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At least 1,171 records · Page 65Linked to original sources
PubMed1998

Haptic memory and handedness in 2-month-old infants.

This study examined the robustness of infant haptic memory, asymmetry between hands, and sex differences in haptic memory in infancy. A total of 96 2-month-old infants (half males, half females) were habituated haptically to an object with their right and their left hand, out of the field of view. Haptic memory was then tested under three conditions: after haptic interference, after a 30-second delay, or after no delay. The results show that haptic habituation occurred for both hands. The girls needed more time to habituate with their left hand than with their right hand, and they habituated more slowly than the boys did. Discrimination was also found in both hands and in both sexes. Haptic delayed recognition memory was only found in young boys mainly after a short delay and under certain conditions after interference. In young girls, recognition memory was found after interference only with the left hand. This result seemed to depend on the information processing speed. Thus, for memory performance, a sex difference was clearly observed. Moreover, the infants' left hand retained better information on object shape than did the right hand for both the sexes. Asymmetries in infancy are discussed in connection with the difference in brain maturation rate.

Journal Article↗
PubMed1986

On the surface lattice of microtubules: helix starts, protofilament number, seam, and handedness.

The tubulin monomers of brain microtubules reassembled in vitro are arranged on a 3-start helix, irrespective of whether the number of protofilaments is 13 or 14. The dimer packing is that of the B-lattice described for flagellar microtubules. This implies that the tubulin core of microtubules contains at least one helical discontinuity. Neither 5-start nor 8-start helices have a physical significance and thus cannot be implicated in models of microtubule elongation, but the structure is compatible with elongation of protofilaments by dimers or protofilamentous oligomers. The inner and outer surfaces of the microtubule wall can be visualized by propane jet freezing, freeze fracturing, and metal replication, at a resolution of at least 4 nm. The 3-start helix is left-handed, in contrast to a previous study based on negative staining and shadowing. The reasons for this discrepancy are discussed.

Cytoskeleton↗
PubMed1992

Correlated nondifferential misclassifications of disease and exposure: application to a cross-sectional study of the relation between handedness and immune disorders.

In cross-sectional studies, misclassifications of exposure and of health status may be related. For instance some subjects may tend to overreport both exposure and disease. A misclassification is said to be nondifferential if the sensitivity and the specificity which characterize it do not depend on the true status of the subjects for the other variables. Nondifferential misclassifications of two dichotomic variables may be correlated if the probability of being misclassified for one of them depends on the presence of an error of classification for the second one. Models are presented to estimate the bias induced by correlated nondifferential misclassifications on an odds ratio whose true value is unity. For most usual situations, when the great majority of the subjects are healthy and nonexposed, the influence of overreporting is shown to be larger than that of underreporting. It appears to be relatively easy to find a spurious, but significant, relationship. Real data are analysed to show that the potential consequences of correlated nondifferential misclassifications are not purely theoretical. In a sample of 1676 subjects from the general population we observed significant relations between left-hand shift and various aspects of health status: reporting a history of eczema, experience of a serious health problem in the past, experience of a serious health problem presently, use during the last month of analgesics or of drugs for circulatory problems, or digestion, consultation with a physiotherapist or hospitalization during the last year. These results, as with many similar ones previously reported, are highly suggestive of an information bias. They are less easily explained by biological hypotheses, e.g. Geschwind's theory of cerebral lateralization, than by correlated misclassifications resulting from overreporting of both the use of the left hand and the existence of some health problems by healthy right-handers. The modelling used in this report supports this hypothesis.

Adult↗
PubMed1987

alpha-DNA-V. Parallel annealing, handedness and conformation of the duplex of the unnatural alpha-hexadeoxyribonucleotide alpha-[d(CpApTpGpCpG)] with its beta-complement beta-[d(GpTpApCpGpC)] deduced from high field 1H-NMR.

The beta-complementary hexamer, beta-d[GTACGC], to the alpha-sequence, alpha-d[CATGCG], was synthesized by the phosphotriester method. The non-exchangeable proton assignments were obtained using 1D- and 2D-NMR techniques, including NOE, COSY and NOESY. The beta-strand exists as a random coil at 21 degrees C; however, at 4 degrees C, it forms an antiparallel self-recognition duplex annealing at positions 1-4. The beta-strand was annealed to the alpha-strand, and confirmation of complete annealing was obtained by detection and assignment of the six base pair imino protons in H2O/D2O solution at 21 degrees C. 1D-NOE experiments of the alpha, beta duplex d[alpha-(CATGCG) X beta-(GTACGC)] reveal that (i) it exists in aqueous solution in a conformation that belongs to the B family, (ii) it is 70 +/- 10% right-handed, (iii) the sugar-base orientations of the beta-strand are anti, and the deoxyribose units exist predominantly in the 2'-endo-3'-exo conformation. NOE measurements of the imino proton signals in the alpha, beta duplex reveal that the duplex exhibits parallel polarity.

Base Composition↗
PubMed2005

Does handedness and altitude affect age at menarche?

Although there is knowledge about earlier mean age at menopause among left-handed postmenopausal women, it is unclear from the literature whether age of menarche is influenced by the prenatal hormonal pattern and cerebral lateralization. We therefore planned to investigate the relation between age of menarche and cerebral lateralization in girls at an altitude of nearly 2000 m. Sixty-two girls, aged between 9.4 and 15.5 years, were interviewed by questionnaire about manual dominance and menarcheal age. All girls were divided into two groups: left-handers (n = 31) and right-handers (n = 31). It was shown that there was a significantly lower average age of menarcheal appearance (12.96 +/- 1.34 years) in the left-handers' compared with the right-handers' (13.72 +/- 1.41 years; p = 0.025). The earliest menarcheal age was 9.4 years in left-handers and 10.1 years in right-handers.A menarcheal age of 13.34 +/- 1.35 years was found for the whole group at an altitude of nearly 2000 m. This data leads us to believe the existence of a link between functional brain asymmetry and menarche. It would appear that the activation of the hypothalamic-pituitary-gonadal axis is earlier in left-handed females than in right-handed females.

Adolescent↗
PubMed2001

Carpal tunnel syndrome in female nurse anesthetists versus operating room nurses: prevalence, laterality, and impact of handedness.

UNLABELLED: Nurse anesthesia may be a high-risk occupation for carpal tunnel syndrome (CTS) in the workplace. We designed a cross-sectional investigation to study the prevalence of CTS in nurse anesthetists (NAs) as compared with operating room nurses (ORNs). Two-hundred forty-four female operating room workers were classified by job title as NAs (n = 63) and ORNs (n = 181). The case definition of CTS was established by a history of surgical correction or a combination of four positive historical and physical findings. There were 10 cases of CTS in NAs and 10 cases of CTS in ORNs. The crude odds ratio (OR) for CTS in NAs was 3.23 (95% confidence interval, 1.27-8.17, P = 0.021). The crude OR for left-hand CTS in NAs was also 3.23 and 3.58 for bilateral CTS. When adjusted for nondominant left-hand or bilateral CTS, the OR for CTS in NAs was 3.85. The Yates-corrected chi(2) for CTS in NAs was 5.346 (P = 0.021) and 5.075 (P = 0.024) for nondominant left-hand or bilateral CTS in NAs as compared with ORNs. On the basis of our data analysis, nondominant left-hand CTS and bilateral CTS were significantly more prevalent in NAs than ORNs. IMPLICATIONS: Repetitive stress injuries have now exceeded back injuries as the most commonly reported workplace injuries in the United States. Female nurse anesthetists may face greater occupational risks for developing left hand and bilateral carpal tunnel syndrome than female operating room nurses.

Adult↗
PubMed1999

Handedness in opposite and same-sex dizygotic twins: testing the testosterone hypothesis.

Prenatal exposure to testosterone is proposed to promote development of the right hemisphere and increase the incidence of sinistrality. This proposition was tested by comparing the hand preference of 59 opposite-sex and 61 same-sex dizygotic twins. Because testosterone is thought to pass between twins in utero, it was predicted that females with a male twin would show a high incidence of sinistrality compared to females with a female twin. Similarly, it was predicted that males with a male twin would be more likely to be sinistral than males with a female twin. Measures of the strength of hand preference and the incidence of sinistrality revealed no difference between the opposite and same-sex twins for either sex. The data also failed to confirm reports that first-born twins are more likely to be sinistral than second-born twins. These data add to a growing body of research which is critical of the testosterone hypothesis.

Adolescent↗
PubMed2002

Cerebral asymmetry for mental rotation: effects of response hand, handedness and gender.

We assessed lateralization of brain function during mental rotation, measuring the scalp distribution of a 400-600 ms latency event-related potential (ERP) with 128 recording electrodes. Twenty-four subjects, consisting of equal numbers of dextral and sinistral males and females, performed a mental rotation task under two response conditions (dominant non-dominant hand). For males, ERPs showed a right parietal bias regardless of response hand. For females, the parietal ERPs were slightly left-lateralized when making dominant hand responses, but strongly right-lateralized when making non-dominant hand responses. These results support the notion that visuo-spatial processing is more bilaterally organized in females. However, left hemisphere resources may be allocated to response preparation when using the non-dominant hand, forcing visuo-spatial processing to the right hemisphere.

Adult↗
PubMed1977

Handedness and the lateral distribution of conversion reactions.

The purpose of this investigation was to determine whether the observation of Ferenczi and Purves-Stewart that conversion reactions occur with higher frequency on the left side of the body than on the right side could be confirmed. Both right-handed and left-handed patients experienced a higher proportion of left-sided symptoms (weakness or paralysis; sensory loss or numbness) than would be expected by chance, indicating a lack of support for the hypothesis that unilateral conversion symptoms occur most frequently on the most "convenient" (nondominant) side of the body. These findings and prior reports of left-sided lateralization of psychogenic pain were interpreted as support for the hypothesis that the right cerebral hemisphere is particularly involved in the mediation of affectively or motivationally determined somatic symptoms. The question of a possible link between these results and certain symptoms of disease of the right hemisphere was raised.

Conversion Disorder↗