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PubMed2001

Side bias and accidents: are they related?

This study purports to examine the role of different forms of side bias, handedness, footedness, eyedness, and earedness, in eliciting accident-proneness in individuals. A representative sample (N = 150) was administered a Side Bias Questionnaire (Handedness: 22 items, footedness: 5 items, eyedness: 5 items, earedness: 5 items) to ascertain their preferential bias. The questionnaire also required subjects to report the number of accidents committed during their lifetime while performing activities like sports, driving, household work, etc., that required attention of medical professionals. Regression analysis of data indicated that accident-prone behavior was significantly predicted from handedness. Analysis of variance, 3 (Accident groups: low, moderate, high) x 4 (Side bias: hand, foot, eye, ear), indicated that 'mixed' handers committed more accidents as compared with clear handers. The other forms of side bias, foot, ear, and eye were unrelated to frequency of accidents.

Accidents, Traffic↗
PubMed1988

Torque and cerebral lateralization: a questionable link.

Past research has suggested that torque (the tendency to draw circles in a clockwise direction) may be indicative of less cerebral lateralization. This notion is based on the finding that left-handers demonstrate a greater incidence of torque than right-handers. The present study attempted to investigate this relationship using both conjugate lateral eye movements (CLEM) and handedness as indices of cerebral lateralization. Subjects were 40 male and 40 female right-handed and 16 male and 16 female nonright-handed university students. Consistent with past studies, torque was significantly related to handedness, with nonright-handers demonstrating a greater incidence of torque. However, no relationship between torque and CLEM was found. On the basis of these findings, it is argued that the observed relationship between torque and handedness may be due more to muscle mechanics of the hands rather than any relationship with cerebral lateralization.

Adult↗
PubMed1988

The relationship between nonverbal intelligence, familial sinistrality and Geschwind scores in right-handed female subjects.

I proposed that there might be a strong relationship between the psychological and motor systems, and argued that hand preference could be related to intelligence; higher IQs are to be expected in right-handers with familial sinistrality (FS) than without FS (Tan, in press). This hypothesis was tested in this work. Cattle's Culture Fair Intelligence Test was used to assess the ability of spatial reasoning in right-handed females. Hand preference was assessed by the Edinburgh Handedness Questionnaire; a laterality score (Geschwind score) was calculated for each subject. The sample from the Nursery High-school had a significantly lower mean IQ than that from the Medical Faculty. The incidence for the consistent right-handers was significantly higher in the sample with lower mean IQ than that with higher mean IQ. The incidence for the weak right-handers was significantly higher in the sample with higher mean IQ than that with lower mean IQ. The incidence for familial sinistrality was significantly higher in the sample with higher mean IQ than that with lower mean IQ. It was concluded that handedness, familial sinistrality, and intelligence are interrelated traits; an attenuation in cerebral asymmetry as a result of an increase in the right hemisphere's mental abilities, reflecting itself in weak right-handedness in conjunction with FS, could be a prerequisite for well-developed nonverbal intelligence.

Adult↗
PubMed1989

Anatomical asymmetries of the human cerebral cortex.

This paper summarizes current knowledge concerning the anatomical asymmetries of the cerebral cortex and presents the main hypotheses proposed so far to account for these asymmetries. The main question raised by the presence of these asymmetries is that of their functional significance and has been explored by attempting to correlate handedness, the most immediate feature of functional brain specialization, with neuroradiological evidence of brain asymmetry using either carotid angiograms or CT scan. These methods, however, yielded controversial or incomplete results. The recent advent of magnetic resonance imaging now makes it possible to perform direct evaluation and measurements of cortical asymmetries. Preliminary results of a personal study using this approach are presented. They show in particular a good correlation between the planum surface and handedness, and confirm the previously reported statistical correlation between handedness and callosal surface. These results are discussed in the light of modern theories about brain development.

Cerebral Cortex↗
PubMed1990

Relationship of testosterone and nonverbal intelligence to hand preference and hand skill in right-handed young adults.

The relationship between serum testosterone level and nonverbal intelligence was studied in right-handed young adults with regard to handedness. Hand preference was assessed by the Edinburgh Handedness Inventory. Hand skill was measured by a peg moving task. Serum testosterone level was determined using tritium-marked-radioimmunoassay. Visual-spatial performance (nonverbal intelligence) was measured by Cattell's Culture Fair Intelligence Test. In men with consistent right-hand preference (GSs: 80 to 100), IQ was found to be positively linearly related to serum testosterone, which exhibited two regression lines belonging to low and high difference in skill between hands. In females with consistent right-handedness, there was a negative linear correlation between IQ and serum testosterone, which also exhibited two different regression lines according to difference in skill between hands. In males with moderate right-hand preference (GSs 50 to 75), IQ was found to be positively linearly related to serum testosterone, exhibiting two different (same slopes) regression lines according to difference in skill between hands. In females with moderate right-hand preference, IQ first increased and then decreased with serum testosterone, exhibiting a quadratic relationship. These results suggested that serum testosterone in young adults may be associated with visual-spatial performance depending upon sex, hand preference, and hand skill.

Adolescent↗
PubMed1994

The diminished number of older left-handers: differential mortality or social-historical trend?

Recent research suggests that left-handers have shorter life spans. This interpretation could be erroneous if there is a social-historical trend in handedness with older individuals more frequently switched to right-handedness. This would result in fewer older left-handers due to social factors. Two samples (N = 1960 and N = 8526), separated by a 12 year interval were tested. Social-historical hypotheses predict that the later sample should have higher proportions of left-handedness. Although both samples showed decreased sinistrality with age, there was no increase in the proportion of left-handers over the 12 year period, suggesting that the rarity of older left-handers is due to reduced longevity.

Adolescent↗
PubMed1996

Associations among familial sinistrality, allergies, and developmental language disorders.

Here we report the results of a study that tested what has become known as the Geschwind hypothesis (Geschwind & Galaburda, 1987). This study involved 526 people who were tested by an allergist for IgE-mediated allergies and who filled out a 12-item handedness questionnaire that also included questions about eyedness, prevalence of left-handedness in the immediate family, and familial developmental language problems. A series of log-linear analyses revealed that if the definition of "anomalous" included left-handedness and having a first-order left-handed relative, one was indeed more likely to be allergic than were those not so classified. When the definition of anomalous simply included those classified as left-handed, the results were not significant. Parallel findings resulted when the criterion variable was the presence of developmental language disorders. No evidence was found for relations between allergies and developmental language problems.

Adolescent↗
PubMed1991

Hearing asymmetry among left-handed and right-handed persons in a random population.

The possible effect of handedness on hearing threshold asymmetry was analysed in a large random population representing a normal population. The left ear was on an average slightly but significantly poorer than the right ear at high frequencies, especially at 4 kHz, while at low frequencies the right ear was on average poorer than the left ear. A matched control group of the right-handed subjects was formed for 211 left-handed subjects. Among the left-handed subjects the average ear asymmetry resembled the ear asymmetry of the whole population, the right-handed subpopulation, and of the matched control group. In conclusion, it seems that handedness cannot be responsible for the average inferiority of hearing in the left ear at 4-kHz or for the average slight superiority of the left ear at 0.125-0.5 kHz. However, this analysis does not rule out possible minor effects of handedness on ear asymmetry.

Adolescent↗
PubMed2001

Lateral asymmetry in grip strength: utility of the ten per cent rule.

OBJECTIVE: To measure asymmetry in grip strength between hands in left, right and mixed handers and to test utility of the ten per cent rule. DESIGN: A cross sectional study. SETTING: Queen Elizabeth Central Hospital, Blantyre, Malawi. SUBJECTS: One hundred and seventy six healthy volunteers (102 males and 74 females) aged 15 to 66 years were selected from visitors to the patients admitted at the hospital. MAIN OUTCOME MEASURES: Bilateral measurements of maximal grip strength, assessment of handedness using a questionnaire incorporating questions on hand preferred for six habitual activities. RESULTS: In about 70% of males and females, the right hand was stronger than the left hand while frequency of left, mixed, and right handers was 5.7%, 4.5% and 89.2%, respectively. Significant association (chi2 = 6.43, n = 2, p<0.05) was found between handedness and stronger hand with preferred hand being stronger in most subjects. However, for about 40% of left and mixed handers and 27% of right handers, the non-preferred hand was stronger. The mean differences between grip strengths varied between 10% and 20% in different categories of handers when stronger hand was taken into consideration. Without considering the stronger hand, the mean bilateral difference in maximal grip strength in the three categories of handedness was between three and six per cent.. CONCLUSION: Distinction between stronger hand and hand preferred for skilled activities should be made and considered when assessing limitations in hand strength in clinical practice.

Adolescent↗
PubMed2001

Mechanisms of twinning. II. Laterality and intercellular bonding in monozygotic twinning.

OBJECTIVE: To utilize observations on laterality and handedness to gain insight into the initiating mechanism of monozygotic human quadruplets. STUDY DESIGN: In a study of thumbprints and handedness in sets of monozygotic quadruplets, homolateral and heterolateral comparisons were used to distinguish mirror-image from symmetric divisions. RESULTS: Data were consistent with a mechanism involving a mirror-image duplication in the first division and a subsequent symmetric separation of the daughters. In addition, these data failed to substantiate a genetic linkage between dermatoglyphics and handedness. CONCLUSION: Reported and reviewed data tend to support the analogy of monozygotic polyembryony in armadillos and humans. The plausible roles of delayed implantation and intercellular bonding are explored, especially as they relate to ambient calcium concentration. Factors tending to enhance the likelihood of monozygotic twinning include calcium channel blockers, lactation, ovulation induction and prolonged in vitro fertilization incubation.

Dermatoglyphics↗
PubMed2001

Is the left cerebral hemisphere more prone to epileptogenesis than the right?

PURPOSE: To determine if there is evidence that the left cerebral hemisphere is more prone to epileptogenesis than the right hemisphere. METHODS: We examined 532 patients with localization-related epilepsy, as documented by long-term EEG-video monitor studies. We identified those with interictal epileptiform patterns on EEG confined to one hemisphere, those with clinical seizures that arose only from one side, and individuals with neuropsychological deficits lateralizing more to one cerebral hemisphere than the other. These data were then related to the handedness of the subjects. RESULTS: For left-handed patients, interictal discharges were significantly more likely to be confined to the left side, seizures more frequently arose from only the left hemisphere, and neuropsychological deficits lateralized more often to the left brain. In contrast, for right-handed subjects, there were no significant differences in unilateral localization of either interictal discharges or of seizure onsets, nor did neuropsychological deficits lateralize more often to one side or the other. Although, as a group, left-handers had an earlier age of onset of epilepsy than right-handers, the lateralizing EEG and neuropsychological patterns seen in left-handers were not related to age of onset of epilepsy, febrile seizures, family history of either epilepsy or left-handedness, or other risk factors. CONCLUSION: In localization-related epilepsy, there is a significant association of left-handedness with left hemispheric lateralization of epileptiform EEG patterns and neuropsychological deficits. These findings do not clearly reflect a greater left than right cerebral hemispheric vulnerability to epileptogenesis, except possibly in left-handers.

Adult↗
PubMed2002

Evidence of a right-shift factor affecting infant hand-use preferences from 7 to 11 months of age as revealed by latent class analysis.

Infant hand-use preferences for apprehending objects were assessed three times at 7, 9, and 11 months of age for 154 infants (79 males) using a reliable and valid procedure. Two classification procedures (differing in Type I classification error rates) were used to identify an infant's preference (right, left, no preference) at each age, and these data were examined using two- and three-group latent class analysis models. These analyses revealed the importance of using a handedness classification procedure with low Type I error rates and evidence of a right-shift factor similar to that expressed in child and adult handedness. Thus, infant hand-use preferences for apprehending objects are likely a developmental precursor of adult handedness. The relation of the right-shift factor to increased susceptibility to social influences during development and the evolution of human abilities also is discussed.

Adult↗
PubMed2003

Reliable callosal measurement: population normative data confirm sex-related differences.

BACKGROUND AND PURPOSE: Corpus callosal cross-sectional area (CCA) may be a clinical indicator of disease progression, but factors influencing callosal morphology in healthy subjects must be determined before comparisons can be made in patients. We sought to define a reliable and easily repeatable method for CCA measurement and to examine the effects of sex, age, handedness, and cerebral volume. METHODS: Neurologically healthy volunteers (age range, 14-68 years; mean age, 32.6 years +/- 12.3 [SD]; 44 men, 56 women; 87 right handed) underwent conventional MR imaging. Data were reoriented in the image space to account for intersubject variations in head position before the midsagittal plane was defined by using midpoints of the anterior commissure (AC), posterior commissure (PC), and interhemispheric fissure (IF). Midsagittal CCA and total cerebral volume were measured and correlated with sex, age, and handedness. RESULTS: The mean CCA was 6.27 cm(2) +/- 0.90. Women had a larger CCA proportional to cerebral volume (6.16 x 10(-3) cm(-1) vs 5.78 x 10(-3) cm(-1) in men; P =.02). The percentage difference for the CCA-cerebral volume from the group mean was +2.6% in women and -3.6% in men. Only a small linear relationship of CCA with cerebral volume was noted (r(2) = 0.15), and CCA was not significantly correlated with age or handedness. CONCLUSION: To our knowledge, this is the largest study of callosal area in a community-based sample of control subjects; such subjects provide controls for future studies. Our findings provide anatomic evidence of sex differences in interhemispheric connectivity. Much CCA variability is independent of cerebral volume.

Adolescent↗
PubMed1986

[Are the left-handed more often allergic?].

Are left handed more frequently allergic patients? With the same evaluation clinical criteria, we find a Non Right Handedness (left handed + mixed handedness) in 48/403 children (11.9%) at school in a town near our consultation place and in 152/625 (24.32%) children of the same age with a mites allergy (p less than 0.001). This non right handedness is among allergic patients more frequently observed for boys: 126/442 (28.50%) than for girls: 26/183 (14.20%). The mechanism is unknown but it has been hypothesized (Geschwind) that a male related factor might slow left hemisphere development and trouble immune system equilibration.

Child↗
PubMedDate not supplied

[Motor asymmetry of the forelimbs of the rat].

Preference was studied of one of the forelimbs during performance of different manipulating movements in white rats. High degree of "handedness" was observed in all studied movements. However it was not absolute--no animals performed all movements by one and the same limb. Degree and character of "handedness" were different for different movements, though the number of "righthanded" rats in most tests as a whole exceeded the number of "lefthanded" ones. The "handedness" depends on the individuality of the animal, the character of the motor task, learning and interference of different motor tasks during training.

Animals↗
PubMedDate not supplied

[Considerations on the cerebral organization of left-handed persons].

Left-handedness, being exception to the rule of right-handedness, has provoked several questions about its origins and the significance of its relationships with some individual traits, like cognitive style, personality, creativity, motor abilities. Investigations on left-handedness in recent years suggest that hand preference is linked to the peculiar functional organization of the two hemispheres of the brain.

Aphasia↗
PubMed1994

Helix sense of gramicidin channels as a "nonlocal" function of the primary sequence.

Gramicidin A (gA) channels are dimers formed by right-handed beta 6.3-helical monomers. The stereochemical basis for the preference of a right-handed conformation remains obscure, but it has earlier been demonstrated that the handedness can be shifted by changing the chirality of each residue in the LD-sequence and therefore is determined by the peptide itself and not by channel-membrane interactions. We now examine the contributions of Trp15, the central Val residues 6-8, and residues 1-5. None of these alone are sufficient to specify the helix sense. To examine the D-Val6-L-Val7-D-Val8 sequence, the register of the 3 valines was shifted by one to L-Val5-D-Val6-L-Val7. The resulting analogue, [Val5,D-Ala8]gA, forms channels with a conductance and duration that are both somewhat less than those of gA channels. The reduced channel duration can be attributed to a steric conflict between the side chains of Val1 in one monomer and Val5 in the other monomer. The helix handedness is not altered by this modification, as shown by circular dichroism and two-dimensional nuclear magnetic resonance spectroscopy and by hybrid channel experiments. [Val5,D-Ala8]gA forms hybrid channels with gA (which forms right-handed channels), but not with des-Val1-gA- (which forms left-handed channels). Similar hybrid channel analysis shows that des-Trp15-gA and [L-Ala1,D-Ala2,L-Ala3,D-Ala4]gA also form right-handed channels. We conclude that the helix handedness most probably is a complex function of the arrangement of both the D-Val-L-Val-D-Val and the L-Trp-(D-Leu-L-Trp)3 segments.

Amino Acid Sequence↗
PubMed1995

Criteria for selecting the side for cochlear implantation.

Choice of the side for cochlear implantation should take into account peripheral (extracortical) factors and central (cerebral dominance) factors. From 111 patients implanted with a Nucleus device, the authors found that significant peripheral factors were the degree of cochlear ossification, the duration of deafness before cochlear implantation, and the preoperative promontory test dynamic range (degree of response on the promontory test in decibels); cause of deafness and residual hearing were not correlated with speech discrimination. Cerebral dominance was indirectly determined by handedness. Handedness laterality was determined by a questionnaire. There was no significant difference in results between patients implanted on their dominant side and patients implanted on their nondominant side. When ears are different according to their peripheral factors, the authors suggest implanting the better ear, provided there is no significant hearing in that ear. When both ears are identical, the side of implantation should be the side of handedness laterality to facilitate device manipulation (a practical reason).

Adolescent↗