Increased prevalences of left-handedness and left-eye sighting dominance in individuals with Williams-Beuren syndrome

Ocular Dominance and Its Association With Central Corneal Thickness: An Observational Study in Central India

Background The aim of this study is to determine ocular dominance and its association with central corneal thickness (CCT). These two parameters are of great significance in clinical practice; identifying the dominant eye helps in planning cataract surgeries, treatment of presbyopia, monovision correction, etc., and assessing the CCT helps in early diagnosis and management of keratoconus, glaucoma, contact lens-related complications, and dry eye. Methods A cross-sectional study that involves patients and volunteers who have come for a checkup to the ophthalmology department of the college hospital. Ninety patients were examined for this study within two months. The hole-in-card test is performed to determine the ocular dominance in people with normal and healthy eyes without any pathologies except refractive errors. Specular microscopy through a non-contact modality will be done to assess the thickness of the central cornea in both eyes. Statistical analysis was done using the paired t-test to compare the patient's eyes and the chi-square test, which helps us associate ocular dominance and CCT.  Results Right eye dominance was seen in the majority of the participants (72.91%), whereas left eye dominance was seen in comparatively fewer participants (27.08%). The CCT of the dominant eye is found to be 520.40 ± 29.83 μm and that of the non-dominant eye is 524.40 ± 29.37 μm. A lower CCT in the dominant eye was seen in 83.33% of the subjects; 14.58% of them had a higher CCT in the dominant eye and 2.08% had the same CCT in both eyes. Conclusion From the observational study that has been made, the majority of the population shows right eye dominance. The CCT is relatively thinner in the dominant eye. About 80-85% of the examined people showed a thinner cornea in the dominant eye. But we cannot generalize that the eye with a lesser corneal thickness will be the dominant eye in all the cases, as a few cases have shown dominance in the eye with a thicker cornea.

Senatorial signatures Absence of male-female differences in left-handedness

A greater frequency of left-handedness among males than females has been observed in general populations. Past studies have explained this difference with reference to males' greater susceptibility to adverse birth events, while more recent studies have identified other contributing factors. On January 16, 2020, U.S. senators signed an oath to act impartially during the president's impeachment trial. This televised event allowed direct comparison of the proportion of right-handedness and left-handedness in a professionally accomplished sample of males and females. As expected, no sex difference in the proportion of left-handed senators was found, although the small sample size offered low statistical power. Replicating this finding with a larger sample would support the view that left-handedness among select groups of males is linked to genetic factors.

A sinister subject: Quantifying handedness-based recruitment biases in current neuroimaging research

Approximately ten per cent of humans are left-handed or ambidextrous (adextral). It has been suggested that, despite their sizable representation at the whole-population level, this demographic is largely avoided by researchers within the neuroimaging community. To date, however, no formal effort has been made to quantify the extent to which adextrals are excluded from neuroimaging-based research. Here, we aimed to address this question in a review of over 1,000 recent articles published in high-impact, peer-reviewed, neuroimaging-focused journals. Specifically, we sought to ascertain whether, and the extent to which adextrals are underrepresented in neuroimaging study samples, and to delineate potential trends in this bias. Handedness data were available for over 30,000 research subjects; only around 3%-4% of these individuals were adextral-considerably less than the 10% benchmark one would expect if neuroimaging samples were truly representative of the general population. This observation was generally consistent across different areas of research, but was modulated by the demographic characteristics of neuroimaging participants. The epistemological and ethical implications of these findings are discussed.

Where is the 'subjective straight ahead' in Williams syndrome?

BACKGROUND

Individuals with Williams Syndrome (WS) are known to have particular difficulties when performing visuo-spatial tasks, which could be related to their difficulties in using a specific reference system to determine spatial relations. The aim of the present study was to assess the internal representation of the body's sagittal plane, which is an important benchmark for an egocentric frame of reference.

METHOD

The results of 18 WS individuals (mean age = 20.5 ± 9.2 years) on the subjective straight ahead (SSA) task were compared with those of two healthy control groups composed of 36 participants matched on chronological age matched on chronological age (CA) and 30 young children matched on non-verbal intellectual ability (YC).

RESULTS

Individuals with WS showed a significant left deviation on the SSA body's sagittal plane representation compared with the chronological age control group and a marginal left deviation compared with the young children control group. A comparison with the objective SA (0°) showed a significant leftward deviation in the WS group but not in the two control groups.

CONCLUSIONS

Individuals with WS showed a significant leftward deviation in the SSA task. This bias of the body's longitudinal axe representation could have a negative impact on the use of an egocentric reference system, which could be the cause for their difficulties in defining spatial relations (e.g. location and orientation) necessary for performing spatial tasks.

Lateral preference in Williams-Beuren syndrome is associated with cognition and language

Williams-Beuren syndrome (WBS) is a genetically defined neurodevelopmental disorder presenting with intellectual disability associated with a specific neurocognitive profile characterized by anxiety, hypersociability, poor visuospatial skills and relatively preserved language. We have defined the lateral preference in 69 individuals (40 males and 29 females, age range 5-47 years) with WBS confirmed by molecular testing, and explored its correlation with cognition, behavior problems, the main aspects of the behavioral phenotype, and specific molecular variants (parental origin and size of the 7q11.23 deletion). Lateral preference (hand, foot, eye and ear) and neurobehavioral features [intelligence quotient (IQ), sociability, visuospatial construction, narrative skills and behavior] were assessed by a battery of tests and parental interviews. A large proportion of WBS individuals showed either left or mixed handedness (26 and 19%, respectively). Hand, foot and ear lateral preference showed significant association with IQ, with individuals with mixed lateral preference presenting lower general IQ, especially verbal IQ, with respect to subjects with well-defined laterality. Approachability, visuospatial ability, behavior problems or molecular variants were not associated with lateral preference. Our results indicate that, as in other neurodevelopmental disorders, laterality is poorly defined in a significant proportion of WBS individuals, and reinforces the idea that a correct definition of lateral preference is important for cognition and language.

The effect of handedness on grip strength in older adults with intellectual disabilities

Grip strength is an important predictor of several health outcomes in the general older population. Grip strength assessment is feasible and reliable in older adults with intellectual disabilities (ID), which makes it a valuable measurement for application in this population. The purpose of this study was to investigate the effect of handedness on grip strength in the older population with ID. Handedness and grip strength were assessed in a sample of 1050 older adults (≥ 50 years) with borderline to profound ID. Results showed that 26.2% of the study sample was left-handed. In right-handed participants the dominant hand (right) was on average 8.7% stronger than the non-dominant hand (p<0.001). For lefthanded participants there was no significant difference between the dominant hand (left) and nondominant hand. However, more detailed analyses revealed that 34.5% of the participants were stronger with their non-dominant hand, (on average 16.6% stronger for right-handed and 16.3% stronger for left-handed participants). Because of the large strength ratios, distributed in favor of both the dominant as the non-dominant hand, it is recommended to assess both hands to get a valid result of grip strength in older adults with ID.

Handedness and corpus callosal morphology in Williams syndrome

Williams syndrome is a neurodevelopmental genetic disorder caused by a hemizygous deletion on chromosome 7q11.23, resulting in atypical brain structure and function, including abnormal morphology of the corpus callosum. An influence of handedness on the size of the corpus callosum has been observed in studies of typical individuals, but handedness has not been taken into account in studies of callosal morphology in Williams syndrome. We hypothesized that callosal area is smaller and the size of the splenium and isthmus is reduced in individuals with Williams syndrome compared to healthy controls, and examined age, sex, and handedness effects on corpus callosal area. Structural magnetic resonance imaging scans were obtained on 25 individuals with Williams syndrome (18 right-handed, 7 left-handed) and 25 matched controls. We found that callosal thickness was significantly reduced in the splenium of Williams syndrome individuals compared to controls. We also found novel evidence that the callosal area was smaller in left-handed participants with Williams syndrome than their right-handed counterparts, with opposite findings observed in the control group. This novel finding may be associated with LIM-kinase hemizygosity, a characteristic of Williams syndrome. The findings may have significant clinical implications in future explorations of the Williams syndrome cognitive phenotype.

Nonverbal communication, play, and language in Greek young children with Williams syndrome

This study investigated nonverbal communicative abilities, functional play, and symbolic play in 11 toddlers with Williams syndrome (WS) during spontaneous communication. The WS group was compared with a group of typically developing (TD) children matched for linguistic abilities. Results demonstrated that children with WS exhibited significantly less spontaneous functional play and imaginary play compared to TD children. On the other hand, children with WS showed significantly more showing and giving guided by their parents than TD children. In addition, it was shown that in both groups aspects of symbolic play are correlated with expressive as well as receptive language. These findings are interpreted through the Theory of Intersubjectivity, which contrasts with the Theory of Mind and suggests that shared arbitrary purposes regarding actions on objects constitute presuppositions for the development of language.

Laterality of amblyopia

PURPOSE

To determine the frequency of unilateral amblyopia in right versus left eyes among children younger than 18 years.

DESIGN

Analysis of data collected in randomized clinical trials conducted by the Pediatric Eye Disease Investigator Group.

METHODS

The laterality of the amblyopic eye was analyzed in 2635 subjects younger than 18 years who participated in 9 multicenter prospective, randomized treatment trials. Eligibility criteria for these clinical trials included unilateral amblyopia associated with strabismus, anisometropia, or both, with visual acuity between 20/40 and 20/400. Logistic regression was used to assess the association of baseline and demographic factors with the laterality of amblyopia.

RESULTS

Among subjects with anisometropic amblyopia (with or without strabismus), amblyopia was present more often in left than right eyes, with a relative prevalence of 59% in left eyes (95% confidence interval, 57% to 62%; P < .001 from a test of proportion, 50%). However, among subjects with strabismic-only amblyopia, there was no laterality predilection (relative prevalence of 50% in left eyes; 95% confidence interval, 47% to 54%; P = .94).

CONCLUSIONS

Anisometropic amblyopia, with or without strabismus, occurs more often in left eyes than right eyes. This finding of amblyopia laterality may be related to microtropia, sighting dominance, or other forms of ocular dominance; developmental or neurological factors; laterality in the development of refractive error; or a combination thereof.

Comparative assessment of 13 of the widely used hand preference items in a Bulgarian sample

The hand preference items included into Chapman and Chapman's (1987) inventory were comparatively assessed concerning the frequencies of the answers given by Bulgarian right, mixed, and left handers, concerning the correlation of each item with the remaining 12, with eyedness and footedness scores. Relationships between writing hand, throwing hand, eyedness, and footedness were studied. Application of a cumulative index of familial sinistrality evidenced the biological significance of the main findings. All the results showed the inferiority of the writing hand as compared to the remaining items and evidenced the full inappropriateness of this item as a single predictor of handedness.

Behavioural indexes of callosal functioning in Williams syndrome

Williams syndrome (WS) is a neurogenetic disorder that stems from a microdeletion on chromosome 7. Recent anatomical studies have found evidence for corpus callosum abnormalities in WS. However, to date, the impact of these structural differences on callosal functionality remains unclear. The aim of the present study was to investigate interhemispheric communication and hemispheric asymmetry in individuals with WS relative to mental age-matched controls. This was assessed using bilateral and unilateral presentations of visual stimuli in a picture-naming task. Results found both groups to exhibit a bilateral field advantage and a left visual advantage on unilateral presentations. However, while a significant performance increase with age was found for controls, no such correlation was found for individuals with WS. Taken together, these findings suggest that despite some evidence for an atypical developmental pathway in WS, both interhemispheric communication and hemispheric asymmetry are functionally intact in this population.

Linguistic profile of individuals with Down syndrome: comparing the linguistic performance of three developmental disorders

An increasing number of studies, addressing the linguistic abilities of individuals with Down syndrome (DS) suggest that they exhibit strengths and weaknesses within the linguistic domain. This article critically reviews the literature on the linguistic profile of individuals with DS, with particular emphasis on the expression and reception of vocabulary and grammar, including nonverbal linguistic expression during infant development. In doing so, attention is given to recent comparative studies of the linguistic abilities of individuals with DS, Specific Language Impairment (SLI), and Williams syndrome (WS). The possibility that deficits in one cognitive system may have consequences in another cognitive system, and that these consequences may define the nature of the impairment in each clinical syndrome is further discussed with suggestions for future research.

Symmetry of cortical folding abnormalities in Williams syndrome revealed by surface-based analyses

We analyzed folding abnormalities in the cerebral cortex of subjects with Williams syndrome (WS), a genetically based developmental disorder, using surface-based analyses applied to structural magnetic resonance imaging data. Surfaces generated from each individual hemisphere were registered to a common atlas target (the PALS-B12 atlas). Maps of sulcal depth (distance from the cerebral hull) were combined across individuals to generate maps of average sulcal depth for WS and control subjects, along with depth-difference maps and t-statistic maps that accounted for within-group variability. Significant structural abnormalities were identified in 33 locations, arranged as 16 bilaterally symmetric pairs plus a lateral temporal region in the right hemisphere. Discrete WS folding abnormalities extended across a broad swath from dorsoposterior to ventroanterior regions of each hemisphere, in cortical areas associated with multiple sensory modalities as well as regions implicated in cognitive and emotional behavior. Hemispheric asymmetry in the temporal cortex is reduced in WS compared with control subjects. These findings provide insights regarding possible developmental mechanisms that give rise to folding abnormalities and to the spectrum of behavioral characteristics associated with WS.

Laterality in persons with intellectual disability II. Hand, foot, ear, and eye laterality in persons with Trisomy 21 and Williams-Beuren syndrome

Laterality (hand, foot, ear, and eye) was assessed in participants with Trisomy 21 (62) and Williams-Beuren syndrome (WBS) (39). Handedness was also assessed in a card reaching task. The comparison group included 184 typically developing persons. Two independent age sub-groups were formed: 7 to 10 years old and 11 to 34 years old. We confirmed previous data: individuals with T21 were more frequently left- or mixed-handed than typically developing persons; individuals with WBS had intermediate scores. The two groups with genetic disorders had less right foot preference. Manual and foot inconsistencies characterized both groups with genetic disorders. Cross hand-foot preference was lower in the typically developing group. Differences in IQ levels did not correlate with differences in laterality scores. Overall laterality profiles were not the same in the two groups with genetic disorders: the greatest differences were observed between typically developing persons and persons with Trisomy 21.