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PubMedDate not supplied

Significance of abnormalities in developmental trajectory and asymmetry of cortical serotonin synthesis in autism.

The role of serotonin in prenatal and postnatal brain development is well documented in the animal literature. In earlier studies using positron emission tomography (PET) with the tracer alpha[(11)C]methyl-l-tryptophan (AMT), we reported global and focal abnormalities of serotonin synthesis in children with autism. In the present study, we measured brain serotonin synthesis in a large group of autistic children (n = 117) with AMT PET and related these neuroimaging data to handedness and language function. Cortical AMT uptake abnormalities were objectively derived from small homotopic cortical regions using a predefined cutoff asymmetry threshold (>2 S.D. of normal asymmetry). Autistic children demonstrated several patterns of abnormal cortical involvement, including right cortical, left cortical, and absence of abnormal asymmetry. Global brain values for serotonin synthesis capacity (unidirectional uptake rate constant, K-complex) values were plotted as a function of age. K-complex values of autistic children with asymmetry or no asymmetry in cortical AMT uptake followed different developmental patterns, compared to that of a control group of non-autistic children. The autism groups, defined by presence or absence and side of cortical asymmetry, differed on a measure of language as well as handedness. Autistic children with left cortical AMT decreases showed a higher prevalence of severe language impairment, whereas those with right cortical decreases showed a higher prevalence of left and mixed handedness. Global as well as focal abnormally asymmetric development in the serotonergic system could lead to miswiring of the neural circuits specifying hemispheric specialization.

Adolescent↗
PubMed2005

A survey of left-handed helices in protein structures.

All naturally occurring amino acids with the exception of glycine contain one or more chiral carbon atoms and can therefore occur in two different configurations, L (levo, left-handed) and D (dextro, right-handed). Proteins are almost exclusively built from L-amino acids. The stereochemical bias of nature is further reflected at the secondary structure level where right-handed helices are strongly preferred over left-handed helices. The handedness of helices has not received much attention in the past and is often overlooked during the analysis, description and deposition of experimentally solved protein structures. Therefore, an extensive survey of left-handed helices in the Protein Data Bank (PDB) was undertaken to analyse their frequency of occurrence, length, amino acid composition, conservation and possible structural or functional role. All left-handed helices (of four or more residues) in a non-redundant subset of the PDB, were identified using hydrogen-bonding analysis, comparison of related structures, and experimental electron density assessment to filter out likely spurious and artefactual hits. This analysis yielded 31 verified left-handed helices in a set of 7284 proteins. The phi angles of the residues in the left-handed helices lie between 30 degrees and 130 degrees and the psi angles lie between -50 degrees and 100 degrees . Most of the helices are short (four residues) and for 87% of them, it was possible to determine that they are important for the stability of the protein, for ligand binding, or as part of the active site. This suggests that, even though left-handed helices are rare, when they do occur, they are structurally or functionally significant. Four secondary structure assignment programs were tested for their ability to identify the handedness of the helices. Of these programs, only DSSP correctly assigns the handedness.

Amino Acid Sequence↗
PubMed2006

Color of illumination during growth affects LHCII chiral macroaggregates in pea plant leaves.

To determine whether the color of illumination under which plants are grown, affects the structure of photosynthetic antennae, pea plants were grown under either blue-enriched, red-enriched, or white light. Carotenoid content of isolated chloroplasts was found to be insensitive to the color of illumination during growth, while chlorophyll a/b ratio in chloroplasts isolated from young illuminated leaves showed susceptibility to color. Color of illumination affects the LHCII chiral macroaggregates in intact leaves and isolated chloroplasts, providing light-induced alteration of the handedness of the LHCII chiral macroaggregate, as measured with circular dichroism and circularly polarized luminescence. The susceptibility of handedness to current illumination (red light excitation of chlorophyll fluorescence) is dependent on the color under which the plants were grown, and was maximal for the red-enriched illumination. We propose the existence of a long-term (growth period) color memory, which influences the susceptibility of the handedness of LHCII chiral macroaggregates to current light.

Cell Aggregation↗
PubMed1999

Hand preference and transcranial magnetic stimulation asymmetry of cortical motor representation.

Human handedness may be associated with asymmetry in the corticospinal motor system. Previous studies measuring the threshold for eliciting motor evoked potentials (MEPs) to transcranial magnetic stimulation (TMS) have provided evidence consistent with this hypothesis. However, TMS asymmetry observed in previous studies may have reflected cortical or spinal differences. We therefore undertook this investigation to test the hypothesis that handedness is associated with asymmetry in cortical motor representations. We used TMS to map contralateral cortical motor representations of the right and left abductor pollicis brevis (APB) and flexor carpi radialis (FCR) muscles in nine normal subjects (three left-handed). Using focal stimulation with a figure-of-8 shaped magnetic coil, we found no differences in MEP threshold or MEP size between the preferred and the nonpreferred hand. However, we observed that the number of scalp stimulation sites eliciting MEPs was statistically greater for APB and FCR muscles of the preferred limb. We found significant asymmetry between right-handed and left-handed subjects, such that in right-handers, the representation of the right APB was larger than that of the left APB, but in left-handers the representation of right APB was smaller than that of the left APB. These results suggest that handedness is associated with asymmetry in cortical motor representation.

Adult↗
PubMed1992

Brain correlates of hand dominance: the association between peripheral and cerebral asymmetries revisited.

Measures reflecting central processing of somatosensory stimulation were recorded in left- and in right-handed subjects in order to evaluate differences between the two handedness groups in the vertical, rather than lateral, axis of processing. Somatosensory evoked potentials were recorded in left- and right-handers following electrical stimulation of the median nerve at the wrist. The relative vertical balance of processing was probed by comparing the amplitudes of the underlying activity in early evoked potentials, presumably originating subcortically, with later, cortically originating potentials. Central conduction time (CCT) of the sensory volleys was also recorded. The data revealed higher amplitude ratios (ARs) between subcortical and cortical potentials, as well as shorter CCTs, in left-handers. These results demonstrate that transmission differences between the handedness groups may occur early in central nervous system (CNS) conductance. The results are further discussed in light of evidence suggesting that stronger reliance on a subcortical mode of processing may underlie phenomenon of left-handedness.

Adolescent↗
PubMed1993

Factor analyses of pooled hand questionnaire data are of questionable value.

A number of researches have used factor analyses and principal components analyses on handedness questionnaire data in order to learn something about handedness. However, these researchers have analyzed pooled data from righthanders and lefthanders. The practice of pooling groups that are known in advance to be heterogeneous is highly questionable because it is not possible to disentangle the sources of variance that are contributed by within group differences from those that arise from between group differences. The factor structure and item loadings that result from pooled data are misleading and cannot inform meaningfully about the relation of hand preference to handedness. Similar problems can be anticipated in other neuropsychological applications of factor analysis, where data from heterogeneous groups is pooled.

Adult↗
PubMed1975

Hand preference and the laterality of cerebral speech.

A theory of the origins of hand preferences (Annett, 1972) is outlined and its implications for the distribution of cerebral speech in handedness groups are examined. Five studies of dysphasia in right and left handers with unilateral cerebral lesions are compared and found surprisingly consistent. Data from three series found alike in all essential respects are combined to give a substantial number of cases with which to test the expectations of the theory. The agreement is close enough to justify a reconsideration of the model in the light of the evidence and also an analysis of possible reasons for the main differences between series. In spite of the many uncertainties involved in inferences from dysphasia to cerebral speech laterality, it is concluded that the evidence is strong enough to offer a useful test of hypotheses as to the distribution of cerebral speech in handedness groups. Other questions bearing on handedness and cerebral speech are briefly considered in order to show the explanatory range and power of the theory.

Aphasia↗
PubMed1977

Failure to confirm a spatial ability impairment in persons with evidence of right hemisphere speech capability.

Levy hypothesized that persons lacking strict left hemispheric dominance for language processing should be impaired in spatial processing ability. This leads to the expectation that left-handers, because they are more often not strictly left hemisphere dominant for language, would, as a group, be impaired in spatial ability relative to right-handers. Evidence regarding this hypothesis has been inconsistent. The present study systematically examined the effects of handedness, sex, and hemispheric language dominance on verbal and spatial ability in 80 right-handed and 71 left-handed university students. Males were found to be superior to females in all handedness-hemispheric language dominance groups on the spatial ability measure. No effects of handedness or hemispheric lanaguage dominance nor interactions of these factors obtained for either verbal or spatial ability measures. It was concluded that the hypothesis of verbal-spatial processing incompatibility within the same hemisphere was not supported.

Dominance, Cerebral↗
PubMed1980

Subject variables and cerebral organization for language.

The present study investigated the usefulness of a variety of subject variables that have been proposed as having predictive value for determining cerebral organization for language. To accomplish this, a total of 373 subjects (117 left-handers and 256 right-handers) were given 240 trials of a consonant-vowel dichotic listening task to assess direction and degree of language lateralization. Each subject was also classified on the basis of eight subject variables (handedness, strength of handedness, familial sinistrality, writing hand posture, sex, sighting dominance, preferred footedness, and overall laterality). The results of the study indicated that left hemisphere language processing is very pervasive and that most of the subject variables examined were not very useful predictors of language lateralization. In addition, surprisingly, footedness and not handedness was the single best predictor of cerebral organization for language.

Adolescent↗
PubMed1988

Correlates of the dichotic right-ear effect.

A total of 302 subjects were tested on a verbal dichotic listening task and a variety of measures related to lateralization, including familial sinistrality, sighting eye dominance, handwriting position, and arm folding behavior. The majority of these subjects were more accurate on the right ear in the dichotic testing, and this right-ear advantage (REA) was correlated with handedness. handwriting position, arm folding, and familial sinistrality (FS), considered in isolation, were not able to improve the prediction of the REA. There was, however, a significant effect of sighting eye, and in interaction between handedness, sighting eye and FS. Left-eyes subjects, regardless of handedness, showed weaker REAs than right-eyed subjects. This effect was most obvious in FS--right-handers and in FS+ left-handers. These data suggest that knowledge of sighting eye dominance may assist in the prediction of cerebral lateralization of language functions.

Analysis of Variance↗
PubMedDate not supplied

Evidence for anomalous lateralization across domain in ADHD children as well as adults identified with the Wender Utah rating scale.

Two studies assessed the relation between ADHD symptomatology and correlates of cerebral dominance. In the first, laterality was examined in school children (N=57), 28 with ADHD. Parental reports of greater attentional symptoms were related to non-righthandedness, but teacher reports were related to anomalous laterality of foot, ear and eye, as well as hand. This suggests that the previously reported association between ADHD and non-righthandedness may not be unique, but instead indicative of a more general condition of anomalous lateralization. This possibility was examined in study two, in which 234 undergraduates were assessed. As expected, the 26 adults identified by the Wender Utah Rating Scale (WURS) as retrospectively reporting more ADHD characteristics were found to be generally male. Also, in a replication of study one, enhanced WURS scores were associated with anomalous lateralization beyond handedness. In this case, ADHD characteristics were associated with a shift away from a right bias for hand, foot, and ear, but not eye. Factor analysis of the extensive Steenhuis and Bryden handedness questionnaire was then undertaken to determine whether all aspects of handedness, or only a subset, are associated with ADHD. The factor analysis indicated that the retrospective reports of ADHD characteristics were associated with only two of the three dimensions. Though limitations such as the gender composition of the groups in study one tempers the conclusions, the results of both studies support previous findings that ADHD is associated with anomalous laterality, but also indicate that non-righthandedness is not an adequate characterization of this relationship.

Adult↗
PubMed2002

Motor control and cerebral hemispheric specialization in highly qualified judo wrestlers.

With the purpose of investigating motor and cognitive lateralization profiles associated with long-term motor training, we investigated differences in hemispheric specialization between proficient judo sportsmen and controls through the assessment of a number of handedness and footedness items including postural preferences as well as dichotic listening and lateralized visual field tests. Our data show that: (1) the different handedness and footedness items did differently relate to each other within the athlete and control groups as revealed by a principle component analysis (PCA); (2) stand side correlated differently to these motor profile factors in athletes and controls; (3) athletes preferred more frequently to perform certain movements with the left hand than controls, although overall right-handed; (4) this was especially true for athletes which proved to be most proficient/skilled; and (5) in a lateralized verbal listening task and a lateralized visual field task athletes revealed enhanced right-hemispheric involvement relative to controls. Our results suggest that during motor and postural skill acquisitions (long-term judo training) lateral preferences are modified, probably due to neuroplasticity. Moreover, the present findings support the multidimensional view of handedness by Steenhuis and Bryden [Cortex 25 (1989) 289] and the notion of a right-hemispheric "praxis system" involved in skilled action routines within peripersonal space [Brain and Cognition 23 (1993) 181].

Adolescent↗
PubMed1998

Bilateral electrodermal activity: relationships to state and trait characteristics of hemisphere asymmetry.

Influences of trait and state characteristics of individual brain lateralization on bilateral electrodermal activity (EDA) were examined. EDA was observed in two different recording conditions: (1) non-specific skin conductance responses (ns.SCRs) were obtained during a stimulus-free recording period of 5 min; and (2) stimulus evoked skin conductance responses (SCRs) were elicited by 80 dichotically presented pairs of pure tones which--at the same time--constituted the items of a test to estimate subject's lateral ear dominance. In addition to ear dominance, degree of right-handedness and hemispheric preference, i.e. preferred direction of conjugate lateral eye movements (CLEMs) were assessed as trait-like characteristics of individual laterality. With respect to asymmetry of ns.SCRs, no effects of the laterality variables were observed. Analysis of SCRs, however, resulted in significant interactions of ear dominance and hemispheric preference with degree of right-handedness indicating higher SCR amplitudes on the hand contralateral to the preferred hemisphere in strong dextrals. Weak right-handers showed a different pattern of bilateral asymmetries, partly in the opposite direction. Additionally, phasic effects of cortical asymmetry on SCRs seem to be modified by trait characteristics of individual laterality. Results underline the importance of precisely controlling degree of handedness in studies of bilateral electrodermal activity. Furthermore, the observed effects support the assumption of cortical influences on EDA, but argue against the existence of a single cortical mechanism modulating asymmetries in the electrodermal system.

Adolescent↗
PubMed1999

Asymmetric leg activity in healthy subjects during walking, detected by electrogoniometry.

AIM: To show asymmetric leg activity during walking in healthy subjects. DESIGN: Two electrogoniometers were used to measure the amplitude of the flexion-extension movements of both knees during walking. BACKGROUND: Walking is considered to be a symmetrical activity. Quantitative studies of walking often only consider one side of the body or remove differences between individuals by averaging results. METHODS: The handedness, lateral eye dominance and footedness of 31 healthy subjects were determined. A strain gauge electrogoniometer was then fitted to the outside of each knee to analyze the flexion-extension movements. The results were recorded automatically. The subject walked a distance of 30 m three times, with different attention levels: free walking (with no other task assigned), walking with attention diverted (whilst performing a mental task), and focused walking (walking as straight as possible in a straight line). RESULTS: 51.6% of the subjects tested displayed asymmetry of the total flexion-extension movement of more than 5 degrees between the two knees during free walking. The side favored (preponderance) by this asymmetry was not related to the handedness or other lateral dominance. The different attention levels did not significantly affect the characteristics of motion of the sub-groups studied (symmetric, right-favoring and left-favoring). CONCLUSIONS: The origin of this asymmetry, which is independent of handedness or attention level, could be the spinal stepping generator for which there is evidence in both animals and humans. Walking should not be considered to be a strictly symmetrical phenomenon. RELEVANCE: The demonstration of asymmetric leg activity during walking may lead to a better understanding of the way in which walking controlled. The presence of such asymmetry is normal, and it should be borne in mind during explorations of walking in both healthy and pathologic individuals.

Adult↗
PubMed2000

M and P double helical complexes of copper(I) with bis-imino bis-quinoline enantiomerically pure chiral ligands.

The enantiomerically pure bis-imino bis-quinoline ligands R,R-ImQ and S,S-ImQ have been prepared by Schiff condensation of 2-quinoline carboxyaldehyde with the pure R,R and S,S enantiomers of trans-1,2-diaminocyclohexane. Both ligands form 2:2 helical complexes with CuI perchlorate, and the crystal and molecular structure of [Cu2(R,R-ImQ)2]ClO4.H2O have been determined by X-ray diffraction methods: the [Cu2(R,R-ImQ)2]2+ molecular cation is a chiral double helix of M handedness, in which the two ligands are entertwined in such an arrangement that half of each ligand is not equivalent to the other half of the same ligand. Coupled circular dichroism and 1H NMR studies reveal that in CH3CN solution a rearrangement takes place toward a more symmetric helical structure (in which the two halves of the same ligand become equivalent), which maintains the same handedness found in the solid state and is a pure M isomer. Solid state and CH3CN solution CD experiments confirm that [Cu2(S,S-ImQ)2]ClO4.H2O, both in solution and in the solid state, is a pure double helix of P handedness, i.e., the enantiomer of the species containing the R,R ligand.

Journal Article↗
PubMed2001

The use of bouts and frequencies in the evaluation of hand preferences for a coordinated bimanual task in chimpanzees (Pan troglodytes): an empirical study comparing two different indices of laterality.

Hand preferences for a coordinated bimanual task were assessed in 109 chimpanzees (Pan troglodytes). Hand preference was evaluated for 4 test sessions using bouts and frequencies of hand use to compare the sensitivity of each level of analysis in evaluating individual variation in handedness. Overall, significant population-level right-handedness was found using several different measures of hand use. Handedness indices based on bouts and frequencies were highly and significantly correlated. Moreover, hand preferences were consistent across tests despite efforts to situationally bias preference during each test. Taken together, these data do not support the view that bouts are a better level of analysis for evaluating hand preference. The results further suggest that hand preferences for coordinated bimanual actions are not influenced by situational factors and may reflect an inherent specialization of the left hemisphere for motor skill.

Animals↗
PubMed1993

Postural effects on manual reaching laterality in squirrel monkeys (Saimiri sciureus) and cotton-top tamarins (Saguinus oedipus).

Squirrel monkeys (Saimiri sciureus) and cotton-top tamarins (Saguinus oedipus) made unimanual food reaches from either a horizontal, quadrupedal posture or a vertical, clinging posture. No population-level handedness occurred in either species. However, in both species, directional lateral preferences weakly expressed for reaching from the stable quadrupedal posture were intensified in the vertical cling posture. This phenomenon, which we designate as soft handedness, may have been an evolutionary precursor to population-level handedness. Right or left turning by the squirrel monkeys before reaching closely predicted use of the right or left hand. However, the magnitude of the association decreased in the more highly lateralized vertical cling condition. This result suggests that as lateral hand preference increases, hand use may become increasingly independent of constraints from prior behavioral and environmental influences.

Animals↗
PubMed1995

Laterality in hand preferences and reaching accuracy of cotton-top tamarins (Saguinus oedipus).

Manual laterality of cotton-top tamarins (Saguinus oedipus) was observed for five different types of reaching. The tamarins displayed species-level right-handedness for spontaneous grasping for food but not for one-arm vertical suspension or any of 3 other types of elicited reaching. The results showed that difficult or novel tasks are neither necessary nor sufficient for the emergence of species-level handedness. Accuracy in retrieving food from a rotating platform was greatest (a) for highly lateralized tamarins, (b) when the preferred hands were used for reaching, (c) for young tamarins, and (d) when the tamarins stood on a narrow, unstable platform instead of a wide, stable one. The results suggest that evolution of species-level handedness is dependent on prior natural selection for increased manual performance that accompanies strongly lateralized hand preferences.

Animals↗