Directional Asymmetry

""Scoliotic vertebrae display asymmetric morphology. Previous research has remarked on the presence of this asymmetry, but it has not yet been quantified. The aim of this study was to produce a quantitative method by which to diagnose scoliotic vertebral asymmetry and compare that method to morphological observations that are currently used to diagnose scoliosis in archaeological human remains. This was done in order to determine a quantitative method is viable in the context of time and effort. Transitional vertebrae (C1, C2, C7, T1, T2, T11, T12, L1, L2) of 74 individuals (666 vertebrae total) from five archaeological sites in the UK were analysed for asymmetry using sliding caliper linear measurements developed for this research. Asymmetric morphology considered suggestive of scoliosis was observed in 10 of the measured individuals for comparison. Intra- and inter-observer error, normality, outlier tests, multiple ANOVAs and test of directional asymmetry were applied to the data. Results indicate that patterns of asymmetry scores reflect the previously reported normal asymmetry observed by clinicians. The measurements were accurate but difficult to repeat by other observers. Though sample size was small, a baseline of normal asymmetry was determined, and scoliosis was detected most often as outliers over two standard deviations from the mean."

© 2009 Hallie M. Smith. Do not cite without permission"

An ethnically homogeneous group of Yakuts (Mongoloid race, Northeast Asia), aged 18-31, was studied to characterize the diversity of particular features between left-and right-handed individuals. A total of 52 left-handed (32 women and 20 men) and 100 right-handed (50 women and 50 men) individuals were studied. Testing included two sets of questions and tasks, dynamometry of the right and left hand, and fingerprint analysis. Left-handed and right-handed people were found to differ in functional asymmetry of psychophysiological and motor reactions. Right-handers were characterized by higher intragroup similarity, while, among left-handers, greater dispersion of these traits was observed. Asymmetry in hand grip strength was less pronounced in the left-handed people than in the right-handed; this difference was statistically significant, and the difference was greater in men than in women. This suggests that the non-dominant hand in the left-handed people was subjected to a greater load and indicates the forced adaptation of the left-handed people to "dextrastress". No significant difference between sexes was found when analyzing fingerprint patterns. Left-handers had arches significantly more often than right-handers. Radial loops were most often found on the index finger, and, in the left-handers, their occurrence was significantly higher on three to five fingers of the left hand compared with the right-handers. The levels of fluctuating asymmetry in left-handers and right-handers were similar.

During large-scale examinations of male genitalia for taxonomic studies of Sericini chafers (Coleoptera: Scarabaeidae), we have found that reversals of directed left–right (LR) asymmetry in male copulatory organs are compared to other insects not common. However, such inversions do occur occasionally and they must be considered a significant ‘source of error’ in taxonomic studies. Our data indicate asymmetry reversal of male genitalia affects only the abdominal segments (genitalia) as changes in asymmetric structures of the head and thorax were not observed. Based on these observations, we believe that this partial abdominal LR asymmetry reversal of terminalia could be due to a local change in the polarity determining LR patterning in the growth zone of posterior abdominal segments as development of these segments begins.Bei umfangreichen Genitaluntersuchungen für taxonomische Studien an Sericini (Coleoptera: Scarabaeidae) konnten wir feststellen, dass Umkehrungen der Links-Rechts-Asymmetrie im männlichen Kopulationsapparat, verglichen mit anderen Insektengruppen, nicht selten auftreten. Auch wenn diese Umkehrungen nicht regelmäßig vorkommen, so sind sie doch als wichtige mögliche Fehlerquelle bei taxonomischen Untersuchungen zu betrachten. Unsere Ergebnisse belegen, dass die Asymmetrie-Umkehr nur die abdominalen Segmente (Genitalien) umfasst, da Veränderungen an asymmetrischen Strukturen von Kopf und Thorax nicht beobachtet wurden. Aufbauend darauf glauben wir, dass diese partielle Links-Rechts-Asymmetrie-Umkehr der Terminalia auf eine lokale Veränderung der LR Polarität in der Wachstumszone der posterioren Abdominalsegmente bei Beginn ihrer Ausbildung zurückgeführt werden muss.

Morphometric studies often consider parts with internal left-right symmetry, for instance, the vertebrate skull. This type of symmetry is called object symmetry and is distinguished from matching symmetry, in which two separate structures exist as mirror images of each other, one on each body side. We explain a method for partitioning the total shape variation of landmark configurations with object symmetry into components of symmetric variation among individuals and asymmetry. This method is based on the Procrustes superimposition of the original and a reflected copy of each landmark configuration and is compatible with the two-factor ANOVA model customary in studies of fluctuating asymmetry. We show a fully multivariate framework for testing the effects in the two-factor model with MANOVA statistics, which also applies to shapes with matching symmetry. We apply the new methods in a small case study of pharyngeal jaws of the Neotropical cichlid fish Amphilophus citrinellus. The analysis revealed that the symmetric component of variation in the pharyngeal jaws is dominated by the contrast between two alternative trophic morphs in this species and that there is subtle but statistically significant directional asymmetry. Finally, we provide some general recommendations for morphometric studies of symmetric shapes.

Domestic cattle possess lateralized cognitive processing of human handlers. This has been recently demonstrated in the preference for large groups of cattle to view a human closely within the predominantly left visual field. By contrast, the same stimulus viewed predominantly within the right visual field promotes a significantly greater frequency of dispersal from a standing position, including flight responses. The respective sets of behaviours correspond with the traditional terms of “near side” for the left side of cattle and horses, and the “off” or “far side” for the right side. These traditional terms of over 300 years usage in the literature communicate functional practicalities for handling livestock and the recognition of lateralized cognitive processing. In this review, the possibility of even earlier recognition and the significance of laterality in cattle-human interaction was argued, from the earliest representations of the letter A a, originally illustrated ...

To report the relationship between infantile esotropia and asymmetry of monocular pursuit tracking. Observational family case series. A twin pair discordant for infantile esotropia was confirmed by DNA analysis to be monozygous at 99.95% probability. Digitally sampled electro-oculographic recordings of monocular horizontal pursuit eye movements were performed for the twins and their orthophoric father. Mean directional asymmetry for right and left eyes was 31% and 5% for the esotropic twin, 10% and 8% for the orthophoric twin, and 5% and 6% for the father. The asymmetry was statistically significant only for the deviating right eye of the esotropic twin (P = 0.0217). In this family, monocular pursuit asymmetry is probably not a heritable predisposition to infantile esotropia, but a consequence of early strabismus. Discordance of infantile esotropia and pursuit asymmetry in monozygous twins implicates environmental in addition to genetic causes.

The 2nd–4th finger length ratio (2D: 4D) shows robust sexual dimorphism, with lower ratios evident in men compared to women. Several lines of evidence suggest that this sex difference is due to variable exposure to prenatal sex steroids in utero. Although not tested sufficiently, it has been suggested that 2D: 4D may relate to sexual behaviour indices, in particular the number of sexual partners. However, this study did not find any significant relations between 2D: 4D and number lifetime opposite-sex and same-sex partners in 159 ...

Many properties of organisms show great robustness against genetic and environmental perturbations. The terms canalization and developmental stability were originally proposed to describe the ability of an organism to resist perturbations and to produce a predictable target phenotype regardless of random developmental noise. However, the extent to which canalization and developmental stability are controlled by the same set of genes and share underlying regulatory mechanisms is largely unresolved. We have analyzed the effects of clinical genetic variation (inversion polymorphism) on wing asymmetry by applying the methods of geometric morphometrics in the context of quantitative genetics using isochromosomal lines of Drosophila subobscura. For the analysis of overall size, developmental stability was positively correlated with levels of heterozygosity and development at the optimal temperature. For analyses of shape, the overall comparisons by matrix correlations indicate that inter-...

The estimation of individual fitness and quality are important elements of evolutionary ecological research. Over the past six decades, there has been great interest in using fluctuating asymmetry (FA) to represent individual quality, yet, serious technical problems have hampered efforts to estimate the heritability of FA, which, in turn, has limited progress in the investigation of FA from an evolutionary

Studies of directional asymmetry in the human upper limb have extensively examined bones of the arm, forearm, and hand, but have rarely considered the clavicle. Physiologically, the clavicle is an integrated element of the upper limb, transmitting loads to the axial skeleton and supporting the distal bones. However, clavicles develop in a manner that is unique among the bones of the upper limb. Previous studies have indicated that the clavicle has a right-biased asymmetry in diaphyseal breadth, as in humeri, radii, ulnae, and metacarpals, but unlike these other elements, a left-biased length asymmetry. Few studies have assessed how clavicular asymmetry relates to these other bones of the upper limb. Bilateral directional asymmetry of the clavicle is examined in relation to the humerus in a large, geographically diverse human sample, comparing lengths and diaphyseal breadths. Dimensions were converted into percentage directional (%DA) and absolute (%AA) asymmetries. Results indicate ...

Degrees of upper-limb bilateral asymmetry reflect habitual behavior and activity levels throughout life in human populations. The shoulder joint facilitates a wide range of combined motions due to the simultaneous motion of all three bones: clavicle, scapula, and humerus. Accordingly, we used three-dimensional geometric morphometrics to analyze shape differences in the glenoid cavity and linear morphometrics to obtain the degree of directional asymmetry in a medieval population. To calculate directional asymmetry, clavicles, humeri, and scapulae from 100 individuals (50 females, 50 males) were measured. Landmarks and semilandmarks were placed within a three-dimensional reconstruction of the glenoid cavity for analysis of shape differences between sides of the body within sexes. Linear morphometrics showed significant directional asymmetry in both sexes in all bones. Geometric morphometrics revealed significant shape differences of the glenoid cavity between sides of the body in females but not in males. Both indicators of directional asymmetry (%DA and %AA) did not show significant differences between sexes. PLS analysis revealed a significant correlation between glenoid shape and two humeral head diameters only in females on the left side of the body. The studied population, perhaps due to a high level of activity, exhibited slightly greater upper-limb bone bilateral asymmetry than other agricultural populations. Results suggest that the upper limbs were involved in similar activity patterns in both sexes but were characterized by different habitual behaviors. To obtain comprehensive results, studies should be based on sophisticated methods such as geometric morphometrics as well as standard measurements. Am. J. Hum. Biol., 2016. © 2016 Wiley Periodicals, Inc.

Background Several studies have reported alterations in finger and a-b ridge counts, and their derived measures of asymmetry, in schizophrenia compared to controls. Because ridges are fully formed by the end of the second trimester, they may provide clues to disturbed early development. The aim of this study was to assess these measures in a sample of patients with psychosis and normal controls. Methods Individuals with psychosis (n = 240), and normal controls (n = 228) were drawn from a catchment-area case-control study. Differences in finger and a-b ridge count and Fluctuating Asymmetry were assessed in three group comparisons (non-affective psychosis versus controls; affective psychosis versus controls; non-affective psychosis versus affective psychosis). The analyses were performed separately for males and females. Results There were no significant group differences for finger nor a-b ridge counts. While there were no group difference for Directional Asymmetry, for Fluctuating Asymmetry measures men with non-affective psychosis had significantly higher fluctuating asymmetry of the index finger ridge count (a) when compared to controls (FA-correlation score, p = 0.02), and (b) when compared to affective psychosis (adjusted FA-difference score, p = 0.04). Conclusion Overall, measures of finger and a-b ridge counts, and their derived measures of directional and fluctuating asymmetry were not prominent features of psychosis in this sample. While directional asymmetry in cerebral morphology is reduced in schizophrenia, this is not reflected in dermatoglyphic variables.

Directional asymmetry is widely found in humans. In the case of the attachments of the musculoskeletal soft tissues to bone, the entheses, asymmetry in entheseal change (EC) presence has been interpreted as indicative of asymmetric muscle usage. Previous studies have shown that there is variation in enthesis area. The aim of this presentation is to study directional asymmetry for enthesis area (standardised by body size) in relation to occupation.

The enthesis size of skeletons from the identified skeletal collection in Coimbra were measured along two chords meeting bisecting perpendicularly at the midpoint of the enthesis. These chord measurements were multiplied together and divided by local joint size to standardise for body size directional asymmetry was calculated. Occupations were categorised as per previously published methods into four categories: heavy manual, manual, nonmanual and soldier. ANOVAs were used to study differences in directional asymmetry with occupation.

Directional asymmetry shows less variability between occupations than was expected. The relationship between enthesis size and muscle cross-sectional area, which is a direct indicator of strength, is still not understood, nor is the development of the enthesis in relation to soft tissue thickness.