested that these trends may reflect some aspect of lateralization of cerebral function and that in mature adults the mixed-dominance left-handers are more influenced by environmental factors than are right-handers. Suggestions for future research include utilization of larger samples of left-handers and employment of longitudinal studies which systematically vary handedness and reading and writing habits. It is also suggested that controls for lateral dominance should be established. In addition it is suggested that reading and writing habits can be broken down into component parts and that their influence on directionality should be examined.

Adolescent↗
PubMed1979

Left-handers and right-handers compared on a motor task.

Finger-tapping performance of 45 subjects of each sex and handedness combination, for a total of 180, was compared. Performance measures were speed (mean intertap interval) and regularity (standard deviation of intertap interval). Males tapped faster but not more regularly than females. The between-hand differences in performance were smaller for both measures in left-handers. When absolute magnitudes of between hand differences were compared, females showed smaller differences in regularity of tapping than males. Speed and regularity of tapping were statistically independent; both measures discriminated well between the preferred and nonpreferred hand of both handedness groups, but the differences in speed were more marked than the differences in regularity. Data on the performance of children on the same task are included for comparative purposes.

Journal Article↗