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PubMed1992

The roles of handedness and stimulus asymmetry in aesthetic preference.

When some pictures are mirror reversed, aesthetic evaluations of them change dramatically. Stimulus features that may be important in contributing to this effect are: (a) location of areas of principal interest or weight in the picture space, (b) cues that suggest a direction of motion within the picture. Dextrals and inverted sinistrals preferred paintings with cues suggesting motion proceeding from left to right over their mirror-reversed versions and also preferred those with weight concentrated in the left portions of the picture space. The explanation that best fits these data is that preference is promoted when the picture content encourages attention to its rightmost portions, thus placing a majority of the picture in the left visual field where it is directly processed by the right hemisphere.

Adult↗
PubMed1987

Asymmetries of nature and the origin of biomolecular handedness.

New developments in the problem of the origin of the asymmetry of the living systems are reviewed. The time of the appearance of the asymmetry was very probably during the chemical evolution. The asymmetry of weak interaction is still considered small to be the cause of chiral purity. New sources of asymmetry should also be considered, like the one proposed by Gilat.

Biological Evolution↗
PubMed1987

Parity violation and the origins of biomolecular handedness.

The violation of parity by the weak interactions ensures that enantiomeric chiral molecules have inequivalent energies, one being inherently stabilized with respect to the other. These parity-violating energy differences have been calculated for a number of fundamental biomolecules including a series of alpha-amino acids, polypeptide structures, and a representative of the sugar series together with its variation over a possible prebiotic reaction path leading to alpha-amino acids. In each case the natural enantiomer found in terrestrial biochemistry was shown to be intrinsically stabilized and preferred over its unnatural enantiomer. The significance of these results in accounting for the prebiotic origins of the terrestrial biomolecular homochirality is discussed and the possible consequences of parity-violating energy differences in mineral catalysts during the prebiotic era considered.

Amino Acids↗
PubMed1990

Left-handedness in homosexual men and women: neuroendocrine implications.

Although numerous researchers have hypothesized a biological factor in the etiology of homosexuality, there is a lack of empirical evidence. Previous investigations did not focus on behavioral functions of the brain. Using neuropsychological testing, we found an increased incidence of left-hand preference (defined as non-consistent right-hand preference) in a group of 32 homosexual women. A trend in the same direction was found in a group of 38 homosexual men. These results suggest that homosexual orientation has a neurobiological component possibly related to hemispheric functional asymmetry. The results are consistent with previous reports that (1) prenatal neuroendocrine events are a factor in the development of human sexual orientation and functional brain asymmetries, and (2) the mechanisms associated with homosexual orientation and related neuropsychological characteristics are different between the sexes, i.e. elevated levels of prenatal sex hormones in women and decreased levels in men.

Adult↗
PubMed1991

On the handedness of the scaffolds of sister chromatids.

We discuss a mechanical model for the mirror-symmetric inversion of the scaffold's helicity of replicated chromatids vis-a-vis that of their templates. The paper ends with comments on the orientability of certain genes and on the effects of such topologies upon (a)symmetric gene expression, in general. Our model and its generalizations apply only to the special subclass of 'coiled' chromatids whose statistical distribution in the genome of normal and of malignant cells is not known precisely.

Biomechanical Phenomena↗
PubMed1995

Correlates of left-handedness in a large sample of schizophrenic patients.

Questionnaire data concerning hand preference from the parents of 686 schizophrenic patients were used to test predictions relevant to neurodevelopmental models of schizophrenia. In line with predictions, left-handed patients (n = 94) had a more frequent history of difficult birth, more childhood cognitive and behavioural abnormalities and more persistent auditory hallucinations than did right-handed patients.

Adolescent↗
PubMed2006

Handedness effects on interhemispheric transfer time: a TMS study.

The crossed-uncrossed difference (CUD) estimates the interhemispheric transfer time (ITT) through the corpus callosum. Previous research has shown that transcranial magnetic stimulation (TMS) to the occipital cortex determines an increased CUD during cognitive tasks. The aim of the present study was to investigate whether TMS stimulation applied at a motor stage can interfere with the ITT, comparing the performance of left- and right-handed people. Results showed a significant TMS effect, i.e. increasing reaction times were reported when stimulation was delivered on the left primary motor area. Effects were more evident when information was primarily perceived through the dominant hemisphere. Both left and right stimulations increased CUD times in right-handed subjects; however, left-handed subjects showed significant effects associated with left stimulation only. Furthermore, in both groups, TMS produced larger effects in the crossed than in the uncrossed condition. TMS stimulation increased reaction times, thus supporting the idea that the interhemispheric transfer of visuo-motor information occurs at a motor processing stage. The dominant hemisphere seems to play a major role within this process: our data indicates that left- and right-handed people have different ITT latencies associated with the transfer of information to the contralateral hemisphere.

Adult↗
PubMed2004

Handedness, hemispheric asymmetries, and joke comprehension.

To address the impact of differences in language lateralization on joke comprehension, event-related brain potentials (ERPs) were recorded as 16 left- and 16 right-handed adults read one-line jokes and non-funny control stimuli ("A replacement player hit a home run with my girl/ball,"). In right-handers, jokes elicited a late positivity 500-900 ms post-stimulus onset that was largest over right hemisphere (RH) centro-parietal electrode sites, and a slow sustained negativity over anterior left lateral sites. In left-handers, jokes elicited a late positivity 500-900 ms post-onset that was larger and more broadly distributed than in the right-handers' ERPs. In right-handed women, the late positivity was larger over RH electrode sites. In left-handed women, the late positivity was bilaterally symmetric. The highly asymmetric slow sustained negativity over left anterior electrode sites was absent from left-handers' ERPs to jokes. Differences may reflect more efficient inter-hemispheric communication in the left-handers, as they are reputed to have relatively larger corpus callosal areas than right-handers. Results support the portrait of more bilateral language representation among left-handers, and suggest language lateralization affects high-level language comprehension tasks such as joke comprehension.

Adolescent↗
PubMed2004

Choosing sides: lateralization in line trisection and quadrisection as a function of reading direction and handedness.

It might be intuited that a person's reading direction will impact linguistic and/or oculomotor tasks. Whether it also influences nonlanguage tasks, and by what means, is less clear. A novel technique to probe this effect is introduced in this paper, and the affirmative results are presented. The line bisection task has been a standard bedside diagnostic technique for assessing hemifield spatial neglect for many years. In recent years, numerous studies have also examined how normal subjects perform on this task. A recent line of study has focused on the reading habits of the subjects and the effect it has on line bisection. Most European languages are read from left to right, and it is thus postulated that readers of those languages will scan a line from left to right. On the other hand, Hebrew is read from right to left. These previous studies have yielded intriguing results about the role that reading direction plays in nonlanguage tasks. The present study utilized two other line partition tasks, line trisection and line quadrisection, and subjects whose principal reading language was either right-to-left or left-to-right. These tasks are ambiguous when used without instructing the subject on which side to perform the line transection. It was found that principal language was correlated with the side on which the subject chose to trisect or quadrisect the line. However, there was no correlation between preferred side and writing hand and there was no significant difference in accuracy between the preferred side and the secondary side. Thus, the preferred side in this nonlanguage task does not seem to be influenced by writing hand or accuracy but rather would seem to depend exclusively upon the earliest legitimate point, as determined by reading direction.

Adult↗
PubMed2006

The effect of handedness on electromyographic activity of human shoulder muscles during movement.

The aim of the study was to investigate whether there was a difference in the electromyographic (EMG) activity of human shoulder muscles between the dominant and nondominant side during movement and to explore whether a possible side-difference depends on the specific task. We compared the EMG activity with surface and intramuscular electrodes in eight muscles of both shoulders in 20 healthy subjects whose hand preference was evaluated using a standard questionnaire. EMG signals were recorded during abduction and external rotation. During abduction, the normalized EMG activity was significantly smaller on the dominant side compared to the nondominant side for all the muscles except for infraspinatus and lower trapezius (P <or= 0.002). In contrast, during external rotation, higher EMG activity was seen in the supraspinatus, infraspinatus, lower and upper trapezius and latissimus muscles of the dominant side (P <or= 0.01). We demonstrated a side-difference in shoulder muscle activity, which was dependent on the type of motion carried out, suggesting a qualitative difference in the activation of muscles during the two types of movement. Dynamic abduction has the characteristics of a dominant arm task (i.e., task performed almost exclusively by the dominant arm) and reduced muscle activity for the dominant side during abduction indicates a dominance-related advantage in arm dynamics.

Adult↗
PubMed2005

Episodic odor memory: influences of handedness, sex, and side of nose.

It is not known whether, or to what degree, odor memory is influenced by lateralized brain processes. In this study, we administered a 12-item match-to-sample odor memory test separately to the left and right sides of the nose of 30 left- and 30 right-handed subjects of equivalent age, sex distribution, and overall general smell ability. For each test item, one of three delay intervals (10-, 30-, and 60-s) was interspersed between smelling the target stimulus and smelling the first of four response alternatives. Women, but not men, performed significantly better on the left than on the right side of the nose, conceivably reflecting greater reliance upon left-hemisphere semantic processes. Subjects who received the first test on the right side of the nose outperformed those who received the first test on the left side of the nose. As in previous work, an age-related decrement in odor memory test scores was present. These data contribute to the debate on the role of lateralized brain processes in episodic odor memory, and suggest that performance on a standardized match-to-sample odor memory task is influenced by a number of interacting factors.

Adult↗