Handedness in preterm born children: a systematic review and a meta-analysis

Preterm-Born Young Women Have Weaker Hand Grip Strength Compared to Their Full-Term-Born Peers

Prematurity has been linked to lower muscular fitness and increased morbidity across the human lifespan. Hand grip strength is widely used as a measure of muscle strength. Previous studies have shown inconsistent results regarding the role of vitamin D in hand grip strength. Here, we investigated hand grip strength and the effects of a yearlong vitamin D supplementation in healthy preterm-born young adults. We recruited 38 young adults born preterm at either ≤32 weeks' gestation or <34 weeks' gestation and weighing <1500 g, as well as 39 gender- and age-matched controls, for this study. Anthropometric measurements, hand grip strengths, and vitamin D concentrations were recorded. These investigations were repeated after a yearlong vitamin D supplementation intervention. There was a significant difference in the age- and gender-specific hand grip strength ranks between the preterm- and full-term-born young adults: 57.9% and 30.7%, respectively, were below average (p = 0.009). In the preterm-born group, the females had significantly lower hand grip strengths compared to their full-term-born peers, with a mean difference of -3.46 kg (95% CI: -6.68 to -0.247; p = 0.035). In a linear regression analysis, the preterm-born female adult height was negatively associated with hand grip strength (R2 = 0.24, F (1.43) = 13.61, p < 0.001). The vitamin D concentrations were increased after the supplementation period, with no association with hand grip strength. According to our results, preterm-born young females are at risk for lower muscle strength, independent of their current vitamin D status.

Effects of size at birth on health, growth and developmental outcomes in children up to age 18: an umbrella review

BACKGROUND

Size at birth, an indicator of intrauterine growth, has been studied extensively in relation to subsequent health, growth and developmental outcomes. Our umbrella review synthesises evidence from systematic reviews and meta-analyses on the effects of size at birth on subsequent health, growth and development in children and adolescents up to age 18, and identifies gaps.

METHODS

We searched five databases from inception to mid-July 2021 to identify eligible systematic reviews and meta-analyses. For each meta-analysis, we extracted data on the exposures and outcomes measured and the strength of the association.

FINDINGS

We screened 16 641 articles and identified 302 systematic reviews. The literature operationalised size at birth (birth weight and/or gestation) in 12 ways. There were 1041 meta-analyses of associations between size at birth and 67 outcomes. Thirteen outcomes had no meta-analysis.Small size at birth was examined for 50 outcomes and was associated with over half of these (32 of 50); continuous/post-term/large size at birth was examined for 35 outcomes and was consistently associated with 11 of the 35 outcomes. Seventy-three meta-analyses (in 11 reviews) compared risks by size for gestational age (GA), stratified by preterm and term. Prematurity mechanisms were the key aetiologies linked to mortality and cognitive development, while intrauterine growth restriction (IUGR), manifesting as small for GA, was primarily linked to underweight and stunting.

INTERPRETATION

Future reviews should use methodologically sound comparators to further understand aetiological mechanisms linking IUGR and prematurity to subsequent outcomes. Future research should focus on understudied exposures (large size at birth and size at birth stratified by gestation), gaps in outcomes (specifically those without reviews or meta-analysis and stratified by age group of children) and neglected populations.

PROSPERO REGISTRATION NUMBER

CRD42021268843.

Inventories of Human Lateral Preference: A Systematic Review

There are a variety of inventories available to evaluate human lateral preference, but no previous review has systematically analyzed and compared them. We conducted a systematic literature review to identify these inventories and describe their characteristics (e.g., dimensions, scales, tasks, psychometric properties). We included 26 articles, each presenting a different inventory to assess lateral preference, published between 1900 and 2022, selected from the following databases: PubMed, SportDiscus, APA PsycNET, and Web of Science. These inventories analyzed tasks performed in everyday life (domestic, work-related, sports, and leisure/recreation activities), covering hand, foot, hearing, visual and other non-usual lateral preference dimensions, such as trunk and head. Most inventories classified individuals based on the direction (left, indifferent or right preference) and degree (consistent or moderate) of laterality. However, many of the reviewed inventories lack established psychometric verification in their original publication, such as validity, reliability, responsiveness, and practical applicability. Inventories also presented tasks that may be specific to a given cultural setting, limiting their application across different countries. Based on these findings, we provide a comprehensive guide for researchers to select a lateral preference assessment tool, but also advocate for a new inventory with a broader approach, containing more than one dimension of lateral preference (i.e., not only handedness) and tasks that are common to different cultures to enhance practical applicability worldwide.

Adaptive olfactory circuitry restores function despite severe olfactory bulb degeneration

The olfactory bulb (OB) is a critical component of mammalian olfactory neuroanatomy. Beyond being the first and sole relay station for olfactory information to the rest of the brain, it also contains elaborate stereotypical circuitry that is considered essential for olfaction. Indeed, substantial lesions of the OB in rodents lead to anosmia. Here, we examined the circuitry that underlies olfaction in a mouse model with severe developmental degeneration of the OB. These mice could perform odor-guided tasks and even responded normally to innate olfactory cues. Despite the near total loss of the OB, piriform cortices in these mice responded to odors, and its neural activity sufficed to decode odor identity. We found that sensory neurons express the full repertoire of olfactory receptors, and their axons project primarily to the rudiments of the OB but also, ectopically, to olfactory cortical regions. Within the OB, the number of principal neurons was greatly reduced, and the morphology of their dendrites was abnormal, extending over large regions within the OB. Glomerular organization was totally lost in the severe cases of OB degeneration and altered in the more conserved OBs. This study shows that olfactory functionality can be preserved despite reduced and aberrant circuitry that is missing many of the elements believed to be essential for olfaction, and it may explain reported retention of olfaction in humans with degenerated OBs.

Handedness and 23 Early Life Characteristics in 37,495 Dutch Twins

In studies of singletons, a range of early-life characteristics have been reported to be associated with handedness, but some of these associations have failed to replicate. We examined associations between 23 early life characteristics with handedness in a large sample of 37,495 5-year-old twins. We considered three definitions of handedness: left-handedness (LH), mixed-handedness (MH), and non-right-handedness (NRH). Our main aim was to test whether the associations with sex, birth weight, gestational age, and season of birth - as reported in singletons - replicate in twins, and to examine twin-specific variables, including zygosity, chorionicity, birth order, and intertwin delivery time. Compared to previously published data from adults born as singletons (7.23%), the prevalence of NRH was higher in both twins (16.19%) and their parents (15.09%). In the twins, LH and NRH were associated with parents' LH. Male sex and lower gestational age were associated with NRH, and LH was associated with not being breastfed. MH was related to neurodevelopmental delays and higher externalizing problems later in childhood. Other previously reported associations were not replicated, and no twin-specific characteristics were related to handedness. These results emphasize the importance of considering multiple definitions of handedness and indicate a small number of replicated associations across studies.

Exploring the emergence of morphological asymmetries around the brain's Sylvian fissure: a longitudinal study of shape variability in preterm infants

Brain folding patterns vary within the human species, but some folding properties are common across individuals, including the Sylvian fissure's inter-hemispheric asymmetry. Contrarily to the other brain folds (sulci), the Sylvian fissure develops through the process of opercularization, with the frontal, parietal, and temporal lobes growing over the insular lobe. Its asymmetry may be related to the leftward functional lateralization for language processing, but the time course of these asymmetries' development is still poorly understood. In this study, we investigated refined shape features of the Sylvian fissure and their longitudinal development in 71 infants born extremely preterm (mean gestational age at birth: 26.5 weeks) and imaged once before and once at term-equivalent age (TEA). We additionally assessed asymmetrical sulcal patterns at TEA in the perisylvian and inferior frontal regions, neighbor to the Sylvian fissure. While reproducing renowned strong asymmetries in the Sylvian fissure, we captured an early encoding of its main asymmetrical shape features, and we observed global asymmetrical shape features representative of a more pronounced opercularization in the left hemisphere, contrasting with the previously reported right hemisphere advance in sulcation around birth. This added novel insights about the processes governing early-life brain folding mechanisms, potentially linked to the development of language-related capacities.

Handedness in low-birthweight children: Insights in lateralization

Low-birthweight (LBW) children (n = 96) weighing less than 2.5 kg at birth and normal birthweight (NBW) children (n = 96) from Delhi, India, between the ages of 5 and 12 years were assessed for intelligence with Ravens Colored Progressive Matrices (RCPM), their handedness and hand proficiency for unimanual and bimanual performance. The objective was to know if there is a relation between birthweight and the development of handedness. Compared with NBW children, the LBW group had lower percentile scores for the RCPM. The LBW children were less lateralized than the NBW children in the hand preference test. The LBW children were faster than the NBW for sorting objects with each hand separately, but they were slower in the bimanual envelope task. This indicates a delay in interhemispheric transfer and the development of the corpus callosum that connects the cerebral hemispheres to enable bimanual coordination. In the absence of more direct evidence, hand skill was used as an index of the extent of lateralized control for performance. Findings indicate a relation between birthweight and lateralization in children tested for hand preference.

The influence of vestibular system and fetal presentation on handedness, cognitive and motor development: A comparison between cephalic and breech presentation

Genetics are undoubtedly implicated in the ontogenesis of laterality. Nonetheless, environmental factors, such as the intrauterine environment, may also play a role in the development of functional and behavioral lateralization. The aim of this study was to test the Left-Otolithic Dominance Theory (LODT; Previc, 1991) by investigating a hypothetical developmental pattern where it is assumed that a breech presentation, which is putatively associated with a dysfunctional and weakly lateralized vestibular system, can lead to weak handedness and atypical development associated with language and motor difficulties. We used the ALSPAC cohort of children from 7 to 10 years of age to conduct our investigation. Our results failed to show an association between the vestibular system and fetal presentation, nor any influence of the latter on hand preference, hand performance, or language and motor development. Bayesian statistical analyses supported these findings. Contrary to our LODT-derived hypotheses, this study offers evidence that fetal presentation does not influence the vestibular system's lateralization and seems to be a poor indicator for handedness. Nonetheless, we found that another non-genetic factor, prematurity, could lead to atypical development of handedness. This article is protected by copyright. All rights reserved.

Social gaze in preterm infants may act as an early indicator of atypical lateralization

Visual field biases have been identified as markers of atypical lateralization in children with developmental conditions, but this is the first investigation to consider early lateralized gaze behaviors for social stimuli in preterm infants. Eye-tracking methods with 51 preterm (33 male, 92.1% White) and 61 term-born (31 male, 90.1% White) infants aged 8-10 months from Edinburgh, UK, captured the development of visual field biases, comparing gaze behavior to social and non-social stimuli on the left versus right of the screen. Preterm infants showed a significantly reduced interest to social stimuli on the left versus right compared to term children (d = .58). Preterm children exhibit early differential orienting preferences that may be an early indicator of atypical lateralized function.

DNA methylation in peripheral tissues and left-handedness

Handedness has low heritability and epigenetic mechanisms have been proposed as an etiological mechanism. To examine this hypothesis, we performed an epigenome-wide association study of left-handedness. In a meta-analysis of 3914 adults of whole-blood DNA methylation, we observed that CpG sites located in proximity of handedness-associated genetic variants were more strongly associated with left-handedness than other CpG sites (P = 0.04), but did not identify any differentially methylated positions. In longitudinal analyses of DNA methylation in peripheral blood and buccal cells from children (N = 1737), we observed moderately stable associations across age (correlation range [0.355–0.578]), but inconsistent across tissues (correlation range [− 0.384 to 0.318]). We conclude that DNA methylation in peripheral tissues captures little of the variance in handedness. Future investigations should consider other more targeted sources of tissue, such as the brain.

Shape variability of the central sulcus in the developing brain: a longitudinal descriptive and predictive study in preterm infants

Despite growing evidence of links between sulcation and function in the adult brain, the folding dynamics, occurring mostly before normal-term-birth, is vastly unknown. Looking into the development of cortical sulci in infants can give us keys to address fundamental questions: what is the sulcal shape variability in the developing brain? When are the shape features encoded? How are these morphological parameters related to further functional development? In this study, we aimed to investigate the shape variability of the developing central sulcus, which is the frontier between the primary somatosensory and motor cortices. We studied a cohort of 71 extremely preterm infants scanned twice using MRI - once around 30 weeks post-menstrual age (w PMA) and once at term-equivalent age, around 40w PMA -, in order to quantify the sulcus's shape variability using manifold learning, regardless of age-group or hemisphere. We then used these shape descriptors to evaluate the sulcus's variability at both ages and to assess hemispheric and age-group specificities. This led us to propose a description of ten shape features capturing the variability in the central sulcus of preterm infants. Our results suggested that most of these features (8/10) are encoded as early as 30w PMA. We unprecedentedly observed hemispheric asymmetries at both ages, and the one captured at term-equivalent age seems to correspond with the asymmetry pattern previously reported in adults. We further trained classifiers in order to explore the predictive value of these shape features on manual performance at 5 years of age (handedness and fine motor outcome). The central sulcus's shape alone showed a limited but relevant predictive capacity in both cases. The study of sulcal shape features during early neurodevelopment may participate to a better comprehension of the complex links between morphological and functional organization of the developing brain.

Hand preference and Mathematical Learning Difficulties: New data from Greece, the United Kingdom, and Germany and two meta-analyses of the literature

Increased rates of atypical handedness are observed in neurotypical individuals who are low-performing in mathematical tasks as well as in individuals with special educational needs, such as dyslexia. This is the first investigation of handedness in individuals with Mathematical Learning Difficulties (MLD). We report three new studies (N = 134; N = 1,893; N = 153) and two sets of meta-analyses (22 studies; N = 3,667). No difference in atypical hand preference between MLD and Typically Achieving (TA) individuals was found when handedness was assessed with self-report questionnaires, but weak evidence of a difference was found when writing hand was the handedness criterion in Study 1 (p = .049). Similarly, when combining data meta-analytically, no hand preference differences were detected. We suggest that: (i) potential handedness effects require larger samples, (ii) direction of hand preference is not a sensitive enough measure of handedness in this context, or that (iii) increased rates of atypical hand preference are not associated with MLD. The latter scenario would suggest that handedness is specifically linked to language-related conditions rather than conditions related to cognitive abilities at large. Future studies need to consider hand skill and degree of hand preference in MLD.

Is Handedness at Five Associated with Prenatal Factors?

The goal of the study was to investigate some of the factors suspected to be related to children's handedness: presentation during the last weeks of gestation and at birth (cephalic or breech), side of presentation (right or left), number of weeks of gestation, season of birth, parents' handedness and sex. We analyzed the relationships between these factors and the child's handedness at five years. Children (n = 1897) from the EDEN cohort participated in the study, among which 1129 were tested for handedness at five. The father's handedness, but not the mother's, was significantly related to the child's hand preference. The percentage of left-handed children was significantly larger when the father was non-right-handed compared to right-handed, and tended to be larger among children in non-left-cephalic presentation compared to left-cephalic presentation. Girls, but not boys, were significantly less lateralized when they were born before 37 weeks of pregnancy than after. Finally, children born in winter or spring were slightly but significantly less lateralized than children born in summer or autumn. All six children who were not lateralized at 5 presented one or several of these factors. These results are discussed in light of the mixed model of handedness.

Effect of multiple pregnancy and laterality on infant neurodevelopment

OBJECTIVE

The objective of this study is to investigate the effect of type of pregnancy (singleton, dizygotic, and monozygotic) on infant neurodevelopment and to explore how laterality operates in this relationship.

METHODS

We constructed a prospective cohort of low-risk women with singleton, monozygotic, and dizygotic pregnancies. Laterality was evaluated using the Edinburgh's scale of laterality, while neurodevelopment was assessed using the Ages & Stages Questionnaire (ASQ). The confounding, modifying, and mediating effect of laterality on the relationship between multiple pregnancy and neurodevelopment was explored by linear regression.

RESULTS

We included 207 singletons, 77 dizygotic, and 75 monozygotic pregnancies. The mean age (SD) at assessment of neurodevelopment was 48.5 (7.5) months. There was a significant trend to poorer neurodevelopment across singleton, dizygotic and monozygotic pregnancies in communication (52.2, 47.6 and 42.3; p < .001) and fine movements (49.6, 44.5 and 35.2; p < .001) even after adjusting for confounders. As compared to singletons, both dizygotic (39.6% vs. 22.7%; p < .001) and monozygotic (39.3% vs. 22.7%; p < .001) pregnancies had a higher frequency of non-right laterality. Laterality was not associated with neurodevelopment, nor confounded, mediated or modified the effect of multiple pregnancy on neurodevelopment.

CONCLUSION

The association of multiple pregnancy to poorer neurodevelopment was independent of children laterality.

Umbrella Review of School Age Health Outcomes of Preterm Birth Survivors

Preterm birth affects approximately 10% of U.S. births, with survival rates close to 95%. All health care providers, regardless of population or setting, are treating preterm birth survivors. The purpose of this manuscript is to present an umbrella review of the health outcomes of 2- to 12-year-old children who were born preterm. The current umbrella review consisted of 29 reviews, 14 meta-analyses, eight systematic reviews, and seven described as both meta-analysis and systematic review. Studies were grouped into six health outcome categories: neurodevelopmental, motor and/or cerebral palsy, pulmonary, mental and/or behavioral health, quality of life and/or leisure, and eczema. The analysis supports a resounding recommendation to recognize preterm birth, at all gestations, as a risk factor to health and educational outcomes. Increased attention to developmental screenings is critical, specifically recognition that children who are on the lower ranges of normal may benefit from therapies or interventions that support the attainment of future skills.

Non-right-handedness in children born extremely preterm: Relation to early neuroimaging and long-term neurodevelopment

Objective

This study aimed to define the prevalence and predictors of non-right-handedness and its link to long-term neurodevelopmental outcome and early neuroimaging in a cohort of children born extremely preterm (<28 weeks gestation).

Methods

179 children born extremely preterm admitted to the Neonatal Intensive Care Unit of our tertiary centre from 2006–2013 were included in a prospective longitudinal cohort study. Collected data included perinatal data, demographic characteristics, neurodevelopmental outcome measured by the Bayley Scales of Infant and Toddler Development at 2 years and the Movement Assessment Battery for Children at 5 years, and handedness measured at school age (4–8 years). Magnetic resonance imaging performed at term-equivalent age was used to study overt brain injury. Diffusion tensor imaging scans were analysed using tract-based spatial statistics to assess white matter microstructure in relation to handedness and neurodevelopmental outcome.

Results

The prevalence of non-right-handedness in our cohort was 22.9%, compared to 12% in the general population. Weaker fine motor skills at 2 years and paternal non-right-handedness were significantly associated with non-right-handedness. Both overt brain injury and fractional anisotropy of white matter structures on diffusion tensor images were not related to handedness. Fractional anisotropy measurements showed significant associations with neurodevelopmental outcome.

Conclusions

Our data show that non-right-handedness in children born extremely preterm occurs almost twice as frequently as in the general population. In the studied population, non-right-handedness is associated with weaker fine motor skills and paternal non-right-handedness, but not with overt brain injury or microstructural brain development on early magnetic resonance imaging.

Hand Preference Develops Across Childhood and Adolescence in Extremely Preterm Children: The EPICure Study

AIM

We attempted to determine how handedness changes with age and its relation to brain injury and cognition following birth before 26 weeks of gestation.

METHODS

We used data from the EPICure study of health and development following birth in the British Isles in 1995. Handedness was determined by direct observation during standardized testing at age 2.5, six, and 11 years and by self-report using the Edinburgh Handedness Inventory at 19 years. Control data from term births were included at six, 11, and 19 years.

RESULTS

In extremely preterm children left handedness increased from 9% to 27% between 2.5 and 19 years, with a progressive reduction in mixed handedness from 59% to 13%. Although individual handedness scores varied over childhood, the between-group effects were consistent through 19 years, with greatest differences in females. In extremely preterm participants, neonatal brain injury was associated with lower right handedness scores at each age and left-handed participants had lower cognitive scores at 19 years after controlling for confounders, but not at other ages.

CONCLUSION

Increasing hand lateralization is seen over childhood in extremely preterm survivors, but consistently more individuals have non-right preferences at each age than control individuals.

Changing handedness: What can we learn from preference shift studies?

Handedness is a dynamic and complex aspect of human behavior. Changing it through practice, either willingly or obliged by some reason, requires a considerable amount of effort. Analyzing studies that presented handedness shifts may expand our comprehension of this phenomenon, since knowing how to change it might provide insights into how it develops. Therefore, we reviewed the outcomes of handedness shifts. The results suggest that neural asymmetries related to handedness are likely a consequence of lateralized practice since they correlate with modifications in the behavioral patterns. Clearly, practice is not the only factor influencing handedness development, but it seems to play a significant role in the formation and consolidation of neural and behavioral asymmetries. Another key finding of our review is the suggestion of a ceiling effect for the capacity to change handedness direction and degree, considering none of the reviewed studies reported complete shifts in behavioral measures and brain activation patterns.

A historical, systematic review of handedness origins

Handedness ontogenesis is still under debate in science. This systematic review analyzed articles regarding the theories and basis of handedness formation, highlighting the historical knowledge path that this literature underwent. Cochrane Library, LILACS, Web of Sciences, Science Direct and PubMed databases were searched. This review included review studies with handedness as the main topic. Only papers written in English with analyses exclusively in neurotypical humans (any age range) were included. Different approaches (genetic, neural, social, and behavioural) were reviewed in light of growing evidence, summarizing the current state of the art. Genetic and environmental/social impacts are common points in most of the reviews, each given more or less importance, depending on the author and theory proposed. Multifactorial, developmental approaches to handedness formation seem to be the most up to date view of the phenomenon. Different control mechanisms between hemisphere and neural asymmetries are also contributing factors to handedness formation.

A large-scale population study of early life factors influencing left-handedness

Hand preference is a conspicuous variation in human behaviour, with a worldwide proportion of around 90% of people preferring to use the right hand for many tasks, and 10% the left hand. We used the large cohort of the UK biobank (~500,000 participants) to study possible relations between early life factors and adult hand preference. The probability of being left-handed was affected by the year and location of birth, likely due to cultural effects. In addition, hand preference was affected by birthweight, being part of a multiple birth, season of birth, breastfeeding, and sex, with each effect remaining significant after accounting for all others. Analysis of genome-wide genotype data showed that left-handedness was very weakly heritable, but shared no genetic basis with birthweight. Although on average left-handers and right-handers differed for a number of early life factors, all together these factors had only a minimal predictive value for individual hand preference.

Triplets, birthweight, and handedness

The mechanisms behind handedness formation in humans are still poorly understood. Very low birthweight is associated with higher odds of left-handedness, but whether this is due to low birthweight itself or premature birth is unknown. Handedness has also been linked to development, but the role of birthweight behind this association is unclear. Knowing that birthweight is lower in multiple births, triplets being about 1.5 kg lighter in comparison with singletons, and that multiples have a higher prevalence of left-handedness than singletons, we studied the association between birthweight and handedness in two large samples consisting exclusively of triplets from Japan (n = 1,305) and the Netherlands (n = 947). In both samples, left-handers had significantly lower birthweight (Japanese mean = 1,599 g [95% confidence interval (CI): 1,526-1,672 g]; Dutch mean = 1,794 g [95% CI: 1,709-1,879 g]) compared with right-handers (Japanese mean = 1,727 g [95% CI: 1,699-1,755 g]; Dutch mean = 1,903 g [95% CI: 1,867-1,938 g]). Within-family and between-family analyses both suggested that left-handedness is associated with lower birthweight, also when fully controlling for gestational age. Left-handers also had significantly delayed motor development and smaller infant head circumference compared with right-handers, but these associations diluted and became nonsignificant when controlling for birthweight. Our study in triplets provides evidence for the link between low birthweight and left-handedness. Our results also suggest that developmental differences between left- and right-handers are due to a shared etiology associated with low birthweight.

National population-based cohort study found that visual-motor integration was commonly affected in extremely preterm born children at six-and-a-half years

AIM

This study aimed to explain the relationship between visual-motor integration (VMI) abilities and extremely preterm (EPT) birth, by exploring the influence of perinatal variables, cognition, manual dexterity and ophthalmological outcomes.

METHODS

This was part of the population-based national Extremely Preterm Infant Study in Sweden (EXPRESS) study. We studied 355 children, born at a gestational age of <27 weeks from April 2004 to March 2007, and 364 term-born controls. At six-and-a-half years of age, we assessed VMI, cognitive function, motor skills and vision. VMI impairment was classified as <-1 standard deviation (SD).

RESULTS

The mean (SD) VMI score was 87 (±12) in preterm children compared to 98 (±11) in controls (p < 0.001). VMI impairment was present in 55% of preterm infants and in 78% of children born at 22-23 weeks. Male sex and postnatal steroids showed a weak association with poorer visual-motor performance, whereas low manual dexterity and cognitive function showed a stronger association.

CONCLUSION

Poor VMI performance was common in this EXPRESS cohort of children born EPT. Its strong association to cognition and manual dexterity confirms that all of these factors need to be taken into account when evaluating risks in preterm born children.

Motorische Entwicklung und Händigkeit in den ersten beiden Lebensjahren

Zusammenfassung. Der Zusammenhang von motorischer Entwicklung in den ersten beiden Lebensjahren und der Händigkeit von Kindern (N = 367) wurde untersucht. 18 motorische Meilensteine wurden erfasst, 14 betreffen die Grob- und vier die Handmotorik. Die Händigkeit wurde durch eine Befragung der Eltern zum Zeitpunkt des Erreichens des Meilensteins („Freies und sicheres Gehen“) ermittelt, den die Kinder im durchschnittlichen Alter von 14 Monaten bewältigten. 42.1 % der Kinder bevorzugten ihre rechte, 9.6 % ihre linke Hand, 32 % gebrauchten beide Hände gleich häufig. 16.4 % der Eltern konnten keine Angaben zur Händigkeit machen. Kinder, die bereits eine ausgeprägte Präferenz für die rechte Hand zeigten, bewältigten die meisten der Meilensteine früher als linkshändige und Kinder ohne Bevorzugung einer Hand. Kinder, deren Eltern keine Angabe zur Händigkeit machten, zeigten keine Nachteile gegenüber Rechtshändern. Unterschiede hinsichtlich der Entwicklung körperlicher Merkmale konnten zwischen den Gruppen nicht nachgewiesen werden. Der Anteil der Jungen unter den Linkshändern war deutlich höher als der der Mädchen. Mit Ausnahme des Meilensteins „Sitzen“ konnten keine Unterschiede im Erreichen der Meilensteine zwischen den Geschlechtern nachgewiesen werden.

Hand Preference and Cognitive, Motor, and Behavioral Functioning in 10-Year-Old Extremely Preterm Children

The association of hand preference (left, mixed, and right) with cognitive, academic, motor, and behavioral function was evaluated in 864 extremely preterm children at 10 years of age. Left-handed and right-handed children performed similarly but mixed-handed children had greater odds of functional deficits across domains than right-handed children.

Developmental progression and side specialization in upper-limb movements from 4 to 8 years in children born preterm and fullterm

This study investigated developmental changes and differences in upper-limb movement organization from 4 to 8 years of age in children born preterm (PT) and fullterm (FT). Kinematic recordings of precision-demanding unimanual movements and lateral assessments were carried out in 37 children (18 PT). All children, particularly children born PT, displayed considerable gain in movement kinematics. Contrary to controls, children born PT displayed persistently less-evident side preference. Gestational age (GA) contributed significantly to kinematic differences shown, with larger upper-limb deviances in the lowest GAs, in agreement with cross-sectional findings of altered hemispheric connections and delayed side-specialization among children born very PT.

Power-up: A Reanalysis of 'Power Failure' in Neuroscience Using Mixture Modeling

Recently, evidence for endemically low statistical power has cast neuroscience findings into doubt. If low statistical power plagues neuroscience, then this reduces confidence in the reported effects. However, if statistical power is not uniformly low, then such blanket mistrust might not be warranted. Here, we provide a different perspective on this issue, analyzing data from an influential study reporting a median power of 21% across 49 meta-analyses (Button et al., 2013). We demonstrate, using Gaussian mixture modeling, that the sample of 730 studies included in that analysis comprises several subcomponents so the use of a single summary statistic is insufficient to characterize the nature of the distribution. We find that statistical power is extremely low for studies included in meta-analyses that reported a null result and that it varies substantially across subfields of neuroscience, with particularly low power in candidate gene association studies. Therefore, whereas power in neuroscience remains a critical issue, the notion that studies are systematically underpowered is not the full story: low power is far from a universal problem.SIGNIFICANCE STATEMENT Recently, researchers across the biomedical and psychological sciences have become concerned with the reliability of results. One marker for reliability is statistical power: the probability of finding a statistically significant result given that the effect exists. Previous evidence suggests that statistical power is low across the field of neuroscience. Our results present a more comprehensive picture of statistical power in neuroscience: on average, studies are indeed underpowered-some very seriously so-but many studies show acceptable or even exemplary statistical power. We show that this heterogeneity in statistical power is common across most subfields in neuroscience. This new, more nuanced picture of statistical power in neuroscience could affect not only scientific understanding, but potentially policy and funding decisions for neuroscience research.

Alterations in white matter microstructure are associated with goal-directed upper-limb movement segmentation in children born extremely preterm

Altered white matter microstructure is commonly found in children born preterm (PT), especially those born at an extremely low gestational age (GA). These children also commonly show disturbed motor function. This study explores the relation between white matter alterations and upper-limb movement segmentation in 41 children born PT (19 girls), and 41 children born at term (18 girls) at 8 years. The PT group was subdivided into extremely PT (E-PT; GA = 25-27 weeks, N = 10), very PT (V-PT; GA = 28-32 weeks, N = 13), and moderately PT (M-PT; GA = 33-35 weeks, N = 18). Arm/hand preference (preferred/non-preferred) was determined through object interactions and the brain hemispheres were designated accordingly. White matter alterations were assessed using diffusion tensor imaging in nine areas, and movement segmentation of the body-parts head, shoulder, elbow, and wrist were registered during a unimanual goal-directed task. Increased movement segmentation was demonstrated consistently on the preferred side in the E-PT group compared with the term born group. Also compared with the term born peers, the E-PT group demonstrated reduced fractional anisotropy (FA) in the cerebral peduncle (targeting the corticospinal tract) in the hemisphere on the non-preferred side and in the splenium of corpus callosum. In contrast, in the anterior internal capsule on the preferred side, the E-PT group had increased FA. Lower FA in the cerebral peduncle, but higher FA in the anterior internal capsule, was associated with increased movement segmentation across body-parts in a contralateral manner. The results suggest that impaired development of sensorimotor tracts in E-PT children could explain a sub-optimal spatiotemporal organization of upper-limb movements. Hum Brain Mapp 38:5051-5068, 2017. © 2017 Wiley Periodicals, Inc.

The Emergence of Tool Use in Preterm Infants

Preterm born children without neurological impairments have been shown to present some visual-manual coordination deficits, more or less depending on their tonicity and the degree of prematurity. In this paper, we compare the development of tool use in 15-23-month-old preterm infants born after 33-36 weeks of gestation without neurological complications with that of full-term infants according to corrected age. Understanding the affordance of a tool is an important cognitive milestone in early sensorimotor period. Using a tool to bring within reach an out-of-reach object, for instance, has been shown to develop during the 2nd year in full-term infants. Here we presented preterm infants with an attractive toy out of reach and with a rake-like tool within reach in five conditions of spatial relationships between the toy and the tool. Like full-terms, preterm infants used the tool with success in conditions of spatial contiguity around 15-17 months. In conditions of a spatial gap between tool and toy, i.e., the only conditions which shows without ambiguity that the infant understands the affordance of the tool, preterm infants as a group showed no delay for tool use: the frequency of spontaneous successes started to increase after 18 months, and demonstration became effective after that age. However, further analyses showed that only the preterm infants without hypotonia and born after 36 weeks of pregnancy developed tool use without delay. Hypotonic preterm infants were still largely unsuccessful in the conditions of spatial gap, even at the end of the study. The degree of prematurity also influenced the performance at tool use. These results, following the observation of a delay in the development of bimanual coordination and of handedness in the same infants at 10-12 months in a previous study, show that low risk preterm infants can still be impaired for the development of new manual skills beyond the 1st year. Thus, hypotonic preterm infants and infants born before 36 weeks of pregnancy should be followed and might benefit from early intervention programs.

Structural connectivity relates to perinatal factors and functional impairment at 7years in children born very preterm

OBJECTIVE

To use structural connectivity to (1) compare brain networks between typically and atypically developing (very preterm) children, (2) explore associations between potential perinatal developmental disturbances and brain networks, and (3) describe associations between brain networks and functional impairments in very preterm children.

METHODS

26 full-term and 107 very preterm 7-year-old children (born <30weeks' gestational age and/or <1250g) underwent T1- and diffusion-weighted imaging. Global white matter fibre networks were produced using 80 cortical and subcortical nodes, and edges were created using constrained spherical deconvolution-based tractography. Global graph theory metrics were analysed, and regional networks were identified using network-based statistics. Cognitive and motor function were assessed at 7years of age.

RESULTS

Compared with full-term children, very preterm children had reduced density, lower global efficiency and higher local efficiency. Those with lower gestational age at birth, infection or higher neonatal brain abnormality score had reduced connectivity. Reduced connectivity within a widespread network was predictive of impaired IQ, while reduced connectivity within the right parietal and temporal lobes was associated with motor impairment in very preterm children.

CONCLUSIONS

This study utilised an innovative structural connectivity pipeline to reveal that children born very preterm have less connected and less complex brain networks compared with typically developing term-born children. Adverse perinatal factors led to disturbances in white matter connectivity, which in turn are associated with impaired functional outcomes, highlighting novel structure-function relationships.

Handedness in man: The energy availability hypothesis

More than 90% of the human species are right handed. Although outwardly our body appears symmetrical, a 50/50% lateralization in handedness never occurs. Neither have we seen more than 50% left handedness in any subset of the human population. By 12-15weeks of intrauterine life, as many as 6 times more fetuses are noted by ultrasound studies to be sucking on their right thumbs. Distinct difference in oxygenation leading to dissimilar energy availability between right and left subclavian arteries in place by week 9 of life may hold the clue to the lateralization of hand function and eventually, the same in the brain. We know there is a higher incidence of left handedness in males, twins, premature babies and those born to mothers who smoke. They may represent a subset with less distinct difference in oxygenation between the 2 subclavian arteries during the fetal stage. This hypothesis if correct not only closes the gap in understanding human handedness and lateralization but also opens a vista for new research to focus on in utero tissue energy availability and its impact on outcome in life.

Do hand preferences predict stacking skill during infancy?

The cascade theory of handedness suggests that hand preferences develop from a history of cascading and sequentially developing manual asymmetries for a variety of actions. Infants who consistently use their preferred hand for a variety of actions likely would gain proficiency using that preferred hand and, consequently, perform more proficiently on other challenging manual tasks. One such task is object stacking, which has been linked with a number of cognitive abilities. If infant hand preference facilitates the development of stacking skill, then this could provide a link by which early hand preference might affect the development of cognition. From a sample of 380 infants assessed for an acquisition hand preference across 6-14 months, 131 infants were assessed for stacking skill from 10 to 14 months at monthly visits. Four unique handedness sub-groups were identified from the 380-infant sample: left, trending right, stable right, or no hand preference. Each of the four hand preference groups exhibited different trajectories in the development of their stacking skills. Left- and stable right-handers stacked more items than infants with no preference by 14 months, whereas infants with a trending right preference did not. The proportion of preferred hand use (right and left) from 6 to 9 months also predicted an earlier initial onset of stacking skill, whereas the proportion of only right hand use did not. Thus, the development of a hand preference predicts an earlier emergence of stacking skill and may have implications for other domains of infant cognitive development.

Visuo-manual coordination in preterm infants without neurological impairments

The extent of and reasons for visuo-manual coordination deficits in moderate and late preterm born infants without neurological impairments are not well known. This paper presents a longitudinal study on the visuo-manual development of twelve preterm infants, born after 33-36 weeks of gestation without neurological complications, between the ages of 6 and 12 months. Visuo-manual integration and grasping were assessed using the Peabody Developmental Motor Scales, along with bimanual coordination and handedness tests. Visual function was examined once prior to the beginning of the study. Gross motor development was also evaluated every month. Preterm infants were compared to a control group of ten full-term infants according to corrected age. Compared to full-terms, the visual perception of preterm infants was close to normal, with only a measure of visual fixation lower than in full-terms. In contrast, preterm infants had delayed development of visuo-manual integration, grasping, bimanual coordination, and handedness even when compared using corrected age. Tonicity and gestational age at birth were the main variables associated to the delays. These results are discussed in terms of the possible factors underlying such delays. They need to be confirmed on a larger sample of preterm born children, and to be correlated with later development. This would allow developing markers of future neuropsychological impairments during childhood.

Asymmetrical motor behaviour as a window to early leg preference: a longitudinal study in infants 7-12 months of age

This longitudinal study explored leg preference in infancy during half-kneel pulling-to-stand (PTS) and asymmetrical four-point kneeling, which is part of the typical motor repertoire of infants. The special characteristics of the half-kneel PTS as a discrete task, performed in a bilateral context provide the opportunity to explore leg preference during an asymmetrical behaviour. Twenty-seven infants were observed in their homes, every 3 weeks between the ages of 7-12 months. Leg preference was determined by the "lead-out" limb used as the infants pulled to stand from the half-kneeling position (half-kneel PTS). As a complementary measure, the leading leg during asymmetrical four-point kneeling and crawling ("asymmetrical four-point patterns") was used in the 10 infants who developed these patterns. The infants studied showed a general preference for using a leading leg during half-kneel PTS, which was mostly consistent over the study period. A strong correlation was found between leg preferences during half-kneel PTS and asymmetrical four-point patterns. The findings documented functional asymmetry in infant lower limbs during half-kneel PTS and asymmetrical four-point patterns, highlighting the importance of the tasks used to define leg preference.

Neural correlates of executive attention in adults born very preterm

Very preterm birth is associated with an increased prevalence of attention problems and may especially impair executive attention, i.e., top-down control of attentional selection in situations where distracting information interferes with the processing of task-relevant stimuli. While there are initial findings linking structural brain alterations in preterm-born individuals with attention problems, the functional basis of these problems are not well understood. The present study used an fMRI adaptation of the Attentional Network Test to examine the neural correlates of executive attention in a large sample of N = 86 adults born very preterm and/or with very low birth weight (VP/VLBW), and N = 100 term-born controls. Executive attention was measured by comparing task behavior and brain activations associated with the processing of incongruent vs. congruent arrow flanker stimuli. Consistent with subtle impairments of executive attention, the VP/VLBW group showed lower accuracy and a tendency for increased response times during the processing of incongruent stimuli. Both groups showed similar activation patters, especially within expected fronto-cingulo-parietal areas, but no significant between-group differences. Our results argue for a maintained attention-relevant network organization in high-functioning preterm born adults in spite of subtle deficits in executive attention. Gestational age and neonatal treatment variables showed associations with task behavior, and brain activation in the dorsal ACC and lateral occipital areas, suggesting that the degree of prematurity (and related neonatal complications) has subtle modulatory influences on executive attention processing.

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fMRI study examines neural correlates of executive attention in preterm-born adults.

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Preterm-born adults show subtle behavioral deficits.

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Preterm-born adults show maintained organization of attention-related networks.

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Modulatory effects of gestational age and neonatal treatment variables are observed.

Neurodevelopmental Outcomes and Neural Mechanisms Associated with Non-right Handedness in Children Born Very Preterm

Non-right handedness (NRH) is reportedly more common in very preterm (VPT; <32 weeks' gestation) children compared with term-born peers, but it is unclear whether neonatal brain injury or altered brain morphology and microstructure underpins NRH in this population. Given that NRH has been inconsistently reported to be associated with cognitive and motor difficulties, this study aimed to examine associations between handedness and neurodevelopmental outcomes in VPT 7-year-olds. Furthermore, the relationship between neonatal brain injury and integrity of motor tracts (corpus callosum and corticospinal tract) with handedness at age 7 years in VPT children was explored. One hundred seventy-five VPT and 69 term-born children completed neuropsychological and motor assessments and a measure of handedness at 7 years' corrected age. At term-equivalent age, brain injury on MRI was assessed and diffusion tensor measures were obtained for the corpus callosum and posterior limb of the internal capsule. There was little evidence of stronger NRH in the VPT group compared with term controls (regression coefficient [b] -1.95, 95% confidence interval [-5.67, 1.77]). Poorer academic and working memory outcomes were associated with stronger NRH in the VPT group. While there was little evidence that neonatal unilateral brain injury was associated with stronger NRH, increased area and fractional anisotropy of the corpus callosum splenium were predictive of stronger NRH in the VPT group. VPT birth may alter the relationship between handedness and academic outcomes, and neonatal corpus callosum integrity predicts hand preference in VPT children at school age. (JINS, 2015, 21, 610-621).

Elevated rates of atypical handedness in paedophilia: theory and implications

Multiple factors determine handedness including genetics, prenatal stress and post-natal environmental conditions. Atypical handedness, whether manifest as increased sinistrality or decreased strength of lateral preference, has been noted in a wide variety of populations with neuropathology. Those with atypical sexual preferences, specifically paedophilia, also manifest reduced rates of right-handedness. This paper uses the largest sample of phallometrically assessed men to date to establish the pattern of atypical handedness in paedophilia. Specifically, whereas prior research has largely characterized participants dichotomously as right-handed or non-right-handed and/or used self-report of writing hand, this paper expands upon such reports by using the Edinburgh Handedness Inventory's laterality quotient. Participants' handedness and phallometrically assessed sexual preference were analyzed both as continuous and categorical variables, and the responses of those scoring in the range of ambiguous-handedness were evaluated to ascertain whether they were ambiguously handed or more accurately described as mixed-handed. Results indicated those producing scores in the range of ambiguous-handedness demonstrated response patterns consistent with ambiguous-handedness, rather than mixed-handedness. Paedophiles demonstrated high rates of non-right-handedness primarily manifested as sinistrality, whereas those who had a sexual preference for pubescent children evidenced increased ambiguous-handedness. Results support a view of ambiguous-handedness as less pathological than previously hypothesized, and of a neurodevelopmental origin of paraphilic sexual preferences.

Long-term influences of a preterm birth on movement organization and side specialization in children at 4-8 years of age

This study explored upper-limb and head kinematics during unimanual goal-directed movements in children born preterm (PT) and full-term (FT) aged 4-8 years. Further, functional lateralization was investigated through side-specific kinematics and hand preference observations. Altogether, 141 children were included, divided into three sub-groups based on gestation week at birth (GW). Children born FT (38-41 GW) and moderately PT (33-35 GW) showed faster, smoother, and shorter movement trajectories than children born very PT (V-PT < 33 GW). Only children born FT expressed evident side differences that were characterized by smoother movements with the preferred side. Regarding hand preference, the children born V-PT showed increased rates of non-right-handedness compared with the other groups. Regardless of hand preference, the children born V-PT showed less well organized movements compared with the other groups. These findings suggest that spatio-temporal movement organization and side specialization at pre-/early school-age are affected by a PT birth, and more frequently so for children born before 33 GWs, indicating long-lasting influences on neuromotor development and specialization.

Power failure: why small sample size undermines the reliability of neuroscience

A study with low statistical power has a reduced chance of detecting a true effect, but it is less well appreciated that low power also reduces the likelihood that a statistically significant result reflects a true effect. Here, we show that the average statistical power of studies in the neurosciences is very low. The consequences of this include overestimates of effect size and low reproducibility of results. There are also ethical dimensions to this problem, as unreliable research is inefficient and wasteful. Improving reproducibility in neuroscience is a key priority and requires attention to well-established but often ignored methodological principles.