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PubMed1979

Influence of sex and handedness on hemispheric functioning.

Forty normal adult volunteers comprising an equal number of right- and left-handed males and females solved simple multiplication problems presented visually to one cerebral hemisphere while various competing stimuli were simultaneously presented to the other hemisphere. The contribution of sex of subject, handedness, hemisphere of presentation and the nature of the competing stimulus in relation to task performance was examined. Each of these variables was significantly associated with correct responses and errors, with few statistically significant interactions. Females and dextrals made more correct responses than males or sinistrals. Type of error depended upon which hemisphere received the problem, with the right hemisphere yielding more errors of commission and the left more errors of omission. Simultaneously presented identical or different arithmetic problems resulted in the most errors compared to the other competing stimuli.

Adult↗
PubMed1980

Birth order, birth stress and handedness.

Left-handed and right-handed parents in personally visited families were asked about the perinatal history of themselves, and their children. Reported birth stress (RBS) was as frequent for right-handers as for left-handers. The children of left-handed mothers were not more likely to have RBS than the children of right-handed mothers. The incidence of RBS was greater for first borns than children of later birth rank. A weak trend to a higher proportion of birth ranks 1st and 4th + among left- than right-handers was found for daughters, but not for fathers, mothers or sons. Empirical and theoretical objections to the hypothesis that pathology of the left hemisphere is a major determinant of left-handedness are reviewed.

Birth Order↗
PubMed1980

The handedness of rhesus monkeys. III. Consistency within and across activities.

The results of this study of the hand preferences of rhesus monkeys on three different tasks are threefold: (1) When retested on the same task at intervals exceeding one month virtually all individuals prefer the same hand as they did during the original test, (2) When retested on the same task, the strength of hand preference displayed by each individual is increased. (3) When tested on differing tasks, monkeys display little consistency in the laterality of hand preference or the strength of handedness expressed during different tasks. Many authors have concluded that the lack of obvious intertask consistency in the laterality of hand preference expressed by lower primates constitutes evidence for a corresponding lack of consistent laterality in the cerebral control of this behavior. This has led to them to conclude that cerebral dominance probably does not exist in these animals (Deuel, 1975; Warren, 1977). However, where data is available from the literature, including the present study, all reports show monkeys to more frequently prefer the same hand on all of the unimanual tasks they were given than would be expected by chance alone. This finding suggests that there is a weak tendency for consistent lateralization of hand usage in the monkey. Presumably, there is a corresponding predominance of the cerebral hemisphere contralateral to the preferred hand over its mate. Other studies consistent with the concept of cerebral predominance in the monkey were reviewed. These findings do not constitute evidence for cerebral dominance in the monkey akin to that found in man. They do suggest that when performing certain activities, monkeys may have one hemisphere predominant over the other even though the degree and laterality of predominance may vary greatly from one individual and task to another.

Animals↗
PubMed1986

The influences of handedness, sex, familial sinistrality and androgyny on language laterality, verbal ability, and spatial ability.

This study assessed possible influences of handedness, sex, familial sinistrality (FS), and self-rated androgyny on language laterality and on spatial and verbal test performances of 225 right-handers and 134 left-handers. Left-handers and right-handers performed differently on all tasks. Right-handers were significantly more lateralized on the language laterality task and were superior to left-handers on the spatial visualization task. Left-handers obtained slightly, but significantly, higher vocabulary scores. Androgyny had a significant main effect on spatial ability, the more androgynous subjects being superior. Androgyny also interacted with sex and FS factors on the spatial task. All in all, present result are consistent with the conclusion that each of the subject factors studied may prove to be of some relevance for a complete understanding of laterality and cognitive ability patterns.

Adolescent↗
PubMed1986

Handedness is not a unidimensional trait.

Most theories about the inheritance of hand preference assume that handedness is a unidimensional trait which forms a continuous distribution. This paper demonstrates that sampling a wide range of manual activities reveals dimensions of hand preference that are independent. 180 right handed and 110 left handed adults indicated their hand preference for 55 activities according to a five point scale. A Varimax Factor Analysis revealed four factors which accounted for 80 percent of the variance. Factor 3 was of special interest because it represented behaviors which rely upon the axial musculature and involve strength more than dexterity. Hand preference for items on this factor were less laterally biased than on factors which included such fine motor behaviors as writing or drawing. These results suggest that manual preference is governed by more than one neural system and that these systems may be independently lateralized.

Adolescent↗
PubMed1987

Spontaneous hand usage and handedness in a troop of baboons.

Hand usage was studied in a troop of 18 Guinea baboons (10 adults and 8 young) for spontaneous activities. Handedness was determined by an analysis of unimanual activities and bimanual asymmetric activities. The distribution of preferential biases gave 5 right-handers and 2 left-handers, other subjects being ambidextrous. Main effects were age related: the strength of the preference was greater for adults than for young; moreover, bimanual activities performed by the adult group were more asymmetric than those realized by the subgroup of young. Laterality thus appears to develop during ontogeny in baboons.

Aging↗
PubMed2000

Interhemispheric asymmetry of the human motor cortex related to handedness and gender.

Most people are right-handed, preferring the right hand for skilled as well as unskilled activities, but a notable proportion are mixed-handed, preferring to use the right hand for some actions and the left hand for others. Assuming a structural/functional correlation in the motor system we tested whether asymmetries in hand performance in consistent right and left handers as well as in mixed handers are associated with anatomical asymmetries in the motor cortex. In vivo MR morphometry was used for analyzing interhemispheric asymmetry in the depth of the central sulcus in the region of cortical hand representation of 103 healthy subjects. Subjects were tested both for hand preference and hand performance. As expected, left-right differences in hand performance differed significantly between consistent right, consistent left and mixed handers and were independent on gender. Male consistent right handers showed a significant deeper central sulcus on the left hemisphere than on the right. Anatomical asymmetries decreased significantly from male consistent right over mixed to consistent left handers. Sixty two per cent of consistent left handers revealed a deeper central sulcus on the right than on the left hemisphere, but for the group as a whole this rightward asymmetry was not significant. No interhemispheric asymmetry was found in females. Thus, anatomical asymmetry was associated with handedness only in males, but not in females, suggesting sex differences in the cortical organization of hand movements.

Adolescent↗
PubMed2003

Perceptual, affective, and cognitive judgments of odors: pleasantness and handedness effects.

The present study sought to examine the differential processing of pleasant, neutral, and unpleasant odors. The effects of the nostril stimulated (left or right) and the type of judgment (perceptual, affective, or cognitive) performed on the olfactory stimuli were also studied. To this end, 64 subjects were asked to smell pleasant, neutral, and unpleasant odors under four conditions (detection, intensity, pleasantness, and familiarity tasks). The participants were to perform these tasks as quickly as possible, while response times were recorded. The results showed that (i) unpleasant odors were assessed more rapidly than neutral or pleasant odors, and that this was specifically true (ii) during right nostril stimulation, and (iii) during pleasantness assessment, suggesting possible differential cerebral hemisphere involvement, with a right-side advantage for processing of unpleasant affect in olfaction. A handedness effect on familiarity judgment is also discussed.

Adult↗
PubMed2003

Development of handedness: comparison of questionnaire and performance-based measures of preference.

Hand preference has been assessed primarily using questionnaires. This approach is difficult to use with children so researchers have frequently used observation of hand choice when children pick up and use tools. Recently we developed such a performance-based measure, the WatHand Box Test (WBT). Participants ranging in age from 2 to 24 years each completed the WBT and the Revised Waterloo Handedness Questionnaire. Analyses revealed a strong preference for the right hand across all age groups on both tests with no significant differences across age and a significant correlation between the two measures. These findings do not concur with other work showing children younger than six years exhibited a much smaller right-hand preference. The concordance between these two preference measures is consistent with our previous findings. However, the relatively small common variance explained in this relationship suggests that these two tests may reflect somewhat different components of preference.

Adolescent↗
PubMed1999

Human taste cortical areas studied with functional magnetic resonance imaging: evidence of functional lateralization related to handedness.

Whole-brain functional magnetic resonance imaging was used to detect local hemodynamic changes reflecting cortical activation in five left handed and five right handed human subjects during bilateral stimulation of the tongue with various tastes. Activation was found bilaterally in the insula and the perisylvian region. These regions correspond to the primary taste cortical areas identified with electrophysiological recordings in monkeys and suggested from former clinical observations in human subjects. Moreover, a unilateral projection was described for the first time in the inferior part of the insula of the dominant hemisphere, according to the subject's handedness.

Adult↗
PubMed2000

Language lateralization and handedness in women prenatally exposed to diethylstilbestrol (DES).

Hand preferences and language lateralization were assessed in women exposed prenatally to the synthetic estrogen, diethylstilbestrol (DES), and in their unexposed sisters. The DES-exposed women showed an increased degree of hand preference (regardless of direction) and were more likely to be left handed for writing. However, the groups did not differ significantly on a dichotic listening measure of language lateralization. Perhaps as a result of the alterations in hand preferences, the typical relationship between hand preferences and language lateralization was disrupted in the DES-exposed group. Also, within the DES-exposed group, exposure early in gestation correlated with left handedness whereas exposure late in gestation correlated with reduced left ear (right hemisphere) scores on the verbal dichotic task. Results are discussed in terms of theoretical perspectives predicting hormonal influences on sexual differentiation of hemispheric asymmetry and in terms of separate critical periods for hormonal effects on individual sexually differentiated characteristics.

Adolescent↗
PubMed2003

Salivary testosterone is related to both handedness and degree of linguistic lateralization in normal women.

The aim of this study was to test the hypothesis that individual differences in testosterone (T) are associated with different patterns of linguistic lateralization and hand preference. Twenty left-handed (LH) and 19 right-handed (RH) women filled in a handedness questionnaire and performed a consonant-vowel dichotic listening test (DL-CV). Salivary T was measured by radioimmunoassay (RIA). LH women showed significantly lower mean salivary T than RH women. T levels were negatively correlated with the absolute value of the DL laterality index. Subjects with right ear advantage (REA) were classified into strongly and weakly lateralized following Wexler et al. method (Brain Lang. 13 (1981) 13). When taking into account hand preference, a pattern emerged in that RH-strongly lateralized and LH-weakly lateralized women showed similar T levels. The lowest level appeared for LH-strongly lateralized women and the highest for RH-weakly lateralized women, being significantly different from each other. The results are discussed in terms of several theories that have proposed a link between testosterone and cerebral lateralization.

Adult↗
PubMed2003

Perspectives on handedness, life and physics.

In contrast to motion, matter will be conserved in all eternity. Structure and function will arise by the angular momentum of spinning spherical particles and their composites. Symmetry prevails in physics by equal amounts of left- and right-hand spinning entities, while life is asymmetric in this respect. Very rare deviations from the ubiquitous one-sided handedness in biology will probably explain the inert degradation resistant proteins in 'mad cow' type diseases. Velocities of physical events seems to be a most important feature and will explain for instance brain function and the true nature of neurodegenerative diseases. This biophysics of mind will in turn provide answers to many disputable aspects of physics such as the true nature of waves and gravity. Many current concepts in quantum physics will be invalidated, among them the uncertainty principle, the relativity to a fixed speed of light, the energy equation and the expansion of the Universe. Instead, decay and formation will balance each other in a continuum of matter in an intuitively cyclic Multiverse.

Biochemical Phenomena↗
PubMed2004

Fetal sensitivity to testosterone, left-handedness and development of bronchial asthma: a new approach.

In contrast to Geschwind, Behan and Galaburda (GBG) theory, there is strong evidence that inheritance through maternal line is responsible for the coexistence of asthma and left-handedness early in childhood. A new model that incorporates GBG's theory and maternal inheritance is proposed. This hypothesis suggests that maternal atopy is the most important factor in the evolution of asthma and that GBG's theory applies mainly in childhood. An inherited enhanced sensitivity of fetus to testosterone may be the underlying mechanism that leads to the development of bronchial asthma.

Asthma↗
PubMed1996

Bony markers at the distal end of the radius for estimating handedness and radial length.

Measurements of the size of the bony markers at the distal end of the radius as well as the length of the radius in 61 left and 64 right dry radii were statistically analyzed. Since 90-95% of the general population is right-handed, as based on differences in the size of the right sided markers relative to the left, it is proposed that the greater distance between the dorsal tubercle and styloid process and the greater dorso-palmar diameter of the carpal articular surface opposite the dorsal tubercle are indicative of right-handedness. The length of the radius correlated with: the radio-ulnar transverse diameter at the distal end; the distance between the dorsal tubercle and the styloid process; the dorso-palmar diameter of the distal end opposite the dorsal tubercle; the dorso-palmar diameter of the carpal articular surface opposite to the dorsal tubercle; the dorso-palmar diameter of the distal end opposite the medial margin of the groove for the extensor pollicis longus; the dorso-palmar diameter of the distal end opposite the floor of the groove for the extensor pollicis longus and, finally, the height of the dorsal tubercle in relation to the posterior margin of the carpal articular surface (P < 0.001). Regression equations of the length of the radius for these markers have been derived.

Carpal Bones↗
PubMed2003

Magnetoencephalographic evidence of the interhemispheric asymmetry in echoic memory lifetime and its dependence on handedness and gender.

The echoic memory trace (EMT) refers to neuronal activity associated with the short-term retention of stimulus-related information, especially within the primary and association auditory cortex. Using magnetoencephalography it is possible to determine quantitatively the lifetime of the EMT. Previous studies assumed that each new stimulus drives the EMT to its full strength, which then passively decays. In this study we show the limitations of this assumption using trains of auditory stimuli designed specifically for computing the EMT lifetime and its contextual sensitivity. We estimated a time-dependent EMT using a data-driven approach, which allows contributions from a relatively wide area around the auditory cortex in our quantitative measures. We identified: (1) internally generated cortical activations during the silent period between stimuli well separated in time from each other, which had influence on the morphology of the neuromagnetic response to the next external stimulus; and (2) EMTs with different lifetimes that modulate the amplitude of the evoked responses at different latencies, suggesting the existence of multiple neural delay lines. Long EMT lifetimes were observed on the descending part of the M100 complex, which showed handedness and gender-dependent interhemispheric asymmetry. Specifically, all subjects showed longer EMT lifetimes on the left hemisphere, except left-handed males. Distributed source analysis of the data for one left- and one right-handed male subject identified a secondary generator in the right-handed subject, which was located posterior to the early primary generator and dominated the auditory response at late latencies, where EMT lifetime asymmetry was high. The identified multiple neural delay lines and their laterality may provide a link between macroneuronal activity and left hemisphere specialization for processing linguistic material.

Acoustic Stimulation↗
PubMed1999

On separating processes of event categorization, task preparation, and mental rotation proper in a handedness recognition task.

We investigated the nature of event-related potential (ERP) effects in a handedness recognition task requiring mental rotation. Thirty subjects were tested with rotated and sometimes reflected alphanumeric characters while ERPs were recorded from 18 electrodes. On each trial, a cue provided valid information about the angular displacement of the following probe. This design allowed a distinction between three processing episodes: evaluation of the difficulty of the forthcoming task, preparation for the task, and the mental rotation task itself. The three episodes were accompanied by distinct ERP effects having distinct polarities, a different rank order of amplitudes for different probe orientations, and a different topography. These data confirm previous findings showing that mental rotation is accompanied by a parietal negativity. However, they also suggest that the rotation-related negativity found after tilted stimuli in standard mental rotation tasks is most likely overlapping with another, simultaneously triggered ERP effect functionally related to an evaluation of task difficulty.

Adult↗
PubMed1980

Sex and handedness as factors in visual-field organization for a categorization task.

When right-handed males categorize faces presented in the right and left visual fields as male or female, a right visual-field advantage results. Subjects in the present study were divided on the basis of Annett's model according to sex and handedness, males and females, right-handers, nonfamilial left-handers, and familial left-handers. It was predicted that males would show a field advantage consistent with the cerebral hemisphere specialized for speech production (the left hemisphere in the case of right-handers and nonfamilial left-handers, and the right hemisphere in the case of familial left-handers). It was also predicted that females would be either weakly or inconsistently lateralized. A signal-detection paradigm in general confirmed these predictions. It was also shown that a subject's ability to change decisional criteria appropriately over trials was a function of visual field for both males and females. Decision making over time may therefore reveal a fundamental duality distinguishing the cerebral hemispheres in both sexes. Some of the implications of these results are discussed.

Discrimination Learning↗