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At least 19 recordsLinked to original sources
PubMed1992

Activity of the hypothalamic-pituitary-adrenal axis in mice selected for left- or right-handedness.

Asymmetry in brain modulation of the immune system has been previously described. In mice, paw preference has been shown to be associated with immune reactivity but the mechanisms involved in such an association are not yet known. The autonomic nervous system and the neuroendocrine system are considered as major candidates for neural influences on the immune system. In the present study, the activity of the hypothalamic-pituitary-adrenal (HPA) axis of adult female mice selected for paw preference (left-handers vs. right-handers) was assessed by measuring both adrenocorticotropic hormone (ACTH) and corticosterone plasma levels, as well as the in vitro responses of hypothalamus and adrenocortical cells to various hormone releasing stimuli. The results reported here showed no difference in the activity of the HPA axis between left- and right-handed mice, suggesting that this neuroendocrine axis is not implicated in the association between functional brain asymmetry and immune reactivity. However, our results do not exclude the possibility that the HPA axis could play a role in such an association under other circumstances, such as during development or stressful situations.

Adrenocorticotropic Hormone↗
PubMed1989

Reflections on the ambivalent helix.

The helix is nature's favourite shape. Because of its elementary geometry and distinctive appearance it is also the clearest instance of an enantiomorphic object--a helix and its mirror image are identical in all respects except their screw sense. This is a distinction that can be ignored from the points of view of pure geometry and pure group theory but any helical structure is actually available as either or both hands. Whether in nature helices do occur as just one hand, or both, is one of the best--perhaps the best--puzzles of the science of form. In this short review I look at a few examples of naturally occurring helices, some where only one hand is found, some where both are commonly found, and perhaps the most interesting examples in biological terms--those where both are found but one hand is very much rarer than the other. I review what mechanisms--physico-chemical, genetic, evolutionary--underlie the different manifestations of left- and right-handedness.

Animals↗
PubMed1990

An epidemiological reconsideration of the Geschwind-Galaburda theory of cerebral lateralization.

To contribute to the Geschwind-Galaburda theory of cerebral lateralization, we examined the relationship of left-handedness to allergic disorders and stuttering, using epidemiological data of two French samples, one of which (N = 9591) is representative of the French male population between 17 and 24 years of age. Results showed a higher frequency of stuttering but not of allergic disorders in left-handers. Extreme right-handedness was observed to be significantly associated with a lower frequency of allergic disorders; response bias might explain such a relationship. Findings were confirmed after allowing for potential confounding factors, such as age and education. In both samples, stuttering and allergic disorders were significantly related.

Adolescent↗
PubMed1975

[Consciousness disorders in focal lesions of the right and left cerebral hemispheres].

In the light of modern concepts of functional asymmetry in the human brain, the authors analyse paroxysmal conditions of changed consciousness which occurred in 160 patients with lesions of the hemispheres due to brain tumors (75 patients) and in epilepsy (85 patients). It is shown that certain forms of changed consciousness are characteristic of disorders of the right and left hemispheres in right-handedness. This clinical fact is taken as a basis for the assumption that in the formation of consciousness both hemispheres in different ways play a certain role and they provide different "formating" kinds of consciousness: the right hemisphere--a direct perception or a sensory perception of the environment and itself, the left--process of abstract perception based on speech, symbols, semantics.

Brain Neoplasms↗
PubMed1990

Bacterial macrofibres: the morphogenesis of complex multicellular bacterial forms.

Bacterial macrofibres are highly ordered multicellular, helically twisted structures that provide a unique opportunity for studying fundamental growth processes and morphogenesis in a procaryotic model. The complex fibres arise, starting either from a single spore or a vegetative cell by the deformation of individual cell shape from cylindrical to helical and the folding and plying of chains of cells into multicellular twisted structures. The dynamics of fibre morphogenesis can be traced to hierarchical interactions beginning with the assembly of cell-wall polymers. Both genetic and biomechanical factors govern the formation and heritability of macrofibre twist states, which can range over the entire spectrum from maximum left- to maximum right-handedness. Forces that arise during growth influence individual cells and their interactions with other cells. Morphogenesis results from the manner in which the cell-wall materials respond to these and other forces. Significant parameters governing response to force are cell wall geometry, visco-elasticity and anisotrophy.

Bacillus subtilis↗
PubMed1992

Anatomical asymmetries and functional laterality.

Anatomical and functional asymmetries were measured using MRI and dichotic, visual field and hand performance laterality tasks in 104 normal right- and left-handed male and female adults. Comprehensive linear and area measures showed consistently larger brains when handedness and language laterality were in the same direction. Right-handers with left cerebral dominance for dichotic listening and left-handers with right cerebral dominance had larger structures. Hand performance was the strongest functional laterality related to anatomical asymmetries. Left hemisphere dominance on this task was associated with larger right frontal and left occipital widths. Dichotic listening or visual field laterality alone was not associated with contralaterally larger temporal, parietal or occipital measurements. Left visual field dominance for reading, interacting with right-handedness, was associated with wider left parietal width. The complex associations between anatomical and functional asymmetries contribute to individual differences in cerebral organization. The demonstrated association of coincident hand performance and language laterality measures with larger anatomical structures may confer biological advantage. Morphometric analysis in vivo may have increasing importance in interpreting behaviour.

Adult↗
PubMed1990

Aphasia due to lesions confined to the right hemisphere in right handed patients: a review of the literature including the Italian cases.

We review most of the work published, to our knowledge, between 1880 and 1988 on aphasia due to right cerebral lesions in right-handed patients ("crossed aphasia"). We summarize the 87 cases found in chronological order within defined groups, dealing in greater detail with the less well-known cases in English-language publications and with the cases from other sources that we consider most representative and convincing. The 87 cases fall into three groups on the following criteria: right-handedness (on standardized tests), absence of left-handers in the family, left hemisphere integrity. Group 1 comprises cases that are unreliable because the handedness data are missing and/or because left hemisphere lesions were known to be present or probably were so. Group 2 comprises cases with full clinical data but no formal test of handedness, with familial cases of left-handedness and/or without satisfactory evidence of left hemisphere integrity. Groups 3 comprises the 26 reliable cases, that is those with proven right-handedness, no left-handers in the family and with proven hemisphere integrity. We discuss the implications of these cases.

Adolescent↗
PubMed1989

Laterality and human evolution.

The question of whether there is a fundamental discontinuity between humans and other primates is discussed in relation to the predominantly human pattern of right-handedness and the left-cerebral representation of language. Both phenomena may go back at least to Homo habilis, 2-3 million years ago. However, a distinctively human mode of cognitive representation may not have emerged until later, beginning with H. erectus and the Acheulean tool culture about 1.5 million years ago and culminating with H. sapiens sapiens and rapid, flexible speech in the last 200,000 years. It is suggested that this mode is characterized by generativity, with multipart representations formed from elementary canonical parts (e.g., phonemes in speech, geons in visual perception). Generativity may be uniquely human and associated with the left-cerebral hemisphere. An alternative, analogue mode of representation, shared with other species, is associated with the right hemisphere in humans.

Animals↗
PubMed1992

Behavioral asymmetries of psychomotor performance in rhesus monkeys (Macaca mulatta): a dissociation between hand preference and skill.

Hand preferences were recorded for 35 rhesus monkeys (Macaca mulatta) as they manipulated a joystick in response to 2 computerized tasks. These preferences were then used to contrast 8 left- and 10 right-handed subjects on performance measures of hand skill. Individual hand preferences were found, but no significant population asymmetry was observed across the sample. However, the performance data reveal substantial benefits of right-handedness for joystick manipulation, as this group of monkeys mastered the 2 psychomotor tasks significantly faster than did their left-handed counterparts. The data support earlier reports of a right-hand advantage for joystick manipulation and also support the importance of distinguishing between hand preference and manual performance in research on functional asymmetries.

Animals↗
PubMed1990

Sex differences and handedness in hemispheric lateralization of tactile-spatial functions.

Sex differences in spatial processing and handedness were studied with a tactile-spatial task in 27 male and 29 female right-handed undergraduate students in psychology. Subjects were asked to identify amorphous shapes to investigate possible male right-hemisphere specialization for spatial functions and bilateral representation among the women. The Annett handedness questionnaire estimated extent of right-handedness. Subjects were classified by major, and women by phase of menstrual cycle. Analysis shows significantly more right-handedness in women and ambidexterity in men. Over-all, men do not perform significantly better than women, although men outperform women with their left hands when handedness is covaried. Within sex, no difference is seen between left and right hand scores for men, but women perform significantly better with right than left hands. Further analyses suggest men appear right-hemisphere dominant for this task whereas women show left-hemisphere dominance. Analyses of hormonal data support recent research, in that for women on the pill there is a trend to perform worse than all other groups. Engineering students perform significantly better than all other majors.

Adult↗
PubMed1977

Concerning the origin of handedness in humans.

The origin of right-handedness as the predominant chirality in humans seems to be related to the tendency of human (and presumably prehuman) mothers to hold infants on the left side. The latter practice has previously been ascribed to imprinting and the soothing sound of the mother's heartbeat on the infant. Given the practice of holding the child in this manner, dextral mothers will be more skillful at manipulation of objects and selectively favored.

Biological Evolution↗
PubMed1979

Schizophrenia: evidence of a subgroup with reversed cerebral asymmetry.

Normal right-handed individuals often show neuroanatomical asymmetries of the brain on computed tomography (CT), with wider right frontal and left occipital lobes. We examined the frequency of reversals of this normal asymmetry in a group of 57 right-handed, the schizophrenic patients. Compared to 80 normal right-handeders, the schizophrenics had an increased frequency of both frontal and occipital reversals. We then divided the patients on the basis of whether they had CT evidence suggestive of brain atrophy. Those without evidence of atropy had increased frontal and occipital reversals. Those with evidence of atrophy had no increase in reversals. This suggests that reversals of neuroanatomical asymmetry, and by implication abnormalities of lateralization, are relevant to a subgroup of schizophrenic patients with otherwise normal CT scans.

Adult↗
PubMed1989

Handedness and anxiety in normal and clinical populations.

Previous research has yielded inconclusive evidence as to the relationship between handedness and anxiety. In order to further examine this relationship, two studies were carried out. In the first study, university students (N = 167) completed the Edinburgh Handedness Inventory, the Fear Questionnaire, and the Maudsley Obsessive Compulsive Inventory. No evidence was found to suggest that phobic fears are more prevalent or more severe among individuals with a tendency to left-handedness than among pure right-handers. Statistical tests reveled a marginally significant positive association between social phobia scores and right-handedness. In the second study, handedness was assessed in 77 anxiety disorder patients and compared with handedness patterns in normal controls. Again, no support was found for the claim that anxiety and left-handedness are related to each other. However, the normal pattern of women being more right-handed than men was reversed in the anxiety disorder group.

Adult↗
PubMed1975

Frequency of left-handedness among the Andhra Pradesh people.

The percentages of left-handed people among the males and females of Andhra Pradesh tribals in India were found to be 15.49 and 7.79, and in Hindus 6.9 and 4.65. The difference between the sexes among tribals is significant. The tribal people studied were Koya Doras, Sugalis (or Lambadis), and Konda Reddis. It is suggested that similar quantitative studies of left-handedness should be made in other tribal and aboriginal populations before they are culturally comditioned to right-handedness.

Ethnicity↗
PubMed1991

Sex, handedness, mathematical ability, and biological causation.

An important part of Benbow's (1988) assertion that sex differences in mathematical ability are primarily due to biological factors is the link between a trait that is assumed to reflect differences in brain organization (left-handedness) and mathematical giftedness. It is shown that the link between mathematical giftedness and an increased prevalence of left-handedness is not convincing. However, Benbow's (1986) data do show a convincing link between strong right-handedness and the lack of mathematical giftedness, in agreement with Annett and Manning's (1990a, 1990b) recent work.

Aptitude↗
PubMedDate not supplied

Right and left hand skill in relation to cerebral lateralization in right-handed male and female subjects: the prominent role of the right brain in right-handedness.

The associations between right and left hand skills to cerebral motor lateralization were studied in right-handed subjects with (FS+) and without (FS-) familial sinistrality. Hand preference was assessed by Oldfield questionnaire and hand skill by the peg moving task. The mean peg moving times (PMTs) and their standard deviations (SDs) were calculated for each hand. There was a significant positive linear correlation between the mean right and left hand PMTs. In males, the mean difference between the left and right PMTs (L-R) showed a significant negative linear correlation with the mean right hand PMTs. There was no significant correlation between these parameters in females. The mean L-R PMTs were found to be positively linearly correlated with the mean left hand PMT in FS- males, FS- and FS+ females (no correlation in FS+ males). The results indicated the contribution of the mean left hand PMTs to L-R hand skill is much higher than that of the mean right hand PMTs. In males, there was no significant correlation between SDs of the mean right and left hand PMTs. In females, SD of the mean right hand PMT was found to be positively linearly related to SD of the left hand PMT. In males, L-R SDs were found to be negatively linearly related to SDs of the mean right hand PMTs and positively linearly related to the SDs of the mean left hand PMTs. In females, only the mean left hand PMT positively linearly correlated with L-R SDs. Here again, the left hand prominently influenced the L-R SDs. In males, SD for the mean right hand PMT showed no relation to right hand PMT. There was, however, a negative linear correlation between SD of the mean right hand PMT and the left hand PMT (no correlations in female). It was concluded that the left hand (right brain) would be of higher significance than the right hand (left brain) in determining the degree of the right-bias in hand skill and its stability in right-handers.

Adult↗
PubMed1978

[Neuroradiologic and clinical correlations in asymmetric lateral ventricles and posterior cornua in pneumo-encephalograms (author's transl)].

Retrospective study of 452 out of 4155 pneumoencephalograms continuously investigated by two independent observers over 20 years. Follow-up and statistics of frequency and sex-differences of asymmetries of lateral ventricles and posterior cornua. Criteria of selection: history and clinical findings in favor of a general cerebral cause and against circumscribed changes due to local damage. Technique standardized and equal bilateral filling in pneumoencaphalography. Results of the numerous findings: 1. Posterior cornua were symmetrical in 370 patients 81.9% (256 male, 114 female, 18.1%). Definite asymmetry of posterior horns in 72 males and 10 males. 2. These asymmetries showed variations from unilateral to bilateral, but clearly different sizes of posterior horns. 3. Unilateral posterior horn "anlagen" seen in 64 (14.1%) of all patients. Males predominated 8:1, left more common than right 3.5:1. 4. Bilateral "anlagen", with one posterior horn predominating, in 18 patients (3.9%). Once more males more common 8:1. Larger "anlagen" on left: 8:1. 5. Accompanying further asymmetries of lateral ventricles with equal bilateral posterior horns were of similar size in 73.7%. In 21.1% the lateral ventricle was larger on the right, in 5.1% on the left. The left side was more common 4.15:1. 6. Large ventricles were of equal size in 45.1 of patients with asymmetry of the posterior horns, 45.1% on left, 9.7% on right the ventricle was larger. Once more the left side predominated 4.6:1. 7. Trying to correlate clinical-neurologic, neurophthalmic, neurophysiologic and tachistocopic findings with pneumoencephalograms with or without asymmetry showed no regular relation with handedness, ocular dominance, limitations of visual fields or--neglect or shapes of ventricles. In all subgroups frequency and sex-distribution corresponded to the norm. 8. Numerical frequency of coupling of right-handedness and right predominant eye with left increased size of ventricle was within the statistically expected and was, therefore, not interpreted as a sign of functional dominance of the left cerebral hemisphere, as done by others. 9. When eliciting from the occiput visually evoked potentials 8 patients showed important findings, in spite of their small number. In 3 patients with symmetrical "anlagen" of the posterior horns, latency and amplitude of potentials were the same; in 5 patients, with asymmetry of posterior horns the side of the larger horn showed significant reduction of amplitude without exception. The investigations show, quantitative statistical findings of frequency and sex-distribution and their negative correlation with examined clinical parameters apart, the anatomic-morphologic variation of asymmetry of posterior horns corresponds to a correlate which can also be shown with a neurophysiologic technique.

Adult↗